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Table of Contents 

Explosion Motors . . . Revised by J. R. Bayston t Page *11 

Historical — Explosion Motor Cycle: Four-Stroke Cycle — Two-Stroke 
Cycle — Six-Stroke Cycle — Types of Explosion Motors: Automobile, 
Marine, Motorcycle — Motor Details: Four-Cycle Type — Crank Case, Cylinder 
Block — Ignition — Lubrication — Cooling — Crank and Firing Arrangements 
— Two-Cycle Type — Four-, Six-, Eight-, and Twelve-Cylinder Motors — 
Power — Governing — Thermodynamics: Indicators, Manograph, Midgley, 
Thermal Efficiency — Otto Cycle in Practice: Suction, Compression, Ex- 
plosion and Exhaust Strokes — Modifications for Modern Motors — Aviation 
Motors — Fuels — Fuel Knock— Horsepower and Hating Calculations 

Gasoline Automobiles 

. By Morris A. Hall. Revised by J. R. Bayston Page 145 

Introductory — General Outline of Motor Car Construction: Chassis As- 
sembly, Clutch Group, Transmission Group, Steering Group, Frame Group, 
Final-Drive Group — Engine Group: General Engine Features: Engine 
Cycles, Cylinder Multiplication, Engine Troubles — Cylinder Forms and 
Construction: Method of Casting Cylinders, Cylinder Repairs (Remov- 
ing Carbon, Use of Stethoscope, Cutting Gaskets, Cylinder Heads, Grind- 
ing Out Cylinder Bore, Cylinder Lapping, Repairing Cracked Water 
Jackets, Replacing Pistons in Cylinders, Two-Piece Pistons) — Pistons 
and Accessories: Construction, Piston Rings, Piston and Ring Troubles 
and Repairs (Aluminum Rods, Straightening Bent Rod, Adjusting Bear- 
ings) — Crankshafts: Design, Bearings, Shims, Crankshaft and Bearing 
Troubles and Remedies — Crank Cases: Function, Construction, Mate- 
rials, Crank-Case Troubles and Remedies (Mending Breaks, Cleaning 
Aluminum, Machining Crank Cases) — Questions and Answers — Carbu- 
retor and Carburetion: Function of Carburetor, Effect of Heavier Fuels, 
Classification, Throttle Valves, Adjustment of Air and Gasoline Supply 
(Handling Fuel Spray, Water-Jacketing, Auxiliary Air Valve, Mixing 
Chamber, Use of By-Pass, Double Carburetors, Multiple Nozzle Carbu- 
retors), Carburetor Operation and Adjustment (Stromberg, Zenith, Holley, 
Hudson, Essex, Ford, Kingston, Master, Miller Racing Type, Webber, 
Rayfleld, Ball and Ball, Newcomb, Marvel, Schebler, Stewart, Johnson, 
Carter, Pierce-Arrow, Packard Fuelizer, Tillotson, Cadillac, Oxygen-Add- 
ing Devices), Kerosene and Heavy Fuel Carburetors (Holley, Foreign 
Types, Master, Bennett, Bennett Air Washer, Parrett Air Cleaner, Ensign 
Carburetor, • Ensign Fuel Converter, Deppe), Carburetor Troubles and 
Remedies — Inlet Manifold Design and Construction: Changes in De- 
sign, Heating the Charge, Inlet Manifold Troubles — Fuel Supply: Tank 
Placing, Fuel Feeding, Stromberg Fuel Pumps, Stewart Vacuum Tanks, 
Reserve Tank, Fuel System Troubles and Repairs — Questions and An- 
swers — Valves and Their Mechanism: Valve Features, Details of Poppet- 
Valve Gears (Valve Settings, Typical Valve Actions, Good Practice, Number 
of Valves per Cylinder, Making Cams, Valve Timing), Repairing Poppet 
Valves and Valve Parts (Removing Valves and Valve Springs, Stretch- 
ing and Tempering Valve Springs, Adjusting Tension, Cutting Valve-Key 
Slots, Grinding Valves, Noisy "Valves, Valve Enclosures, Valve-Timing 
Gears, Valve Cage Repairs, Guides, Caps, Twisted Camshafts, Sliding 
Sleeve Valves, Rotating Valves) — Exhaust System: Importance, Forms of 
Exhaust Manifolds, Muffler, Cut-Outs — Cooling System: Water Cooling 
(Water-Jacketing, Radiators and Piping, Circulation, Fans, Anti-Freez- 
ing Solutions), Air Cooijng, Cooling Troubles and Adjustments — Lubrica- 
tion System: Motor Lubrication (Splash Pressure, Single-Pump Pres- 
sure, Individual Pump, Gravity Feeding, Splash Lubrication, External 
Lubrication), General Lubrication, Oil Tests, Oils and Greases, Lubrica- 
tion Troubles and Remedies, Summary of Troubles with Lubrication 
Systems — Bearings: Types, Plain Bearings, Roller Bearings, Ball Bear- 
ings — Flywheel Sub-Group: Importance of Flywheel, Characteristics, 
Methods of Fastening, Flywheel Markings 

Index Page 493 

•For page numbers, see foot of pages/ 

tFor professional standing of authors, see list of Authors and Collabo- 
rators at front of volume. 

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A General Reference Work 


Prepared by a Staff of 


Illustrated with over Fifteen Hundred Engravings 




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COPYRIGHT, 1909. 1910, 1912, 1915. 1916, 1917, 1918, 1919, 1920. 1921 

Copyrighted in Great Britain 
All Rights Reserved 

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Authors and Collaborators 


President and General Manager, The Stirling Press, New York City 

Member, Society of Automotive Engineers 

Member, The Aeronautical Society 

Formerly Secretary, Society of Automotive Engineers 

Formerly Engineering Editor, The Automobile 


Automobile Engineer 

With Inter-State Motor Company, Muncie, Indiana 

Formerly Manager, The Ziegler Company, Chicago 


Editor, Automotive Engineering 

Formerly Managing Editor, Motor Life; Editor, The Commercial Vehicle, etc. 

Author of "What Every Automobile Owner Should Know" 

Member, Society of Automotive Engineers 

Member, American Society of Mechanical Engineers 


Late Editor, Motor Age, Chicago 
Formerly Managing Editor, The Light Car 
Member, Society of Automotive Engineers 
American Automobile Association 


Formerly Secretary and Educational Director, American School of Correspond- 
Formerly Instructor in Physics, The University of Chicago 
American Physical Society 


Late Lecturer, Automobile Division, Milwaukee Central Continuation School 
Editorial Representative, Commercial Car Journal and Automobile Trade Journal 
Member, Society of Automotive Engineers 
Member, Standards Committee of S. A. E. 
Formerly Technical Editor, The Light Car 


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Authors and Collaborators— Continued 


Professor of Industrial Engineering, Pennsylvania State College 
American Society of Mechanical Engineers 


Specialist in Technical Advertising 
Member, Society of Automotive Engineers 
Formerly Associate Editor, The Automobile 


Consulting Mechanical Engineer, Chicago 
American Society of Mechanical Engineers 


Superintendent, Union Malleable Iron Company, East Moline, Illinois 


Formerly Dean and Head, Consulting Department, American School of Cor- 
Member, American Society of Mechanical Engineers 


Head, Automobile Engineering Department, American School of Correspond- 
Member, Society of Automotive Engineers 
Formerly Lecturer, Federal Association of Automobile Engineers, Chicago 


President, W. R. Howell and Company, London, England 


Associate Editor, Motor Age, Chicago 



Head, Publication Department, American Technical Society 

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Authorities Consulted 

THE editors have freely consulted the standard technical litera- 
ture of America and Europe in the preparation of these 
volumes. They desire to express their indebtedness, particu- 
larly, to the following eminent authorities, whose well-known treatises 
should be in the library of everyone interested in the Automobile and 
allied subjects. 

Grateful acknowledgment is here made also for the invaluable 
co-operation of the foremost Automobile Firms and Manufacturers 
in making these volumes thoroughly representative of the very latest 
and best practice in the design, construction, and operation of Auto- 
mobiles, Commercial Vehicles, Motorcycles, etc.; also for the valu- 
able drawings, data, illustrations, suggestions, criticisms, and other 


Consulting Engineer 

First Vice-President, American Motor League 

Author of "Roadside Troubles" 


Late Consulting Engineer 

Past President of the American Society of Civil Engineers 

Author of "Artificial Flight," etc. 


Member, American Society of Mechanical Engineers 

Author of "Gas-Engine Handbook," "Gas Engines and Their Troubles," "The 
Automobile Pocket-Book," etc. 



Member, American Society of Mechanical Engineers 
Engineer, General Electric Company 
Author of "Elements of Gas Engine Design" 


Author of "Horseless Vehicles, Automobiles, and Motorcycles," "Gas, Gasoline, 
and Oil Engines," "Mechanical Movements, Powers, and Devices," etc. 


Associate Member, American Institute of Electrical Engineers 
Author of "The Storage Battery : A Practical Treatise on the Construction, 
Theory, and Use of Secondary Batteries" 

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Authorities Consulted— Continued 


Director, H. J. Willard Company Automobile School 
Author of "The Complete Automobile Instructor" 


Editor, The American Cyclopedia of the Automobile 

Author of "Motor Boats," "History of the Automobile," "Automobile Driving, 

Self-Taught," "Automobile Motors and Mechanism," "Ignition Timing 

and Valve Setting," etc. 


Mechanical Engineering Department, Columbia University 
Author of "Gas Engine Design" 

P. M. HELDT ** 

Editor, Horseless Age 

Author of "The Gasoline Automobile" 


Professor of Experimental Engineering, Sibley College, Cornell University 
Author of "Internal Combustion Engines" 


Author of "Light Motor Cars and Voiturettes," "Motor Repairing for Ama- 
teurs," etc. 


Professor of Mechanical and Electrical Engineering in University College, 
•Author of "Gas and Petroleum Engines" 


Member, Institution of Automobile Engineers 
Author of "Motor-Car Mechanisms and Management" 



Professor of Experimental Engineering, Sibley College, Cornell University 
Author of "Internal Combustion Engines" 


Technical Director, The New York School of Automobile Engineers 
Author of "Motor-Car Principles" 

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Authorities Consulted— Continued 


Formerly Editor, Motor Age 

Author of "Automobile Troubles, and How to Remedy Them" 


Associate Member, Institute of Electrical Engineers 
Author of "Electric Ignition for Motor Vehicles'* 


Member, American Society of Civil Engineers 
British Association for the Advancement of Science 
Chevalier Legion d'Honneur 
Author of "Artificial and Natural Flight," etc. 


Author of "Complete Automobile Record," "A B C of Motoring" 


Lecturer on Manufacture and Application of Industrial Alcohol, at the Poly- 
technic Institute, London 
Author of "Industrial Alcohol," etc. 


Consulting Engineer 

Author of "Modern Gas and Oil Engines" 


Head of Department of Electrical Engineering, Columbia University 
Past President, American Institute of Electrical Engineers 
Author of "Electric Lighting," Joint Author of "Management of Electrical 


Captain and Instructor in the Prussian Aeronautic Corps 
Author of "Airships Past and Present" 


Associate Member, Institute of Mechanical Engineers 
Author of "Petrol Motors and Motor Cars" 

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Authorities Consulted— Continued 


Director of Sibley College, Cornell University 

Author of "Manual of the Steam Engine," "Manual of Steam Boilers," etc. 


Motoring Editor, The London Sphere 
Author of "The Amateur Motorist" 


Major and Battalions Kommandeur in Badischen Pussartillerie 
Author of "Pocket-Book of Aeronautics" 


Professor of Steam Engineering, Massachusetts Institute of Technology 
Author of "Steam Boilers" 


Author of "Operation, Care, and Repair of Automobiles" 


Author of "Motor Boats," etc. 


Editor, Work and Building World 
Author of "Motorcycle Building" 


Author of "Self-Propelled Vehicles" 


Editor, The Encyclopedia of Motoring, Motor News, etc. 


Author of "Ignition Devices," "Magnetos for Automobiles," etc. 


Consulting Electrical Engineer 

Associate Member, American Institute of Electrical Engineers 

Author of "Storage Battery Engineering" 

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THE period of evolution of the automobile does not 
span many years, but the evolution has been none 
the less spectacular and complete. From a creature 
of sudden caprices and uncertain behavior, it has become 
today a well-behaved thoroughbred of known habits and 
perfect reliability. The driver no longer needs to carry war 
clothes in momentary expectation of a call to the front. 
He sits in his seat, starts his motor by pressing a button 
with his hand or foot, and probably for weeks on end will 
not need to do anything more serious than feed his animal 
gasoline or oil, screw up a few grease cups, and pump up a 
tire or two. 

C, And yet, the traveling along this road of reliability and 
mechanical perfection has not been easy^ and the grades 
have not been negotiated or the heights reached without 
many trials and failures. The application of the internal- 
combustion motor, the electric motor, the storage battery, 
and the steam engine to the development of the modern 
types of mechanically propelled road carriages has been a 
far-reaching engineering problem of great difficulty. 
Nevertheless, through the aid of the best scientific and me- 
chanical minds in this and other countries, every detail 
has received the amount of attention necessary to make it 
as perfect as possible. Eoad troubles, except in connection 
with tires, have become almost negligible and even the 
inexperienced driver, who knows barely enough to keep to 
the road and shift gears properly, can venture on long tour- 
ing trips without fear of getting stranded. The refinements 
in the ignition, starting, and lighting systems have added 
greatly to the pleasure in running the car. Altogether, the 
automobile as a whole has become standardized, and unless 
some unforeseen developments are brought about, future 
changes in either the gasoline or the electric automobile 
will be merely along the line of greater refinement of the 
mechanical and electrical devices used. 

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Q Notwithstanding the high degree of reliability already 
spoken of, the cars, as they get older, will need the atten- 
tion of the repair man. This is particularly true of the 
cars two and three seasons old. A special effort, therefore, 
has been made to furnish information which will be of value 
to the men whose duty it is to revive the faltering action of 
the motor and to take care of the other internal troubles 
in the machine. 

Q Special effort has been made to emphasize the treatment 
of the Electrical Equipment of Gasoline Cars, not only be- 
cause it is in this direction that most of the improvements 
have lately taken place but also because this department of 
automobile construction is least familiar to the repair men 
and others interested in the details of the automobile. A 
multitude of diagrams have been supplied showing the con- 
structive features and wiring circuits of the majority of 
the systems. In addition to this instructive section, par- 
ticular attention is called to the articles on Welding, Shop 
Information, Electrical Eepairs, and Ford Construction 
and Kepair. 

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General Description. The term explosion motor as herein used 
tefers primarily to gasoline engines such as are used on aerial crafts, 
automoBiles, motorcycles, motorboats, and small stationary instal- 
lations. There is nothing mysterious about this form of engine, it 
being similar in most respects to the ordinary 
steam- engine, except that the force which 
develops the power is derived not from the 
expansion of steam, but from the explosion of 
a gaseous charge consisting of a mixture of oil 
vapor and air 

The simplest type of motor, Fig. 1, consist^ 
primarily of a cylinder A in which there is a 
hollow piston B (free to slide up and down), a 
crank shaft C, and a rod D, connecting the 
piston through the piston pin E to the crank 
on the shaft. As the piston moves up and 
down in the cylinder this reciprocating motion 
is converted by the operation of the connecting 
rod on the crank F into a rotary motion, as 
shown by the arrow near C. The whole action 
may be compared to that of a boy on a bicycle, 
D representing the boy's leg and F the pedal. 
At the head of the cylinder are shown two 
valves, G and H, and a spark plug 7, whose functions are to admit 
the charge, explode it, and permit it to escape, by which operations 
and their repetition the reciprocating motion of the piston is set up 
and maintained. The successive explosions of the charges produce 
considerable heat and, therefore, in actual practice the cylinder A i$ 
usually surrounded by a jacket. Water is circulated around in the 
space between this jacket and the cylinder, thus cooling the cylinder. 
Another cooling method is by air, in which case the outer wall of the 

Fig. i. 

Simple Explosion 


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cylinder is constructed as shown in Figs. 16 and 17. In order, there- 
fore, to secure the above action, the following mechanical devices 
must be provided: (1) A cylinder containing a freely moving piston, 
capable of being lubricated effectively; (2) a combustion chamber 
in whose walls are valves for the admission and exhaust of the gas, 
and valve seats so arranged that the joints will remain gas-tight 
when desired; (3) an outside, dependable means of ignition, with 
sparking points inside the combustion chamber; (4) a source of fuel 
supply, which, in the ordinary engine, must convert liquid into a 
vapor; and (5) a cylinder construction which will carry off the 
surplus heat or allow of its being carried off. 

Historical. The first workers in this field were perhaps 
Huyghens, Hautefeuille, and Papin, who experimented with motors 
using gunpowder as a fuel in the latter part of the seventeenth 
century. A patent was obtained in England by John Barber, in the 
closing years of the eighteenth century, on a turbine using a mixture 
of gas or vapor and air for the fuel. A few years later Robert Street, 
another Englishman, built an oil engine in which the vapor was 
ignited by a flame at the end of the first half of the outward stroke. 

From 1800 to 1854 several French and English patents were 
granted for internal combustion engines, most of the engines being 
double acting, i.e., one explosion acting on one side and the next 
explosion acting on the other side of the piston, and some using 
electrical ignition. In 1858, Degrand made a big advance by com- 
pressing the mixture in the cylinder instead of in separate pumps. 

First Practical Engine. The first commercially practical engine 
was developed about 1860 by Lenoir, who marketed in Paris a 
1-horse-power, double-acting gas engine closely resembling a hori- 
zontal steam engine. This used what is now called jump-spark 
ignition and was made in sizes up to 12 horse-power. It gave con- 
siderable trouble in many cases, but the principal reason for its 
failure was the excessive amount of gas required, viz, 60 to 100 cubic 
feet of illuminating gas per brake-horse-power hour,* which was 
more than three times the consumption of a modern gas engine, 
and prevented competition with steam. 

Otto Engine. The gas engine industry as^We know it today was 
really started in 1861, when a young German merchant, N. A. Otto, 

♦Brake horse-power (b. h. p.) is the power delivered from the shaft of the engine. When 
delivered for one hour it is called a b.h.p.-hour. 


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developed an experimental engine in which admission, compression, 
ignition, and exhaust were accomplished in the one working cylinder. 
Otto failed to realize fully the great promise held out by his engine 
and temporarily abandoned its development. 

De Rochas' Theory. In the year 1862 it was pointed out by 
a French engineer, Beau de Rochas, that in order to get high economy 
in a gas engine certain conditions of operation were necessary, the 
most important being that the explosive mixture shall be compressed 
to a high pressure before ignition. In order to accomplish this, he 
proposed that the cycle of operations should occupy four strokes or 
two complete revolutions of the engine and that the operation should 
be as follows: 

(1) Suction or admission of the mixture throughout the complete for- 
ward stroke. 

(2) Compression of the mixture during the whole of the return stroke, 
so that it finally occupies only the clearance space between the piston and 
cylinder head. 

(3) Ignition of the charge at the end of the second stroke and expansion 
of the exploded mixture throughout the whole of the next forward stroke. 

(4) Exhaust beginning at the end of the forward stroke and continuing 
throughout the whole of the last return stroke. 

De Rochas had developed a brilliant theory but never put it into 

practical use. The pamphlet containing this idea remained practically 

unknown until about 1876, when it was discovered and published in 

the course of a patent-lawsuit against Otto and his associates, who 

were using this cycle in their engine, Otto having returned to the 

development of his engine in 1863. Although the original idea was 

perhaps Beau de Rochas', the credit really belongs to Otto, who 

made practical use of what would otherwise have been an unknown 

theory. In recognition of this fact the four-stroke cycle which Otto 

adopted in his engine and which is used in the majority of our 

modern motors is generally known as the Otto cycle. 


•The cycle of the explosion motor, therefore, consists of four 
distinct steps, viz, (1) Admission of the charge of explosive fuel; 
(2) compression of this charge; (3) ignition and explosion of this 
charge; and (4) exhaust or expulsion of the burned charge. If this 
complete process requires four strokes of the piston rod in any one 
cylinder, the motor is designated as a four-cycle motor, although it 


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would be more exact to call it a four-stroke cycle. If the complete 
process is accomplished in two strokes of the piston, the motor 
is designated as a two-cycle motor. 

Four-Stroke Cycle. One complete operation of a single-cylinder 
Otto or four-cycle explosion motor is shown in Figs. 2, 3, 4, and 5. 
Fig. 2 shows the end of the first or suction stroke of the cycle. At 
the beginning of this stroke when about ^ inch past the dead center 
the inlet valve A is opened by an eccentric rod whose movement is 
controlled by the eccentric on a secondary shaft driven through gears 
at half the speed of the motor. This allows the vapor supplied by 
the carbureter, which is an instrument for converting the liquid fuel 

\3s \^j \^y \^j 


Figs. 2, 3, 4, and 5. Diagrams Showing One Complete Cycle of a One-Cylinder Explosion Motor 

into a vapor or gas, Fig. 6, to be drawn into the cylinder by the 
suction produced by the downward-moving piston. During this stroke 
the exhaust valve B has remained closed. 

The conditions shortly after the beginning of the second or 
compression stroke are shown in Fig. 3, both valves being closed. 
The piston, traveling as indicated by the arrows, compresses the 
charge to a pressure of about 60 pounds, when it is ignited at or 
before the end of the stroke by a spark taking place in the spark 
plug as shown in Fig. 4. Its arrangement is shown in detail Fig. 7, 
the spark passing between the points A and B. The force of the 
explosion drives the piston downward as shown in Fig. 4, ^which 
represents the power stroke. During these last two strokes, namely, 
the compression and working strokes, both valves if correctly timed 
should be completely closed. 

Fig. 5 illustrates the conditions existing after the piston has 


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Fig. 6. Typical Modern Carbureter with 

Water Jacket 

CovtrUay of Ray field Carbureter Company, Chicago 


begun the fourth or exhaust stroke. The exhaust valve B has been 
opened slightly before the end of the third stroke, and during this 
fourth stroke the gases are expelled from the cylinder through the 
open valve as shown. At the 
end of this stroke, piston and 
valves are again brought to the 
proper positions for the be- 
ginning of the suction stroke 
illustrated in Fig. 2. 

Compounding. The pres- 
sure is high at the end of the 
expansion in the Otto cycle, 
and the efficiency (the ratio 
of work gotten out to work 
put in) of the cycle can be in- 
creased considerably if the gas 
is expanded more completely. 
Ordinary steam engine prac- 
tice suggests that more complete expansion can be obtained by com- 
pounding. A compound steam engine has two or more cylinders. 
The steam or gas after doing work in the first or high-pressure cylinder 
completes its expansion in the other cylinder or cylinders. While 
the success of the compounded steam engine would lead us to 
expect the same increase in efficiency in the gas-engine type, 
no satisfactory compound gas engine has thus far been devel- 

Double- Acting. One of 
the main objections urged 
against the Otto cycle is 
that it requires two revo- 
lutions of the engine for 
its completion, so that the 
expansion or power stroke 
comes but once in four 
strokes. There results from 
this a very irregular driving 
effort, making large flywheels necessary if the main shaft is to rotate 
uniformly, or else requiring the use of several engines working on the 

Pig. 7. Typical Forms of Spark Plug 


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same shaft. The power strokes can be made twice as frequent if the 
cylinder is double acting, with admissions and explosions occurring 
on both sides of the piston. Many double-acting engines are used 
for stationary power purposes but not for automobiles. For the 
latter, the irregular driving effort in single cylinders is overcome 
by using a large number of cylinders, as four, six, or eight, so ar- 
ranged that the power impulses space out evenly. 

Fig. 8. Vertical Section of Two-Cycle Fig. 9. Vertical Section at Right 

Smalley Motor Angles to View in Fig. 8. 

Two=Stroke Cycle. An increased frequency of the expansion 
or motive stroke can be obtained by a slight modification of the Otto 
cycle which results in the cycle being completed in two strokes, and 
which is consequently called the two-cycle method. Single-acting 
motors using the two-cycle method give an impulse every revolution, 
and consequently not only give a more uniform speed of rotation of 
the crank shaft, but also develop 60 to 80 per cent more power than 
four-cycle or Otto cycle motors of the same size. Moreover, they 
are generally of greater simplicity, having fewer valves than the f our- 


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cycle motors. An example is shown in Figs. 8 and 9 of a two-cycle 
motor of small size and of the two-port type; Fig. 8 is a vertical 
section showing the piston at the bottom of its stroke, and Fig. 9 is 
a vertical section in a plane at right angles to the previous section 
plane and showing the piston at the top of its stroke. As the trunk 
piston A makes its upward stroke, it creates a partial vacuum below 
it in the closed crank chamber C and draws in the explosive charge 
through B. On the downward stroke, the charge below the piston is 
compressed to about 10 pounds pressure in the crank chamber C, the 
admission through B being controlled by an automatic valve (not 
shown) which closes when the pressure in C exceeds the atmospheric 
pressure. When the piston reaches the lower end of its stroke, it 
uncovers exhaust port K and at the same time brings admission port 
D in the piston opposite the by-pass opening E, and permits the 
compressed charge to enter the cylinder G through the automatic 
admission-valve F, as soon as the pressure in the cylinder falls below 
that of the compressed charge. The return of the piston shuts off 
the admission through E, and the exhaust through K, and compresses 
the charge into the clearance space. The charge is then exploded, 
Fig. 9, and the piston makes its down or motive stroke. Near the 
end of the down stroke, after the opening of the exhaust port K^the 
admission of the charge at the top of the cylinder sweeps the burned 
gases out, the complete escape being facilitated by the oblique form, 
Fig. 8, of the top of the piston. The motor is so designed that the 
piston on its return stroke covers the exhaust port K just in time to 
prevent the escape of any of the entering charge. The processes 
described above and below the piston are simultaneous, the up-stroke 
being accompanied by the admission below the piston and compression 
above it, while the down-stroke has expansion above the piston and 
a slight compression below it. In large engines the charge is com- 
pressed by a separate pump, and not in the crank case. 

Six=Stroke Cycle. A few of the early motors operate on the 
six-stroke two-cycle principle. This cycle was identical with the 
four cycle, two scavenging strokes being added after the exhaust 
stroke and acting as an internal cooling system. It was necessary 
to have a large number of cylinders to produce a continuous flow 
of power, as this motor developed only one power stroke in three 
revolutions; consequently it has been considered impractical. 

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Automobile Motors. Modern automobile motors are multi- 
cylinder four-cycle engines, designed to run at speeds of 800 revo- 
lutions per minute, or over, with long strokes, battery ignition, 
and four or more mechanically operated valves; use gasoline as a 
fuel; are generally of the pair or en bloc type; and develop usually 
not more than 6 horse-power per cylinder at 1,000 revolutions. The 
power is commonly controlled by throttling with hand and foot 

The Autocar light truck still uses the double-opposed con- 
struction. The motor, Fig. 10, has two cylinders lying on opposite 
sides of the crank shaft, with their cranks set at 180 degrees. 

Fig. 10. Typical Horizontal-Opposed Engine for Commercial Car Chassis 
The Autocar Company, Ardmore, Pennsylvania 

It is standard practice in automobile work to use a motor 
composed of four, six, eight, or twelve cylinders. The fours and 
sixes are always arranged in one plane. The eight consists of 
two sets of four cylinders set at an angle of 90 degrees. The 
twelve has two sets of six cylinders set at an angle of 60 degrees. 
A few racing motors are built with eight cylinders in one plane, 
thus eliminating the more complicated V construction. 

Valves. There are several standard arrangements of valves 
in automobile motors. The two valves may be (1) both on one 
side of the cylinder; (2) one on each side of the cylinder; (3) both 
in the head; or (4) one on one side of the cylinder and one in the 
head. When more than two valves per cylinder are used, the 

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arrangement varies from these just given, of course. With three 
valves, as used on the Franklin car at one time, there were two 
valves in the head and one on the side. The Holmes, an air- 
cooled motor, uses three valves, one intake and two exhausts. 
Racing motors, with four valves per cylinder, usually have all 
four in the head or two in the head and two in the side walls at 
a 90-degree angle to the axis of the cylinder. The Pierce-Arrow, 
Locomobile, and Stutz use four valves per cylinder. These cylin- 
ders are T head in form. 

Fig. 13. Automobile Motor with Valves on 
Opposite Sides 

The arrangement of an automobile motor cylinder with valves 
on opposite sides is shown in Fig. 13. This design requires two 
cam shafts, which are shown driven through an intermediate gear. 
Later practice uses a silent chain for this drive. The spark plugs 
may be over either set of valves or, when double ignition is used, 
they may be over both. 

When the valves are placed on top, it is necessary to use 
levers between the push rods and the valves as in Fig. 17. 
Sometimes the inlet valves are placed over the exhaust valves. 


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The latter is operated directly by a push rod. The inlet is worked 
by a separate push rod through a rocker arm, working from a 
fulcrum on the cylinder head. 

When valves are overhead, rocker arms may be used or an 
overhead cam shaft like that shown in Fig. 14. This shaft is 
driven by spiral gears through a vertical shaft, which is driven by 
the motor. A universal joint is mounted on the vertical shaft so 
that the cam shaft and cover can be swung to one side. 

Fig. 14. Overhead Valves Driven by Overhead Cam Shaft 
Courtesy of Maudslay Motor Company, Coventry, England 

A marked departure in valve construction is that shown in 
Fig. 15, which is the Steams-Knight type of sleeve valve motor. 
This valve action consists of two concentric sleeves sliding up and 
down between the piston and cylinder walls. These sleeves open 
and close the ports, which are side slots opening directly into the 
combustion chamber. These sleeves are moved up and down by 
small connecting rods from a crank shaft driven by a silent chain. 

A modern tendency is toward the use of more valves, one 
development (following racing successes) having six per cylinder. 

Motorcycles. The motor used in the motorcycle is of the 
ribbed, air-cooled, four-cycle, vertical type, usually single cylinder 

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CI > 

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I If M 

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Excelsior Motor Manufacturing 
Chicago, IUv 

and Supply Company, 

Fig. 17. Excelsior Twin Motor 

or V-twin cylinder. Some of 
the later models, however, 
are showing four-cylinder 
motors. In Figs. 16 and 17 
are shown the standard types 
of engines found in motor- 

Aeronautical Motors. The 
principal requirements of an 
aeromotor are greater power 
per pound of weight, reliabil- 
ity, simplicity, freedom from 
vibration, and fuel economy. 
This field is just now 
receiving a great deal of 
attention from inventors and 
manufacturers. The motors 
are of the two-cycle or four- 
cycle type, either air-cooled 
or water-cooled, with ver- 
tical, horizontal, or 
revolving cylinders. 

The principal aim of 
the majority of inven- 
tors seems to have 
been to reduce the 
weight. The average 
weight of these mo- 
tors alone without 
accessories is about Si- 
pounds per horse- 
power, few exceeding 
4£ pounds, the light- 
est one weighing only 
1.8 pounds per horse- 
power. However, it 
should be understood 
when considering this 


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remarkably light weight that sustained flight has been sacrificed 
to obtain it, although the flying life of a motor has been length- 
ened gradually so that it is now more than 100 "air hours." 


Unit Power Plant. While discussions of explosion motors 
must deal in fundamentals, a practical study of a standard type 
will give the greatest benefit to the student. The Chalmers car 
has been chosen as the subject of this careful analysis of the func- 

Fig. 20. Rear View Showing Transmission, Shifting Lever and Starter 

tions of each part of the motor and of the relation of each part 
to the other parts. The motor is of the vertical, six-cylinder, 
four-cycle, water-cooled, L-head type. Fig. 18 is a plan view 
of the unit power plant showing the intake side of the motor. 
The transmission is mounted on the back of the crank case, which 
is the general method of mounting on the modern car. This 
mounting tends toward compactness and proper alignment of 


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^t: - 

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s «Hr 



ie of the motor. 

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parts. The clutch and the break pedal are also mounted on this 
casting, which ensures the proper relative location to the working 

In Fig. 19 is shown the right side of the motor. The genera- 
tor, self-starter, oil pump, ignition system, and emergency break 
are mounted on this side of the motor. The generator is driven 
from the timing gears by a spur gear, while the ignition is driven 
by the generator shaft through a spiral gear. The distributor is 

Fig. 21. Front View of the Chalmers Motor 

mounted over the breaker points, thus making a very compact 
arrangement. The ignition coil is also mounted on top of the 
generator. The starter is fastened to the side of the transmission 
case, and as this case is set in proper alignment with the flywheel, 
the starter is always in proper position. The oil pump is also 
mounted on this side. This pump draws the oil from the crank 
case and circulates it through the bearings and inside of the motor. 


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A front and a rear view of this motor are given in Figs. 20 
and 21. The timing-gear case, fan, and fan pulley are clearly shown 
in the front view, while the rear view shows an excellent detail of 
the universal joint, shifting levers, etc. 

Crank Case and Cylinder Block. A view of the crank case 
and cylinder block with the cylinder head and oil pan removed 
is given in Fig. 22. By referring to Fig. 19, it is evident that 
the cylinder block and the crank case are cast as one piece. 
This method of casting is very popular, as it eliminates a great 

Fig. 25. Differential and Ring Gear of the Chalmers Car 

deal of expense, secures proper alignment, reduces the number 
of manifold connections, and also eliminates a great many oil 

The crank shaft is of the three-bearing type, having a bearing 
at each end and one in the center, or between cylinders 3 and 4. 
Crank pins 1 and 6 are in the same plane, as pistons 1 and 6 
must travel together; 2 and 5 are also in the same plane; and 
3 and 4. The angle between crank pins 1 and 2 and also between 
crank pins 2 and 3 is 120 degrees. 

Valves. In Fig. 28 is shown a sectional end view of the 
motor, giving all details such as spark plugs, valves, valve springs, 
push rods, cams, etc. Each cylinder has two valves, an inlet 


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valve and an exhaust valve. The cylinder head of this motor is 
detachable, which allows the valves to be removed very easily. 
The inlet valves are connected to the intake manifold, which is 
connected to the carburetor, while the exhaust valve is connected 
to the exhaust manifold, allowing the burnt gases to escape into 
the atmosphere. 

Ignition. The ignition system, Fig. 23, is composed of a 
battery, ignition switch, spark coil, breaker, and distributor. The 
current is taken from the storage battery or generator and passes 
through the ignition switch, the high-tension coil, and the breaker 
points. When the points open, a high-tension current is induced 




Fig. 26. Rear Axle Construction of the Chalmers 

in the coil. This current goes to the distributor and from there 
to the spark plugs, where it jumps the gap and explodes the gas 
in the cylinder, driving the piston down. If current is taken from 
the battery, it must be recharged. The generator performs this 
work, generating current in proportion to the speed of the car. 
This current flows from the generator through the control instru- 
ments and into the battery, the circuit being completed through 
the ground to the generator. Charging the battery causes a 
chemical action in the battery, and electric energy may be obtained 
by reversing this chemical action, which is what happens when a 
battery is discharged. The battery ignition system, as illustrated, 
is a very popular type and is used on the majority of modern 

Cooling System. The water circulation system is clearly 
illustrated in Fig. 24. As the explosions develop a great deal of 

31 Digitized by G00gle 


heat, the cylinders must be cooled so that proper lubrication 
can be accomplished. The cooling system of this car is of the 
thermo-siphon type. It is a well-known fact that hot water will 
rise to the top as it is much lighter than cold water. This 


principle is utilized In the thermo-siphon cooling system. The hot 
water rises to the top of the motor and enters the radiator through 
the top water connection. It then passes through the radiator 
where it is cooled by the continual flow of air. The cold water 
leaves the radiator at the bottom and enters the cylinder block 

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through the lower water connection. This type of cooling offers 
some advantages, such as the elimination of the water pump. 

Transmission. A cross-sectional view of the transmission is 
shown in Fig. 27. This transmission is of the three-speed forward 
and one reverse type, having two sliding gears on the main shaft, 
the low and reverse gear and the high and intermediate gear. 

Fig. 28. Cross-Section of the Chalmers Motor 

The main drive gear, which is connected with the clutch shaft, is 
continually in mesh with the countershaft drive gear. There are 
two other gears on the countershaft, one the intermediate-speed 
gear and the other the low-speed gear. When the low and reverse 
sliding gear is meshed with the countershaft low-speed gear, a low 
car speed is produced or, in other words, the engine runs faster 
than the main transmission shaft. To obtain second speed, the 

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low-speed gear is placed in neutral position and the high and 
intermediate slide gear is meshed with 'the intermediate-speed gear 
on the countershaft. The motor is still running faster than the 
main shaft, but the main shaft has increased to a greater speed 
than when in low gear. To secure high speed, the high and inter- 
mediate gear on the main shaft is moved forward, interlocking 
with the main drive gear. The main shaft of the transmission is 
then operating at the same speed as the clutch shaft. 

Differential Unit. The differential and the ring gear are 
shown in Fig. 25. The main drive shaft, Fig. 27, is connected to 
the ring gear by means of a drive shaft and spiral bevel gear. This 
gear, which is turned by the motor, continually meshes with the 
ring gear and turns the rear axles, thus causing the car to move. 

Braking System. The emergency and foot brake arrange- 
ment of the Chalmers car is of the average construction. The 
emergency brake shoe is located on the inside of the drum, exert- 
ing its pressure outward, while the foot, or service, brake operates 
on the outside of the drum. As the service brake lever is pulled 
forward, the brake band will contract, which causes considerable 
resistance to the turning of the rear wheels. 

In Fig. 26 is given a sectional view of the rear axle, which is 
of the semi-floating type. The axle is held in place with a Timken 
roller bearing. The wheel hub is mounted on the end of this axle 
shaft and is tapered. A long axle shaft key is inserted to prevent 
the wheel from turning. The entire load of the car is supported 
by the axle at the Timken bearing in this type of axle and the 
axle is also called upon to turn the wheels, thus performing a 
double duty. 

The side elevation of the chassis, Fig. 29, shows the relative 
position of the units when assembled. 

Crank and Firing Arrangements. The order in which the 
explosions should take place 4n the cylinders and the best arrange- 
ments of cranks for multi-cylinder four-cycle motors are shown 
in diagram in Fig. 35. 

Two-Cylinder Motor. With the cranks set at 180 degrees, 
Fig. 35A, the two cylinders fire one-half revolution apart, and 
hence during one revolution there are two power strokes and at 
the next no power stroke. 


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C/tAIMJ 4T3G0 

120° FIRED t-3-2 

~~2~ ~~3 



FIRED i'342 

FIRED 1-5-3-6-2-4 




V CfiAUKS A* /60 i 


E/REO - /f?-4L -JJ?~2 > L.-+P'/L-tt-JL 

|V 35. Crank and Firing Arrangements for Multlcylinder Four-Cyole Motois* 


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With the cranks set at 360°, Fig. 355, we get a power stroke 
at each revolution. This arrangement, however, requires careful 
balancing to counteract the vibration which results from all parts 
moving in the same direction at the same time. The order of action 
in the two cases is given as follows: 

180 3 360° 

First Cylinder 

Second Cylinder 

First Cylinder 

Second Cylinder 

















If the amateur finds the above difficult to follow, it may be 
simplified as follows: Duplicate the actions below those given, that 
is, repeat the action in two revolutions. Then mark off at the left 
the revolutions, indicating the first pair of actions for one, the second 
for two, etc. This applies right across the table. Then, one notes 
that the firing in the first cylinder comes on the second revolution 
and the first stroke, while that in the second cylinder comes on the 
same revolution but the second stroke. This gives two firing 
impulses on one revolution, followed by another with none, then two 
more firing, etc. In the cylinders set at 360°, it will be noted that 
the second cylinder fires on the first stroke of the first revolution, 
while the first follows, firing on the first stroke of the second revo- 
lution, then the second on the first of the third, and the first on the 
first stroke of the fourth, etc., thus distributing the firing evenly. 

Four-Cylinder Motor. In the four-cylinder motor of the four- 
cycle type, we have two power strokes for each revolution of the 
crank shaft or flywheel. In order to secure smooth working, these 
power strokes should occur exactly one-half revolution apart. From 
Fig. 35Z) it will be seen that the four-cylinder crank shaft has two 
pairs of cranks just one-half revolution apart, pistons 1 and 4 moving 
up, while pistons 2 and 8 move down, or vice versa. 

Suppose for instance, that piston 1 has just been forced down 
on the power stroke. Then pistons 2 and S will be up and one of 
these should be ready to receive the force of the explosion, and 
should have, therefore, just compressed an explosive charge in its 
cylinder ready to be ignited. For the sake of illustration let us choose 
piston S to make the next power stroke. Piston 3 now moves down 



and pistons 1 and 4 move up. Since it is evidently impossible to 
have piston 1 contain an explosive charge without giving it one more 
up and down motion, piston 4 must make the next power stroke. 
This piston, therefore, moves down as a result of the explosion in 
cylinder 4> and it is now necessary for piston g to make the next 
power stroke. Thus the order of firing is 1-3-4-2. 

A study of Figs. 35C, 35F, and 35E will show the method of 
firing in the cases of the three-cylinder, the two-cylinder horizontal- 
opposed motors .; and the six-cylinder, respectively. In Figs. 350 and 
35 H will be found the corresponding methods for the two-cylinder 
and eight-cylinder V types. The last named is more difficult to 
follow out, but by treating it as a pair of fours which must fire first 
in one pair and then in the other, and considering this in conjunction 
with 35Z), the scheme of arrangement will be plain. The actual 
order used on De Dion (French) and Cadillac motors is 1R, 4L, 3R, 
2L, 4R, 1L, 2R, 3L. 

Just as the firing order of the eight, or twin four, is followed 
through by considering it as a pair of fours, so the twelve or twin 
six may be considered as a pair of sixes. There is this important 
difference between the eight and the twelve, however; in the eight 
the two sets of cylinders are set at an angle of 90 degrees with 
each other, while in the twelve, the two "six groups" are usually set 
at 60 degrees. This makes a different interval in the firing; the 
firing order of any twelve might be 1R, 6L, 5R, 2L, 3R, 4L, 6R, 
1L, 2R, 5L, 4R, 3L. 

Theory of Crank Effort. One-Cylinder Motor. In a single- 
cylinder motor, four strokes of the piston are required to complete 
its cycle, i. e., the suction stroke, compression stroke, power stroke, 
and exhaust stroke. Note that only one of these strokes, the third, 
makes power. Roughly speaking, power is not produced throughout 
even the entire part of this stroke, but only through about four- 
fifths of it. Hence, in a single-cylinder motor with a 5-inch stroke, 
the piston travel for one complets cycle will be 20 inches. In only 
about 4 inches of this distance is power produced. (See Figs. 36 
and 37.) Hence four-fifths of the total piston travel is a non-pro- 
ducer of power. 

Two-Cylinder Motor. In the two-cylinder motor we have two 
power strokes in two revolutions, as follows: 



First Stroke 

Inches of Power 

Cylinder 1 Suction 

Cylinder 2 Power 


Second Stroke 

Cylinder 1 Compression 

Cylinder 2 Exhaust 

Third Stroke 

Cylinder 1 Power 


Cylinder 2 Suction 

Fourth Stroke 

Cylinder 1 Exhaust 

Cylinder 2 Compression 

Total inches of piston travel representing power. 


Total inches of piston travel 


Hence, the motor furnishes power during only 40 per cent of the cycle. 

Four-Cylinder Motor. With the four-cylinder motor we have 
one power stroke during each half revolution of the crank shaft. 




/R£V /REV /jsREV 



Fig. 36. Curves Showing Duration of Power in Four-, Six-, and Eight-Cylinder Motors 

This gives us power during 16 inches of piston travel or power during 
88 per cent of the entire cyle. 

Six-Cylinder Motor. In the six-cylinder motor (the cylinders 
being the same size as those above considered, and the stroke the 


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same) we have 4 inches of power produced by each cylinder, making 
a total of 24 inches of power with a total piston travel of 20 inches. 
On the basis of the percentage values given in the two- and four- 






Fig. 37. Power Distribution Chart in Various Motors 

cylinder types this would mean an application of power during 120 
per cent of the cycle. As this is impossible and as the six cylinders 
are evenly spaced, the power in the cylinders must overlap each 
other. This results in continuous power. Diagrams showing the 
relation between the application of power in the four-cylinder motor, 
in the six-cylinder, and in the eight-cylinder, are shown in Fig. 36. 

Fig. 38. Diagram of the "Dead Center" Problem 

Eight-Cylinder Motor. In the eight-cylinder motor— the cyl- 
inders being of the same size as those considered previously, and the 
stroke the same — we have 4 inches of power produced by each 
cylinder, making a total of 32 inches of power with a total piston 
travel of 20 inches. On the basis of the percentage values given 


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for the other types, this would mean the application of power over 
more time in the cycle than is possible, so, as in the case of the six- 
cylinder motor, there is an overlap. In this instance, however, 
the overlap is three times as great as in the six-cylinder, consequently 
the delivery of power is that much more even and continuous. 

Twelve-Cylinder Motor. In the twelve-cylinder motor, with 
the same size cylinders as before, we have the same 4 inches of 
power in each cylinder, or 48 inches total, with a total piston travel 
of 20 inches, showing again a large amount of overlap. Here the 
overlap is seven times as great as in the six-cylinder form, conse- 
quently the output of power should be that much more even. 

The diagram of Fig. 37 gives a clear idea of this distribution 
of power in the various motors discussed. The six-cylinder motor 
has a small overlap, while the eight-cylinder has a wide overlap. 
The twelve-cylinder motor has a power overlap of two cylinders 
continuously, while the power impulses from three cylinders over- 
lap part of the time, thus giving greater flexibility. 

Effect of Dead. Centers. In both the two- and four-cylinder 
motors, the cranks being set 180 degrees apart, each piston is always 
one complete stroke ahead of the succeeding one. When the cranks 
of the motor are as shown in Fig. 38 (a) in direct line with the con- 
necting rod, the entire motor is on dead center. Fig. 38 (b) shows 
the same condition with offset cylinders. 

In the six-cylinder motor, the cranks are set at 120 degrees, 
Fig. 38 (c), and, therefore, we have no condition when the entire 
motor is on dead center. It is impossible to have more than two of 
the cranks on dead center at once. Hence, there is never a time in 
the six-cylinder cycle when the motor does not produce power. 

In the eight-cylinder V-type motor, Fig. 39, the cranks are set 
180 degrees apart, as in the four-cylinder, but the cylinders are set 
at 90 degrees, 45 each side of a vertical, as shown in Fig. 38 (d). 
The connection of the side by side cylinders of each pair of fours to a 
common crank pin — the two number one cylinders, for instance, 
working on the first pin, the number twos on the second, etc. — 
eliminates all dead centers. This is one advantage of the V-type 
over the straight-line type for the latter has a dead-center cylinder. 

In the twelve-cylinder V-type motor (Fig. 40), the cranks are set 
at 120 degrees as in the six, but the cylinders are set at 60 degrees, 30 


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on each side of the vertical, the only difference from Fig. 38 (d) being 
in the angle. The crank-pin attachment in the twelve is similar to 
the eight, the first two cylinders working on the first crank pin, 
the second two on the second pin, and so on. Obviously the form 
of the crank and the setting of the cylinders at an angle eliminate 
all dead centers. 

Sixteen or More Cylinders. The constant demand for more 
and more power, especially for airplanes, dirigible balloons, and 
fast motor boats as well as motor ships, has produced many 
engines with more than twelve cylinders. There is a limit to the 
power which can be produced from a single cylinder, so that 
more power has meant more cylinders. 

The problem of securing a greater number of cylinders has 
been worked out in a number of ways; for example, large marine 
engines have been built which are practically two or three sets 
of four-cylinder engines set in line and with a single connected 
crankshaft for all eight or twelve cylinders. Other engines are 
of the sixteen-cylinder V type, that is, they are simply two eight- 
cylinder engines set at an angle and working on a single common 
eight-cylinder crankshaft. A more recent development consists of 
three sets of six-cylinder engines built in a fan shape with a 
common crankshaft, making an eighteen-cylinder motor. 

The radial forms also have been used to produce high power, 
another unit and another crank being added. Thus, two five- 
cylinder engines together make a ten-cylinder, two seven-cylinders 
a fourteen-cylinder, two nines an eighteen-cylinder, two tens a 
twenty-cylinder, etc. The future cannot be predicted, but con- 
struction in the United States inclines toward the V forms and 
• in England and France toward the air-cooled radial forms. 

The firing order of a sixteen-cylinder engine follows that of 
an eight and a twelve, of a V type, that is, alternating from one 
side to the other and back and forth on the two sides according 
to the layout of the crankshaft. Similarly, eight or twelve cyl- 
inders in line depend upon the crankshaft layout for their firing 
order. The radial and rotating forms fire in alternations; thus, a 
five-cylinder engine would fire 1-3-6-2-4, then begin over with 1, etc. 

In the sixteen-cylinder V-type motor, with the same size 
cylinders as before, there are 64 inches of power with a total 


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piston travel of 20 inches, so that the overlap is so great as to 
give practically the smooth continuous operation of steam. By 
comparison, then, the respective cylinder forms show these rela- 
tive overlaps, the piston travel of 20 inches being the same for 
all: six-cylinder, 24 inches; eight-cylinder, 32 inches; twelve- 
cylinder, 48 inches; and sixteen-cylinder, 64 inches. With the 

Fig. 39. Front View of Eight-Cylinder V-Type Motor 

Courtesy of Cadillac Motor Car Company, Detroit, Michigan 

sixteen, as with the twelve, the dead-center consideration is 
entirely eliminated. 

Power Exerted against the Pistons. In a single-cylinder, 48- 
horse-power motor the explosion of the mixture practically results 
in the striking of a hammer blow against the piston of 28,800 
pounds. In a four-cylinder, 48-horse-power motor each piston 


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receives a blow only one-fourth as great, or 7,200 pounds. In a 
six-cylinder, 48-horse-power motor each piston receives only 4,800 
pounds. Similarly, in an eight-cylinder 48-horse-power motor each 
piston receives a blow of 3,600 pounds. Compared with the four- 
cylinder motor, this is a reduction of one-half; relative to the six- 
cylinder, it is a reduction of one-fourth. 

So too, with the twelve-cylinder, 48-horse-power motor each 
piston receives a blow of only 2,400 pounds, one-half the blow 
exerted in the six-cylinder motor and two-thirds the blow exerted 
in the eight. It is this small amount of hammering which makes 
the multiple cylinder motor — in either eight- or twelve-cylinder 

Fig. 40. View of Packard Twelve-Cylinder V-Type Motor Mounted in Chassis 

form — much more quiet and easy running than can 6ver be the 
case with the four- or six-cylinder forms. In addition, the small 
size of the pistons for equal power development allows a much 
stiffer and stronger construction, even when a lighter metal, like 
aluminum or any of the various aluminum alloys, is used. The lighter 
reciprocating parts increase the output per cubic inch of cylinder, 
thus making the multiple type of motor relatively more efficient. 
Repair Man's Interest in Multiple Cylinders. Every repair 
man should be well posted on eights and twelves for two reasons. 
In the first place, the average owner knows little about them, and 
as he considers that the repair man knows all about every kind of 

45 Digitized by GO-Ogle 


motor, he will go to him for information at the first sign of trouble. 
In the second place, the repair man should be able to handle and 
repair these forms of motor, for the fact that they have more parts 
and are more complicated makes them more likely to need skilled 
attention. Moreover the average owner, knowing of this greater 
complexity of construction, will be averse to turning his eight or 
twelve over to any but the best repair men — skilled mechanics with 
a thorough working knowledge 
of the principles of the new 
motors. Any intelligent re- 
pair man with a thorough 
knowledge of the principles 
around which these new motor 
forms are built, and with an 
equally thorough and intimate 
knowledge of how fours and 
sixes are constructed, ad- 
justed, and repaired, need have 
no fear to tackle any kind of 
engine new or old. 


The general practice with 
small stationary engines differs 
quite radically from the stand- 
ard motor practice just con- 
sidered. [However, as the fields 

of the tWO Overlap, the disCUS- Fig * 41 * Stationary Engine with Single Valve 

sion of the small stationary type at this point will not come amiss. 
Two-Cycle Type. A modification of the type of explosion 
motor shown in Figs. 8 and 9, which makes its construction 
even more simple, is the use of a single valve— an automatic 
valve which admits the charge to the crank case. In this 
engine, Fig. 41, the series of operations is precisely similar to 
that described for Fig. 8, the only difference being in the 
by-pass connection E, which has no valve between it and the 
cylinder. The exhaust is made to open a little earlier than the 
admission, so as to make sure that the pressure in the cylinder 


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shall have fallen below the pressure of the slightly compressed charge 
when the admission port opens. If the opening of the exhaust and 
admission ports were simultaneous, as in the engine just described, 
some of the exhaust gases would force their way through E to the 
crank case, and, being at a high temperature, would ignite the charge 
there. The piston is so shaped that the entering charge is directed 
to the top of the cylinder, forcing out the burned gases before any 
of the charge can escape through the exhaust port. 

In place of the automatic inlet valve at B, there is sometimes 
used a revolving disk valve turning with the crank and containing 
a slot which registers with the crank case inlet during part or all of 
the up-stroke of the piston. The disk is pressed against its seat by 

Fig. 42. Smalley Three-Port Two-Cycle Motor 

a light spring. This arrangement controls the admission of the 
charge to the crank case, permitting of adjustment of the duration 
of admission, and consequently of the volume admitted. It sac- 
rifices, however, the reversibility of the engine. 

A further and last modification of this engine makes it entirely 
valveless and of the utmost simplicity. This feature is illustrated 
in Fig. 42. The admission of the charge is through the port B, which 
is covered and uncovered by the piston, and which consequently does 
not require any automatic valve. During the up-stroke of the pis- 


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ton, a vacuum is created in the closed crank case, till near the top 
of its stroke, when the admission port B is uncovered, and the 
explosive charge rushes into the crank case, filling it until the pressure 
there is approximately atmospheric pressure. The rest of the opera- 
tions are exactly as in the engine just described, the charge being 
compressed in the crank casing during the down-stroke, and then 

Fig. 43. Vertical Four-Cycle Stationary Engine 
Courtesy of Fairbanks, Morse and Company 

transferred through a port D, in the hollow piston, and through the 
port E in the cylinder wall, to the upper side of the piston when this 
latter is near the end of its down-stroke. This modification is gen- 
erally known as the three-port type of the two-cycle motor. 

Four-Cycle Type. Figs. 43 and 44 illustrate the details of a 
standard vertical four-cycle type of engine. This engine may be 


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equipped with a carbureter as in automobile practice, but is more 
often provided with a pump, Fig. 45, which introduces the fuel 
directly into the cylinder in the form of fine spray. 

Ignition. In this type instead of producing ignition by means 
of a spark plug, the spark is usually obtained by making contact 



Fig. 44. Vertical Four-Cycle Stationary Engine 
Courtesy of Fairbanks, Morse and Company 

and breaking contact between the electrodes or contact points of 
what is called a "make-and-break" igniter, shown in Figs. 43 and 46. 
The igniter plug in Fig. 46 has been removed from the cylinder 
head. The movable electrode B is at the end of an arm which is 
fastened to the spindle C. When the interrupter lever D, which is 
loose on the spindle C, and is connected to it through a coiled spring, 
is lifted by an arm from the cam shaft of the engine, it rotates the 


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spindle C so as to bring B into hard contact with the stationary and 
thoroughly insulated electrode A. This completes a circuit and 
permits a current to flow from A to B. When ignition is desired the 

Fig. 45. Pump for Liquid Fuels 

Courtesy of Fairbanks, Morse 

and Company 

Fig. 47. Spark Coil 

Courtesy of Thordarson Electrical 

Manufacturing Company 

Fig. 48. Wiring Diagram for Igniter System 

lever D is tripped and flies back, carrying with it the shaft C, abruptly 
breaking the contact and causing an electric arc to form between 
A and B. The spark from an ordinary battery is greatly increased 


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by allowing the current to flow through a make-and-break ignition 
coil, Fig. 47, which consists of a coil of insulated copper wire in which 
a laminated magnetic circuit is used in connection with an air gap. 
The igniter circuit is arranged as in Fig. 48. 

Governing. Stationary engines are governed by either the 
"hit-and-miss" governor or the throttling governor, the latter being 
the form used in practically all motors. The action of the throttling 
governor is such that more or less fuel is admitted at each charge, 
according to the load, the richness of the mixture remaining the 
same and the engine making regular explosions. With the hit-and- 
miss governor, a greater or less number of fuel charges are admitted 
to the cylinder according to the load on the engine, the mixture and 
the quantity of each charge always remaining the same. The result 
of this is that the number of explosions per minute will vary with 
the load. 


In explosion motors the explosive mixture in the cylinder 
consists of air mixed with a smaller volume of the vapor of the 
liquid fuel. This mixture will behave up to the time when explosion 
takes place, practically as if it were merely air. Also the products 
of combustion, after the explosion is completed, have physical 
properties differing only slightly from those of air, and consequently 
the working substance in the cylinder may without serious error be 
regarded as consisting entirely of air. In the discussion of what 
occurs in the engine cylinder, this assumption is made. 

Indicators.* In order to more clearly understand what follows, 
it is necessary to have some knowledge of the indicator diagram. 
These are made by two forms of engine indicator, the modified 
steam engine form which is satisfactory up to about 500 r. p. m. 
and the manograph used above that speed. The former is. described 
as consisting of a drum carrying a sheet of paper which, by rotation, 
is moved an amount proportional to the piston travel. An arm 
whese motion is governed by the pressure in the cylinder carries a 
pencil which traces on the paper a diagram whose vertical values 
are proportional at every point to the pressures in the cylinder. 

♦See also page 62. 


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Watt' 8 Diagram of Work. James Watt was the first to see the 
need of accurate knowledge of the action of steam in the cylinder 
of a steam engine and to him 
belongs the credit of devising 
and using the first indicator. 
Fig. 49 illustrates the method 
adopted by Watt. The hori- 
zontal line AC, called the 
abscissa, represents the length 
of stroke and is divided into 
ten equal parts. The vertical 
line AB, called the ordinate, 
indicates the pressure of the 

Fig. 49. Watt Ideal Diagram 

Fig. 50. Crosby Indicator in Part Section 

When the piston has moved from B to E, the steam is cut off, 
that is. a volume of stearn equal to one-fifth the volume of the cylinder 

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Pig. 51. Crosby Indicator Complete 

Fig. 52. Crosby Indicator witlf External Springs 

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is allowed to expand until it fills the entire cylinder. The area of 
the figure BEDCA may be found by adding the several pressures 
shown by the vertical dotted lines, dividing by the number of divi- 
sions, and multiplying by the length AC. The study of similar 
diagrams on a small scale when drawn by an indicator represents 
the only method of obtaining a correct idea of the action of steam 
in the cylinder of a steam engine or of the mixture in the cylinder 
of an explosion motor. 

Figs. 50 and 51 show an inside and an outside view of the Crosby 
indicator. In gas engine work, the spring located as shown in Fig. 
49 is liable to be injured by heat. To lessen the difficulties due to 
this, most of the makers supply indicators with external springs, as 
shown in Fig. 52. 

Manograph. As has been stated previously, the steam engine 
form of indicator* is satisfactory up to speeds of 500 r.p.m., but as 
the majority of gas and gasoline engine work is above that — particu- 
larly automobile and aeroplane motors in which the speed may 
reach a maximum of 4,000 r.p.m., while 1,000 r.p.m. would be 
considered a slow speed and 1,800 an average — some other form is 
necessary. The reason for this lies in the fact that at speeds above 
500 r.p.m., the inertia of the indicator piston, pencil arm, and 
other moving parts is so great that the diagrams become distorted 
and do not show a true shape compared with the events within the 
cylinder. Another difficulty lies in making the passages between 
the cylinder and the indicator large enough so that the pressure 
fluctuations in the motor cylinder will be followed exactly by those 
in the indicator cylinder and, consequently, be reproduced exactly 
in the diagram. 

These difficulties have led to the use of a device called the 
manograph. In this a beam of light travels over a visible ground 
glass of a darkened surface so as to be visible to the observer all of 
the time; or by replacing this with a sensitized piece of paper, pre- 
pared for the purpose, a print is made which must be developed and 
fixed the same as any photographic print. When the engine is 
being tested out for faults in the design and construction, the latter 
method is followed and the cards are preserved for future study and 
as a matter of permanent record. However, when the design and 
construction are satisfactory and the engine is simply being tuned 


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up to its best performance, the former method is followed and no 
permanent records are kept. 

It can be seen at once that this is a tremendous advantage for 
the indicator diagram of the engine under test is visible at all times 
to the tester, who can increase or decrease engine speed and note at 
once the changes in the diagram, right in front of him; can alter 
carbureter or magneto settings and see at once the changes which 
these make in the diagram. To facilitate the use of this, it is made 
with as many compartments as the motor has cylinders, although 
all the illustrations which are shown indicate a single-cylinder outfit, 
which has, of course, only one compartment. 

This result is obtained by the use of a small aperture through 
which a beam of light is admitted to the interior of the box. At 
one end of the latter, there is a small concave mirror, upon which 
the beam of light impinges. This mirror is connected to the crank 
shaft or other moving part of the engine in such a way that the rota- 
tion of the motor imparts to the mirror a horizontal rocking move- 
ment limited to a small angle of, say 20 degrees. This movement 
is, of course, at a speed which corresponds with the speed of the 

In addition, the mirror has a connection with the cylinders of 
the motor by means of which the pressures there are imparted to 
the mirror in a vertical direction, rocking it in that direction. The 
first motion — that of rotation — would make nothing but a straight 
horizontal line of a length proportional to the motor's stroke and at 
a rate proportional to its speed. But by adding the motion pro- 
duced by the internal pressures, there is created a diagram or closed 
figure which represents accurately the events taking place within 
the cylinder. 

Description of Manogragh. A general exterior view of a mano- 
graph, the Carpentier (French), is shown in Fig. 53, with horizontal 
and vertical sections at Figs. 54 and 55, and a detail of the mechanism 
which moves the mirror at Fig. 56. In Fig. 53, it will be noted 
that it consists primarily of a light-tight box B, which is generally 
mounted on a tripod for convenience. To one end of this is fixed 
a casting A, inside of which the mirror is secured, together with 
the mechanism for causing its movements. A ground-glass screen 
C is shown partially withdrawn from its position On the front of the 




box, but, as has been explained, when a permanent record is desired, 
an ordinary photographic plate holder is substituted for this. A 
lamp D with an acetylene burner communicates with the interior 
by means of the tube E and furnishes the beam of light. 

Kg. 53, General View of the Carpentier Manograph Mounted on Tripod 
Ready for Use 

The horizontal movement of the mirror is brought about by a 
crank and reducing arrangement, actuated by the flexible shaft e. 
This is driven directly by the motor crank shaft, a special taper 

Fig. 54. Horizontal Section of Carpentier Manograph 

socket being applied so that the flexible shaft may be connected or 
disconnected at will. In order that the motion of the beam of light 
and that of the piston shall correspond, an adjusting means is pro- 
vided in the chamber at the right by means of the screw F. 


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The vertical movement which corresponds to the pressures 
in the cylinder is transmitted by means of the pipe G, which corn- 

Fig. 55. Vertical Section of Carpentier Manograph, Showing Interior 

municates with a diaphragm within the nut H. A pin bears against 
the center of the diaphragm and also against the back of the mirror. 
This may be seen in the vertical section, Fig. 55, in which this pin 
is marked J, and the mirror inside the box is marked J. 

Fig. 56. Detailed Section of the Diaphragm of the Hospitalier Manograph, 
Which Is Similar to the Carpentier 

In the horizontal section, Fig. 54, the interior arrangements 
are shown quite clearly, the lettering being the same as in Figs. 


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53 and 55. Note how the beam of light from the lamp D passes 
through the tube E, is deflected by the prism against the mirror J, 
and then thrown on the screen or plate C. Referring to the detail 
view, Fig. 56, A, F, G, H, I, and J are the same as before. Gears 
n and m have an equal number of teeth, n being driven by the flexible 
shaft e. It will be noted that m carries a pin to which is attached 
a small connecting rod I. This is attached to the lever k, which is 
pivoted on the small screw o shown about midway of its length. 
The far end of this lever presses against the pin j, which in turn rests 
against the triangular plate t, to which the mirror J is held by the 
spring s. 

Fig. 57. A Four-Cylinder Manograph as It Is Rigged up Ready for Use, Indicating 
How the Four Cards Are Viable at One Time 

From this it is apparent that the engine turns the gear n, which 
rotates the gear ra. This carries the pin around and thus recip- 
rocates the connection I and with it one end of the lever k. The 
movement of the other end of k moves the pin j, which moves the 
mirror J. The resistance of the spring s forces pin j against the end 
of lever k even when it is moving away from the pin. From the 
foregoing, it can be seen that the manograph is well adapted to 
taking diagrams from high-speed motors, for there is no limit to the 
speed of movement of the beam of light, while the error caused by 
the inertia of the few moving parts is so small as to be practically 
negligible. ' 

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A view of the complete manograph, rigged up for four cylinders 
and with the engine running, indicating the four diagrams simul- 
taneously, is seen in Fig. 57. This gives a better idea of the device, 
its method of use, and very evident utility than anything which 
has been said on the subject. Note that the arrangement of the 
mirrors inside is such that the curves of each pair face each other, 
instead of all facing in one direction. This explains, also, the fact 

Fig. 57a. The Pressure Element 

that some of the manograph curves, Figs. 66 to 70, face in different 
directions. The reader is referred forward to these diagrams, as 
showing just what is performed by the instrument described. 

To return to the slower speed or steam engine form of indicator, 
this makes a neat diagram and one which represents, within its 
speed limits, the Otto cycle taking place within the cylinders. 

Midgley Indicator. This instrument is not only designed to 
give accurate data relative to m.e.p. (mean effective pressure), but 


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it also enables the engineer to make an accurate study of fuel 
behavior in the internal-combustion motor. The Midgley can be 
used to indicate either pressure-volume or pressure-time rela- 
tions; the manograph is limited to the study of pressure- volume 

This type of indicator produces optical cards which are visible 
at all times; a permanent record can be made merely by holding 

sensitized paper over the 
glass, no plates or films 
being needed. This instru- 
ment is composed of two 
units, one connected to the 
crank shaft and the other 
to the combustion chamber 
of the cylinder to be tested. 
These units are electrically 
connected when pressure- 
time cards are taken and 
mechanically connected 
when pressure- volume cards 
are taken. 

The pressure element, 
Fig. 57a, is connected to 
the combustion chamber. 
This element consists of a 
small cylinder containing a 
piston at its lower extrem- 
ity. A small rod connects 

Fig. 57b. Midgley Optical System ^ piston ^ ft p ; vote( J arm 

at the top, a mirror being mounted on this arm. Pressure in 
the cylinder operates against the piston and causes a spring to 
be compressed. This vertical movement of the rod develops a 
variable angle between the mirror and its base, the angle being 
in proportion to the pressure exerted on the piston. 

Optical System. The function of the optical system, Fig. 57b, 
is to provide means for indicating either the pressure-volume or 
the pressure-time relations within the cylinder by making use of 
a beam of light. This system consists of a light bulb (used as a 


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Fig. 57c. Section of the Optical System 

Fig. 57d. The Photographic System 


source of light), a box called the motor box, a concave mirror 
operated by the pressure element, and a mirror in the form of an 
eight-sided prism. When the system is in operation, the beam of 
light issues from a small opening in the metal case surrounding 
the light bulb. This beam of light passes through the motor box 
onto the concave mirror of the pressure element. It is then 
focused and reflected onto the eight-sided mirror on the inside of 

Fig. 57e. The Pressure-Time Synchronizer 

the box. This mirror may be either rotated or oscillated according 
to whether a pressure-time or a pressure-volume card is desired. 
The ray of light, after it is reflected by the eight-sided, mirror, is 
projected forward upon a curved glass which forms the front of 
the motor box. This beam is moved both vertically and hor- 
izontally by the joint action of the two mirrors, thus tracing out 
an image on the curved glass. A section of the optical system 
is shown in Fig. 57c. 


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Photographic System. This system, Fig. 57d, is so con- 
structed that a light is produced bright enough to develop a sharp 
black line on the photographic bromide paper during one complete 
cycle of operation only. To produce this bright light a 10-volt 
battery is used in connection with the original 6- volt battery. A 
device is connected to the crank shaft so that 16 volts can be 
applied to the bulb for one complete cycle of operation only. The 

Fig. 57f. Section of the Pressure-Time Synchronizer 

parts are so arranged that one operator can take a photograph 
with but little inconvenience. 

Pressure-Time Synchronizer. The function of the pressure- 
time synchronizer, Fig. 57e, is to rotate the eight-sided mirror 
at a speed that will always bear an exact ratio to the speed of 
the engine. This instrument consists of a mechanism attached 
to the engine shaft and a synchronizer and rotating mirror located 
in the motor box. A sectional view is shown in Fig. 57f. The 


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synchronizing is accomplished electrically through a distributor 
operated by the shaft of the crank shaft attachment. This 
synchronizer is geared to the revolving mirror so that the mirror 
revolves at exactly § engine speed, and as the arc of the ground 
glass is 90 degrees, a beam of light reflected from the revolving 
mirror will move across the ground glass once for each revolution 

of the engine. As the 
beam of light reaches 
the limit of the screen, 
the next face of the 
rotating mirror en- 
gages the light and 
simultaneously reflects 
it to the other end 
of the ground glass. 
In this way the pres- 
sure-time relations 
within the cylinder 
for two revolutions, or 
one cycle of operation, 
are made completely 
visible on the ground 
glass as a pressure- 
time card. 

Pressure - Volume 
Synchronizer. The 
function of the pres- 

Fig. 57g. Pressure-Volume Synchronizer . , 

sure-volume synchro- 
nizer, Fig. 57g, is to oscillate the eight-sided mirror within the 
motor box in synchronism with the reciprocating motion of 
the engine piston. Included in the crank shaft attachment is a 
motor driven by a crank attached to the distributor head and 
having a reciprocating motion in a vertical direction. A fine 
wire connects this member with the eight-sided mirror, trans- 
mitting an oscillating instead of a rotating motion to the eight- 
sided mirror, one face only being used. In making a photo- 
graph, the optical system is used as previously explained, the 
mirror oscillating in synchronism with the engine piston instead 


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Fig. 57h. A Pressure- Volume and a Pressure-Time Card Taken by a Midgley Indicator 

Fig. 57i. Two Cards Indicating Fuel Knock Taken by a Midgley Indicator 

of rotating. The card produced indicates the pressure-volume 
relations within the cylinder. The relation between the moving 
parts is such that the pressure-volume card is one-half as long 
as the pressure-time card. 


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In Fig. 57h are shown a pressure-volume and a pressure- 
time card taken by a Midgley indicator. When these cards were 
taken, the engine was operating normally. 

Two cards which show that a fuel knock is present are repro- 
duced in Fig. 57i. 

The pressure-time card shows that there are several explo- 
sions occurring after the first one. Note that the fuel knock 
occurs after the ignition point and is due to a very abrupt rise 
in pressure. A detailed description of fuel knock is ^iven under 
the heading "Fuel Mixture. ,, 


Indicator Cards 

Analysis of Ideal Diagram. Watt's work diagram may be profit- 
ably applied to the analysis of the ideal Otto cycle by means of the 
indicator diagram, Fig. 58. Vertical distances along the line A B rep- 
resent pressures in pounds per 
square inch absolute,* while 
horizontal distances measured 
along AC represent piston 
travels or, as the cross section 
of the cylinder is constant, 
these distances may also rep- 
resent cylinder volumes in 
cubic inches. Thus point 4 
represents a pressure of 350 
pounds per square inch in the explosion chamber of the cylinder 
when the volume in cubic inches of this chamber is F c . 

As the line 1-2 represents the entire piston travel, any point d 
on AC represents a certain cylinder volume or marks the position 
of the piston at that point in the stroke. 

Stroke One. At the beginning of the cycle the piston is at the 
end of its path, point 1, and is about to begin its out stroke, Fig. 59(a). 
The clearance space V c is full of products of combustion. The 

Fig. 58. Ideal Indicator Card of Otto Cycle. 

♦Absolute pressures are always referred to zero pressure, i. e., a perfect vacuum, as a start- 
ing point. Atmospheric pressure, therefore, is 14.7 pounds absolute. Gage pressures, on the 
other hand, start at atmospheric pressure, so that 80 pounds absolute would be 65.3 pounds gage 


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Fig. 59. Diagrams of Various Steps in an Explosion-Motor Cycle 

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pressure is atmospheric pressure (about 14.7 pounds per square inch) 
because the cylinder has been in communication with the atmosphere 
through the exhaust valve which has just closed. The conditions 
existing in the cylinder at this instant are represented in the diagram, 
Fig. 58, by the point 1, which is at a horizontal distance from the 
vertical axis, representing the clearance volume V c , also Fig. 59 (a) 
and at a vertical distance above the horizontal axis representing the 
atmospheric pressure. As the piston makes its outward stroke, the 
admission valve opens, admitting the charge to the cylinder through- 
out the stroke at atmospheric pressure. On the diagram the admission 
of the charge is represented by the line 1-2, its length representing 
the volume of the charge taken in, or the distance through which the 
piston moves. The point 2 represents the condition at the end of 
the first stroke, the volume being V u Fig. 59 (b). 

Stroke Two. The admission valve now closes and the piston 
makes its return stroke and, since all the valves are closed, the charge 
can not escape and is crowded into a smaller and smaller volume at 
increasing pressure until the piston reaches the end of its stroke, at 
which time the whole charge is compressed into the clearance space. 
This process is represented by the line 2-3, which shows the rise in 
pressure resulting from the compression. At point 3 the volume is 
again V c , Fig. 59 (c). A compression of this kind causes an 
increase not only in the pressure but also in the temperature of the 
gas, a fact often noted in the working of an ordinary bicycle pump. 
If it is assumed that during this compression the gas retains all of 
the heat formed and receives none from the outside, it is called an 
adiabatic compression. The relation between the pressure of air and 
its volume when subject to adiabatic compression is: 

p F i.405 =Constant 

In this equation P means the absolute, not the gauge pressure. 

When the charge has reached the conditions represented by the 
point 3, it is ignited and the heat generated by the explosion raises 
the temperature and consequently the pressure of the mixture. As 
the volume during the explosion will not have time to change, the 
gas will follow the general gas law, viz, that at constant volume 
the pressure P is proportional to the absolute temperature T, where 
absolute temperature is found by adding 461 to the temperature in 

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degrees Fahrenheit. The rise of pressure during the explosion is 
shown on the diagram by the line 8-4, the volume of the gas being 
constant at V c , Pig. 59 (d). 

Stroke Three. The hot products of combustion at point 4 are at a 
high pressure, consequently they now force the piston out and, expanding 
behind it, fall in pressure. This expansion is assumed to occur without 
communication of heat to or from the gas and is, therefore, an adiabatic 
expansion. It is consequently accompanied by a fall in the temperature 
of the gas, the expansion curve being shown in Fig. 58 as 4-5. This curve 
is similar to the compression curve 2-3 and has a similar equation. 

Stroke Four. At the point 5 the piston is at the end of its stroke 
and no more expansion is possible, the volume being again V t9 
Fig. 59 (e). The exhaust valve now opens and the pressure in the 
cylinder falls immediately to atmospheric pressure, as shown by the 
line 5-2 in the diagram, the volume remaining Vt, Fig. 59 (f). 
Throughout the last return stroke 2-1, the exhaust valve remains 
open, so that the pressure in the cylinder remains atmospheric, and 
at point 1, the end of the cycle, the volume is again V c , Fig. 59 (g). 

Work Done by Motor. The work done by any heat engine is 
equal to the difference between the heat energy that goes to the 
engine and that which is rejected by the engine, for whatever heat 
disappears can not have been destroyed and must have been con- 
verted into work. In the Otto cycle, the heat taken in is the total 
heat which it is possible to liberate at the explosion of each charge. 
In the ideal cycle no heat is rejected from the engine except during 
the process represented by the line 5 — 2 in Fig. 58, because, when the 
charge gets back to the condition at 2, it has returned to its original 
volume and pressure and consequently to its original temperature. 

Thermal Efficiency. 'The thermal efficiency of the ideal cycle 

b the fraction of the heat supplied that is converted into work, or 

, , . x . . (heat input) — (heat rejected) 

when expressed in ratio form, ^ — — r -r— . 

(heat input) 

In the theoretically ideal cycle, the thermal efficiency is calcu- 
lated to be from 40 to 50 per cent, depending upon the conditions 
assumed. All departures from ideal conditions result in decreasing 
the actual thermal efficiency of the motor. This efficiency is always 
less than that of the ideal cycle, usually being only from 50 to 60 
per cent as great. 


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General Analysis 

In the discussion of the ideal Otto cycle we assumed that the 
compression and expansion curves were adiabatic and that the walls 
surrounding the combustion chamber were impermeable to heat. 
We also assumed perfect and instantaneous ignition, that we had a 
charge of uniform composition possessing all the physical properties 
of air, and that combustion was complete. None of these assump- 
tions are quite true in practice and each variation from the ideal 
condition has its influence upon the performance of the motor. In 
addition to the above, we did not consider the loss due to the 
necessary cooling of the cylinder. In fact, the water jacket around 
the cylinder (this applies to air cooling as well), without which the 
cylinder would be too hot to be properly lubricated, is the main cause 

""1 o* v 


Fig. 60. Indicator Card of a Motor Following Actual Otto Cycle 

of the difference between the real and ideal cycles, as the cooling 
agent absorbs about 40 per cent of the total heat of combustion. 

In order to analyze the differences between the ideal and the 
actual or practical cycles, let us compare Fig. 58 with Figs. 60 and 
61, which represent, respectively, the cards of a motor which is 
supposed to follow the actual Otto cycle, and of a four-cycle gasoline 
engine as found in practice. 

Suction Stroke. At the end of the exhaust stroke, the clearance 
volume V c , Fig. 60, is filled with burned gases at a pressure P e 
and temperature T e . Nothing definite is known of the temperature 
T e , except that it varies from 1,200 to 1,800 degrees Fahrenheit, 
while Pe ranges from 16 to 18 pounds absolute pressure per square 
inch. At the beginning of the suction stroke the pressure decreases 


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from P e to the suction pressure P2 along the curve determined by 
the re-expansion of the burned gases in the clearance space. This 
is the curve shown at A. The fresh charge can not be drawn into 
the cylinder until after this re-expansion of the burned gases. 
Anything — such as a badly formed exhaust port, restricted exhaust 
passage, or a too early closure of the exhaust valve — which may give 
us too high an exhaust pressure or too large a volume of exhaust 
gases remaining behind, will decrease the cylinder capacity and 











Fig. 61. Indicator Card of Four-Cycle Explosion Motor 

hence materially reduce the efficiency of the cycle. The dotted line 
curves near A show how the above would affect the card. 

Scavenging. If by any means we can reduce the effect of the 
clearance exhaust, we would increase the efficiency. This is actually 
accomplished by what is termed scavenging. Since the exhaust gases 
which occupy the clearance space are usually at a high temperature 
T e , their mixture with the entering charge heats it, decreasing 
its density and, therefore, its amount. Consequently, it is very 
essential that these exhaust gases be excluded from the cylinder 
before the fresh charge enters. This clearing-out or scavenging of 
the cylinder with fresh air has been accomplished in several ways. 
The simplest method is by the use of an exhaust pipe of such length 
that the gases, exhausting from the cylinder with great velocity, 


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create a vacuum in the cylinder near the end of the exhaust stroke. 
This vacuum causes the automatic air-admission valve to open; and 
the consequent rush of air from the air-valve to the exhaust port 
flushes out the cylinder, especially if the air and exhaust valves are 
on opposite sides of the clearance space. Scavenging may also be 
accomplished by pumping air through the clearance space. 

Suction Pressure. Another factor affecting the efficiency is the. 
suction pressure P2, Fig. 60. Owing to friction losses in the admis- 
sion valves and pipes through which the fuel enters, the admission 
pressure is less than atmospheric pressure, 12 J pounds per square 
inch absolute being the average value for P2 in this type of motor. 
Owing to this reduction in pressure, the charge, if it were brought 
to atmospheric pressure, would occupy a volume V\ instead of V 8f 
Fig. 60. This reduction in the amount of the charge, of course, 
decreases the pressure developed at the end of the compression 
stroke and, therefore, reduces the heat developed by the explosion, 
which reduces the power developed within a given size of motor. 
Hence, the smaller the suction pressure, the less power we get, and 
the closer P2 is kept to atmospheric pressure the greater will be the 
possible power output. We thus see that modifications occur at 
each end of the suction line which tend to decrease the efficiency of 
the cycle. This effect produced by the reduction of P 2 permits the 
motor to be governed by means of a throttle valve. P 2 is increased 
or decreased as required by the use of a control valve whose suction 
responds to the load on the engine, thus controlling the charge 
Volume and hence the engine capacity. 

The temperature U of the charge has been found by experiment 
to be between 200 and 300 degrees Fahrenheit. 

Compression Stroke. The compression is not adiabatic because 
it occurs in a cast-iron cylinder, which takes heat from the gas while 
it is being compressed and so makes the final temperature and 
pressure less than those calculated on the assumption of adiabatic 
compression. In general, however, the compression curve may be 
considered in actual practice to follow the general gas law. During 
the first part of the stroke the charge receives heat from the walls, 
but due to the heat generated by compression, this is soon over- 
balanced and during the last and greater part of the stroke the charge 
loses heat to the walls. As a result of this the compression curve is 

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found to be between an adiabatic and an isothermal.* As a result of 
this exchange of heat, first from the walls and then to them, the expo- 
nent n in the general gas law equation PV n = Constant is not constant 
along the entire curve. In actual practice n is found to average about 

(1+c) 1 - 86 

1.35. We thus have in the actual cycle, Ps = 12.5 instead of 


(1+c) um 

f 3= 14.7 for the ideal cycle, where c is the percentage 


of clearance. (See page 58 and Table I.) The less effective the 

cooling, the greater will be the value of n. Any leaks past the piston 

or in the valves will result in a flattened compression curve which 

results in a decrease in the value of n. 

Theoretically an increase in compression pressure Pz will give 
an increase in efficiency. Practically this is true only up to a certain 

The amount of compression that can be used is limited in two 
ways. First, it is not commercially practicable to construct motors 
which will work properly under very high pressures rapidly imposed 
by explosion. With an engine compressing a charge to 100 pounds 
and using a strong explosive mixture, the pressure in the cylinder 
rises suddenly to about 350 pounds and this is at present about the 
practical limit. If the explosive mixture is very weak, the compres- 
sion may be increased as high as 200 pounds, resulting in a maxi- 
mum pressure of about 300 pounds. 

The second objection to the use of high compression is that the 
rise in temperature of the mixture resulting from the compression 
may easily be sufficient to explode the mixture before the piston has 
reached the end of its stroke. Such pre-ignition of the charge tends 
to ftrce the piston back, giving rise to a great shock, which is not 
only very destructive to the engine but reduces its efficiency and 
consequently should be avoided. Pre-ignition may occur even with 
low compression, if any part of the clearance is not water jacketed, 
or properly air-cooled, or if there is any metallic projection in the 
clearance space, Lucke states that compression pressures of from 

♦Adiabatic compression, as already stated, is one in which all the heat resulting from 
the compression is retained in the gas compressed; in an isothermal compression, the heat is 
removed as rapidly as it is produced. In this case some of the resultant neat is retained and 
some of it is lost; therefore, the curve partakes of the properties of both adiabatic and isother- 
mal lines and is found to lie between the two. 


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Effects of Clearance 

Percentage Clearance 

of Otto Cycle 


Pressure at End of 


Lbs. per Sq. In. 

Efficiency of Otto 

Efficiency of Cycle 
with Increased Ex- 
pansion, but with 
Same Compression 
Pressure as Otto 









45 to 95 pounds per square inch are safe as regards the danger of 
pre-ignition in the type of motor under consideration. 

Effects of Clearance. The efficiency of an engine depends not 
at all upon the temperature and the pressure at the end of the explo- 
sion, but only upon the ratio of the temperatures at the beginning 
and at the end of the compression. Since this ratio in turn depends 
only upon the ratio of compression, and since, further, the charge 
is always compressed till it occupies the clearance volume, the effi- 
ciency is seen to depend only upon the percentage of clearance. In 
other words, in engines using the same gas and following the Otto 
cycle, with the same percentage clearance, the percentage of the 
heat liberated in the cylinder that is converted into work is always 
the same, whatever be the size of the engine or the strength of the 
charge. The effect of the clearance on the efficiency is exhibited 
in Table I, where it is seen that the smaller the clearance the 
greater is the efficiency of the engine. The pressures at the, end 
of compression are also given in the table, and are calculated on 
the assumption that the atmospheric pressure is 14.7 pounds per 
square inch absolute. 

Explosion. The shape taken on the indicator diagram by the 
line representing the explosion of the charge depends mainly upon the 
inter-relation of three things, viz, the particular composition of the 
charge, the ignition point, and the piston speed. 

For each power of engine there is a certain relation between 
the proportions of air and vapor in the mixture which will give the 


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most rapid combustion. Any increase in the amount of air or burned 
gases contained in the charge will result in a lowering of the rate of 
combustion until a point is reached where the mixture will no longer 

A t, ' 3 C 

Fig. 62. . Cards Showing Varying Rates of Combustion 

explode. In Fig. 62, A is a diagram of a motor with throttle full 
open, speed constant, and proper ignition; B shows the conditions 
of the same engine after partly closing the throttle, thus increasing 
the proportion of burned gases contained in the charge; and C shows 
the conditions on further closing the throttle. Similar diagrams 
would have been obtained had the throttle been left full open and 
the proportion of air in the first charge considerably increased in 
B and C. A vertical or nearly vertical explosion line such as that in 
A indicates proper combustion. The more slanting the explosion 
line, the poorer the ignition. Referring to C, it is readily seen that 
the maximum pressure of the explosion does not begin to act on the 
piston until the piston has traveled a considerable distance out on 
the power stroke. v 

From the above, it will be seen that for each different fuel 
mixture and each different piston speed there will be a different point 

of ignition if we are to 
secure maximum results. 
This shows that it is ad- 
visable that each motor 
have adjustable ignition ap- 
paratus, because the only 
way to determine a proper 
time is by actual trial. Fig. 
63 shows a set of diagrams 
given by Clerk which illus- 
trates the results of improperly timed ignition. A is the normal 
diagram with proper ignition, while B, C, and D show what occurs as 

Fig. 63. Card Showing Results of Varying 
Time of Ignition 


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the ignition is made later and later. With the time of ignition remain- 
ing constant, successive increases in piston speed would have given 
diagrams similar to those of Fig. 63. The maximum pressure reached 
during combustion depends upon the heating value of the charge 
and should be reached at or before one-tenth stroke. The pressure 
maximum pressure 


usually has a value of between 3 and 

compression pressure 
5, for gasoline. 

The maximum explosion pressure (see point 4> Fig- 60), even 
with proper ignition is never as high for the actual cycle as for the 
ideal cycle. The principal reason advanced for this is the loss of 
heat to the water jacket, or air, if air-cooled, this loss amounting to 
usually about 40 per cent of the total heat of combustion, i. e., heat 
which results from the explosion of the charge. Some of the other 

Fig. 64. 

Card Showing Result of 

Fig. 65. Card Showing Case of 

reasons are the rise in specific heat* of the gases with rise in tempera- 
ture, and the fact that perhaps not all of the heat of the charge is 
liberated when the piston starts forward, which results in after 

Fig. 61 shows the card actually taken from a gasoline engine 
as given by Lucke. The engine had a compression of 80 pounds 
and a maximum pressure of 372 pounds. Fig. 64 shows the results 
of pre-ignition, the card clearly indicating that the explosion has 
occured before the end of the compression stroke and that considerable 
of the stored-up energy of the engine is spent in overcoming the maxi- 
mum force of the explosion. This results in this particular case in 
cutting the power of the engine nearly in half. 

♦Specific heat of a substance is the ratio of the heat required to raise the temperature 
of a certain weight of the given substance 1° F. t to that required to raise the temperature of 
the same weight of water from 62° to 63°F. 


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Fig. 65 shows the difference between a case of back-firing and 
the case of pre-ignition shown in Fig. 64. The explosion occurs in 
the suction pipe during the suction stroke. Back-firing, however, is 
more apt to occur in the exhaust pipe than in the suction pipe. 

Power Stroke. The curve of expansion in the actual cycle 
follows the general law and, because of the loss of heat through 
the cylinder walls, should lie below the adiabatic curve. In prac- 
tice, however, it is found that it does not fall off as quickly as expected, 
sometimes coinciding with the adiabatic, but usually being found 
between this and the isothermal. An evolution of heat along the 
expansion curve is supposed to be the cause of this. A great many 
theories have been advanced to explain this, nearly all trying to 
prove that, owing to certain reasons, after-burning takes place. 
However, up to the present time no really satisfactory explanation 
has been advanced. A value of 1.35 is a fair average value for n, 
thus making the general equation PF 1,35 = Constant. 

Exhaust Stroke. At the instant the exhaust begins, the velocity 
of efflux of the burned charge is from 2,500 to 3,500 feet per second. 
The exhaust valve should start to open at about one-tenth before 
the end of the stroke. The port should be so proportioned that 
the pressure has been equalized by the time the outer dead center 
is reached. If this is not the case there will be an increase in the 
work lost, due to higher back pressure, higher mean cylinder tem- 
peratures, and smaller cylinder capacity. In actual practice the 
pressure at the beginning of the exhaust stroke has been found in 
many cases to average about 25 pounds per square inch. 

The movement of the burned gases out through the exhaust 
pipe is resisted by friction in the various parts. These gases are 
forced out against atmospheric pressure, hence the pressure inside 
the cylinder which expels them must be above atmospheric pressure. 
This pressure is maintained by the piston which follows up the 
retreating gases. The difference in pressure between that inside 
the cylinder and that outside, L e., the exhaust pressure and the 
atmospheric pressure, respectively, opposes the motion of the piston 
on the exhaust stroke and hence causes a loss. This loss is clearly 
shown in Fig. 60 by the fact that the exhaust line on the indicator 
card is above the atmospheric line, thus decreasing the area of the 
card which is proportional to the amount of work done. 



Modifications for Modern Motors 

Large Valve Ports. In modern motors; it has been found 
possible to modify the actual indicator card and the output of the 
engine very materially by slight modifications in the ports and their 
arrangement, as just pointed out. Thus, relative to drawing in the 
fresh charge of gas, after the exhausting has been nearly completed, 
it has been found that larger exhaust valves and ports would carry 
out the burned gases quicker and more completely, so as to leave a 
cleaner cylinder for the fresh charge to enter. 

Similarly, larger inlet valves and ports have been found to 
give a quicker and more complete inflow of fresh charge. The two 
items combined — better scavenging and a more complete charge 
of purer gas — have had a material influence upon the efficiency. 
In the same way, larger intake ports and valves have operated to 
increase the suction pressure. As has been pointed out, this influ- 
ences the pressure at the end of compression, and, therefore, the heat 
developed by the explosion, and ultimately the power developed. 
Thus, larger valves and ports producing increased suction pressure 
have increased the power output. This tendency has been carried 
up to the point where the diameter of the clear valve opening has 
been as close to one-half the cylinder diameter as was practicable, 
that is to say, a motor of four-inch bore nowadays would have 
valves with a clear opening of approximately lit -inch diameter, 
or just ^ inch below half the cylinder diameter. 

Exhaust Qas Friction. Also the exhaust gas friction pro- 
duced by the pipes has been made an almost negligible quantity 
by making the pipes of much larger diameter, with fewer and easier 
bends, while larger mufflers of better design have tended to give 
a greater vacuum. With all these influences at work, it has been 
found possible to increase the speed of exhaust gases. Several 
recent motor designs have an important departure in that the 
the exhaust pipe, instead of turning directly toward the rear, has 
been carried forward in a long, easy bend, coming as close to the 
rear of the radiator as possible and then passing beneath the engine 
supports to the muffler at the rear. The close proximity of the 
exhaust pipe to the radiator and the cold air flowing through it 
have produced an internal cooling and condensing effect which has 
increased the vacuum pressure in the exhaust system and in this 

' - 78 Digitized by G00gle 


way has produced superior and more complete scavenging, which 
always results in greater power. 

In some six-cylinder motors and all in the eight-cylinder forms 
now being produced, a similar result has been attained by using 
double sets of exhaust pipes, leading to a pair of distinct mufflers on 
opposite sides of the chassis or else to one unusually large one. In 
the case of the six-cylinder engines, usually the first three cylinders 
have been considered as one group with their own exhaust pipe and 
muffler, while the rear three formed the other group. In the case 
of eight-cylinder V-types, the right-hand group formed one unit 
for exhausting purposes, and the left-hand lot of cylinders the 

Effect of Large Ports on Silence of Motor. While it has no bear- 
ing upon the subject under discussion, this seems a good place to 
mention the fact that anything tending to make more complete, 
easier, and quicker any natural function of the motor, as the 
inflow of fresh gas, the outflow of burned gases, etc., also tends to 
increase its silence, as well as to increase its volumetric efficiency. 
This combination, with the demand for more economical motor cars, 
has brought about the high-speed small-bore motor of today. To 
make this statement more pointed, it should be said that motors 
are now being constructed and sold in many popular types of car, 
which have a bore one inch less than it was considered practicable 
to build five years ago. 

Manograph Cards. Before turning to the two-cycle form of 
motor and the diagrams, both theoretical and actual, it will be well 
to look at some manograph cards in order to see just what kind of 
cards the manograph makes and how they compare with those made 
by the steam-engine form of indicator. 

In Fig. 66 is presented what might be called a good card. This 
was taken from a motor of 120-millimeter bore (4.72 inches, in 
round figures, 4J) by 130-millimeter stroke (5| inches), running 
at about 1,100 r. p. m. As will be seen at once, this is a combina- 
tion of a number of successive diagrams, superimposed. The line 
DB indicates excellent admission, with a slight rise near the end 
of the line, showing a slight increase in pressure due to the inertia 
of the inflowing gases. Then BF shows a good compression line, 
indicating that the amount of gas admitted has been good, that is, 




that admission had been complete. Next, the vertical line from F 
upward indicates a first-rate explosion. 

From the maximum explosion point down to A, the curve 
indicates the expansion. At E will be seen the variation in the 
successive cards, all of them good but varying slightly from one to 
another as a better or more complete charge was drawn in, a slightly 
higher compression pressure obtained, u better or hotter spark 
produced, or according to other condition? in the cycle. The sharp 

Fig. 66. A Good Manograph Card from a Medium-Sized Four-Cylinder 
Motor, Showing How a Large Number of Cards Are Taken at Once 

end of the expansion curve at A, which indicates the opening of the 
exhaust valve, is very good, as is also the line from A to D and the 
end of the exhaust stroke. Near the end of this it will be noted 
that the exhaust line goes below the intake line, indicating a slight 
vacuum in the exhaust system. 

Fig. 67 shows another card taken from the same engine but at 
a reduced speed, which was being lessened further as the card was 
taken. The mixture was good, and the charge very complete, while 


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the slower speed allowed of a better mixing of gas, a superior diffu- 
sion of the gases in the cylinder, and a better explosion. The lower 
pressures of admission and exhaust do not show up as plainly, but 
the explosion line above F is very marked. The agitation in 
the gaseous mixture is plainly 
shown in the several waves 
of the first part of the ex- 
pansion curve at E. Sim- 
ilarly, a good free exhaust is 
indicated from A to the base 
line and to the end of the 
stroke at D. 

Fig. 68 points out the 
evil results of retarded spark, 
'this curve indicating the 
loss of power due to this 
cause. Note that from F 

UrvnrarA +V»a r»nrv*k iq nrk-r Fig. 67. Another Good Manograph Card, Taken on 
pwam tne CUrve IS not the Same Motor When Slowing Down, Conse- 

vertical as in the preceding quently Showing a SmaTler Area 

diagrams but slopes off to the left. This, of course, indicates a 
loss of power. Note also the poor expansion curve from E down- 
ward, and the comparatively poor exhaust, starting too early and 
continuing too long and too slowly, as indicated by the length and 
slope of the curve around A. 
The diagram at Fig. 69 
indicates poor compression. 
This may be caused by leak- 
ing piston rings, a piston or 
cylinder which has worn 
oval, too small or restricted 
inlet ports or valves, and a 

number Of Other things. The Fig<68 . A Manograph Card from the Same Motor, 
„.„,.. p n r»*mr*a.c,*iT*4-B +V.^ ^ Indicating the Disadvantages and Results 

CUrve DKj represents the in- from Over-Retarded Spark 

take, in which it will be 

noted first that it starts higher than usual, the upturn at B 
indicating that the exhaust closes too soon, leaving gases under 
pressure in the cylinder. The droop in this line indicates the 
remarkably poor suction, which is followed by the line CDE, indi- 



eating the compression and expansion, while EFA indicates the 
expansion and beginning of the exhaust. It will be noted that all of 
these are poor, the fact of the expansion line being below the compres- 
sion line indicating negative 
work, that is, this shows that 
more power was required to 
compress the gases than they 
gave out during their ex- 
plosion and subsequent ex- 
pansion. The exhaust line 
AB is fairly good, excepting 
only the early closing as 
previously pointed out, indi- 
cating that the trouble here 
, , lies mainly in the suction 

Fig. 69. A Manograph Card Indicating Remarkably 

Poor Compression and What It Produces (CarburetlOn SVStem ) . COm- 

in the Cycle x # . ' * /' 

pression, and expansion (cyl- 
inder construction and condition), with incidentally a poor spark 
(ignition system). 

Finally, Fig. 70 shows a diagram taken from an engine with 
a suction inlet valve. This form is no longer used for automobile 
engines, but is of interest because it indicates that this form of 
valve had a considerable influence on the power of the motor. It 

will be noted that the inertia 
of the valve was considera- 
ble, and the suction not suffi- 
cient to hold it wide open 
all of the time. This can 
be noted in the waves of the 
admission curve. Its influ- 
ence on the power can be 
seen in the poor explosion 

Fig. 70. A Manograph Card Taken from an Engine line, following a Very good 

with a & ™ tio ?™£ t l^ IO £ ot * Variation compression curve, and this 

in turn, followed by but 
a fair expansion. Finally, there is shown a poor exhaust, as indi- 
cated by the rising straight line. This means increasing pressure as 
exhausting proceeded, whereas it should show a drop, if anything. 




The compression, explosion, and expansion lines of the indicator 
diagram are the same for the two-cycle as for the four-cycle motor, 
the only difference between the two types being in the way the 
exhaust and charging actions are carried on. In Fig. 71 is shown 
the indicator diagram of a motor which exactly follows the ideal 
two-stroke cycle. The exhaust opens at A, the burned gases escape, 
the intaking of the charge commences and is completed at B, where 
compression commences. From the above it is seen that the exhaust 
and intake actions must be done during the time that the piston 
moves from A to the end of the stroke C, and back again to B. 

Admission of Charge. The very short interval of time between 
the beginning of the exhaust and the admission of the new charge 
(which enters as soon as the pressure in the cylinder has fallen 
enough to permit the admission valve to open), makes premature 
ignition of the charge, or back-firing, of not infrequent occurrence. 
If the mixture is weak, or the 
speed is very high, so that 
the charge is still burning 
when admission begins, or if 
the frequency of the explo- 
sions brings any part of the 
cylinder to a red heat, the 
charge will be ignited on Fig - 71 - Ideal Two " c y cle Dia * ram 

entering, and the explosion then travels back to the crank case, 
which has to be made strong enough to resist it. 

In all explosion motors a certain amount of work has to be done 
in getting the explosive mixture into the cylinder during the suction 
stroke, and in expelling the exhaust gases during the exhaust stroke. 
This gas-friction work is represented on the indicator card of an Otto 
cycle motor by the negative loop, Fig. 72, which has to be subtracted 
from the positive loop in order to give the indicated horse-power of 
the motor. Iri the four-cycle motor this negative work is usually 
from 2 to 5 per cent of the total work, and is a dead loss. In the 
two-cycle motor, considerably more work must be done in order to 
get the gas into the cylinder. The time available for the admission 
of the charge is extremely short. In a small high-speed motor, it 
will be from one- to two-hundredths of a second; in a large two- 

83 Digitized by GoOglt? 



cycle motor, it may amount to one-twentieth of a second. In any 
case it will not be more than one-third to one-fifth of the time avail* 
able for admission in a four-cycle motor. 

Pre-Comjpressionl In order to overcome the back-pressure, of 
the exhaust, and also in order to be able to enter with the very high, 
velocity necessitated by the short duration of admission, the explosive 
mixture has to be pre-compressed to 8 or 10 pounds above atmospheric 
pressure before its admission to the cylinder. Whether this pre- 
compression is done in the crank case, as in small motors, or in sepa- 
rate compression pumps, as in large engines, it requires the expendi- 


/G/y/r/o//-~ : 






|^/yz?. REVOLt/WON 

Fig. 72. Diagram Showing Operations of Four-Stroke Cycle. Lower Part of Diagram, 
Called the Negative Loop, near Atmosphere, Exaggerated 

tare of a considerable amount of work — an expenditure which 
decreases the available power of the motor without giving anything 
in return other than the possibility of maintaining the cycle of 
operations. This loss of power in compressing the charge is ordi- 
narily from 15 to 20 per cent of the total work done in the cylinder. 
Valve Timing. Another loss of efficiency in the two-cycle 
motor results from the fact that the admission and exhaust ports 
are open at the same time. An endeavor is made to have the exhaust 
port close before .any of the entering charge has reached it; but it 
is not practically possible to accomplish that-— particularly in a 
motor which is to run at various speeds. If, in an endeavor to 
prevent such loss of charge direct to the exhaust, the exhaust port 


Digitized by 



closes early, too large a volume of the exhaust gases will be retained 
in the cylinder; the amount of the charge which can enter will be 
correspondingly decreased; and both the efficiency and the capacity 
of the motor will suffer. In large engines, this trouble is to a great 
extent obviated by forcing air into the cylinder slightly ahead of 
the explosive charge, and closing the exhaust port when the charge 
of fresh air is passing through. This device is also valuable in 
preventing back-firing of the charge. 

Scavenging. The success of the two-cycle operation depends 
primarily upon how thorough the scavenging action is carried out, 
since upon this depends the explosibility of the charge, as well as 
its volume, which in turn determine whether the engine runs at all, 
and if so what its efficiency will be. 

For successful action, point A, Fig. 71, should be at atmos- 
pheric pressure, any increase above that given tending to increase 
the volume of exhaust gases remaining in the cylinder as well as 
the work done by the piston during exhaust. Practice has shown 
that scavenging, in order to be thorough, must be commenced 
somewhere between A and C. 

Throttling. The power of a small two-cycle motor can be varied 
by throttling, that is, by varying the amount of the charge taken into 
the cylinder. This is accomplished either by throttling the admission 
to the crank case, or else by throttling in the by-pass between the 
crank case and the cylinder. There is probably but little to choose 
between these two methods. 

Reversibility. Besides its simplicity and compactness, the two- 
cycle motor may claim reversibility as one of its advantages. The 
direction of rotation in the valveless two-cycle motor is determined 
solely by the timing of the ignition. It is possible to reverse such 
a motor merely by making the point of ignition very early. This 
causes an explosion well before the ending of the compression stroke 
and may develop sufficient pressure to stop the piston before it gets 
to the end of the stroke and start it going in the other direction. 
When once started in the other direction, the ignition, if unchanged, 
will be a very late ignition, giving comparatively small power; shifting 
the ignition back a little will give the motor its full power in its re- 
versed direction. This process is practicable only in motors with light 
reciprocating parts; it is most convenient for small motorboat use. 

Digitized by VjOOQ IC 


Summary. In theory, the two-cycle motor develops about 65 
per cent more power than a four-cycle motor of the same size and 
speed; it uses from 10 to 20 per cent more gas per brake horse- 
power. In actual practice, however, it has been difficult for two- 
cycle designers and advocates to show more than 10 per cent 
increase for equal size, while the two-cycle form cannot produce 
as low a minimum nor as high a maximum speed. The latter has 
a large influence on the power output, as the four-cycle engine 
develops the greater part of its power at the upper or high speed 
end of the power curve. Consequently, the maximum output of 
a four-cycle motor has always been greater than that of a two- 
cycle motor of equal size because of the greater speed possibilities 
of the former. Moreover, the majority of car manufacturers and. 
independent designers have, in the past six or eight years, worked 
on the four-cycle form with the result that it has approached a 
high state of perfection. The same cannot be said of the two- 
cycle motor. 

Except for the above-mentioned differences and the difference 
in the form of the diagram, as has just been pointed out, the 
thermodynamics of any two-cycle type of motor is exactly the 
same as that on any four-cycle type. 


Aviation vs. Automobile Motors. One of the great results of 
the War has been to produce some very large and high-powered 
engines for use fn airplanes, seaplanes, and dirigibles and to call 
popular attention to them. This fact was perhaps most strikingly 
presented at the aeronautic show in Madison Square Garden in 
the spring of 1919, when there were exhibited no less than six 
different eight-cylinder, one nine-cylinder rotary, five different 
twelve-cylinder, two sixteen-cylinder, and one eighteen-cylinder 
motors, developing up to 800 horse-power. 

The production of airplane engines by the thousands for war 
use and the wide publicity given to the details of these have pro- 
duced much popular interest in the special airplane engine. This, 
it should be understood, is not by any means an automobile 
motor adapted to other work. The most important of the essen- 
tial points of difference is the fact that the airplane engine 

86 Digitized by G00gle 


requires first of all light weight, not just low weight, but the 
minimum weight possible, consistent with regularity of operation. 
This requirement has been the cause of much additional machining 
to remove useless weight and has forced the use of various light 
materials or of heavy materials in a new way. Both of these 
practices have had the effect of making the cost of air engines 
tremendously high, approximating $10,000 per engine, whereas a 
very good automobile engine can be produced for one-tenth of 
this sum, and a fair engine for a low-priced car, such as a Ford, 
a Maxwell, and the like, for one-hundredth of it. 

Another point of difference relates to the service demanded 
of the motor. An automobile engine starts at low speeds and 
then probably runs first fast then slow, its speed constantly 
varying; in fact, it has been estimated that no average touring- 
car motor is run at its maximum speed in excess of 18 per cent 
of its useful life. The airplane engine, on the other hand, oper- 
ates at high speed from the start all the time it is in use and 
then is shut off entirely; that is, it operates at high or highest 
possible speed for 90 to perhaps 97 or 98 per cent of its useful life. 

There is also an important difference in the matter of regu- 
larity of operation. If an automobile engine does not work well 
or needs adjustment, the car can be stopped and the driver can 
get out and fix it; in an airplane, on the contrary, not only can 
this not be done, but such irregular operation or lack of adjust- 
ment may mean the death of pilot or passengers or all. 

An automobile engine works always upon the level, with the 
exception of climbing or descending hills — and then the angle is 
comparatively slight. The airplane engine must work as well 
upside down as right side up; must work at all intermediate 
angles from zero to 90 degrees; and must work inclined sideways 
at any or all angles. 

The automobile engine works practically always at the one 
altitude above sea level and consequently at the one air pressure 
and under the one set of air conditions. The aerial engine works 
at all altitudes and may pass from a level of a few hundred feet 
to an altitude of 15,000 to 20,000 feet within twenty minutes. 
The differences in air pressure and conditions at these radically 
different levels, succeeding one another with rapidity, have a 



tremendous influence upon the engine as well as upon the machine 
and the driver. 

All these points have been emphasized because they indicate 
how and why the automobile and the airplane engine not only 
are at present but always must be radically different in design, 
construction, and use. In outward appearance and in number 
and functions of parts and units used the two may be alike, but 
there the resemblance ceases. 

Moreover, aside from differences in details of design and con- 
struction, the search for maximum power and speed, combined 
with minimum weight and minimum space occupied, or, more 
correctly, minimum head resistance, has brought out many types 
of motor not used for any other purpose. Thus, the rotary form 
of engine was used on only one automobile, which was built in 
very small quantities and given up many years ago. It is widely 
used in airplane work, its use is steadily increasing, and there are 
dozens of different designs. Similarly, the radial form of engine 
with stationary air-cooled cylinders has never been tried for 
motor cars, but finds wide and increasing use in airplanes. These 
two forms also involve the use of an odd number of cylinders. 
Except for the one car already mentioned (which had a five- 
cylinder motor) and another of about the same general descrip- 
tion and fate (which had a three-cylinder vertical compound 
engine), all automobiles of recent years have had an even number 
of cylinders, such as two, four, six, eight, and, most recently, 
twelve. For airplane use the three-, five-, seven,- and nine- 
cylinder forms are common; doubles of these are also used, giving 
ten, fourteen, and eighteen cylinders. 

The air-cooled motor is coming into more prominence, as its 
construction is better understood, and since its efficiency is much 
higher than that of the water-cooled motor. The Franklin and 
Holmes are both air-cooled motors, the Holmes being a compara- 
tively new car in this field. For aeroplane work, the air-cooled 
motor is fast losing its prestige. American makers are using the 
water-cooled motor and almost all altitude and speed records are 
now held by planes equipped with water-cooled motors. 

The crying demand for speed and more speed and the equally 
great outcry for enormous carrying capacity have produced some 




airplane engines of tremendous size, and have brought about 
their use in multiples. The practical limit of output per cylinder 
in airplane engines having been found to be between 45 and 50 
horse-power, the matter of securing great power has now settled 
down to a question of how many cylinders can be used per engine 
advantageously and with very high powers, such as 2,000 horse- 
power, how many units used and where located. 

Classification. The general differences which have been out- 
lined lead up to a classification of the types and forms of engines 
now in use, which may be put in tabular form as follows: 



4 cylinders (air-cooled V) 

5 cylinders (air-cooled rotary) 

6 cylinders 




3 cylinders 
5 cylinders 
7 cylinders 
9 cylinders 
10 cylinders 

5 cylinders 
7 cylinders 
9 cylinders, 

6 cylinders 

10 cylinders 

and doubles^ 14 cylinders 

18 cylinders 

20 cylinders 

{10 cylinders 
14 cylinders 
18 cylinders 

Opposed 2 cylinders 
12 cylinders 

V type 4 cylinders 

8 cylinders 

12 cylinders 

Radial 9 cylinders 

10 cylinders 

Vertical 6 cylinders in line 

8 cylinders in line 
12 cylinders in line 

8 cylinders in 2 parallel lines of 4 each 
16 cylinders in 2 parallel lines of 8 each 

V-typeJ 4 cylinders 

8 cylinders 

12 cylinders 

16 cylinders 

Fan or W type 12 cylinders in 3 sets of 4 each 

' * 18 cylinders in 3 sets of 6 each 

IX-type iq cylinders in 4 sets of 4 each 

* These represent only the types and forms now constructed, not all the possible forms. 
JV-type engines are made with varying angles between the cylinders (as the fan, or W, 
types probably will be also), but for this tabulation this difference is disregarded. 



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It will be interesting to note the construction of some of the 
principal types of engines in as much as the subject is a live one 
and airplane engine success is expected to be reflected in auto-> 
mobile work; thus, the use of small valves and high gas speeds in 

Fig. 73. General View of Frederickson Five-Cylinder Two-Cycle Rotating Motor 

airplane engines having been proved successful, it is now being 
tried on automobile engines. The use of more than two valves 
per cylinder, having found a great, in fact, almost universal 
adoption in aviation engines, is now being tried on motor car 
engines. The advanced metallurgical practice and shop practice 

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necessary in aircraft engine construction is about to be reflected 
in better-built medium- and low-priced automobiles. 

Air-Cooled Engines. Frederickson. There are very few two- 
cycle airplane engines, and not very many five-cylinder forms, so 
that the Frederickson motor shown in Fig. 73 presents several 
novelties. Its construction can be seen better in Fig. 74, where it 
will be noted that the connecting rods each carry a cone-shaped 
sliding sleeve actuated through a ball joint at the upper end to 
move sideways as the rotation of the crankshaft moves the rod 
sideways. In so doing the sliding sleeve opens and closes the con 

Fig. 74. Drawings Showing General Construction of Frederickson Five-Cylinder Motor 

necting port between the crankcase where the charge is drawn in 
and compressed and the by-pass through which this partly com- 
pressed combustible mixture passes into the cylinders. To make 
this movement more clear, Fig. 75 shows it in flat projection, 
representing the successive steps in each cylinder base. At A the 
slide closes the port; at B it is beginning to open, and the piston 
has passed its lowest point and is beginning to rise. At C the piston 
is almost at the top, with the chamber full of gas; and the by-pass 
is cut off. At D the piston has passed the top center; the charge is 
presumably exploded; and the slide has cut off the connecting port. 


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This motor has five air-cooled cylinders, a 4^-inch bore and a 
3f-inch stroke. It is rated at 70 h.p. and develops slightly more 

Fig. 75. Sketches Indicating Operation of Frederickson Sliding Port Valve 
Courtesy World Motor Company, Burlington, Illinois 

than that, and its weight, bare, is 180 pounds, giving 1 h.p. for 
each 2\ pounds. This, it will be noted, is a single-crank engine, 

Fig. 76. View of Marlin-Rockwell Two-Cylinder Airplane Engine 
Courtesy Marlin-Rockwell Corporation, New Haven, Connecticut 

as are, in fact, all radial and rotary engines, this feature contribut- 
ing largely to their light total weight. 


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Marlin-RockwelL A novel development for small one- and 
two-place sporting planes is the two-cylinder engine, like the 
Marlin-Rockwell shown in Fig. 76. Generally, the two-cylinder 
opposed type has shown such a lack of balance that it has grad- 
ually gone out of use, but for aeronautic work it is so compact 
and takes up so little space as to warrant its use. The engine 
shown is actually running, the shadow of the propeller being visi- 

Pig. 77. Wasp Seven-Cylinder Radial Airplane Engine 

ble. The bore is 5 inches, the stroke 6 inches, compression about 
86 pounds, weight 134 pounds, power 72 h.p. at 1,825 r.p.m. — 
1 h.p. for each 1.86 pounds weight. This engine will be produced 
in a ten-cylinder radial air-cooled form, which is expected to 
develop 500 h.p. and weigh about 1^ pounds per h.p. Special 
attention is called to the fact that the cylinders are steel, machined 
out of a solid bar, whereas those shown in the preceding case 
were cast iron. 

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Wasp. Originally it was thought to be impossible to con- 
struct an air-cooled engine that wpuld be efficient with a bore 
greater than 4\ inches, but the British ABC engine proved this sup- 

Fig. 78. View of Jupiter Nine-Cylinder Radial Engine, Showing Operation 
of Four Valves per Cylinder 

position to be wrong. The Wasp model shown in Fig. 77 is one 
of this type. It is a fixed radial seven-cylinder unit with 4f-inch 
bore and 6j-inch stroke and develops 200 h.p. at 1,800 r.p.m. It 

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weighs but 320 pounds, which is 1.6 pounds per h.p. This motor 
is fitted with two carburetors feeding a circular inlet manifold, 
from which the separate radial inlet pipes to the cylinder heads lead. 
'Jupiter. As has been stated previously, the majority of air- 
plane engines have more than one inlet and one exhaust valve per 
cylinder, the various designers using all the following combina- 

Fig. 79. Front Appearance of Mercury Fourteen-Cylinder Radial Engine, Consisting of 
Two Staggered Sets of Seven Cylinders 

tions: two inlets and one exhaust; two exhausts and one inlet; 
two of each; three inlets and two exhausts; and three exhausts 
and two inlets. In Fig. 78 is shown the Jupiter, another fixed 
radial air-cooled form, viewed from above so that the valve tap- 
pets and springs for the four valves per cylinder are plainly seen. 
This model is constructed by the Cosmos Engineering Company, 
Bristol, England, and has nine cylinders of 5f -inch bore and 

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7^-inch stroke. It has a circular inlet manifold fed by three car- 
buretors which is somewhat similar to that in the Wasp. The 
engine weighs 662 pounds and the normal output at 1,800 is 450 
h.p., although the engine rates at 500 h.p. The former output 
gives 1.47 pounds per h.p., the latter 1.32 pounds. 

All these forms are single-crank engines (which is also true of 
Fig. 80 discussed later) ; that is, all the connecting rods are attached 
to a single crankpin or, as is usually the case, to the master con- 
necting rod. One rod is bolted to the pin, and all the others are 
either of the forked type and bolt around this master rod or are 
attached to ears constructed on it. This means that what might 
be called the thickness of the engine is equal to the thickness of a 
single cylinder. 

Mercury. When a pair of motors is coupled together and a 
two-throw crank used, we get a double such as indicated in the 
tabular analysis of aerial engines. Thus, the fourteen-cylinder 
engine shown in Fig. 79 consists of two batteries of seven cylinders 
each. These are of the air-cooled fixed radial type and have a 
bore of 4f inches and a- stroke of 5yf inches. The normal output is 
315 b.h.p. (brake horse-power) at 1,800 r.p.m., and the weight 
587 pounds, or 1.86 pounds per h.p. There are three valves per 
cylinder, one inlet and two exhausts, while ignition is supplied by 
two seven-cylinder magnetos, and mixture by two carburetors 
feeding a circular manifold. 

B.R.I Type. The rotary form much resembles the fixed 
radial, the difference being merely in the valve-operating mechan- 
ism, ignition gearing, and the like, due provision being made for 
these to function as the cylinders rotate. Some of this mechan- 
ism may be seen in Fig. 80, which presents a detailed view of the 
B.R.I, a famous British war engine. This is a nine-cylinder rotat- 
ing air-cooled form, of 4.72-inch bore and 6.66-inch stroke. It 
develops 150 h.p. at 1,250 r.p.m. on a weight of 2.67 pounds per 
b.h.p. In a larger size this engine as the B.R.2 developed 250 
h.p. on 1.9 pounds per b.h.p. 

Water-Cooled Engines. Coming next to the water-cooled 
forms, the six cylinders in line so often found in motor cars is not 
very widely used in airplanes. For one thing, it does not produce 
sufficient power, and furthermore, it occupies considerable space in 

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from a vertical shaft at the front of the engine. It will be noted 
that the propeller is direct driven, not geared down. The Hall- 
Scott is a very reliable motor and was much used in aviation 
work during the War. 

Curtiss V Type. No one form of engine has made as much 
headway in the United States as the V type, in which two groups 
of cylinders, usually normal four-, six-, or eight-cylinder groups, 
are used on a common crankcase with a common crankshaft, thus 
forming a single larger power unit. To achieve this result satis- 

Fig. 85. Intake Side of Hall-Scott Six-Cylinder Vertical Type Airplane Engine 
Courtesy Hall-Scott Motor Car Company, San Francisco, California 

factorily, the cylinders are mounted at an angle, which varies 
from 90 degrees (45 degrees each side of the vertical) down to as 
little as 30 degrees. The larger angles were used at first to secure 
better balance in the running of the engine. Subsequently, it was 
found that the smaller angles not only gave a more compact and 
more accessible member but reduced head resistance also, which is 
a very important point in airplane engines. Beginning with two- 
cylinder V's used for motorcycles, the popularity of this form and 
its successful use have continued until now it is made in fours 
(two twos), eights (two fours), twelves (two sixes), and sixteens 
(two eights). 

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The most popular engine for high-power output, approximat- 
ing 400 h.p., which type of motor was imperatively needed in the 
War in large quantities, is the twelve, or twin six. Among the 
most widely used forms of the twelve are the Curtiss, the Liberty, 
and the Packard. 

The Curtiss was actually produced before the War, but has 
been so refined as a result of war experience that it is now pre- 

Fig. 86. General View of Curtiss Twelve-Cylinder V-Type Aviation Motor 
Courtesy Curtiss Aeroplane and Motor Company, Buffalo, New York 

sented as a post-war model which is quite different from the ante- 
war model. It will be noted in Fig. 86 that the six cylinder 
bases on each side (twelve in all) and the upper half of the crank- 
case are cast as a unit, the separate cylinder covers for each 



group being bolted on. The large cylinder-crankcase unit is of 
aluminum, and the cylinder liners, which are steel foigings machined 
all over with the cylinder heads integral, are threaded and screwed 
into the cast cylinder covers. 

Kg. 87. End View of Liberty Motor at National Bureau of Standards, Washington, D.C. 

The bore is 4£ inches, the stroke is 6 inches, and the normal 
power rating is 400 h.p. at 2,500 r.p.m. while 420 h.p. is actually 
developed at 2,650 r.p.m. With this high rotative speed, a 
geared-down propeller is used, the regular gear reduction being 
5:3. Two two-spark six-cylinder magnetos are used and two 

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duplex carburetors. The motor without oil or water weighs 680 
pounds, giving a dead weight per rated h.p. of 1.70 pounds. 

Liberty V Type. The Liberty motor was developed purely 
and simply for war work by American engineers, along American 
lines, and specifically for American methods of production. It was 
not strictly an original design, many major elements and groups 
of elements being adopted bodily from existing American engines, 
notably the Packard aviation engine and the Hall-Scott. This 
made possible quick production, for these two companies started 
immediate manufacture of these adopted parts and in addition 

Fig. 88. Side View of Liberty Motor Ready for Tests at National Bureau of Standards 

started at once to instruct subcontractors on these same parts. 
All this was done practically without waiting for the design to be 
completed, tried out, and improved as a result of the try-outs; in 
fact, many thousand changes were made as production proceeded. 
More than 20,000 engines were produced, of which number more 
than 14,000 were delivered before November 11, 1918, and more 
than 16,000 during the calendar year 1918. 

In Fig. 87 is shown an end view and in Fig. 88 a side view of 
a completed Liberty motor ready for tests at the Bureau of 
Standards. Fig. 89 gives a cross-section of the form using a cast 
cylinder, showing incidentally the crankshaft and connecting rods, 

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piston and cylinder construction, valve location and operation, and 
water-jacketed inlet manifold. 

Fig. 89. Cross-Section of Liberty Motor with Cast Cylinders 

This motor has a bore of 5 inches and a stroke of 7 inches, 
and the cylinders are set 45 degrees apart (22| degrees each side of 


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the vertical). It normally develops 400 h.p. at 1,750 r.p.m., but 
420 h.p. is produced in all tests and a special type, with special 
fuel, has produced 526 h.p. The weight is given as 806 pounds, 
but there is every reason for believing that this has been increased 
to approximately 825 pounds, 1.96 pounds per h.p. for the normal 
output and 1.56 pounds for the maximum. There are two duplex 
carburetors, two valves per cylinder, and battery ignition with 
two distributors, one on the end of each overhead camshaft and 
each one firing all twelve cylinders. A novelty is that the cylin- 
ders are hollow steel forgings with water jackets and valve port 
cages welded on. 

Packard and Liberty. It has been stated that many parts of 
the Liberty design and subsequent construction were taken bodily 
from the Packard aviation engine, and it almost might be stated 
that without the Packard engine available as it was and when it 
was, the Liberty motor would have been quite different — perhaps 
not nearly so good — and certainly it would have been produced 
more slowly. 

The original Packard was a small engine with a piston dis- 
placement of but 299 cubic inches, having been designed to be 
below the 300 cubic-inch racing-car motor limit established by the 
A.A.A. In the engine which was brought out late in 1915 the 
size was increased to a 4-inch bore by a 6-inch stroke, giving 
905 cubic inches piston displacement. This engine, in turn, was 
improved late in 1916 and again early in 1917. Model 3 was 
the engine which immediately preceded the Liberty, the Jatter, 
however, having a larger bore and stroke because of the need for 
greater power. This process of development is shown in Fig. 90, 
the last motor at the right being a Packard-built Liberty motor, 
Model B. The similarity of this design to that of the preceding 
Packard motor will be noted. 

Duesenberg. Among the very large motors must be men- 
tioned the Duesenberg sixteen-cylinder V. This has a bore of 6 
inches and a stroke of 7 J inches, the largest dimensions in the world 
with the exception of those of the large Fiat model, which has a 
bore of 6.69 inches and a stroke of 8.27 inches. In as much as the 
Fiat has only twelve cylinders while the Duesenberg has sixteen, 
the latter probably can be considered the largest single aviation 


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s i 



J § 

.S -s 
§ 3 

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unit. It develops 700 h.p. driving the propeller direct and 800 
h.p. driving through gears at 1,350 r.p.m.; it is rated at 850-900 
h.p., so it must have reached a maximum between these two 
figures in the block tests. It has four 2J-inch carburetors located 
on the outside of the cylinders, and ignition is provided either by 
two eight-cylinder magnetos or by battery ignition with distribu- 
tors on the ends of the overhead camshafts, much as in the Lib- 
erty. As Fig. 91 shows, there are three valves per cylinder, 
arranged to work horizontally in the individual cylinders, although 
mounting the cylinders 22| degrees out of vertical brings these 

Fig. 92. Sunbeam-Coatalen Eighteen-Cylinder Fan- 
Type Aviation Engine 

valve axes just that much out of horizontal. With direct drive 
the weight is 1,390 pounds, and with gear reduction, 1,575 pounds, 
both less than 2 pounds per h.p. 

Sunbeam-Coatalen Fan Type. Just as the radial and rotating 
engine builders have found it advantageous to produce high 
power by doubling or tripling the number of units used, thus pro- 
ducing the eighteen-, twenty-, and twenty-one-cylinder units, so in 
the .production of high-powered V-type motors it has been found 
possible to double up. This gives a fan, or W type, the three sets 
of cylinders radiating from a common crankcase and crankshaft. 
Notable examples of this form include the Napier Lion twelve^ 

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cylinder unit consisting of three sets of four cylinders each, the 
central set being vertical and the two outer ones each inclined at 
an angle of 60 degrees. 

In the Sunbeam eighteen, Fig. 92, there are three groups of 
six cylinders each. Six carburetors are used, each serving a 
block of three cylinders. There are six enclosed magnetos, each 
of the six-cylinder form, two sparks being furnished each cylinder. 
There are four valves per cylinder, two inlets and two exhausts, 
located in the head and operated by overhead camshafts. The 
engine is rated at 475 h.p. and takes no more space fore and aft 
than the same firm's six-cylinder engine of the same bore and 


Explosion motors can be made to work with any explosive 
mixture, those of air with gaseous fuels being naturally the mixtures 
most easily made and controlled. Mixtures of air with liquid fuels 
offer generally no particular difficulty, but those with solid fuels 
(such as powdered coal), although they have been tried, are not 
practicable on account of the ash which remains in the cylinder and 
rapidly abrades it. The single exception to the above statement is 
naphthalene. As will be described later, this is a solid fuel which 
has to be converted first to a liquid and then to a gas. It has 
been used with very great success abroad, and at a surprisingly low 
cost. A number of French and English commercial vehicles are 
now being operated with it. 

Recent tests have shown that ether and kerosene are violent 
burning gases which produce a great many fuel knocks. Pennsylvania 
commercial gasoline is composed of compounds which cannot be 
separated and consequently does not produce many knocks. Cali- 
fornia gasoline — composed mainly of paraffin and naphthalene 
hydrocarbons — is distilled at a lower temperature than Pennsyl- 
vania gasoline and produces a little better results. 

Mixtures of two different kinds of liquid fuels, and of a solid 
and a liquid fuel have generally been successful in cases where, the 
two components were carefully chosen as to their suitability. As an 
example of this last statement, kerosene and gasoline mixtures will 
operate successfully where kerosene alone cannot. Many drivers 


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economize on their fuel bills in this way, adding kerosene in quan- 
tities up to 40 per cent of the total to their gasoline. Similarly, 
with gasoline and alcohol, kerosene and alcohol, naphthalene in 
gasoline or kerosene (when the fuel is preheated), and others. 

Table II gives the heat values for most of the commercially 
available fuel materials for explosion motors. 

The liquid fuels are the only ones with which we are concerned, 
and of these gasoline is by far the most important, since it is the 
one almost exclusively used in the motors which we are considering. 

Petroleum Products. Crude petroleum furnishes us the follow- 
ing commercial products for power purposes: Gasoline, naphtha, 
kerosene, gas oil, and crude oil. 

These products are separated from the crude petroleum by distil- 
lation, i. e.y the crude petroleum is heated and its various products 
are given off as vapors; the lightest or most volatile product is 
given off first, then as the temperature is raised still higher, the 
next most volatile ingredient is given off, and so on through the 
entire list. 

Rhigolene, sp. gr.* 0.60, distills off at 113° F.; cymogene, sp. gr. 
0.625, at 122° F.; gasoline, sp. gr. 0.636 to 0.657, at from 140° to 
158° F.; C. Naphtha, sometimes called benzine, sp. gr. 0.66 to 0.70, 
at from 158° to 216° F.; B. Naphtha, sp. gr. 0.71 to 0.72, at from 
216° to 250° F.; A. Naphtha, sp. gr. 0.72 to 0.74, at from 250° to 
300° F. Various authorities differ concerning these values, but the 
ones here given are safe average figures. 

Gasoline. What we in America know as gasoline is really a 
combination of the above fractional distillates whose specific gravity 
runs from 0.63 to 0.74f. The boiling point of gasoline such as is 
usually used in explosion motors ranges from 150° to 180° F., and 

♦Specific gravity. 

fSpecific gravity is figured in two ways, one a decimal quantity and the other an arbitrary 
figure, as determined on the scale of an instrument known as a Baume* hydrometer. The latter 
figures are called degrees Baume\ This quantity is used in America more than the actual specific 
gravity, although the former is usually spoken of as the specific gravity. The increase in weight 
of the usual fuels, as we pass from the lighter gasoline up to kerosene, and beyond that to heavier 
forms, would be reflected by the specific gravity. As everyone knows, however, we speak of 
gasoline as getting poorer, now we get but 56 whereas we used to get 76, etc. These figures refer 
to the Baume* scale, which gives a lower reading for a heavier liquid. Thus specific gravity may 
be figured from degrees Baume* by adding the Baume* reading to 130, and then dividing 140 
by the result, or 


Specific Gravity = 

130 + Baume* 

Using this on the figures given above, we find that 56 Baume* equals .75 s. g. and 76 Baume^ .(& 
s. g. The remark then translated into actual specific gravity would read, now we get .75 £«*- 
oline, whereas we used to get .68. This is correct, for present-day fuel is heavier than that cf 


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Explosion Motor Fuels 

Gases, Vapors, Liquids, and Solids 

Heat Units* 
per Pound 

Heat Units 
per Cubic Foot 






Crude Petroleum 








Alcohol, Methyl 


Denatured Ethyl Alcohol 





19-can. power Illuminating Gas 


16-can. power Illuminating Gas 


15-can. power Illuminating Gas 


Gasoline Vapor 



Natural Gas, Leechburg, Pa. 


Natural Gas, Pittsburg, Pa. 








*A heat unit or British thermal unit (B. T. U.) is, practically speaking, the quantity of 
heat required to raise the temperature of one pound of water one degree Fahrenheit. 

the flashing pointt of the liquid ranges from 10° to 14° F. A mix- 
ture of one part of this gasoline vapor to 7.3 parts of air produces 
what is theoretically a perfect combustion mixture. A decrease in 
the proportion of air may leave, as a residue in the exhaust, uncon- 
sumed vapor, while an excess of air up to a limit of 10 parts of air to 
1 part of vapor may increase the fuel efficiency. As a matter of 
fact, the modern automobile engine will operate on any mixture 
between 5 to 1 and 15 to 1. 

A sample of gasoline of specific gravity 0.71 showed 83.8 per 
cent carbon, 15.5 per cent hydrogen, and 0.7 per cent impurities, 
and had a heating value of 18,000 B. T. U's per pound. The various 
grades of gasoline differ mostly by the percentage of hydrogen 

five years ago. By referring to the s. g. of kerosene, it can be figured out readily that the actual 
case is that fuel now sold as gasoline contains a considerable amount of what was formerly sold 
separately as kerosene. Except for the name this is no disadvantage, but on the contrary an 
advantage so long as the carbureter will handle it, for kerosene contains a greater number of 
hea$ units per pound. 

- _; tThe flashing point of a substance is the lowest temperature at which it gives off vapor 
1 |n sufficient amount to form with the surrounding air a mixture which is capable of burning when 


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contained. A gallon of liquid gasoline will in the form of a vapor 
fill about 160 cubic feet, or about 1,200 times its liquid bulk. Gaso- 
line of 0.74 specific gravity will weigh 6.16 pounds per gallon, and its 
pure vapor, which occupies about 26 cubic feet per pound, has a 
heating value of 690 B.T.U's per cubic foot. The recent shortage 
of gasoline has produced many efficient kerosene vaporizers and 
caused a wide use of kerosene, both straight and mixed. 

Kerosene. Kerosene is distilled from crude petroleum at a 
temperature of 300° to 500° F. Its specific gravity is 0.76 to 0.80. 

Coal Gas. Coal gas has a specific gravity of 0.80, given off 
above 500° F. Crude oil remains after the above distillation process. 

Miscellaneous Distillates. The former simple division of crude 
petroleum products into four parts, gasoline, kerosene, coal gas, 
and crude oil, is no longer correct. The tremendous demand for 
motorcar and boat fuels has brought about the need for a larger 
percentage of gasoline, which has been supplied by making it heavier 
through the inclusion of much of what was formerly sold as kero- 
sene. To keep up the quantity of the latter, this too has been 
made heavier by the inclusion of considerable quantities of what 
formerly was distilled over as coal gas. In addition, the distillation 
is further split up by the separation of the naphthas, first the lighter 
benzine naphtha, then naphtha, then benzine. Finally, what was 
formerly lumped as crude oil remainder is now split up into a number 
of different oils, with the final remainder, now called "residuum" or 
"tailings". The latter is sometimes fluid, but more often a viscous 
semi-solid dark-green or dark-brown substance with an unpleasant 
odor. As a matter of fact, several carbureters have been developed 
on the Pacific Coast, by means of which this former waste material 
can be first liquefied, then converted into a gas and burned in motor 
truck engines. When this is done, an important economy is effected, 
for this material sells for about three cents a gallon, and in some 
localities as low as \\ cents, when sold in barrel lots. 

Denatured Alcohol. There are two kinds of alcohol, viz, (1) 
ethyl alcohol (C 2 H e O), which can be made from corn, rye, rice, 
molasses, beets, or potatoes, by a process of fermentation and distil- 
lation; and (2) methyl or wood alcohol (CH 4 0), which is obtained 
from the destructive distillation of wood. Ethyl alcohol is that 
which is present in alcoholic beverages; wood alcohol is a virulent 


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poison. Denatured alcohol is ethyl alcohol which has been rendered 
unpalatable and unfit for consumption by the addition of wood 
alcohol and a little benzine or other substance. It gives up about 
11,800 B. T. U's per pound on burning; consequently it does not 
give up much more than one-half as much heat per pound as gaso- 
line or kerosene. The weight and volume of denatured alcohol 
required to develop a given power in a motor is considerably greater 
than the amount 6f gasoline for the same power; and, therefore, if 
a gasoline motor is to be used with alcohol, the orifices in the car- 
bureter or other spraying device have to be enlarged so as to admit 
a greater volume of the liquid. Wood alcohol can not be used by 
itself in a motor, as it corrodes the cylinder. Denatured alcohol, 
in its volatility, lies between gasoline and kerosene, the amount of 
vapor which it gives off to air that passes over it being generally 
sufficient to give an explosive mixture, if the temperature of the air 
and alcohol are above 70° F. With an ordinary spray carbureter 
a considerable excess of alcohol may be sent to the cylinders, as such 
carbureters act also as atomizers. 

Recent tests have demonstrated that any gasoline or kerosene 
motor can operate with alcohol without any structural changes, and 
that about 1.8 times as much alcohol as gasoline is required to 
develop the same power. Alcohol can be used with greater com- 
pression, as there is little danger of pre-ignition through too much 
compression on account of its comparatively high ignition tempera- 
ture and also because it is always mixed with some water. An 
alcohol motor can be made to give somewhat higher power than a 
gasoline motor of the same size. It is not as sensitive to poor adjust- 
ment of the explosive mixture; that is, it will work with a great 
range of strength of mixture, and it does not accumulate a deposit 
of carbon inside the motor. An explosion motor of good design 
should use about 1.15 pounds of alcohol per brake-horse-power hour; 
of gasoline, 0.7 pound. 

Despite' all these advantages, denatured alcohol as a fuel has 
not come into wide use, partly because of its high price as compared 
with gasoline and kerosene, partly on account of poor distributing 
facilities, and partly for other reasons. It has, however, attained a 
considerable use among, motor car owners as an anti-freezing solu- 
tion and as a decarbonizer. For the former, a small quantity is 


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added to the water in the radiator in the winter months, reducing 
the temperature at which this will freeze, according to the quantity 
added. It is possible to add enough to give a solution which will 
not freeze until 32 degrees below zero is reached. As a decarbon- 
izer or remover of carbon formations in the cylinder, denatured 
alcohol is excellent, while its use is the essence of simplicity. It is 
to be hoped that the production will be materially increased in the 
next few years so as to reduce the price, increase its availability, 
and thus help out the fast-failing gasoline supply. 

Other Automobile Fuels, Benzol. In England, a fuel called 
"benzol" is used to a considerable extent. This is a by-product of 
the destructive distillation of coal, that is, it is produced in the 
manufacture of coal gas. In large plants a considerable quantity 
can be made, for the yield is something like three gallons per ton of 
coal burned. It is naturally a foul-smelling, dark-brown liquid, 
but by a refining process is made a transparent white, like water, 
and the odor partly removed. It has a specific gravity of .88 at 60 
degrees F., a flash point of 32 degrees F., and a heating value of 
about 17,250 B. T. U's per pound. Although not as volatile as 
gasoline, it starts readily and, when carefully refined, does not leave 
a residue, or carbonize in the motor. In Germany the lack of gasoline 
has brought forth a benzol-alcohol mixture. Up to 1 benzol to 5 
alcohol it gives better mileage than gasoline or pure benzol. 

Electrine. In France, a mixed fuel composed of half benzol and 
half denatured alcohol is much used, this bearing a number,of trade 
names. One of these, "Electrine," has an s.g. at 15° C. of .835. 

Naphthalene. Mention has been made previously of a solid 
fuel, naphthalene. This is a white solid substance, produced during 
the manufacture of gas from coal, and previously was a waste prod- 
uct. It now sells at a few cents a pound. In a less pure state it 
is well known to all in the form of camphor balls, so-called. To use 
this as a fuel in an automobile engine, it must be melted to a liquid, 
then turned into a gas and mixed with the right proportion of air. 
None of these offer any particular difficulty, and it has been used 
abroad with marked success, particularly on a long test by a 40- 
horse-power motor truck. After the trip, the cost, using naphthalene, 
figured out to 0.6 of a cent per horse-power hour, while a similar 
truck, running side by side with this one, on gasoline cost 2.6 cents 

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per horse-power hour. In its first trial then, this fuel showed four 
times the economy of gasoline. 

Solid Gasoline. A number of attempts have been made to 
produce gasoline in a solidified form so that it could be handled 
more easily and much more safely. In Europe, this has been 
accomplished satisfactorily, the resulting substance being of about 
the consistence of jelly. In general its properties are about the 
same as liquid gasoline, except that it occupies less space, a gallon 
when solidified taking up about 185 cubic inches as compared 
with 231 before. The principal argument against its use is the size 
of the vaporizing device needed to change it to a gas and add air. 

War-Time Fuel Developments. It took the War and its tre- 
mendous demands for fuel for thousands of war trucks, cars, air- 
planes, motor patrol boats, airships, tanks, and other automotive 
units to show the public how scant was the margin between the 
actual production of crude oil and the motor fuel produced from 
this and the actual consumption. Patriotic efforts and the high 
price of all oil products brought about greatly increased produc- 
tion in 1918; the total crude petroleum produced in the United 
States in that year reached 345,896,000 barrels, the average monthly 
production having been increased from about 25,000,000 barrels 
to almost 30,000,000 barrels. At the same time the Mexican oil 
field outputs, imported mainly into this country, were increased 
very materially. From the domestic total about 2,250,000,000 gal- 
lons of motor fuel were produced, this being slightly over 15 per 
cent of the total world supply. 

Against this fuel production there are now in use more than 
7,700,000 automobiles, while the year 1920 will add 2,700,000 
pleasure cars and trucks. At the end of 1920, it is authoritatively 
asserted there will be more than 10,000,000 automotive units in 
service, exclusive of aeroplanes and allowing 400,000 to go out of 
use for various reasons. Each unit consumes approximately 400 
gallons of fuel per year, which makes a total of 4,000,000,000 
gallons a year. With these figures in view, it will be necessary to 
develop the gas motor to a higher point of efficiency so as to utilize 
the available fuel to the best advantage. 

During the War many special fuels were developed to meet 
the demands, and some of these must be used, or modifications of 


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them, in peace times, as the above figures indicate. Among the 
methods presented for increasing the fuel supply are the following: 
more efficient distillation methods to stop refining losses; raising 
the end point in distilling to make more but uniformly heavier 
fuel; recovery of gasoline now lost in refinery operations; and 
wider use of "cracking" processes. With the use of the first 
three methods an increase of 30 per cent in fuels suitable for 
automotive units is predicted, and by adding the fourth an addi- 
tional 100 per cent. 

There are the further possibilities of a huge production of 
alcohol by breweries, which are preeminently fitted for this work, 
of a big production of benzol from by-product coke ovens, and of 
the addition of large quantities of fuel from the shale beds of 
Colorado and Utah, from extensions of the natural-gas condensa- 
tion processes, and from other sources. The idea is to mix all 
these to make a single fairly uniform fuel, which will not be gaso- 
line, but will be heavier than the present gasoline and will contain 
practically all the elements of the present kerosene and benzol, 
most of the elements of alcohol, and all the other fuels. 

The so-called Liberty fuel was developed in this way by mix- 
ing, and it was found that it consists of approximately 65 per 
cent benzol, 25 to 30 per cent kerosene, and the balance amy! 
acetate, naphthalene, alcohol, other volatile liquids not yet deter- 
mined, and dissolved solids. This fuel has a B.T.U. content of 
18,590 per pound and a heating value of 131,200 B.T.U. 's per 
U. S. gallon. Its specific gravity is 0.848 at 60° F. and its Baum6 
is 35.0 degrees, a gallon weighing 7.07 pounds. Equal power out- 
put and fuel consumption only 3 per cent greater than commercial 
gasoline were shown in actual tests of various engines for car, air- 
plane, and truck uses. In a few instances greater power was 

Subsequently, it was found that this fuel produces gumming 
to an almost impossible extent, the tendency being to gum up 
carburetors, spark plugs, cylinder heads, and other parts. It was 
discovered further that it crystallizes at 18° F. and solidifies com- 
pletely at 15° F., so that it would be impossible to use it at any 
low temperature. Thus, despite its apparent value and desirable 
qualities, it is not suitable for wide use. Moreover, its high 


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benzol content makes the possible output of Liberty fuel small as 
the total benzol now produced in the United States is only 3,500 
barrels a day; this means that this country could produce a maxi- 
mum of only 82,000,000 to 83,000,000 gallons a year of Liberty 
fuel, too small an amount to warrant the risks of gumming, freez- 
ing, and possible bad odor. 

The fuel problem is thus very little nearer solution, although 
some progress was made during the War. In spite of its serious 
defects, the performance of Liberty fuel showed that there is the 
possibility of developing a substitute for gasoline, it being in 
many ways the equal of commercial gasoline and yet containing 
no gasoline whatever, but only the heavier kerosene and liauids or 
substances not produced from crude petroleum. 

In England 32,000,000 gallons of benzol were produced in 
1918, 11,000,000 gallons by gas companies and 21,000,000 gallons 
from coking ovens. This was 16 per cent of a total of 200,000,000 
gallons of motor spirit consumed in Great Britain. It is now 
pointed out that by diminishing slightly the legal calorific value of 
gas, the gas companies could increase their output to 40,000,000 
gallons of benzol a year, making the grand total 61,000,000 gal- 
lons. Attention is also called to the fact that many London busses 
are running regularly and successfully on a mixture of 25 per cent 
benzol and 75 per cent duty-free domestic alcohol. On this basis 
the benzol produced in 1918 would make (with the suitable 
alcohol addition) half the country's total motor spirit, without 
using any gasoline or kerosene whatever. 

Future Fuel a Mixture. These items indicate that the motor 
fuel of the near future will be a mixture and not & single separate 
liquid, as gasoline, kerosene, benzol, or alcohol. Moreover, this 
mixture will have qualities the present fuel does not, and its 
universal use will modifiy engine design in general and carburetor 
design in particular. 

Qas and Qas Generators. Scarcity of fuel and unusually high 
prices in the last two years have brought out the use of gas in 
various forms. An English truck (and motor bus), which has 
been very successful, uses ordinary gas from the city's mains, 
compressed into tanks and diluted with air as carbureted and used. 
A car has been developed to use a very high grade gas produced 


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from peat. American workers have brought out a device which 
will handle water, gas, and other forms having high fuel value and 
which can be compressed readily. In outward appearance, these 
cars do not differ from any other, the carburetor or gasifier and 
the extra tank, which is larger than an ordinary gasoline tank, 
being the only differences. This use of gas opens up wide pos- 
sibilities for the future. 


Explosibility. There is no one process in the cycle of opera- 
tions in an internal combustion motor which has more influence on 
its reliability than the proper mixing of the gasoline vapor with 
the air and its introduction into the cylinder. If a combustible 
vapor be mixed with air in certain proportions, the result is an 
explosive mixture. When a portion of the mixture is ignited — say, 
by a spark from the ignition system — the combustion travels to 
the surrounding mixture at a rate depending upon (1) the chemical 
affinity of the gas or vapor for oxygen; (2) the heat of combustion 
of the gas or vapor; (3) the proportion of atmospheric oxygen 
present in the mixture; and (4) the pressure. Now when a sub- 
stance, like gasoline vapor, enters into union with oxygen, it does 
so in certain definite proportions. Therefore, when the mixture 
contains an insufficient supply of air (a rich mixture, as it is called) 
there will be a quantity of unburned gas or vapor left over. On 
the other hand, if there is present any excess of air over the 
amount required for the reaction (a lean mixture), this excess in 
turn will be left over. The highest pressures and temperatures 
result from the explosion of those mixtures which contain just 
sufficient oxygen to support the combustion of the explosive vapor 
contained in the charge. According to Clerk, the highest velocity 
of flame propagation occurs when the vapor is a trifle in excess of 
that contained in the ideal mixture. 

The proper proportions of gas and air depend on the nature 
of the gas and differ in every case. The range between the mini- 
mum and maximum proportions by volume required is termed the 
explosive range of that gas or vapor. 

Any variation in the composition of the mixture either way 
from the theoretical ratio results in decreasing the maximum pres- 

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sures and temperatures of combustion and in making the explosion 
occur more and more slowly until finally we have a slow combustion, 
i.e., the mixture ceases to be explosive. It has been found that 
approximately 15 pounds of air are required per pound of gasoline 
for the true explosion mixture. 

In actual practice, to make sure that complete combustion 
results, an excess of air is usually employed, the latter being beneficial 
also in that the maximum temperatures are reduced, which reduce 
the per cent of heat lost to the cooling water. This excess also 
reduces the danger of pre-ignition. The theoretical ratio of the 
number of volumes of air per unit volume of gasoline vapor for 
the true explosive mixture is between 25 and 30, while the explosive 
range of the mixture extends below these values to about 19.5 
and above them to a value of about 40.5. 


General Analysis 

Fuel Knock. There are a variety of causes for the many 
different knocks which are continually developing in motors. 
Among these knocks is the one like a sharp clang, often called a 
pre-ignition knock, as it disappears when the spark is retarded. 
But this knock is not an explosion occurring before the piston has 
reached upper dead center, for it has been proved by accurate 
tests that it occurs after the piston has started down. 

The question then arises: How can an explosion which 
occurs after upper dead center cause such a loud "slap" at the 
moment the knock occurs? The answer is: There are a great 
number of small explosions occurring simultaneously when the 
fuel changes its chemical construction. These small explosions 
combine to form violent explosions, hence the result is the fuel 

Gasoline is a very complex chemical compound, its main 
constituents being carbon and hydrogen. Before going farther, 
it is advisable to consider a few principles of chemistry. Water, 
for instance, is a chemical compound; its formula is H 2 0. This 
symbol means that there are two parts of hydrogen to one part 
of oxygen in each particle (or molecule) of water. These parts 


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are called atoms, and therefore two atoms of hydrogen mix with 
one atom of oxygen, forming one molecule of water. Gasoline and 
kerosene are chemical compounds. Neither of them has an exact 
chemical representation, as the component elements occur in 
variable proportions according to the temperature required when 
refining takes place. 

Fig. 92a. Card Showing the Kerosene Fuel Knock 

Fig. 92b. Card Showing the Ether Fuel Knock 

The formula C 6 Hi 4 represents a good grade of gasoline. As 
gasoline is a blended mixture of various grades of refined hydro- 
carbons, its representation will vary between the limits of C5H12 
and C 8 His. It should now be easily seen that gasoline is made 
up of fractional distillates. When a spark occurs, there is a certain 
lapse of time between the moment of ignition and complete com- 


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bustion or burning of the fuel. The fuel which is most volatile will 
be ignited first and burn much quicker than the fuels having a 
heavier gravity. The less volatile fuels will be consumed in an 
order determined by their gravity, the heaviest fuel burning last. 
Just after the spark occurs, the fuel undergoes a complete chemi- 
cal change. The fuel particles start to slide on one another, so 
breaking up their structure that the atoms — which had previously 
formed molecules — now represent something else. This action 
is similar to the bursting of a flywheel, where the force causes a 
few molecules to give way and allow the wheel to separate into 
several pieces, but the molecules in these pieces are unchanged. 
In the case of the fuel, the millions of molecules, sliding around 
on each other, cause a serious detonation or piston "slap"; this 
develops the fuel knock. The first detonation occurs when the 
heat and the pressure are sufficient to cause the fraction of the 
fuel with the highest flash point to catch fire. The burning of 
this distillate raises the temperature and pressure to a point where 
the distillate of the next highest gravity will ignite. In like 
npiethod, the burning of all* the different fuels is accomplished. 

A great number of these free atoms combine to form com- 
pounds of hydrogen and carbon, as atoms having unlike polarity 
have a mutual attraction. A few hydrogen atoms become scattered 
through the mixture, and as hydrogen burns very rapidly, a series 
of small explosions occur at various points in the combustion 
chamber. When these explosions combine into one explosion, a 
fuel knock is produced. As the hydrogen is free, it burns very 
rapidly and the flame darts from one atom to another with great 
rapidity. There are perhaps several million of these atoms catch- 
ing fire at the same instant, the atoms belonging to the most 
volatile fractional distillates igniting first. A few of the remaining 
atoms then unite with the next lowest fractional distillate and 
cause a second detonation, and so on until the entire explosive 
mixture is consumed. 

This knock may be reduced or completely eliminated by 
lowering the compression, but to do this is not advisable, as it 
will also decrease the power and efficiency of the motor. If the 
compression is decreased, the temperature of the explosion will 
also be decreased, but this temperature will not be hot enough to 

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start the series of auxiliary hydrocarbon explosions. If a com- 
pound is added which will combine with the left-over hydrogen 
atom, a fuel of uniform burning rate will be formed, thus elimi- 
nating the knock/ If 1.5 per cent of iodine, by weight, is added, 
the necessary element will be furnished which will combine with 
the free hydrogen. 

Many engines built prior to 1913 and operated on the present 
fuel are susceptible to this fuel knock. The compression pressure 
of these motors is fairly high, ranging between 75 and 90 pounds, 
which, in some cases, is 20 pounds greater than that used in the 
modern motor. A fuel knock will vary to a great extent as the 
result of slight changes, for instance, changes in the spark-plug 
location, the valve sizes, the manifold arrangement, the shape of 
the combustion chamber, and the carburetion. 


The unit of mechanical power, the horse-power, is equivalent to 
the performance of 33,000 foot-pounds of work per minute. In a 
four-cycle motor, as an explosion occurs every two revolutions, 
there are twice as many revolutions as explosions or cycles per 
minute. To calculate the horse-power of such a motor, therefore, the 
number of foot-pounds of work done at each explosion (call it W) 
must be multiplied by the number of explosions or by one-half 

the number of revolutions per minute ( ' J, and this product 

divided by 33,000. The result will be the horse-power (h. p.) of 
the motor. Expressing this in equation form it becomes 

, fFXr.p.m. 

h.p. = 

F 2X33,000 

Indicated Horse-Power. ,In actual practice the indicated horse- 
power of an automobile engine means little or nothing. What is 
needed is a simple, easily understood formula by means of which 
anyone can figure out a rating horse-power. This is used for pur- 
poses of comparison, for a basis of automobile taxation, for legal 
purposes, handicapping races, and otherwise. In gasoline engines 
for stationary power purposes, and, at times, in automobile motors, 
the indicated horse-power is desired for figuring. When this is the 

* 123 Digitized by G00gk 


case, it is figured from the indicator card by means of the following 


i.h.p.- 33(K)() 

in which P is mean effective pressure (m.e.p.) in pounds per square 
inch; L, length of stroke in feet; A, piston area in square inches; 
N, number of cycles per minute or one-half the number of revolu- 
tions per minute; and K, number of cylinders. 

The mean effective pressure P is obtained from the indicator 
card by going around it with a planimeter* in the way in which it 
was traced, that is, in order 1-2-3-11-5-1 , Fig. 93. The indicator 
card consists really of two areas or loops, of which 3-4-5 represents 
positive work, and 1-2 negative work. The total work done on the 
piston is represented by the difference between these two areas. The 
small area 1-2 represents the work done in overcoming the friction 
resistance of the gas when being admitted to and expelled from the 
cylinder. It is work that has to be done by the motor; is a definite 
loss of power; and should be made as small as possible. The area 
3-4-5 is the work that is actually done on the piston, less the work 
required to compress the gas; it is the true work of the cycle, all of 
which would be available for driving the engine, were it not for the 
gas-friction resistances represented by the area 1-2. See also the 
negative loop, Fig. 72. If a planimeter is made to trace the diagram 
in the order in which it was drawn, it will go around the area 1-2 
and 3-4-5 in opposite directions; that is, if it goes around one clock- 
wise, it will go around the other counter-clockwise. The consequence 
is that the readings of the planimeter will give the desired difference 
in square inches between the two areas 3-4-5 and 1-2. The mean 
effective pressure is then obtained in the usual manner by dividing 
this area by the length of the diagram and multiplying by the "scale" 
or constant of the indicator spring. 

Mechanical Efficiency. The figures just given refer to the 
indicated horse-power (i.h.p.), which is the work done upon the 
piston by the charge. The object of the motor, however, is to drive 
some other machine or apparatus. It is, therefore, important to rec- 

* A planimeter is an instrument which indicates the area of an irregular figure by tracing 
the boundary of the figure. The area of the indicator card may be approximated by dividing it 
into a series of rectangles and taking the sum of the areas. 


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ognize the distinction between the indicated work done in the 
cylinder and that quantity of work, always smaller, which the 
motor does against external re- 





Fig. 93. Indicator Card from Otto 
Cycle Motor 

sistance. This work against 
external resistance is termed the 
brake horse-power (b.h.p.), or de- 
livered horse-power (d. h. p.) . The 
term brake horse-power is usually 
applied to the power absorbed by 
a friction brake attached to the 
rim of the flywheel or to the shaft. 

Prony Brake. The most commonly applied form of friction 
brake is that one known as a prony brake, one form of which is shown 
in Fig. 94. This device consists of a series of wood blocks D con- 
nected by a leather or iron strap and arranged so as to rub on the 
surface of the flywheel of the engine to be tested. The two arms of 
the brake rest on a pair of scales. The hand wheel, shown at E, is for 
varying the amount of friction. The horizontal distance R from the 
center of the wheel to the end of the arms is known as the brake arm. 

In using the brake, the load is applied by turning the screw E 
and is measured by the reading on the scale. Before the load is 
applied, and the brake arms are resting on the scale, as shown in the 
figure, the scale must be read to determine the amount required to 
balance the overhanging brake arms. This amount must be deducted 

Fig. 94. Prony Brake for Testing Motor Efficiency 

from the reading of the scales when the load is applied, in order to 
give the net load. This may be done in either one of two ways: 


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The scales can be turned back and readjusted so as to record nothing 
when the break arm is resting on the scales; or, without correcting 
the scales, the deduction can be made when the final power is figured 
out, that is, the weight which the brake arm alone depresses on the 
scale beam must be subtracted from the total scale reading to give 
the net load on the scale. 

The b.h.p. is calculated by the formula 
, . 2iranW 

bjLp '-%o6o 

in which n is revolutions per minute; a, length of brake arm in feet; 
W, the net load on the scales; and w, 3.1416. 
The formula then assumes the form 

, , anW 

bhp - = 5252 

and with any given brake, the length a will be a fixed quantity, so that 
that also can be inserted. Suppose it happens to be 4 feet. Then 
the formula becomes 

u nW 

b.h.p. = — 

All the repairman needs to construct a brake of this kind is 
the scales, a good hardwood beam of about 3x5 inches in section, a 
band of strap iron, a few wooden blocks to fasten to it, and a thumb 
nut with which to tighten it. For general use, it is best to have a 
special shop flywheel and make the band to fit this. Then when an 
engine is to be tested, the flywheel can be removed and the shop wheel 
bolted on in its place. Otherwise, there would be a lot of bother with 
the difference in the sizes and shapes of various engine flywheels, 
and the consequent difficulties of making the brake fit. 

The brake horse-power is less than the indicated horse-power 
by an amount which represents the loss due to friction of one kind 
and another in the mechanism of the motor itself. 

The ratio of the b.h.p. to the i.h.p. is the mechanical efficiency of 
the motor, that is, 

mechanical efficiency = ' 


Good motors have a mechanical efficiency of from 80 to 95 per cent, 
referring to modern automobile motors. Other motors, as stationary 

126 Digitized by G00gle 


gasoline or gas engines, have a lower figure, say from 70 to 80 or, 
possibly, 82. 

Estimating Motor Horse-Power. An inspection of the i.h.p. 
formula above given will show that if we are able to presuppose 
some certain mean effective pressure (m.e.p.), we have the most 
practical way of estimating the horse-power of any explosion motor 
whose length of stroke, piston area, and revolutions per minute are 

The mean effective pressure secured in gasoline engine prac- 
tice ranges from a minimum of 45 or 50 pounds to the square inch, to 
a maximum of about 125 pounds to the square inch. For the above 
purpose, 60 pounds may be assumed as very close to the m.e.p. 
of most automobile motors, though in sleeve valve and other types 
in which the combustion chamber is approximately spherical, the 
mean effective pressure will often be as high as 85 pounds. In any 
case, for a given type of motor there is never any considerable varia- 
tion from a certain mean effective pressure that is characteristic of 
its type. This pressure being known, it becomes a matter of simple 
arithmetic to calculate the power from a given stroke, cylinder 
diameter, or piston area, at a given number of revolutions per 
minute, i.e., by a direct substitution in the formula for i.h.p. 
given on page 114. 

For two-cycle motors the compression is usually lower than in 
the four-cycle type, and it is safe to assume that the m.e.p. is not 
over 70 to 75 pounds. In applying the formula for the i.h.p. to the 
two-cycle motor, N becomes the number of revolutions per minute, 
since there is an explosion in each revolution. 

Electric Dynamometer. The electric absorption type of 
dynamometer is a testing device, operating on the same principle 
as the Prony brake. It is, however, more accurate, more complete, 
easier to use and, in other ways, has a distinct advantage over the 
older form of hand-applied brake, which is now nearly obsolete, as 
well as over other forms of absorption brake, such as the coil of rope 
form, the water brake, the centrifugal pump, the air fan, and others. 
The electric type is practically a measuring dynamo, which is driven 
by the engine being tested and, when so driven a magnetic action 
is set up between its field pieces and armature, which can be meas- 
ured precisely in electrical units. When this is done, the quantity, 

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in foot-pounds of energy exerted through a given radius, is an exact 
measure of the torque or turning power of the engine. 

The radius, like that of the brake arm of the hand-operated 
form, may be of any desired length, but if l&ff inches is used, this 
simplifies the usual Prony brake formula to 

, , _ weight in pounds Xr.p.m. 
' P ~~ 4,000 

in which the weight is measured by means of a pair of scales, usually 
of the double-beam type, with a fine reading to pounds and tenths 
on one beam and a rougher reading for quick but approximate 
determinations on the other. The revolutions, will be indicated by 

Fig. 95. Electric Dynamometer for Testing High-Speed Automobile Engines 
Courtesy of Sprague Electric Works, New York City 

means of an electric speedometer, supplemented usually by a form 
of tachometer to be used as a check. With but two variable quan- 
tities, the weight and speed, it is possible to lay down the curves 
for every possible combination of speed and weight, so that the 
power can be read at a glance by simply following out the two lines 
to their point of intersection. 


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With this form of device, it is possible to have the electric load- 
ing arranged in such a manner that it resembles the well-known 
rheostat used on trolley cars, and like it is turned on by means of a 
rotating handle or wheel. In that case, the tester simply sits at a 
table making his readings and gradually turning the wheel to 
increase or decrease the load. 

Auxiliary Apparatus. When using electrical testing apparatus 
of this kind, it is possible to have many additional auxiliary features 
of value. For instance, by turning on the electric current, the 
dynamo acts as a starting motor to turn the engine over, until it 
starts. In case the test is to be a long-drawn one, the electrical 
energy generated need not be wasted as with other forms of brakes, 
but can be wired to electric motors elsewhere in the plant and 
utilized, this disposition of it having no influence whatever upon 
the measurement of the energy. In addition, automatic or self- 
registering instruments may be had, so that an operator is not 
needed, after the test has been started, except to stop it. Further, 
an automatic gasoline-measuring scale may be had, which is elec- 
trically operated, this being constructed to register the number of 
revolutions and the elapsed time for each pound of fuel consumed. 

Fig. 95 shows the complete dynamometer with scales and 
measuring devices, as made by the Sprague Company, while Fig. 96 
shows the complete layout of a similar outfit as made by the Diejil 
Manufacturing Company, this indicating the actual test of a six- 
cylinder motor. 

In Fig. 97 is shown a modern testing room with a number of 8-V 
motors mounted for testing. This view shows the importance at- 
tached to preliminary testing of motors by big manufacturers. 

Importance of Testing to Repair Man. It is particularly impor- 
tant that the repair man be well equipped in the matter of testing 
apparatus. In fact, every well-equipped garage should have some 
form of horsepower testing outfit, either one of those just described 
or else some similar homemade affair. What is needed by the 
repair man, however, is not so much a measuring apparatus as a 
loading device, whereby loads may be thrown upon engines which 
have hidden troubles, or which have just been repaired, so as to 
allow the motor to act as it would when actually pulling the car 
with a standard load. 

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An advantage of a loading device of this kind is that troubles 
which are otherwise hard to find can be discovered in a short time 
inside the shop instead of after long, extended, and expensive outside 
runs to determine the exact part which is at fault. With a loading 
device, a stethoscope (such as is described elsewhere in this work), 
and a full set of electrical testing instruments, a garage or repair 
man, who is onto his job, can in a short time locate the trouble with 
any engine, transmission, or any other part of a complete car. With 
the trouble located, the difficulty is half overcome. 

Fig. 96. Electric Dynamometer Coupled up to Six-Cylinder Engine for Test 
Courtesy of Diehl Manufacturing Company, Elizabeth, New Jersey 

The repair man can buy at a reasonable figure testing outfits 
which are designed solely for the purpose of finding out electrical 
sources of troubles (and many others) in the shortest possible time. 
These are called trouble-finding or trouble-shooting outfits, and a 
number of them are now marketed. 

Lacking a stethoscope to use with a testing or loading outfit, 
many garage men make use of a substitute in^the form of a plain 
steel rod of small diameter. By holding one end of this rod between 
the teeth with the other end placed on or near the suspected engine 
part, one can train the ear to recognize, by means of the vibrations 


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a I 





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which come to it through the rod and teeth, whether or not the part 
is running exactly right. In many cases, such a testing or loading 
outfit is a good preventive of trouble, enabling the owner to locate 
the trouble and correct it before it can get serious enough to cause 
excessive difficulty or expense. The adage "A stitch in time saves 
nine" applies equally well to an automobile and many owners 
would have much less trouble if they or their chauffeurs understood 
this better. 

Rating. At one time practically all automobile engines were 
given a hyphenated rating, as for instance, 30-60 horsepower. -This 
represented the power developed at a normal speed and the maximum 
output of which it was capable. In general, the difference was not 
as great as in the example given, although this represents an actual 
rating of a well-known American car motor. As has been stated, 
rating allows of a comparison when the same basis is used by every- 
one; that is all it is for. Now, ratings are worked out from various 
formulas. The one used throughout the United States is that known 
as the S.A.E. formula, after the Society of Automotive Engineers, 
sponsors for it. This was formerly called the A.L.A.M. formula 
because the now-defunct Association of Licensed Automobile Man- 
ufacturers placed their seal of approval upon it, and brought it into 
general use in this country. It originated in England, where it is 
still in universal use as the R.A.C. formula. It is as follows: 

in which D is the diameter of the cylinder bore in inches and N is 
the number of cylinders. As N is usually 4, 6, or 8, it is possible to 
simplify the formula to: 

h.p. = 1.6Z) 2 (for four cylinders) 
h.p. = 2.4Z) 2 (for six cylinders) 
h.p. = 3.2Z) 2 (for eight cylinders) 

While no account of the stroke appears to have been taken in figuring 
this out, yet in the original determination of the value of the con- 
stant 2.5 used, 1,000 feet per minute was considered as a fair 
average piston speed. As the length of the stroke determines the 
piston speed, it is apparent that consideration was given to the 


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length of the stroke, and that this factor is in the formula. How- 
ever, for the benefit of those desiring the length of the stroke L incor- 
porated, the following formulas have been developed and are in use: 
Roberts' formula, 

D 2 LNR 

h - p ' = -i80oT 

Dendy-Marshall formula, 


substituting the number of cylinders, this becomes 

h.p. = .33 D 2 S (for four cylinders) 
h.p. = .5 D 2 S (for six cylinders) 
h.p. = .66 D 2 S (for eight cylinders) 

White and Poppe formula, 




in which, however, the diameter D and the stroke S are in centi- 
meters. Substituting the number of cylinders as before, this becomes 

h.p. = .25 DS (for four cylinders) 
h.p. = .38 DS (for six cylinders) 
h.p. = .5 DS (for eight cylinders) 

Racing Boat Formulas. The following formulas are for high- 
speed racing boat engines of four-cycle type, and are based on 1,000 
feet per minute piston speed. For engines of ordinary design, two- 
thirds of the above values should be taken; 10 per cent should be 
added to the ratings if the charge is forced into the cylinders by any 
mechanical device. 
American Power Boat Association, 

D 2 N 
h ' P ' = 2^338 

For motors of less than 6-inch stroke, 

D 2 LN 


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Two-Cycle Formula. The following are two-cycle engine for- 
mulas, the first being by Roberts for racing-boat engines and the next 
two by the American Power Boat Association: 

D 2 LRN 



D 2 N 


D 2 LN 


The above formulas by the American Power Boat Association 
are only for racing-boat engines. For ordinary two-cycle-boat 
engines two thirds of the value resulting from the use of these for- 
mulas should be taken. For engines having one or more displacer 
cylinders, the above rating should be increased in the ratio that the 
displacer pistons' displacement bears to that of the working cylinders. 

Comparison of Power of Two- and Four-Cycle Motors. It wilUbe 
noticed that in a two-cycle engine having double the number of power 
strokes of a four-cycle, the h.p. would be multiplied by 2. This, 
however, would give an erroneous result, as there are many inherent 
conditions connected with two-cycle engine design which tend to 
lower its horse-power output, such as the lower compression, lower 
m.e.p., due to inefficient scavenging, etc. For these reasons the 
output varies more in two-cycle engines than in four-cycle engines, 
and is very often taken as approximately 1.35 of that of a four- 
cycle engine of the same bore and stroke. There are, of course, 
exceptional cases where two-cycle engines have shown considerably 
better than this value, but it is considered an average result. 

Other Testing Work. There is considerably more to testing 
than the simple use of a form of dynamometer or prony brake. After 
bearings have been rescraped and set up, after new pistons or new 
cylinders, new crank shaft, new cam shaft, or any other important new 
parts have been added, "running in" is fully as important as testing. 
After a car has been worked on and important changes made, as new 
transmission gears, new axle, new driving shaft, new springs, or 
others of equal import, "running in" on the roads is more important 
even than testing. The "running in" process makes certain that 
everything is working right and will continue to work correctly con- 


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tinuously. In the case of important engine changes it smooths out 
any rough spots left in machining. Running in of engines after 
important changes is usually done by driving the engine from an 
overhead line shaft by means of a leather belt. When this is done, a 
heavy oil is used for the lubricating system, much heavier than will 
be used later, this being forced around the system by the power 
drive. On many cars and trucks, the running in process takes more 
time, is given more attention, and costs the manufacturer much more 
than the actual testing. Every good mechanic and repair man 
should run in each engine or car repaired before delivering it, if only 
to assure himself that a good job has been done. The running in and 
testing are in a sense the proof of the work. 


Q. To what is the term explosion motor applied? 

A. The term explosion motor is generally applied to the gaso- 
line engine used as a source of power in automobiles, motor trucks, 
motor cycles, aeroplanes, motorboats, and small gas and gasoline 
engines as well. A recently coined term for this entire field is 
automotive. The explosion motor is frequently called the internal - 
combustion motor. 

Q. Is there anything strange or mysterious about this source 
of power? 

A. No. It works very much the same as a steam engine, except 
that the expansion of ignited gasoline vapor which has been highly 
compressed is used instead of the expansion of steam. 

Q. Describe the efficiency of the internal=combustion motor? 

A. The efficiency of the internal-combustion motor, which is 
a heat engine, is the proportion of useful work obtained to the 
amount of heat put into the motor. 

Q. What is a cycle? 

A. A cycle is a series of events occurring in regular sequence 
between the explosions, or power strokes. 

Q. What is the cycle of an explosion motor? 

A. The cycle of the modern automobile motor consists of 
four strokes: (1) the suction, or intake, stroke; (2) the compression 
stroke; (3) the explosion stroke; (4) the exhaust stroke. 

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A. No. There are two general types of engines, those in which 
the cycle is completed in four strokes and those in which it is completed 
in two. The former are called four-stroke cycle engines, generally 
abbreviated to four-cycle, and the latter two-stroke cycle engines, 
usually spoken of as two-cycle. The former are also quite often 
spoken of as Otto-cycle engines because of the pioneer Otto who 
developed this type. 

Q. Are there other than these two arrangements of the cycle? 

A. Yes. Engines have been built to operate on a six-stroke 
cycle, the two extra strokes being used to draw in cold air and thus 
keep the engine cool, with the primary idea of dispensing with water- 
cooling apparatus. In addition, other cycles have been proposed 
from time to time by inventors. But the two- and four-cycle engines 
are the only successful ones. 

Q. What is the generally accepted type of automobile motor? 

A. Automobile motors are, as a rule, multi-cylinder four-cycle 
vertical forms, designed to run at 800 to 900 r.p.m., or higher, with 
long strokes, magneto ignition, four or more mechanically operated 
valves, using gasoline as fuel, and having speed control by means of 
spark and throttle levers and foot accelerator. The vertical four- 
cylinder and six-cylinder are the most popular forms, although a 
considerable number of eight- and twelve-cylinder V-type or inclined- 
cylinder engines are now being built. Practically all automobile 
engines now have two or more mechanically operated valves per 
cylinder, the latest development being the use of four valves per cylin- 
der. By long stroke is meant a longer stroke than the bore, 
generally longer in the ratio of 1.1 (or higher) to 1. 

Q. What is standard practice in cylinder arrangement? 

A. The two most popular cylinder arrangements are those in 
which the cylinders are cast in pairs, and those in which they are cast 
in a block, or single unit. The latter is gaining way rapidly, its 
simplicity and compactness being big arguments in its favor. 

Q. What is the usual practice in valve arrangements? 

A. With two valves per cylinder, there are three general 
arrangements and one combination form. These are : (1 ) both valves 
on one side; (2) one valve on each side; and (3) both valves in the 
cylinder head. The combination arrangement is one valve on one 
side and one in the head, usually directly over the other. 



Q. Do these valve arrangements change the type of cylinder? 

A. The cylinder form is ordinarily named from the valve 
arrangement or from the shape of the combustion, or explosion, 
chamber which this arrangement brings about. Thus, the type where 
both valves are on one side of the cylinder is called an L-head, because 
the combustion chamber has the shape of an inverted letter L with 
the valves in the projecting arm. When the valves are on opposite 
sides of the cylinder, it is called a T-head cylinder because the com- 
bustion chamber has the shape of a letter T with one valve in each 
branch of the top. When the valves are both in the head, the cylinder 
is called an l-head, or valve-in-the-head. The form in which one 
valve is in the side and one in the head, is called an L-head also 
because the combustion chamber has an L-shape. 

Q. What is the Knight, or sleeve-valve, motor? 

A. A motor similar in appearance to other motors but having, 
instead of the usual poppet valves, a pair of sliding sleeves which have 
openings, or ports, through them. By the operation of these sleeves 
VP and down, the inlet and exhaust ports are opened and closed in a 
manner similar to the ordinary poppet valves. 

Q. How is this action brought about? 

A. The two sleeves are cylindrical, and fit between the cylinder 
and the piston. Both have holes, or ports, on the two sides, corre- 
sponding to the valves on opposite sides of a T-head motor. The 
sleeves are moved up and down by rods attached to eccentrics oper- 
ated by an eccentric shaft. When the movements of the two sleeves 
bring together the inlet ports and bring these into register with the 
port in the cylinder walls on the inlet side, the inlet opening is com- 
pleted and the piston draws in its mixture. Similarly, when the ports 
in the two sleeves and that on the other side of the cylinder register, 
the exhaust opening is completed, and the burned gases are forced out. 
At other times, the ports do not register and the cylinder is practically 
sealed, this being the case on the compression and expansion strokes. 

Q. In what way is this an advantage? 

A. The valve timing always remains the same, never varying 
with time, wear, lack of care, or anything else, which is not true of 
poppet valves. Again, the movement of the sleeves can be such as to 
give a quicker opening and quicker closing; that is, it can produce a 
wide-open port more quickly, and close from a wide-open port to no 


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opening at all more quickly than the poppet form, because the sleeves 
do not move up and down together. They can be made to move in 
opposite directions so that a port is opened or closed with double the 
usual speed. There is no possibility of leakage of gases either by 
time, wear, lack of care, or other factors. All of these things make for 
a larger and a more regular power output throughout the motor's life. 

Q. What is the usual form of motorcycle engine? 

A. Usually the motorcycle is a one-cylinder vertical, or two- 
cylinder V-type air-cooled engine, although a few four-cylinder verti- 
cal air-cooled ones have been built and are still being turned out. All 
these are of the four-cycle form except the Shickel which is two-cycle. 

Q. What is the firing arrangement of explosion motors? 

A. The firing arrangement varies with the number of cylinders 
and in engines of the same number of cylinders, varies with the form of 
the crankshaft, and often varies in similar crankshafts. 

Q. What is the general two=cylinder firing arrangement? 

A. Two-cylinder motors with the cranks set at 180° (that is, the 
horizontal opposed form like the Autocar commercial car) fire one-half 
revolution apart, so that they have two power strokes on one revolu- 
tion and none on the next. 

Q. How does the engine continue to run with an arrangement 
like this? 

A. After the first explosion, the flywheel supplies the power 
necessary to carry the engine over the idle strokes, in fact this is the 
function of the flywheel — to store up energy or rotation on the firing 
or explosion strokes and give this back on the idle, or suction, com- 
pression and exhaust strokes. 

Q. What other two=cylinder firing arrangement is used? 

A. That in which the cranks are set at 360°, or in the same posi- 
tion. In this form, there is an explosion each revolution, but exces- 
sive vibration results from all the parts working in the same direction 
all the time. That is, both pistons go down together, then both go up, 
etc. The evenness of firing is overbalanced by its excessive vibration. 

Q. What is the usual four=cylinder firing arrangement? 

A. As a rule the cranks are at 180° in pairs, cylinders 1 and 4 
being together, and cylinders 2 and 3. This allows of two very 
similar firing arrangements, as 1-3-4-2, or 1-2-4-3. There is little 
choice between them, although the first is more popular. 

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Q. What is the general six=cylinder firing arrangement? 

A. Usually, the cranks are set at 120° apart in pairs, 1 and 6 
acting together, 2 and 5, and 3 and 4. The firing can be any combi- 
nation of these in which the first comes from one group, the second 
from another, the third from a third, then the fourth, fifth, and sixth 
come from the remaining member of each group in the same order. 
Thus, 1-5-3-6-2-4, or 1-5-4-6-2-3, or 1-2-3-6-5-4, or 1-2-4-6-5-3. 

Q. What is the usual eight-cylinder firing arrangement? 

A. The eight-cylinder firing is always the firing that a single 
group of four cylinders on one side would have with that same form of 
crankshaft, and this firing order is applied first to one side and then 
to the other. Thus a typical four-cylinder firing order of 1-3-4-2 
applied to an eight-cylinder, similarly arranged, would be 1R-4L-3R- 
2L-4R-1L-2R-3L. If these are repeated a second time it will be seen 
that the 1-3-4-2 order follows out on both sides, only one starts in 
later, and the two alternate from right to left, thereafter. 

Q. What is the theory of crank effort? 

A. Only one of the four strokes of the motor is a productive one, 
and not all of that, so in the one-cylinder engine 20 per cent of the 
cycle must produce all the power. In the two-cylinder this is in- 
creased to 40 per cent, in the four-cylinder to 80 per cent, and in the 
six-cylinder to 120 per cent. This last indicates the overlap at various 
points, for the cycle like anything else can never have more than 100 
per cent power. In the eight-cylinder it is 160 per cent, and in the 
twelve-cylinder 240 per cent, indicating the relatively greater overlap, 
and consequent smoother running. 

Q. How does the average small two-cycle motor work? 

A. The mixture is admitted to the crankcase, which is built very 
close to the revolving parts, and in this way the downward movement 
of the piston compresses somewhat the charge in the crankcase. At a 
certain point in the downward movement of the piston an opening 
through it registers with a by-pass which leads up into the combustion 
chamber with suction inlet valve. Thus the single downward stroke 
of the piston compresses the charge and fills the cylinder with it. 
This gas really flows in at the end of the combination power and 
exhaust stroke, but as the exhaust port is at the bottom of the 
cylinder, little or none of the incoming gases flow out through 
it. On the return of the piston, the gas is compressed, and at 

139 Digitized by GO0gIe 


the end of that stroke when the piston is ready to descend, is ignited 
and expands. Just before the end of this power stroke, the exhaust 
port is uncovered and, being rather large, the exhaust gases flow out 
very quickly, the entire cylinder being emptied in a very short portion 
of the stroke. Consequently, when the end of the power stroke is 
reached, the exhaust also has been completed. In this way, the entire 
cycle is performed in two strokes of the piston. 

Q. What are the disadvantages of this? 

A. The preliminary compression is not sufficient to force in a 
full charge, nor is the suction strong enough to hold open the suction- 
operated valve and draw in a full charge at the same time. Conse- 
quently, the inlet, or suction stroke, is seldom efficient. Further, 
not all of the exhaust gas is removed, the balance remaining to dilute, 
or offset, fresh gas, thus further lowering the suction or charging 
efficiency. If the exhaust port is so made as to give a good full- 
cylinder charge, some of the incoming gas is likely to sweep over and 
out with the exhaust, thus being wasted. Either arrangement gives 
an inefficient exhaust; for with the one, exhausting is not complete, 
with the other, the power part of the stroke is cut down. The result 
is that instead of giving double the power from a given size of cylinder 
as compared with a four-cycle engine, the relative output is about 
1 J times the four-cycle of equal size. 

Q. How is this form sometimes varied? 

A. By adding an automatic inlet valve to the crankcase and 
eliminating the suction-operated valve in the cylinder head. This 
also shortens and simplifies the by-pass. The exhaust is made to open 
a little earlier than the suction connection to the cylinder, and the 
piston is made with a projecting lip to deflect the incoming fresh gases 
upward while the exhaust gases are flowing downward. This method 
reduces the dilution of the incoming charge and the losses of fresh 
gas flowing out of the exhaust opening, and the engine is made more 
simple and slightly more efficient. 

Q. What general disadvantages render two-cycle engines 
unsuitable for automobile and motor-truck work? 

A. The two-cycle engine will not throttle down, so as to run 
slowly, but must be kept turning at a fairly high rate of speed. This 
is a double disadvantage when the car or truck is standing idle at the 
curb, as it makes a noisy engine and uses much fuel. In addition, the 


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engine will not run at very high speeds, its normal maximum being 
close to or below 1500. This means a small gear reduction to give fair 
speed in the average car, and that in turn raises the lower speeds too 
much, or else complicates the gear box. Further, the two-cycle motor 
does not respond well to sudden changes of speed. 

Q. Is there any work for which these are not disqualifying 

A. Yes. On the motorboat, particularly on the smaller sizes. 
In a motorboat, after starting, the speed is generally continuous and 
even; there are no sudden spurts, no slowing down, no speed changing. 
For this all-day running at constant speeds the two-cycle motor is 
quite suitable. In addition, it is a very low-priced motor to build, 
and as the smaller motorboats must be sold at an extremely low price, 
it is quite suitable. The fact that it has no parts which can be 
changed or adjusted renders it quite suitable to the unmechanical 
class which buys this form of boat. However, even for this kind of 
work, it seems to be going out of favor. 

Q. How is the power of a gas engine measured? 

A. In one of two ways, theoretically on the indicator or mano- 
graph, or actually by means of the dynamometer or Prony brake. 

Q. How do the Midgley and the manograph cards differ? 

A. The Midgley indicator- produces both a pressure-volume 
and a pressur6-time card, while the manograph produces a 
pressure-volume card only. The pressure-time card is of such a 
shape that the length of time required for each change in pressure 
and the time taken for the gas to burn can be readily determined. 
The pressure-volume card indicates the m.e.p. in the same manner 
as the manograph. 

Q. Are there several ways of measuring actual power? 

A. Yes. The dynamometer gives its measure in electrical units, 
which in well-designed apparatus, can be read off directly on the 
electrical instruments. The Prony brake gives a measure of the power 
output in weight on the scales which the engine will support, and by 
figures the power output can be worked out from this. 

Q. What is the mechanical efficiency of an engine? 

A. The proportion of the power which the engine should give, as 
measured by the indicated horsepower, to that which is actually 
given, as measured by the brake horsepower (either Prony or electrical 


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dynamometer). By dividing what the engine gives by what the indi- 
cator card says it should give, a figure is obtained for the mechanical 

Q. What is the usual horsepower formula now in use? 

A. All automobile engines in this country, England, and many 
other foreign countries, are rated by means of the formula which was 
originated by the Royal Automobile Club of England, adopted by the 
Association of Licensed Automobile Manufacturers, then by its suc- 
cessor, the National Automobile Chamber of Commerce, and, finally, 
by the Society of Automobile Engineers. Its form is 

in which D is the bore of the cylinders, N the number of cylinders, and 
2.5 a constant worked out from tests on a number of automobile 
engines. In other words, to find the rating horsepower of a motor, 
square its bore, multiply by the number of cylinders, and divide 
by 2.5. 

The formula can be simplified to the following form: 
h.p. = Z> 2 iVx0.4 
that is, the square of the bore times the number of cylinders 
times 0.4 will give the S.A.E. rating. It must be remembered 
that the result obtained from this formula is the horsepower 
developed at a piston speed of 1,000 feet per minute. Suppose a 
motor has a stroke of 5 inches; the piston would then travel 10 
inches, or {% foot, in one revolution of the crank shaft. In 
order to travel 1,000 feet, it would be necessary to operate at a 
speed found by dividing 1,000 by xf, which is 1200 r.p.m. If 
the motor had a stroke of 6 inches, the piston would then travel 
1 foot in one revolution. The rating would then be at 1,000 r.p.m. 


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Of all the applications of the internal-combustion motor, it is 
safe to say that none is more important than that applied to the 
propulsion of the modern motor vehicle^-the automobile — which 
nowadays throngs the roads and streets of nearly every country in 
the world, and serves a myriad of utilities as they never have been 
and never could be served by animal transportation. 

Standardized, inexpensive to buy, and inexpensive to operate, 
almost unfailingly reliable, and proved capable of use in the hands 
of even the most unmechanical of operators, the automobile is at 
last coming fully into its own. Its design has become recognized as a 
branch of engineering by itself, its manufacture constitutes one of 
the greatest of the mechanical industries, and its use is a common 

Naturally, in so tremendous a development, there is sustained 
by the general public every possible sort of relationship with the 
automobile, from that of the merely casual observer and occasional 
user, to the more interested owner; and thence on, in ever closer 
touch with the full significances of this field of engineering, to the 
high-skilled and well-paid drivers of cars, the experts who repair 
them, the shopmen who build them, and the engineers and draftsmen 
who design them. 

All along this line there is an increasing need for knowledge — a 
demand for definite, specific, usable information concerning the 
science upon which the motor vehicle is based, and the practice upon 
which its construction and performance are founded. 

In no other important field of engineering is there such a lack of 
correct and authoritative literature as in the automobile field. 

This undoubtedly is due to two conditions that have been 
involved in the rapid growth of the automobile from a mere experi- 
ment to an achieved and commercial fact. The first condition is 

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the circumstance that the men who have deeply studied the auto- 
mobile from an engineering standpoint, and who are best informed 
about it, have not had the time to place upon paper the facts with 
which they are acquainted. The second condition — resulting from 
the rapid development of automobile design and engineering practice 
has left no time for the establishment of a formulated science, upon 
which textbooks of a genuine and permanent authority may be based. 

What follows will be an advanced and comprehensive treatment 
of the very latest devices applied in automobile engineering. All 
are carefully described, their essentials fully analyzed, and their 
important details fully illustrated. 

Historical material of any kind is useless in a work of this sort, 
which is intended primarily for the man in the shop, who does the 
actual work of completing the car in the first place, and the man in 
the garage who keeps it in running order thereafter. It will suffice to 
say that while most of the worthy efforts and early progress in the 
development of the explosion motor and the automobile were made 
abroad, American designers and American workmen have since 
shown the way in this field to the whole world, so that today we import 
a negligible number of motors and cars, while we export to every other 
country of the world. 


In general, all motor cars follow along the same broad lines. So 
much has this become the case in the last few years that a large 
number of the parts, units, and accessories entering into the con- 
struction of the car have become standardized and may, to a certain 
extent, be taken off one car and placed on another without exten- 
sive alteration. This has been done, too, without interfering in any 
way with the initiative of the various designers. 

Groups and Parts. Practically all modern gasoline motor cars 
may be divided, in a mechanical sense, into six groups of parts or 
units. These are: (1) the engine, or power-producing group; 
(2) the clutch group, needed, as will be explained later on, with all 
forms of explosion motor; (3) the transmission, or gearset, for pro- 
ducing the various car speeds and different powers, while the engine 
gives a practically constant speed and power output; (4) the final 
drive group, which connects the speed variator or transmission with 


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the rear wheels, and thus propels the car. Of necessity, this includes 
the rear axle, while the front axle is usually grouped with the rear; 

(5) the steering device, for controlling the direction of motion; and 

(6) the frame, upon which all these and their various accessories 
are hung, with the springs for suspending the frame upon the axles 
of the car. There is, of course, a seventh group, the body, but that 
need not be discussed here, since reference is now made only to the 
mechanical parts. 

Chassis Assembly. In the large diagram of a modern motor 
car, Fig. 1, the relative positions of the various units are clearly 
shown. In this, note that the engine is placed at the front of the 
outfit. This is now the position all the modern motor-car manu- 
facturers use. The engine is to generate the power by drawing in, 
compressing, and exploding gas from gasoline. 

Cylinder and Crankshaft Sub-Group. All this work is actually 
done within the cylinder, which really forms the basic working medium 
of the engine. The actual drawing-in of the gas, its compression and 
explosion are accomplished by the movements of the piston up and 
down in the cylinder bore. The piston is moved upward and down- 
ward by the rotation of the crankshaft except when the explosion 
reverses the situation, and the piston moves the crankshaft, to which 
it is attached by means of the connecting rod. The piston is made to 
fit tightly in the cylinder by means of* piston rings, which are com- 
pressed into slots formed in the outside of the piston for this purpose. 
The connecting rod is forced to rotate by its attachment at the lower 
end to one of the crankpins of the crankshaft, which is held in the 
crankshaft bearings fastened in the crankcase. It is enabled to turn 
slightly at the upper, or piston, end by being pivoted on the piston 
pin or wrist pin. For convenience the crankcase is usually made in 
two parts, called the upper and lower halves. The cylinders are 
usually made with a removable cylinder head or a smaller remov- 
able cylinder cover. 

Carburetion Sub-Group. The production of the gas necessi- 
tates what is called a carburetor, a good-sized fuel tank, and piping 
to connect the two. The fuel is not always pure and must be 
filtered through a strainer. There is a cock in the piping for turn- 
ing gasoline from the tank to the carburetor on and off, while 
the gas produced is taken into the engine through an inlet 




Fig. 1. Plan View of the 1920 Marmon Chassis 

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manifold. These and other parts, the functions and construction 
of which will be explained in full later on, constitute the carburetion 

Inlet and Exhaust Valves. In order to get the gas, which is 
produced by the carburetion group, into the motor cylinders at the 
proper time and in the proper quantity, inlet valves are necessary. 
These valves are operated by cams on a camshaft. The camshaft, 
which will be explained in detail later, is driven from the crankshaft 
of the engine. After the gas has been admitted into the cylinders, 
compressed, and exploded, it is of no further use and must be removed 
from the cylinders. As this must be done at the proper time, and as 
the proper quantity must be removed, additional valves known as the 
exhaust valves are necessary. These are also operated by cams on a 
camshaft, driven from the crankshaft. 

Exhaust System. The exhaust gases pass from the cylinder 
through a particular pipe, known as the exhaust manifold, and thence 
to the back of the car. As there remains considerable pressure in 
these gases when allowed to escape freely, they make much noise 
and considerable smoke, so that all cars are required by law to carry 
and use a muffler. The exhaust gases pass through this and thence 
out into the atmosphere. This whole group of parts is called the 
exhaust system. 

Ignition System. The explosion comes in an intermediate stage. 
It is produced by means of an electric spark, made within the cylinders 
by means of a spark plug. The electric current, which is the original 
source of this spark, may be produced by a rotary current producer, 
known as a magneto, or it may be taken from a battery. In either case, 
the current must be brought up to a proper strength, and the various 
sparks must be produced at the exact time they are needed. All this 
calls for auxiliary apparatus. Moreover, the current producer, if it 
be a magneto, must be driven from some rotating shaft, and there 
must be a suitable place provided on the engine to attach it in such a 
way as to provide for quick and easy removal. All this, as a complete 
unit, is called the ignition system. A complete treatment of this 
subject will be found under "Electric Equipment for Gasoline Cars". 

Cooling System. A great amount of heat is created by the fol- 
lowing explosion and subsequent expanding and exhausting of the 
gas. Some idea of this may be gained from the two following state- 

149 Digitized by G00gle 


ments: The explosion temperature often runs up as high as 3000° F., 
and the exhaust temperature frequently is as high as 1500° F. In 
order to take away this heat, which communicates itself to the walls 
and to parts of the engine wherever it comes in contact with them, 
and, by conduction, to other parts with which it does not contact, 
the parts which are exposed to the greatest heat are surrounded by 
hollow passages, called jackets, through which water is forced, or 
allowed to flow. This might be called a collector of the heat, for it 
is then conducted to the radiator, a device for cooling the water. 
It is there cooled off and then used again. In order to circulate 
the water, a removable pump, driven from some rotating shaft, is used. 
All this, with the necessary piping to connect the various parts, is 
called the cooling system. 

On some cars, notably the Franklin, and on motorcycles, there 
is another type of engine with an air-cooled system. This type will be 
taken up later. 

Lubrication System. To make the various parts rotate within 
one another, bearings, or parts specially designed to facilitate easy 
and efficient rotation, must be used. In and on all such bearings 
a form of lubricant is necessary, also between all sliding parts. 
In order to have a copious supply of oil at certain points, various 
forms of lubricators or oil pumps are needed to circulate it; pipes must 
be provided to carry it; a sight feed, or visible indication that the 
system is working, must be placed in sight of the driver (usually on 
the dashboard) ; an oil tank for carrying the supply must be provided; 
and a location found for the lubricator or pump, as well as means for 
driving, removing, adjusting, and cleaning it. All this comes under 
the head of the lubrication system. This system covers, in addition, 
isolated points requiring lubrication and the different ways used to 
supply them. 

Starting System. In order to start the engine, a starting handle 
is provided on all older cars, with possibly a primer working on the 
carburetor, and other parts. On modern cars, this work of starting 
is done by electricity, which requires a starting motor, a battery, a 
switch for connecting the two, wiring, buttons, and other parts. 
All this combined is called the starting system. For a complete 
treatment of Starting and Lighting Systems see the article er 
"Electrical Equipment/' 

150 Digitized by G00gk 


Lighting System. Nearly all modern motor cars have an electric 
lighting system. This includes an electric-current generator; a battery 
to retain the electric current until needed; suitable governing devices 
to control the generation and flow of current; lamps to use the current; 
wiring to connect them with the source; switches to turn the current on 
and off; and other parts. 

Flywheel. At one end of the engine shaft is the flywheel. This 
is a large, wide-faced member of metal, comparatively heavy, the 
function of which is to store energy (by means of rotation) as the 
engine produces it and to give it back to the engine at other parts 
of the cycle when energy is needed, and none is being produced. In 
short, it is a storehouse of energy, absorbing the same from the engine 
and giving back the excess when it is needed. In general, this effect 
is greatest when the mass of metal is farthest from the center, con- 
sequently flywheels are made of as large a diameter as is possible, 
considering the frame members. Note this in the illustration, Fig. 1. 

Clutch Group, l^he clutch is generally located inside the rim of 
the flywheel. This is a device, by means of which a positive connec- 
tion can be made with the engine or a disconnection from it effected 
at the driver's will. When such disconnection is made with the engine 
running, it will continue to run idly, and the car will come to a stand- 
still. Conversely, when the positive connection is made, the motor 
will drive the clutch and such parts beyond it as are connected-up 
at the time. This arrangement is necessary because of a peculiarity 
in the gas or gasoline engine which cannot start with a load, but must 
be started and allowed to get up speed before any load is thrown upon 
it. The function of the clutch, then, is to disconnect the balance of 
the driving system from the engine, so that it may attain the necessary 
speed to carry a load. When this has been done, the proper gear is 
engaged, the clutch is thrown in, and the engine picks up its load. 

Like other groups, this must have a means of connecting and 
disconnecting, a proper place, proper fastenings, means for adjust- 
ment and removal, means for lubrication, and easy access to its parts. 
All this, collectively, is called the clutch group. 

Transmission Group. As has just been pointed out, the gasoline 
engine cannot start with a load; it must get up speed first. When the 
load is first applied it must be light. This necessitates certain gearing, 
so that, when starting, the power of the engine may be multiplied 


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many times before reaching the wheels and applied to the propulsion 
of the car. Furthermore, it has been found convenient to have a 
series of such reductions or multiplications. These correspond to the 
various speeds of the car, for, obviously, if the power is multiplied by 
means of gearing, it is reduced in speed in the same ratio. This whole 
group of gearing is the transmission or gearset, and the various reduc- 
tions are the low, intermediate, and high speed in a three-speed gear- 
box; and low, second, third, and high in a four-speed gearbox. A 
gearbox is always spoken of by its number of forward speeds, but 
there is in all of them, in addition to the forward speeds, a reverse 
speed for backing the car. 

In the usual form, these gears are moved or shifted into and out 
of mesh with one another, according to the driver's needs. For this 
purpose, shifting gears must be provided within the gearbox, that is, 
the arrangement must be such that the proper gears can be moved 
back and forth, with a shifting lever outside for the driver's use, and 
proper and accurate connections between the two. The gears must 
be mounted on shafts, these in turn on bearings, the bearings must 
be supported in the gear-case, and this must be supported on the frame. 
In addition, there must be suitable provision in the gear-case cover 
for inspection, adjustments, and repairs; all the moving parts must 
be lubricated; all parts must be protected from the dust, dirt, and 
moisture of the road, etc. All this comprises the transmission or 
gearing group, which properly ranks second to the engine group in 

Final Drive Group. Driving Shaft. The connection from the 
transmission to the rear axle in pleasure cars is usually by shaft, 
called the driving shaft. On the majority of motor trucks, however, 
it is by means of the worm drive, which will not be discussed here. 
This shaft is sometimes inclosed in a hollow torque tube, with suitable 
connection at the front end to a frame cross-member, and at the rear 
to the axle housing. Its construction is generally such that it contains 
a bearing for the driving shaft at both front and rear ends. In addi- 
tion, the majority of final drives contain at least one universal 
joint, and many of them contain two. As its name indicates, this 
will work universally, that is at any angle, its particular function 
in the driving shaft of an automobile being to transmit power 
from a horizontal shaft — that of the engine clutch and trans- 
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mission— to an inclined one — the driving shaft — with as little loss 
as is possible. 

Rear Axle and Differerrdial. The driving shaft drives the rear 
axle through some form of gear, either bevel, worm, or other variety, 
and is usually a two-part shaft. The reason for cutting the rear axle 
is that each wheel must be driven separately in rounding a curve, for 
one travels a greater distance than the other. This seemingly com- 
plicated act is produced by a simple set of gearing called the differen- 
tial, which is located within the driven gear in the rear axle. Each 
half of this is fixed to one part of the axle shaft All these gears and 
shafts must have bearings, lubrication, means for adjustment, etc. 
On the outer ends of the axle shafts are mounted the rear wheels, 
which carry some form of tires to make riding more easy. The 
brakes are generally in a hollow drum attached to the wheels. All 
this goes to make up the driving system. 

Steering Group. The front wheels perform a different function. 
They are hung on the steering pivots, so that they can be turned to 
the right or the left as desired. In order to have the wheels work 
together, a rod, called the cross-connecting rod, joins them, while the 
motion is imparted to them by means of another rod, called the 
steering link, which joins the steering lever or arm with the right-hand, 
or left-hand steering pivot The last-named lever projects downward 
for this purpose from the steering-gear case and is moved forward and 
backward by the rotation of the steering wheel in the driver's hands. 

The transformation of the rotation or turning motion of the hand 
wheel into a longitudinal movement is accomplished within the 
steering-gear case by means of a worm and gear, a worm and partial 
gear, or by a pair of bevel gears. All these parts need more or less 
adjustment, lubrication, fastening means, etc., the complete group 
being designated as the steering group. 

In addition, the steering wheel and post carry the spark and 
throttle levers, with the rods, etc., for connecting them to the igniting 
apparatus (magneto, timer, etc.) and the carburetor, respectively. 
The purpose of the spark lever is to allow the driver to vary the power 
and speed of his engine by an earlier or later spark, according to his 
driving needs. Similarly, the throttle lever is for the purpose of 
opening or closing the throttle in the intake manifold of the carbu- 
retion system and regulates the amount of gas entering the engine, 


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thereby increasing or deqreasing its power output, or speed. Actually, 
these are parts of the ignition and carburetion systems, respectively, 
but they are usually classified with the steering group, because they 
are located on the steering wheel and post. 

Frame Group. Little need be said about the frame. The side 
members are generally supported by the springs at the front and rear 
ends. The springs are connected to the axles and support the car. 
Thb front cross-member usually supports the radiator and sometimes the 
front end of the engine, too. The rear cross^member usually supports 
the gasoline tank when a rear tank is used. The other cross-members 
may support the engine, transmission, shifting levers, and other parts, 
according to their location. In general, the number and character 
of frame cross-members is slowly changing; the modern tendency 
is toward their elimination. By narrowing the frame at the front, 
the engine can be supported directly on the side members. With the 
units grouped, the same is true of the other important units. 

Formerly, practically all motors and transmissions were sup- 
ported on a sub-frame, but it has been found that the same results can 
be obtained when this extra weight is eliminated. Fig. 1 shows a 

When the shifting levers are placed on the outside, they are 
fastened to the frame, as is the steering gear; all step, fender, and body 
parts, the under-pan, or splash-pan, for protecting the mechanism 
from road dirt; and usually the headlights. The frame is constructed 
with this idea in view, six bolts generally being used. The muffler 
is usually hung from a rear-frame member. When electric lighting 
and starting are used, the battery is very often hung in a cradle, sup- 
ported by the frame, while the hood or bonnet is supported equally 
by the side members of the frame (usually covered with wood), and 
by a rod running from radiator to dash.' 

In Fig. 1 it will be noted that the engine group and the 
clutch group are together, forming one unit. The transmission is 
mounted on the front end of the drive shaft, thus forming another 
unit. When the motor and the transmission are so located, they 
form a two-unit power plant. The single-unit power plant, in 
which the transmission and the motor are in one unit, is the most 
used construction at the present day. A few manufacturers still 
mount the transmission on the rear axle. 


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In the following pages, the general grouping just outlined will be 
followed consistently, so that the student and worker will be able to 
follow through the construction and repair of the entire car in a reason- 
able and logical manner. 

The principles of engine design, and the methods and details of 
engine construction are second to none of the other factors that com- 
bine to produce the complete modern automobile. 

How automobile engines operate, the reasons underlying the 
various details of different designs, and the relative merits of different 
constructions are all too little understood by most of those who have 
to do in a practical way with the new conveyance. 

Four-Stroke and Two-Stroke Cycles. The word cycle is used 
customarily when referring to the internal-combustion engine. 
When we speak of a four-cycle motor, we omit the word "stroke/ ' 
but if we want to be exact, the four-stroke cycle is the correct 
expression. In other words, a cycle is a series of operations 
which generates heat and then transforms that heat into mechanical 
energy, at the same time expelling the unused heat. This process 
is a true cycle and is generally composed of four strokes of the 

A four-stroke cycle is composed of four parts, as follows: The 
downward movement of the piston, taking in a fresh charge of 
gas; the upward movement of the piston, compressing this gas; 
the working stroke, where the gas is expanded by the heat of the 
explosion and drives the piston down; the upward movement of 
the piston, forcing the burnt gases from the cylinder. The cycle 
starts at the beginning of the intake stroke and finishes at the end 
of the exhaust stroke. 

A two-stroke cycle is composed of two strokes, four operations 
taking place in these strokes. In this cycle the piston is driven 
down by an explosion. As the piston reaches the lower end of the 
stroke a port is uncovered, allowing the exhaust gases to escape. 
This is the first work of the cycle. At the same time that the 
exhaust gases are escaping, a fresh charge is coming in at the 
intake port at the opposite side of the cylinder. This gas is under 


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compression and tends to force the burnt gases out at the exhaust 
side. On the second stroke of the cycle, the piston is driven 
upward and thus compresses the gas when it is fired and the explo- 
sion takes place as described. 

With the succession of suction, compression, explosion, and 
exhaust strokes afforded by the four-cycle motor, a very positive 
and reliable functioning is secured; and by the expedient of a sufficient 
cylinder multiplication to afford good mechanical balance and fre- 
quent power impulses, its flexibility, durability, and practical quality 

Pig. 2. Eight-Cylinder V-Type Motor of Cadillac Car, Shown Installed in Chassis 

can be brought to a very high standard in a well-designed and honestly 
built motor. 

At the same time, the fact that so much more attention has 
been paid to the four-cycle motor than to any of its possible com- 
petitors for popular favor, undoubtedly accounts in some measure 
for its present pre-eminence, and it is an open question with many 
engineers as to just what virtues might or might not be realized 
with other constructions, were they as exhaustively experimented 
with and exploited. 

Cylinder Multiplication. There seems to be no reasonable limit to 
the extent to which cylinder multiplication can be carried in the effort 
to improve the mechanical balance and to even the torque of gasoline 
motors. But established practice has, nevertheless, settled upon 


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four-cyclinder vertical engines as those most suitable for the propul- 
sion of the average automobile, as this is the least number of vertical 
cylinders with which mechanical and explosion balance can be secured. 

The use of six cylinders, with the crank throws 120 degrees apart 
and the explosions occurring once for every 120 degrees of crankshaft 
rotation, affords a smoother-running motor than the four-cylinder. 

Still better than the "six," from every standpoint except that of 
cost, which has prevented its wider application to automobiles, is the 
V-shaped, eight-cylinder motor, of the type illustrated in Fig. 2, 

Fig. 3. Overhead View of Stearns-Knight Eight-Cylinder Sleeve- Valve Motor 
Courtesy of F. B. Stearns Company, Cleveland, Ohio 

which gives a good view of the unit power plant of a well-known 
American machine. In both of these, a four-throw shaft, similar 
to the ordinary four-cylinder crankshaft, is used, is much cheaper to 
manufacture than a six-cylinder crankshaft, and the two rows of 
cylinders, each practically constituting a separate four-cylinder engine, 
are made to work upon the common crankshaft at 90 degrees apart. 

The most recent tendency in car motors is toward the eight-cylin- 
der V-type, following the marked success of this form in aviation use. 

Not only has the V-form been produced in the poppet-valve 
form, but also in the Knight sleeve-valve tvoe an example of which 

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is shown in Fig. 3. Furthermore, a considerable number of twelve- 
cylinder V-type motors have been built, a good example being shown 
in Fig. 4. 

An answer to the demands of the- <sft* owners for the flexibility 
and power of the multi-cylinder types has been recently given by the 
issue of a very flexible and quick starting four-cylinder motor with 16 
valves, two intake and two exhaust valves in each cylinder. Four 
of these of widely varying design have already been announced— 
Stutz, White, and Drexel Motor Car Companies, and Wisconsin Motor 
Company. The details of the Wisconsin motor are given in the sec- 

Fig. 4. Side View of National Twelve-Cylinder V-Type Motor 
Courtesy of National Motor Vehicle Company, Indianapolis, Indiana 

tion on "Valves". The large increase in the size of the valve openings 
makes clean mixtures and adequate scavenging easily obtainable, 
with a corresponding gain in the flexibility and power of the motor. 
In aviation work, no form of motor has made as great progress 
as the rotating-cylinder type, which has been built usually with an 
odd number of cylinders, as five, seven, or nine; or when these are 
paired with an even number, as ten, fourteen, or eighteen. As yet, 
this type has not been applied to motor cars, but considering its 
advantages, it would not be strange to see this done at an early date. 
These motors have a single-throw crankshaft of very light weight; 
the rotation of the cylinders at a rapid rate allows of their being air- 
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cooled, and also very light in weight, eliminating all of the parts and 
also the weight in the water-cooling system. The large revolving mass 
does away with the need for a flywheel, while the practical elimination 
of reciprocating parts reduces vibration to a minimum. 

In the extreme, motors of the V-type have been constructed with 
sixteen cylinders, eight in each group. These have been very suc- 
cessful in aeroplanes and motorboats, particularly the latter. 

Engine Troubles 
Deposits of Carbon in Cylinder. These are loosened by intro- 
ducing two or three tablespoonfuls of kerosene, put into the cylinder 
when warm through spark-plug hole. Replace the spark plug, but 
do not connect up the wires. Turn the engine over slowly to work 
kerosene back of rings. Allow it to stand a few minutes. Then 
connect the wires and start the engine running out of doors, as dense 
smoke will come for a time. Clean spark plugs and replace. 

Knocking. Knocking should not be permitted. It is likely to 
result in injury to the engine. Ordinarily, knocking is avoided by 
retarding the spark. In starting up a hill where considerable power 
will be needed, an open throttle with advanced spark should be 
employed before beginning the climb. Should the motor begin to 
knock when part way up the hill, the spark should be gradually 
retarded. Continued pounding is caused by the connecting rod and 
main-shaft bearings becoming loose. 

Failure to Start. Try the following remedies: 
See that current is switched on. 
See if throttle valve is open. 
Be sure gasoline tank is filled. 
Be sure gasoline valve is open. 
See that air can enter filling cap of gasoline tank. 
Flood carburetor. 
If weather is cold, prime cylinders by squirting a little 

gasoline in through each compression relief cock. 
See that spark plugs are clean. 
Missing of Explosions. See "Troubles with Ignition System. ,, 
Popping in Carburetor. Snapping or popping in the carburetor 
is caused by lack of gasoline, so that the mixture fed to the motor is 

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not rich enough, and as a result it burns so slowly that one of the 
admission valves may be open before the charge is completely burned, 
and part of the burning charge is forced back through the pipe lead- 
ing from the carburetor to the combustion chambers. If adjustment 
of carburetor is such that a weak mixture should not occur, inspect 
the gasoline piping system carefully for an obstruction. Popping in 
the carburetor may also be caused by a leaky joint in the piping and 
by connections between the carburetor and the combustion chambers. 

Poor Compression. Valve stem may be broken and sticking. 
Valve spring or valve stem may be clogged with dirt. Cylinder or 
explosion chamber may be cracked. Piston rings may be broken or 
turned so that cuts line up, allowing pressure to escape. Cylinder 
may be gummed. Cam may be loose. Water may leak into cylinder 
through plugs in cylinder head. Valves may not seat properly due 
to being covered with soot. Valves may have to be reground. 

Engine Starts, but Stops, after a Few Revolutions. Engine bear- 
ings may have seized from lack of lubricant. There may be too 
much oil in crankcase. Water may be entering cylinder through 
cracks or through plugs in cylinder head. Carburetor float may be 
sticking. Poor water circulation may be due to broken pump shaft 
or clogged water piping. 

Engine Runs Well on Slow Speed but Not on High Speed. .Muffler 
may be stopped up. Carburetor air valve not properly adjusted. 

Engine Pulls on High Speed but Not on Low Speed. There may 
be a leak in the inlet pipe. Carburetor adjustment not proper. 

Knocking Continues Even after Spark Is Properly Adjusted. 
There is a possibility of the flywheel being loose, of loose or worn 
bearings in the engine, or of something broken inside the engine. 


General Instructions. By far the most important part of the 
car is the engine, and this should, therefore, receive the greater 
portion of the time and attention during any repair or overhaul 
work, even by going so far as to take it out of the chassis if the trouble 
is at all serious. For this purpose, all ignition wires and carburetor 
and magneto operating rods are detached. Next, the various mani- 
folds are removed, the water system is drained, and all hose connec- 
tions are broken. Usually it is necessary also to take the radiator 


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Fig. 5. Dismounting Engine for Repair 

Fig. 6. Engine Dismounted, Showing Cylinders Removed 


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off. When this is done, the appearance of the vehicle and of the 
work is very much like that presented in Fig. 5, which shows two 
men engaged in loosening up certain parts of the engine preparatory 
to taking it out. 

When all accessories have been removed or loosened up, the 
holding bolts are taken out, the clutch disconnected, and the motor 
is left free to be swung out by means of a small crane or hoist. In 
some cases, the work can be completed without disturbing the base 
of the motor, as in Fig. 6, which shows a big car partly disassembled 
for repairs, the radiator and cylinders having been removed at this 
stage. The trouble here was found within the cylinders, hence, 
as soon as they had been removed, the balance of the six-cylinder 
motor and its chassis could remain undisturbed. 

Hoists and Cranes. Yale & Towne Form. For lifting out an 
engine or other unit approximating several hundred pounds (possibly 

500 pounds in the case 
of a big engine) an effi- 
cient form of overhead 
hoist is needed. There 
is nothing better than 
the Yale & Towne 
triplex hoist, although 
this is not a cheap form. 
It can be attached to 
any channel or I-beam 
built into the roof of the building, or if that is impossible, it can be 
hooked into any wire or rope loop over a ceiling beam. It multiplies 
the power which one man can apply to such an extent that one man 
can lift out a 500-pound engine with it very readily. 

Home-Made Ceiling Hoist Lacking one of these, a substitute 
can be made as indicated in the sketch, Fig. 7. The track is plain 
rectangular metal, known as § inch by 2 inches flat, while the brackets 
supporting it can readily be forged by any good blacksmith. The 
trolley consists of a forged and bent arm for one side and a 
straight bar for the other. The wheels can be found in any hardware 
store. The bottom end should be drilled and tapped, and the ring 
made in the lathe to fit into it. For this purpose, the threads should 
be large and numerous. The ring could be forged integrally, but that 

Fig. 7. 

Method of Constructing Track Attached to 
Ceiling of Shop 


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would complicate the job. When hung, any crane, hoist, or any block 
and tackle, can be hooked into it and when the load has been lifted 
clear, it can be run along the track until the desired point is reached. 
If this expense is too great, the same results can be obtained 
by taking a sliding-door track and suspending it from the ceiling 
beams. Then the two door carriers can be joined by the large end 
of a V-shaped piece of steel, not less than J inch by 2 inches in section; 
while the carriers are separated and held separated by a simple straight 
distance piece. The lower end, or point of the V, supports the 
hook or eye, whichever is used. That is, from an old sliding door, 

Fig. 8. Overhead Support and Trolley, Used When Roof Trusses Are 
High or Weak 

a traveling hoist can be constructed easily and quickly to handle 
engines or other large and heavy units. 

Floor Type of Hoist Support. When the construction of the roof, 
or ceiling, is such that it will not permit a suspended hoist, one which 
works from the floor can be constructed. This consists, as Fig. 8 
shows, of a double track beam supported on castor-mounted triangu- 
lar ends, which extend as high as the garage will allow. By this 
means, the weight can be lifted clear, and the entire structure moved 
to the desired place. It is constructed a good deal like those just 

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described; the ends are fair sized angles, say 2 inches by 2 inches 
by rs inch; the braces lighter stock, say 1£ inches by 1| inches by 
i% inch; and the castors are anything that is available. It is not 
necessary that the track be metal; wood can be used if it is wide 
enough to withstand the wear of the wheels and deep enough to 
carry the heavy loads. 

Commercial Forms. If sufficient money is available to purchase 
a hoist, these makeshifts are, of course, unnecessary. There are a 
number of portable cranes for garages on the market, costing from $90 
up. These usually have a U-shaped base of heavy cast iron with 

two castors at the points, and one 
at the back of the U . At the back 
also i*s a vertical pillar about 6 
feet high, with a curved exten- 
sion. At the end of the extension 
is a grooved pulley carrying a 
chain hoist. The crane runs back 
to a sheave and set of gears for 
winding it up. It has a suitable 
handle for this, as well as a long 
folding handle for moving the 
crane around. Among those 
available are: the Champion, 550 
pounds shipping weight, of f -ton 
capacity, with a lift of 4 feet 8| 
inches; the Franklin, which will 
lift 2000 pounds, and weighs 480 
pounds; the New Jersey, which will lift 6 feet 8 inches, weighs 600 
pounds, and has a capacity of 2000 pounds; the Canton, which will 
handle 2000 pounds, and lists at $100; the Hilite, which is built in 
two capacities and four different lifts; and others. 

Form of Cradle. Many times, even with a suitable crane or hoist, 
it is necessary to make a cradle for the motor because of difficulty in 
attaching the chains or ropes to it, difficulty of balancing it safely, 
or for other reasons. A cradle for a six-cylinder motor is seen in Fig. 9. 
This is, of course, applicable only to this particular motor, but in a 
shop handling one car continuously, there is enough saving to warrant 
making such an outfit. The four bars are mad 3 from two pieces of 

Fig. 9. 

Sling for Engine Which Saves Much 
Tiine in Attaching 


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round stock, put through the drilled holes in the upper or supporting 
bar, then bent over and shaped. Before anything is done, the ends 
of the bars must be turried down and threaded. In this instance, 
there is a hole at the four points on the shelf of the motor, so these 
holes govern the size of the ends of the rods and also their spacing. 
On almost every motor, there will be some means of attachment which 
can be studied out in advance, and the rig built to fit it. 

Portable Engine Stands. If the engine is removed from the 
chassis, the first thing needed is a suitable engine stand. One of these 
is shown in Fig. 10, a form that can be purchased at a reasonable 
price, and which possesses many excellent features. The frame is made 

Fig. 10. Handy Form of Engine Stand Constructed from Piping 
Courtesy of Shew alter Manufacturing Company, Sprijigfield, Ohio 

of tubing, which gives a maximum of strength in a minimum of space. 
The oil drip pan beneath is a good feature, as is the shelf arrangement 
at the open end. The large castors allow it to be moved around readily 
and can be clamped to hold it any place. One can be constructed 
out of heavy galvanized pipe and pipe fittings at a moderate cost. 
This form of engine stand holds the motor in its natural, or upright, 
position. But it is not always desirable to have the eiigine in that 
position; in fact, when working on crankshaft bearings and other parts 
on the under side, it is necessary to have it inverted. There also is 
work which makes an intermediate position desirable. For this 
purpose, an engine stand is needed which can be turned to any desired 

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angle and fastened there. Such a stand is shown in Fig. 11, which 
represents one made by the International Motor Company, Plainfield, 
New Jersey, for its own use. It would hardly pay to make one of these, 
as the ends are castings which require a pattern, but if a couple of 
garages wanting, say two each, would go in together, it would pay to 
have patterns made for the four. After making castings for their own 
frames, the garage owners could later make them for sale if they 
wanted to go into the business. The sketch explains the construction, 
but this explanation might be added : the central part, projecting from 

Fig. 11. Engine Stand Which Allows Motor to Be Turned to Various Positions 

the left-hand member is attached to the rear crankcase arms, and 
when the engine is turned, this turns with it. The central rotating 
member on the upper part of the right-hand unit is made to take the 
starting crankshaft, and the clamp at the upper left is to lock it in 
the desired position. Eight holes are provided, but a person making 
one could have as many as he wished, since they are drilled. As will 
be noted, there are six pieces, but the two bases are made from the 
same pattern, so five patterns are all that would be needed. 



Materials Used. Gasoline-engine cylinders are variously made 
of cast iron, cast steel in the form known as semi-steel, forged steel, 
aluminum alloys, and other materials. For durability, and the ability 
to withstand high temperatures without warping, nothing has been 
found superior to cast iron, even though the lightness of steel and of 

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aluminum alloys has commended them for aviation use and in some 
cases for racing automobiles. 

Method of Classifying Cylinder Forms. Cylinders are generally 
named according to two things: first, the method in which they are 
cast or produced; and second, the shape of the combustion chamber, 
or arrangement of the valves. Thus, according to the first method, 
they are divided into those which are cast separately, that is, each 
cylinder by itself; cast in pairs, or each two cylinders cast together; 
cast in threes, a modern modification fitted to the six-cylinder engine; 

Fig. 12. Typical T-Head Cylinder Units with Other Cylinder Parts 
Courtesy of Locomobile Company of America, Bridgeport, Connecticut 

and cast together, or en bloc, that is, all of the cylinders cast as a 
single unit. 

According to the second method of naming, cylinders are of the 
L-head type, in which the combustion chamber has the shape of an 
inverted capital letter L, formed by the placing of all valves on one 
side; of the T-head type, with the combustion chamber shaped like a 
capital T, because the valves are equally distributed; of the I-type, 
or valve-in-the-head type, so called because the combustion chamber 
is left perfectly straight and round by placing the valves in the head; 
and modifications of these. 

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Usually in speaking of the cylinders, both names are used as one, 
as, for instance, those of Figs. 2, 3, and 4, all of which happen to be 
alike, would be spoken of as L-head blocks, Figs. 12 and 16 as T-head 
pairs, etc. 

Methods of Casting Cylinders. Cast Separately. The early and 
still common practice in the building of multi-cylinder gasoline motors 
is the casting of cylinders separately. This policy makes it easier to 
secure sound castings, simpler to machine and finish them, and less 

C&055 Section or Engine: 

Fig. 13. Section through Locomobile Cylinder Shown in Fig. 12 

troublesome to disassemble parts of the motor without disturbing 
the rest. 

In a number of cases, where extremely light weight was desired, 
this method was followed, but the cylinders were machined all over 
and a sheet-copper water jacket was applied in assembling. This has 
been most successful in aeroplane work and also for motor cars, but 
when the Cadillac changed to the form shown in Fig. 3, this construc- 
tion lost its principal American adherent. In addition to this con- 
struction, there have been a number of motors built with ar A applied 


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water jacket of sheet metal of the built-on form. These have shown 
splendid cooling abilities, but, under the twisting and racking of 
automobile frames, particularly in later years, with the use of more 
flexible frames, they have shown too much tendency toward leakage 
to become pbpular. 

Cast in Pairs. Just as soon as two-cylinder and four-cylinder 
engines were produced, the cast-in-pairs form of cylinder appeared 
and is almost as widely used today as then. While the modern 
tendency toward smaller bores, compactness, and light weight has 
greatly increased the number of cylinders cast en bloc, the paired 

Fig. 14. Studebaker Six-Cylinder Motor, Showing Block Castings of the Six Cylinders 

form, including the cast-in-threes modification for six-cylinder 
engines, holds its. own. 

Cast Together. The great advantage of having the several 
cylinders of one motor cast together — en bloc, as the French term it — 
is that the alignment and spacing of the different cylinders is thus 
rendered absolute and permanent, regardless of any differences in 
adjustment that may otherwise occur in assembling. 

This construction has been applied to a large proportion of the 
small and of the medium-sized fours, a fair proportion of the larger 
fours, and to a considerable number of sixes, Fig. 14 . 


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& o 
•8 S 




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Another advantage is, that the water connections, exhaust and 
iitake manifolds, etc., are rendered simpler both in their form and 
the number of their points of attachment. 

In some advanced motor designs, the passages for the incoming 
mixture and for the exhaust gases, and in one case even the carbu- 
retor itself, are all incorporated in the main casting. 

Fig. 16. Section Through Continental 7R Cylinder Showing the L-Head 
Valve Construction 

Another example of simple construction is that illustrated in Fig. 
15, which depicts one of the latest Ford motors, in which the cylin- 
ders and the upper half of the crankcase are all cast in one piece. 
The lower half of the crankcase and the gearbox are similarly 


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constituted of another simple pressed steel unit, while a second casting 
is used for the heads of the cylinders and for the water connection. 
Cylinders Classified as to Fuel Chamber or Valves. L-Head 
Forms. In the L-head form, the valves are all located on one side, 
and usually because of this, all the accessories are on the same side. 
This makes a lop-sided engine, with carburetor, inlet pipe or manifold, 

magneto and wiring, exhaust 
manifold, and sometimes elec- 
tric generator and other parts 
all grouped on one side, with 
little or nothing on the other. 
While a disadvantage in four- 
and six-cylinder motors, this 
is somewhat of an advantage 
in eight- and twelve-cylinder 
forms, for all the parts and 
auxiliaries can be grouped in 
the V between the cylinders, 
leaving the outside clear. On 
the other hand, where this 
grouping has been found unde- 
sirable for four- and six-cylin- 
der motors, it has been possible 
to overcome it in part by taking 
the magneto and carburetor 
over on the other, or plain side, 
of the cylinders, leading a con- 
duit back for the wires in the 
one case, and a long inlet mani- 
fold in the other. An L-head 
cylinder is shown in Fig. 16. 
T- Head Forms. A desire 

Fig. 17. 

Section through Dorris 1920 I-Head 
ylinder as Used with Valve-in-Head Motors 

for more symmetry and a better arrangement has brought about the 
T-head form, which has the inlet valves, carburetor, and inlet mani- 
fold on one side, and the exhaust valves and manifold on the other. 
This separation gives more space on both sides, and allows the dis- 
tribution of the other engine accessories so that each has more 
accessibility. This is important, for some parts, like the magneto, do 


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Fig. 13. Cylinder and Cylinder-Head Assembly of the 1920 Chevrolet 
Showing the Valve in the Head Construction 


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not withstand the heat well, and consequently should be far away from 
the heat of the exhaust manifold. See Figs. 12 and 13. 

/- Head Forms. The valve-in-the-head, or overhead valve, motor 
requires an I-head cylinder, because, with this location of the valves, 
there is no necessity for the valve pockets of the other forms. Con- 
sequently the cylinder can be straight and plain, while the head, 
which is separate, is fastened on instead of being cast integrally. 
It may have either the L- or T-form, according to the location of the 
valves and the inlet and exhaust manifolds. Fig. 17 shows an I-head 

in which the manifolds are 
located on the opposite side. 
Note that in this form the 
cylinder head is removable, 
the valves being set directly 
in the head, as shown in the 
view of the Chevrolet motor, 
Fig. 18. 

The forms are not so 
clearly separated as they 
were formerly, for the inclu- 
sion of cylinder heads in one 
case, and their exclusion in 
another; the integral casting 
of manifolds, water passages, 
etc.; the casting of crankcase 
upper halves and also of gear 

Fig. 20. Detail of Marmon Cylinders Showing Cast- COVerS, flywheel enclosures, 
iron Sleeves Inserted in Aluminum Casting . transmission cases and other 

parts, all of which are quite common; no longer leave the cylinder 
casting as a single simple clear-cut unit. 

An I-head motor with a removable head is also shown in 
Fig. 18. In removing the valves on this motor, the rocker arms 
and shaft should first be removed by taking out the shaft bear- 
ing bolts. Care should be taken in marking the rockers, as they 
will operate best in their original position. 

The cylinder head is then removed and the valve keys taken 
out of the valve stems. This valve construction predominates 
when the motor is of this type. Better valve cooling is secured by 


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having the valve seat in the cylinder head proper instead of in a 
removable cage. 

Cylinder Repairs 

Removing Carbon. Scraping. The two standard methods of 
removing carbon are by scraping and by burning with oxygen. 
If the carbon is to be removed by the scraping process, the 
cylinder head is first taken off and the carbon then removed 
with a putty knife or carbon scraper. While this is a satis- 
factory method, it requires considerable time. This operation 
can be done with but little expense if the cylinder head is easily 

Oxygen Process. In removing carbon by the oxygen process, 
first a spark is applied to a mixture of carbon and oxygen and 
then combustion takes place. The 
carbon will continue to burn until 
it is completely exhausted or until 
the supply of oxygen is cut off. 

Setting the Motor. The motor 
should be turned by the crank until 
piston 1 is on upper dead center, 
ready to fire. When the piston is in 
this position, both valves are closed 
and the carbon on top of the piston 
is nearer the oxygen supply. The 

Spark plugs are then removed and a &&• 21 - Oxygen Regulator for Carbon 

r r ° Burning 

little oxygen allowed to escape from 

the torch into the combustion chamber through the spark-plug hole. 
This is done so that there will be sufficient oxygen to support 
combustion when a match is dropped through the spark-plug 
hole before the oxygen torch is inserted. After the regulator, 
Fig. 21, has been adjusted to a pressure of about 15 pounds, the 
torch nozzle is inserted through the spark-plug opening, which 
causes the carbon to burn very rapidly. It is important always to 
have at hand a reliable fire extinguisher as some sparks or hot 
carbon may drop in the oil pan and cause a fire. It is unneces- 
sary to turn off the gasoline supply to the carburetor or to remove 
the carburetor, as the closing of the inlet valves prevents any 

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chance of a fire in this instrument. Fig. 22 shows an operator 

removing carbon by this method. 

Sequence of Burning. After the carbon is removed from 

cylinder 1, the crank should be turned until the piston of the "next 

cylinder in firing order is at 
upper dead center. If the motor 
is a six-cylinder type, the crank 
may be turned one complete 
revolution and the carbon then 
removed from cylinder 6. It 
will then be necessary to find 
the firing position of cylinder 2 
and, after burning, the crank 
should be turned one complete 
revolution; then cylinder 5 will 
be in its firing position and 
w n . „ ^ . _ ready for the burning process. 

Fig. 22. Burning Carbon with Oxygen ^ , i 

After the carbon has been re- 
moved from this cylinder, it is necessary to find the firing position 
of cylinder 3, and after the carbon is burned, the crank should 
be turned one revolution and then cylinder 4 will be in position 

for carbon burning. 

If the motor is a four- 
cylinder type, the same method 
may be used; first finding the 
firing position of cylinder 1 
and cleaning it and then re- 
moving the carbon from cyl- 
inder 4> after the motor has 
been turned a complete revo- 

Fig. 23. Imperial Oxygen Burning Outfit. lution. The firing position in 

(Without Oxygen Tank) ^ ^ ° r 

cylinder 2 is then found, and 
after one complete turn of the crank, cylinder 3 will be in position 
for carbon burning. 

Finding Firing Position. There are several methods of find- 
ing the firing position. If the motor is equipped with battery 
ignition, the best and quickest method is to turn on the ignition 
switch, having the spark lever fully advanced and holding No. 1 

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spark-plug wire near the ground. The crank should be turned 
until a spark jumps. The ignition switch is then turned off and 
the carbon removed from cylinder 1, as this is its firing position. 
The firing position of the other cylinders is found by the same 
method. In any four-cylinder motor, cylinder 1 is ready to fire 
when exhaust valve 4 has just closed. In the case of any six- 
cylinder motor, cylinder 1 is just ready to fire when exhaust valve 
6 just closes. 

Precautions. In burning carbon one should guard against 
using a too high pressure on the oxygen nozzle as this is likely to 
cause sufficient heat to melt the nozzle, thereby making it neces- 
sary to stop the operation and refit a new nozzle. 

It is also important to see that the valves are seated, as they 
are likely to warp if not in this position. 

A supply of oxygen may be secured from any reliable manu- 
facturer in tanks of several capacities, the most used, however, 
being the 100- and 200-foot tanks. 

The oxygen regulator hose and torch, Fig. 23, can be pur- 
chased from welding equipment supply houses or from the manufac- 

Removing Carbon by Scraping Tools. When the carbon cannot 
be burned with oxygen, the repair man must go back to hand scrap- 
ers. In any case, these are the most simple and fully as effective 
as any provided the extra time needed to use them and do a good 
job is available. When the offending member has been brought 
out so it can be handled, the removal of the carbon can be accom- 
plished in a few minutes. A flat piston head can be scraped off 
with any knife or chisel, but a special scraper made from an old 
file, flattened out at the end and ground down so as to present one 
sharp edge is better. Every garage man should accumulate from 
five to a dozen shapes and sizes of scrapers for various work, includ- 
ing a flexible one with which to reach into corners. The carbon 
is brittle and comes off readily. After its removal the surface 
should be cleaned with air and gasoline to make it smooth, in order 
to delay the formation of a second coat. This is true of carbon 
in other places, but usually it is impossible to smooth the sur- 
face, in which case the process must stop when the part is scraped 


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There are a number of excellent plain and special forms of 
carbon scrapers which the average garage should have. Old files 
prove to be splendid material. 

Compression Indicating Gage. Before taking off the cylinder to 
look for trouble inside, the repair man should do all he can to find out 
what and where the trouble is. A compression gage is handy, as 
this indicates the pressure in each cylinder. These should all agree 

Fig. 28. Using Stethoscope to Listen to Engine Noises 

when the motor is right, but if pistons or rings are not right, or if the 
cylinder is scored, the gage will show a lower figure than the other 

Such gages can be purchased or they can be made from old 
materials which lay ready at hand, as, for instance, an indicator 
made from an old spark-plug shell and a tire gage. The stem of the 
latter was set inside the shell and firmly fixed there by means of 
babbitt after both were scored so the metal would take a firm hold. 
Whenever a motor acts peculiarly, the spark plug is removed from 
each cylinder in turn, the home-made gage inserted, and the reading 
noted (with the motor running or being turned over by hand). 
Many times leaky valve pistons or valve-stem guides will cause a miss 


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which nine persons out of ten would blame to the carburetor. This 
gage will show up these leaks. 

Locating Noises by Means of a Stethoscope. Besides this, it 
should be borne in mind that there are many sources of noise in 
and on the engine other than that produced by valves and valve 
motions. In fact, the noises made by the valves, while an indication 
of loss of power, do not represent anything like the possibilities for 
trouble indicated by a piston slap, a crankshaft or connecting-rod 
pound, the whirr of worn timing gears, and others. In order to locate 
such sources of noise exactly, at a time when the beginner lacks famil- 
iarity with the motor and its troubles he should purchase or borrow 
and learn to use a stethoscope, Fig. 28. A modification of the sur- 
geon's well-known instrument is now made for use in automobile 
trouble finding. 

The stethoscope, or its modification, simply magnifies all noise; its 
construction is such that one end is held against the suspected part, 
while the other end constitutes an ear piece. When the engine begins 
to make a great deal of noise, particularly heavy pounding noises, this 
should be brought into play. With the motor running, place the free 
end against the various parts of the engine, going slowly from one 
to another. In this way it will soon be found where the trouble lies. 

A piston slap is not so easy to define or so easy to repair. It 
may be called a noise which comes from within the cylinders, trace- 
able to the pistons, or to one piston, as the case may be, which 
sounds very much like a shaft pound, except that it is a louder noise. 
It occurs when pressure is put on the piston, as at the beginning of 
compression, at the time of explosion, or at times at the end of each 
stroke. It is said to be due to different causes. Some say it is 
caused by a loose piston pin, but the writer knows of two cases in 
which a new tight pin left the piston slap just as clear and distinct 
as before. Others say it is caused by rings which are loose up and 
down in their grooves, but in the cases above, new rings which fitted 
tightly in this way did not help any. It has been ascribed to a piston 
which was out of round, so that it did not fit the cylinder, and also to 
a groove and shoulder having been worn in the cylinder surface, the 
piston striking this each time. Whatever is the real cause, and the 
writer is inclined to blame it to a poorly fitting piston, nothing will 
really remedy it but a new piston, complete with rings. 


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Punch for 
Making Holes 

Making Gaskets. Anyone who is going to do much repair work 
will soon have to learn the art of making gaskets, for, in almost every 
case, the removal of a paper gasket is accompanied by its breakage, 
so it is rendered unfit for further use. A gasket, it might be explained, 
is a formed sheet of heavy paper, cardboard, or special material fitted 
between two surfaces of a joint which must resist the leakage of gases 
or liquids under pressure. By means of the bolts or screw threads 
which hold the two parts of the joint together, the gasket is com- 
pressed and, in its compressed state, it resists the internal pressure. 

The following method of making gaskets applies alike to round, 
oval, and odd-shaped ones, which cannot be said of special tools and 

fittings for gasket cutting : Select 
a good piece of heavy brown 
wrapping paper or special gasket 
paper without too many wrinkles, 
and free from cracks or flaws. 
Clamp the part for which the 
gasket is to be made in a vise to 
steady it and lay the paper over 
it. Then go around the edges 
of the part, tapping lightly on the 
paper with the flat face of a ham- 
mer, holding the paper in position 
meanwhile with the other hand. 
This method is illustrated in Fig. 29, where a workman is shown 
making a gasket for the base of a cylinder. In this particular 
instance, holes must be made through the gasket for the cylinder 
bolts. These are made with the round or peen end of the hammer 
or with the punch. When made, the punch is stuck into the hole to 
help hold the paper steady. In this case, too, it was necessary to cut 
the inside of the gasket out first, then this material (the paper from the 
inner or smaller hole) was removed, the sheet put back in place on 
the base of the cylinder, and work started on the exterior cutting. 
If the hammer be held at a sharp angle with the edge of the 
part for which the gasket is being cut, each blow will cut through, 
or partly through, the paper. By repeating this operation enough 
times, going around the part meanwhile, the result is the finished 
gasket which will fit the desired place exactly. 

Fig. 29. Cutting Gaskets on the Parts with 
a Hammer Is the Best and Quickest 


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Cylinder Heads. A great many motors have detachable heads, 
and their quick removal is a great convenience, when there is carbon 
to be scraped off, pistons to be looked over, or other internal work 
to be done. However, replacing them is never quite so easy as 
removing them, partly on account of the cylinder heads themselves 
and partly on account of the pistons. The latter are particularly 
troublesome when the cylinder head is hinged. The cylinder head' 
should be replaced with great care, and after replacement it is fully 
as important to bolt it on properly. 
If one bolt or a series of bolts is 
tightened too quickly and too hard, 
it is likely to result in cracking the 
cylinder casting or the head casting 
or both. 

Proper Method of Bolting on 
Head. Usually, on an L-head type 
of motor, there are three rows of 
bolts for the cylinder head — one row 
along the middle, screwing into one 
side of the cylinders; another row 
screwing into the other side of the 
cylinders; and a third along the valve 
side. These should be tightened in 
order: first the middle bolts of the 
middle line, working out to the ends; 
next in turn, the middle bolts of the 
back of the cylinder, the middle bolts 
of the valve side, the ends of the 
cylinder; and finally, the *nd bolts on 
the valve side. All these should be 
tightened but a few turns at a time, and after all are down, a 
second round should be made in about the same order, to give 
each bolt a few more turns. In this way the cylinder head casting, 
which is both large and intricate, is slowly pulled down to the 
cylinder straight and true so that it is not warped or twisted. More, 
over, if the cylinder is pulled down straight in this manner, all the 
bolts can be tightened more than if the first bolt were tightened very 
much, for the latter would result in cocking up the opposite side. 

Construction of Simple Rig for 
Measuring Worn Cylinder Bores 


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Checking Up Cylinder Bore. Before any work is done upon the 
cylinder bore, such as turning, grinding, etc., it should be checked up 
very carefully. An expert workman, accustomed to the tool, would 
use an inside micrometer, but when this tool is lacking, as well as the 
experience necessary to use it, a fairly simple tool which can be used 
by almost anyone may be constructed as follows : As shown in Fig. 30, 
a short angle iron forms one side of the bore-measuring part; its length 
is sufficient to keep the entire tool perfectly vertical when the cylinder 
is vertical, and thus gives an accurate right-angle measurement of the 
bore. A central arm is fastened to this and the framework adjustably 

Pig. 31. Grinding Engine Cylinders 

View Shows Exhaust for Dust, Jig for Holding Cylinders, and Eccentric Wheel Spindle 

Courtesy of Heald Machine Company, Worcester, Massachusetts 

bolted to it. This includes the indicating dial at the top. At the 
lower corner is the indicating member, which is simply an L-shaped 
piece with a very short base and a very long stem; this is pivoted at 
the center of the bend. It is held against the side of the cylinder by 
means of a light spring. After adjusting the tool to the approximate 
cylinder bore, it is inserted, and a reading is taken; the tool is then 
moved, and another reading taken. The length of the arm is so 
great that any movement of the small arm is magnified about 15 
times. In this way a difference of tfsu" in the bore shows as iooff 
on the dial, or wz. In a shop where most of the work is on one motor, 

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the micrometer could be improved by eliminating the adjustable 
feature and making the frame and angle face a solid piece. 

Grinding Out Cylinder Bore. As the usual amount of metal 
which would be removed from a worn cylinder would not exceed a few 
thousandths of an inch, grinding should be the process used. Other 
processes, except possibly lapping or hand grinding, are too inaccurate. 
For this reason, a typical grinding set-up is shown in Fig. 31. This 
shows the cylinder bolted against a large angle plate, attached to the 
grinding machine table. The angle plate is drilled out to take the 
bolts which hold the cylinder casting to the crankcase. When bolted 
up for work, the air hose is connected up through the cylinder head 
to blow out the dust or particles ground off. Not more than three or 
four thousandths of an inch should be taken off at one time; if more 
must be removed, a second operation over the surfaces is necessary. 

If the cylinder is worn badly enough to warrant re-boring, which 
calls for new pistons and rings, it should be borne in mind that a 
standard set of oversizes has been adopted by the Society of Automo- 
bile Engineers, and that all manufacturers are working to them, by 
stocking pistons and rings according to these dimensions: 

Oversize Standard 
For 1st Oversize 
For 2d Oversize 
For 3d Oversize 
For 4th Oversize 

Inches Large 
10 thousandths (.010") 
20 thousandths (.020") 
30 thousandths (.030") 
40 thousandths (.040") 

Methods of Cylinder Lapping. When the cylinder must be 
lapped or ground out to a true surface, not re-bored, and when no old 
piston is available for 
this purpose, there are 
several methods avail- 
able. One is to use a 
standard lead lap, that 
is, a solid round bar of 
cylinder size. The abra- 
sive may be either emery 
and oil, carborundum 
dust and oil, or, in some cases, ground glass and oil imbedded in 
the soft surface of the lead, yet it projects enough to abrade the 

Fig. 32. Home-Made Lapper for Cylinder Bores 
(Note Spiral Grooves) 


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cylinder surface a little at each revolution. Another good way of 

doing this is to use a round block of wood, as shown in Fig. 32. This 

is made a close fit in the cylinder, with spiral grooves cut in its surface, 

and a split along one side. Into the latter a wedge is driven to adjust 

for wear. The emery and oil is put on the surface, and the lapping is 

done as usual. The spiral grooves distribute the abrasive evenly so 

that a true surface results. 

Another way of doing this is to make a large special boring bar, 

say 2 inches in diameter, and drill a hole into this at right angles. 

Then, a small round section of carborundum, say \ inch in diameter, 

is placed in this hole with a spring back of it to keep it up against its 

, work. This arrangement can 

8 Cylinder Motor^ be ^ Qn ft j^ ^ bar 

being rotated in the usual way, 
and the cylinder fed up to it 
either by the carriage feed or 
by hand. It will give a very 
fine cylinder surface, and use 
up very little of the carborun- 
dum, which costs very little to 
begin with. The advantage 
of this method is that the 
same outfit can be used on 

Fig. 33. Tool Made from Wire for Indicating manV different sizes of CvKn- 
Dead Center in V-Type Motors J J 

Simple Dead Center Indicator. In a great deal of engine work, 
it is necessary to know when the pistons in the various cylinders are 
on dead center, either the upper or the lower center. For this 
purpose a form of indicator which is simple, easy to use, and accurate, 
is needed. A good one is shown in Fig. 33. This consists of nothing 
more than a \ -inch steel wire, or narrow steel strip, bent to the form 
shown. It is indicated as setting into one cylinder of an eight* 
cylinder V-type motor, but with slightly more bending it is applicable 
to any form of V-type or vertical cylinder motor. The bent end is 
inserted, and the engine gradually turned by means of the crank until 
the tip end of the wire extending from the cylinder stops moving. 
This point is the upper dead center, and the lower center is found 
similarly. The advantage of the shape shown and of the long 




extended end is that a very minute movement of the piston is mag- 
nified and shown as a considerable movement at the end of the wire. 
Thus, it is possible to determine the dead center point very exactly. 

Repairing Cracked Water Jackets. Very often the first cold 
spell of fall will catch the owner napping in the matter of heat for 
his motor, and will freeze up the water, which finds a weak spot in the 
water jacket and cracks it. When the crack is small and localized, 
it can be repaired very simply as follows: Drill each end of the crack 
as shown at A and B, Fig. 34, and screw in small f -inch brass plugs to 
prevent the crack from spreading. Then cut back the outer sides 
of the crack with a small cold chisel to permit inserting a considerable 
amount of rusting compound, being careful not to cut away any 
quantity of good metal. Then fill the 
crack up very fully and carefully with 
the compound consisting of two parts iron 
filings and one part sal-ammoniac. Just 
enough water should be added to this to 
make a paste which can be handled better 
than the dust or powder. After inserting, 
let tL? cylinder stand for a day or two, 
and if it does not seal up quickly and 
entirely, add a little water. If this does 
not complete the job, it may be necessary 
to go over it again, adding more of the 
rusting compound. After a couple of tries, 
almost any skillful repair man will get the hang of this job, and be 
able to seal a water jacket crack perfectly every time. 

Welding Breaks in Cylinders. Welding is used very frequently 
now on cylinder breaks, probably more than any other method, since 
it has proved to be quick, accurate, and cheap. It has all the 
desired qualities, which cannot be said of any other process. More- 
over, it can be used with almost any form of metal, which also cannot 
be said of any other method. A separate chapter deals with welding, 
very exhaustively. It is recommended that every repair man study 
it; then get an outfit and learn to use it, for it represents a source of 
large profit when its use is once mastered. With a welding outfit, 
the method of procedure is often the reverse of other processes. Thus 
when a water jacket is cracked, the first operation is generally the 

§. 34. Method of Plugging 
mall Crack in Water Jacket 


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cutting away of sufficient metal to enable the workman to see the 
whole extent of the crack and also to permit getting at all the surface 
with the welding torch. With a crack of small size, such as that just 
described, enough of the sides should be cut away to allow working 
the torch in between them. This crack should be gradually refilled 
with new solid metal, melted in from a fuse bar or melt bar. The 
sides should be cut away so as to take off more on the inside if possible, 
as this gives the new metal a natural hold on the inside in addition to 
the fusing together of the old and new metal. 

When the crack is larger, but still not a big one, as a small curved 
or circular shape, say 2 inches long, a formed steel plate can very often 
be cut which exactly fits around and over the crack. This is then 
welded into place. This steel-plate method is particularly effective 
where the pieces of the water jacket are cracked out in chipping the 

hole or crack, or when a single 
piece to be welded is broken 
into two or three pieces dur- 
ing the chipping. Another 
similar water jacket crack 
repair is that necessary when 
the forward cylinder water 
jacket containing the boss in 

Fig. 35. Process of Welding Cylinder Jacket . . p . 

which the steel tan shalt is 
screwed, becomes wholly or partly cracked or broken away. This is 
shown, and the repair partly indicated, in Fig. 35. The difficulty here 
is to make a repair which will withstand subsequent tendencies to crack, 
that is, to make the repaired part stronger than it was in the first place. 
This can be done as follows: Starting at the bottom of the crack, all 
work proceeds upward. A hole is first burned through, as at A. 
By starting here and working upward on the right side, the hole is 
gradually filled with new iron from a melt bar as indicated at 2. In 
all this work, excess iron is left both inside and outside. 

Having reached the top, the work starts again at the bottom and 
proceeds up the other side to the top. When this is reached, and the 
two welds joined, the job is completed. It has the appearance shown 
in the sectional plan at 3, with extra metal inside and out, all around 
the crack. In work of this kind, precaution must be taken not to 
melt or otherwise weaken the cylinder wall inside. 


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Another cylinder weld frequently met is a flange cracked around 
a holding bolt. In such a break the fracture is usually confined to the 
flange, no part of the cylinder wall being broken or cracked. Thus, 
all the repair work is external, and proceeds more easily and quickly 
than would be the case when dealing with the more accurate cylinder 
wall. This is a simple repair, and is performed entirely from the 
outside by cutting the crack away on both sides to allow new metal 
to be added without increasing the thickness, then setting the piece 

Fig. 36. Method of He-Assembling Piston Mechanism 

carefully in place, clamping it there and fusing new metal from a melt- 
bar into the V-slot formed by chipping. In case the crack does extend 
to the cylinder walls or bore, it is advisable to stop the weld about 
rfr inch from the interior surface of the bore. In this weld, as in 
previous ones, excess metal is left on the outside; in fact, this is done 
whenever and wherever possible, as the excess metal compensates 
for the somewhat brittle character of the weld and guards against a 
recurrence of the trouble by making the break stronger than it was 
in the first place. 


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Working in Valve Cages. In overhead valve engines, when the 
valves are set in removable cages, it is often necessary to put in a new 
cage. This is worked in or seated in the cylinder by grinding it down 
to a perfect seat the same as a valve. Oil and emery are placed on 
the seat in the cylinder, the cage set in place and gradually worked 
around and down, until a perfect surface is obtained. The same is 
applied to renewing the seat when a valve cage shows signs of leakage. 
Replacing Pistons in Cylinders. When cylinders or pistons 
have been removed to be worked on, replacing these is a difficult job. 
There are two ways of doing this: viz, by a special form of ring closer, 
and by hand, using a string. The former is a shaped device which 

is clamped around the ring and squeezed 
together with pliers, using one hand, while 
with the other hand the ring is guided 
into the groove. The second and more 
usual method is illustrated in Fig. 36, and 
requires two men, unless the cylinder is 
of such a shape that it can be clamped 
in a vise. As the picture brings out, 
one man holds the cylinder while the 
other forces the piston carrying the rings 
into place. The piston is shoved in until 
the expanded top ring prevents further 
movement, when a heavy cord is placed 
around the spring, and the ends are 
crossed, thus closing up the ring and 
allowing the piston to slide in as far as the next ring. The operation 
is repeated successively for the other rings. This is a very simple 
method but it requires patience. 

When a block cylinder is to be replaced, this job is not so easv, 
for all the pistons, four or six as the case may be, must be lined up, 
and two of them entered at one time. This requires either special 
apparatus to help hold them or the services of several men. Most 
cylinders have a small bevelled edge at the bottom to facilitate this, 
but it is best to make a rig for a motor which is handled in sufficient 
numbers to warrant this. A handy form, and one easily made, is 
that shown in Fig. 37. This consists of a sheet-iron band of a depth 
equal to the total depth of the rings in the upper part of the cylinder 

Fig. 37. 

Simple Rig to Assist 
itons Entering Cylinder 


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and is flanged over at the top to give it extra stiffness and prevent 
its entering the cylinder. It is made a little bit small for the size of 
the pistons over which it is to be used, so it will have to be sprung 
into place. When this is done, it will have a tight hold on the rings, 
compressing them so they will enter the cylinder. In applying it, 
care should be used to put it on squarely, and similarly in pushing it 
down by forcing the piston upward into the cylinder, as it should not 
be moved off of a ring until that ring has been entered in the cylinder 
enough so it is held therein. That is, the spring clamp should not be 
moved down below a ring until that ring is engaged and held within 
the cylinder. Its use is restricted to one size of motor, which is no 
hardship in a big shop where one make of car is handled exclusively. 

Fig. 38. Marmon Two-Piece Piston as Used on the 1920 Car 

The small shop handling a variety of work would find half a 
dozen different sizes useful and economical. Moreover, the cost of 
this device is very small. 

A modification of the above device consists of a similar small- 
sized band of sheet metal, made very wide but without the upper 
flange. It is made, however, with a pair of right-angle lips where 
the two sides meet; these are drilled for a clamping bolt. This 
bolt has a wing nut with clamping rings to compress the lips 
of the band. 

Another modification of this is a loop or strap of narrow 
sheet metal having an additional loop to go over the two ends. 
These ends are made with a right-angle bend close to the piston- 

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curve portion, and the compression of the rings is effected by- 
pressing the sides of the clamp tightly against them, then sliding 
the small loop along the ends to hold this tightness. 

Piston Construction. The pistons of automobile motors have long 
been made of cast iron, with the piston pin held in bosses on the piston 
walls. For all ordinary service this construction, well carried out, 
serves every purpose, but with the development of very high-speed 
motors, with piston speeds- twice and three times as high as past 
practice has sanctioned, there is a growing tendency to substitute steel 
for cast iron in this important reciprocating element. 

Particularly in aviation motors has this been the case; the pistons 
of one well-known revolving motor, for example, are machined 
to the thinnest possible sections, out of a high-grade alloy steel. In 
this motor, the connecting rods are hinged to the head of the piston 
instead of to the walls, which can be made much thinner than other- 
wise would be possible. This practice has been followed to a slight 
extent by some automobile manufacturers. There are now a few 
stock cars of established quality provided with pressed-steel pistons. 

In cars, too, the movement toward smaller bores and higher 
efficiency has brought about the use of much lighter pistons; this 
is done by making them thinner and shorter. The latest develop- 
ment has been the use, not only of aluminum pistons and die-forged 
aluminum alloy connecting rods, but also of aluminum cylinders 
having cast-iron sleeves driven in to form the actual cylinder 

Marmon Two-Piece Piston. The body of this piston, Fig. 38, 
is of aluminum, and the cast-iron sleeve is bolted on to this body.' 
The aluminum part is die cast and carries three rings and the 
piston pin as well as the four studs which hold the skirt of the 
piston. The skirt is a light cast-iron cylinder whose only connec- 
tion with the head portion is at the flange, where they are bolted 
together. This construction allows the aluminum head to expand 
or contract without effecting the cast-iron skirt and thereby com- 
bines the aluminum and cast-iron pistons. 

Modern Tendencies. The modern tendency is to cut down the 
weight. This has been done by lightening the piston all over and 
by taking out rings. With fewer rings, it is necessary that each should 
be more efficient, consequently there has been much experimenting 


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done with new forms. The lightening of piston weight has not 
materially changed the old open-end trunk form, although the use 
of aluminum has modified its straight shape somewhat in the hour- 
glass and similar forms. Attempts to utilize so-called free pistons, 

Fig. 39. Old and New Types of Pistons 

Former Heavy Piston at Left; Present Lighter Type at Right 

Courtesy of Locomobile Company of America, Bridgeport, Connecticut 

in which the upper part is flexibly connected to the lower, and the 
use of combinations of pressed steel and other metals have done 
much to modify the general form. 

Both these tendencies are well shown in the illustrations, Figs. 
39 and 40. The former shows how a certain piston was lightened by 
taking out two rings at the top, one rib inside, and generally using 
thinner metal. The old form is shown at the left, the new at the 
right. The other tendency is seen in Fig. 40 
which is an aluminum alloy. Note how this 
is cast to have less metal at the piston boss 
and also to be strong without extra ribs. 

Characteristics of Piston Rings. ' Cast 
iron for piston rings, long used to the exclu- 
sion of everything else, is in slight degree 
yielding its pre-eminence for this purpose 
also. This is because it has been found, in 
aviation motors with steel cylinders, that 
bronze affords greater durability and 
smoother running against the steel-cylinder 
wall, for which reason bronze rings — with steel or cast-iron springs, 
or "bull rings", behind them — have been found most advantageous. 
Multiple rings, three or more in a groove, are finding favor. Their 
thinness necessitates the use of steel. 

Fig. 40. Typical Piston Cast 

in Aluminum Alloy for 

Minimum Weight 


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Fig. 41. New Types of Piston Rings Designed to Retain Compression and to Increase 
Power, at the Same Time Reducing Wall Fnction 


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Types of Piston Rings. Where formerly three or four plain rings 
were used, each one filling a groove, many pistons are now equipped 
with multiple rings of various patented forms, for which many- 
advantages are claimed. Some idea of the variety of these may be 
obtained from Fig. 41 which shows a number of different forms. 

Thus, A indicates a ring with a double form, yet really it is un« 
continuous piece, cut so as to appear as two. It is difficuit to see any 
advantage in this, while it is much more expensive than the old- 
fashioned form. At B is seen a type which has an outer thin but 
high ring within an L-shaped inner form, both with plain vertical slots, 
and without holding pins of any kind. A somewhat similar form is 
seen at C, but with this difference, the inner ring has two steps 
instead of one, both have diagonal slots, and a pin keeps the outer one 
from turning. 

The form at D has a pair of thin and very flexible high rings, set 
one within the other. They are concentric, and both have stepped 
joints. The extreme flexibility would appear to take all the value out 
of their use as compared with the ordinary form. Another seen at E 
differs in that one part is placed above the other and held from rotat- 
ing by a pin. Both have diagonal joints. Both are eccentric and 
the pins hold them so the slots are 90 degrees apart. In the form at F, 
there are three pieces, including an inner one of full height with a deep 
outer slot, a modified U. The two outer parts are L-shaped and the 
L-projections fit into the slot of the big ring. All have diagonal slots 
and are pinned in place. 

An eccentric form, which has a tongue-and-groove arrangement at 
the open or thin end, is shown at G. The makers call this the lock 
joint. Practically the same effect is produced in the form shown at H, 
except that the opening is closed by a separate piece. This is called 
a guard, and it is machined to fit under one portion of the master ring 
and on either side of the slender ends, so that it makes up the full 
width. This use of the old-fashioned simple ring seems good. 

The form at / is that of B reversed, that is, the small square ring 
is placed on the inside of the L-shaped ring, and has, in addition, a 
horizontal step joint, while the outer member has a vertical step joint. 
An entirely different principle is utilized in the form at J, the inner 
L-shaped member having a taper, and the outer thin but high mem- 
her having a corresponding taper to fit against it. The idea of the 

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taper is that the spring of the two rings, slightly opposed, will work 
through this to hold both against the cylinder walls. The outside 
of the inner ring is knurled to hold the outer one from rotating. Both 
have diagonally cut slots. 

In the form shown at K, there are three parts, divided vertically, 
but in such a way that the top and bottom are really dependent upon 
the middle to hold them in place both vertically and horizontally. 
It is difficult to see greater merit in this form than of three plain rings. 
The form at L is somewhat like that at F, except that the inner full- 
height ring has a pair of projecting ridges in place of the single central 
slot. Each of the small half-width outer rings has a central slot, or 
groove, and end ridges to fit around this. Like F, this has the small 
outer rings pinned, but differing from it, all have diagonal slots. 

In the form seen at M , three parts are used, but the center full- 
height piece has its outer surface in the form of a double taper, upon 
each half of which one of the small half-height outer rings of triangular 
cross-section rests. In that shown at N, the ring is a continuous 
spiral, being somewhat similar to A in this respect. Its cut, however, 
is upon a slope all the way, so that its thickness varies continuously. 
It is made of heat-treated steel. It is difficult to see how the vertical 
spiral effect can make it tighter in a horizontal direction. 

Piston Pins. Piston, or wrist pins, as they are variously called, 
are usually very simple. In general, when the pin is a light drive 
fit or any easy fit in the piston, it is made from a high quality of car- 
bon steel tubing of considerable thickness, ground on the outside to 
size, and drilled for the locking pin (when one is used). It is then 
hardened and finish ground. In some instances it is simply a tight 
fit, with a ring fitted around the outside of the piston at its center, 
to form a lock. In other forms it is clamped in the connecting rod 
and turns in bushings in the two piston bosses. The general method, 
however, is the use of a hollow pin, the variation coming in the method 
of locking. Thus there is the use of two locking pins which project 
into holes; of two set screws which bear against grooves for this pur- 
pose; expansion plugs screwed into the split ends; spring plungers in 
holes in the piston; and of complex built-up pin sections with tapers 
bearing upon each other so as to be self-locking. The really important 
point is to have the pin so locked in place that it can never work out 
and score the cylinder walls, and yet be easy to disassemble. 


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Piston and Ring Troubles and Repairs 

Removal and Replacement of Pistons. Speaking of pistons, 
there are several things that the beginner should learn about their 
removal and replacement. While it is not a difficult matter to pull 
a piston out of a cylinder, when both have been previously lubricated, 
and all proper precautions taken to loosen connecting parts, there 
are a few important things to remember. 

The piston should be drawn out as nearly parallel to the axis 
of the cylinder as is possible, accompanied by a twisting motion not 
unlike taking out a screw, in case it sticks a little. If the piston 

Fig. 42. Method of Removing Piston Rings 

sticks badly, pour in a little kerosene and work the piston in and out 
so as to distribute the kerosene between the two surfaces. 

To get at the spaces the rings must be removed, and as they 
are of cast iron and very brittle, this is a delicate task. Two 
methods of accomplishing this are illustrated in Fig. 42. If the 
owner has a pair of ring-expanding pliers, the rings can easily be 
expanded enough to lift them over the edge, as shown in (a). As 
very few owners possess this useful tool, however, a more common 
way is shown in (6). Secure a number of thin, flat steels about 


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\ inch wide and ys inch thick — corset steels, flat springs, or hack-saw 
blades may be used, although the latter require more care on account 
of the teeth along one edge. The length of these steels should be 

Check Jcrewto 
^F>is Ion Ring Frevenl Straining Ring 

[Fig. 43. Tool for Moving Piston Rings Which Prevents Breakage 

such as to reach from about an inch below the last ring, to the top. 
Lift out one side of the ring with a small pointed tool and slip one 
of the steels between the ring and the piston, then move around 
about one-third of the way and insert another, taking care to hold 

the first in place; repeat the opera- 
tion with a third steel. When these 
are in place, the steels will hold the 
ring out from the piston far enough to 
be slid over the "lands" between the 
grooves and along the steels to the top. 
Always begin at the bottom and 
work up when removing rings, and 
just the opposite, from the top down, 
when replacing them. After one is 
mastered, the removal of the others 
is a simple matter of repetition. The 
grooves can now be scraped free of 
the offending carbon, a process which 
is but an inversion of the previous 
method. After this it will be neces- 
sary to replace the rings. 
A modification of the simple home-made ring spreader just shown 
is that depicted in Fig. 43. This is made with a stop, which prevents 
opening the pliers beyond a predetermined distance and thus 
prevents breaking a ring by continued pressing on a stiff or stuck 





Fig. 44. Simple Piston Ring Remover 


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one until it gives suddenly and is then spread beyond the resisting abil- 
ity of the iron. It is applicable to all forms of rings, except those with 
diagonal slots. In addition to the construction shown, it is desirable 
to fit a spring which will draw the handles together when not in use, 
This closes the jaws and keeps them closed, ready for immediate use. 

An even better and more simple form, but without the safety feat- 
ure of that just mentioned, consists of a large diameter steel spring, 
shaped not unlike a very big piston ring, which has a pair of handles 
fitted to the ends. This is shown in Fig. 44, which indicates how 
the nubs on the two handles are shaped so as to take hold of stepped 
joint rings. By making these nubs differently, any form of ring can 
be handled. A device of this sort saves the repair man lots of time. 

Loosening Seized Pistons. When the pistons and rings freeze 
into the cylinder, or seize because of a lack of lubricant, there is 
nothing quite so good nor quite so quick acting as kerosene. The 
cylinder head should be opened as quickly as possible, and the 
kerosene poured in liberally on top of the pistons. This should be 
done in each cylinder. Kerosene is thin and will work down between 
cylinder wall and piston rings, gradually cut- 
ting away the two where they have frozen 
together. If kerosene is not available, take 
the thinnest lubricant at hand; heat it so that 
it will be still thinner and more penetrating, 

Fig. 45. Simple Piston-Pin Pulling Outfit 

Fig. 46. Piston Ring Puller 
Which Allows for Exit of Pin 

then pour it in. At times, olive oil can be combined with kerosene 
to advantage. 

Freeing Wrist Pins and Bushings. When the piston pin or 
wrist pin is inserted directly in the piston,, it is usually a tight fit, 
so tight, sometimes, that the repair man experiences difficulty in 
getting it out. To overcome this difficulty, a piston pin puiler is 


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needed. One of these, shown in Fig. 45, is made from a piece of steel, 
a steel strap, and a large cap screw. This piece of steel is drilled and 
tapped for the cap screw, and for the bolts to hold the steel strap. 
Then the latter is fastened so as to be about i inch larger in diameter 
than the piston, or still larger if a long cap screw is available. When a 
pin is to be removed, the strap is put around the piston and the cap 
screw screwed in until it bears against the end of the pin. This can 
be done by hand. Then a wrench is applied, and as the screw is 
forced in, the pin is forced out on the opposite side. Be careful to see 
that the far side of the steel band is below the piston pin hole, so the 
pin will be able to come out without touching it. 

This can be simplified by having an endless steel band with a 
nut on the inside of it to form a backing for the cap screw to work 

against, or, the steel band can 
be welded to the nut. 

A form which removes 
the above difficulty is that 
shown In Fig. 46. This is 
made so that it holds around 
the piston at two points, 
above and below the piston 
pin, leaving room for the pin 
to come out. While more 
elaborate than the first one 
described, it is still very simple. For hollow piston pins, a different 
form of tip on the screw is needed, as the point, or tip, must press 
against the outer circular ring instead of against the center. This 
can be obviated, however, by laying a special round piece of metal 
over the end of the hollow pin before starting to apply pressure to 
force it out. 

Bushing Removers. When the piston pin is fixed in the con- 
necting rod and rotates in bushings in the piston bosses, it is some- 
times necessary to remove these bushings. A somewhat similar 
device will do this work, except that a shoulder or stop is needed to 
come up home against the side of the bushing, while the screw or 
threaded end must be small enough to pass through the hole in the 
bushing, and long enough to come out on the other side so a nut can 
be applied. One of these is shown in Fig. 47. The disadvantage of 

Fig. 47. Piston Pin Bushing with Shouldered 


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this type is that the nut shown on the right, which is operated to 
force the bushing out, must rest against the surface of the piston 
while being turned around. If a small U-bar be made to rest against 
the piston side, with a central drilled hole through which the threaded 
end passes, the nut will bear against the outside surface of this, so 
that even if the nut should scratch, no harm will be done to the piston. 
These pullers are used as substitutes for an arbor press, but this is 
desirable, as the use of the press is likely to distort the more or less 
delicate piston. With aluminum and the lighter weight cast-iron 
pistons, this is a thing which it is desirable to avoid. 

Some motors have the wrist pin locked in place by means of an 
expanding nut with a sunken square hole for turning. To start these, 
a wrench with a square projection or tit to fit this is needed. Such 
a wrench is used on certain lathe chucks, so one can always be bor- 
rowed in a machine shop or tool room. 

Mandrel for Turning Pins. Because of its being hollow in 
many cases, the wrist pin is difficult to handle when any work must 
be done upon it. For this 
purpose, a mandrel is needed. 
The method of constructing 
and using this is shown in 
Fig. 48. This consists of a 
shaft with a taper at one 
end and thread at the other, 
for a tapered nut. The wrist 
pin is slipped on the outer 
end, the taper nut put in 
place against it, and the 
backing nut put on behind that. Then these are screwed up until 
the two tapers hold the pin firmly, after which it may be placed in 
the lathe and work done upon it. 

Speeding Up Old Engines by Lightening Pistons, Etc. As 
will be pointed out later under "Cams", one way to speed up an 
old engine is to replace the old camshaft and cams with new ones 
giving more modern timing. Another and a less expensive and 
troublesome way in which this can be done is by lightening the 
pistons and the reciprocating parts. This the repair man will surely 
be called upon to do, as the manufacturer probably would refuse. 



Fig. 48. 

Tapered Mandrel for Holding Hollow 
Piston Pin for Lathe Work 


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Fig. 49. 

Appearance of Piston Lightened 
for Racing Purposes 

In order to get out any amount of metal worth the trouble, it 
will be necessary to drill from 12 to 20 or more holes of from §-inch up 
to 1-inch diameter, depending upon the size of the piston as to bore 

and length. In a six-cylinder motor, 
this amounts to almost 100 holes 
(even more in some cases), and as 
these must be drilled with consid- 
erable similarity in the pistons, it is 
well worth while to construct a fix- 
ture to aid or speed up this work. 

One idea of the way such a 
lightened piston should look when 
finished is given in Fig. 49, which 
shows the steel pistons used in the 
Sunbeam racers. These are made 
this way to give the maximum of 
lightness with strength. Although 
made from steel, this is done 
simply to get very light side 
walls, and the general appear- 
ance of the skirt with its 
many drilled holes is just 
what the repair man should 
try to get when he starts to 
cut down the weight of stand- 
ard pistons for racing or speed 

Clamp for Pistons. The 
first requisite is a clamp, Fig. 
50, to keep the piston from 
turning, so that it will not 
break the drill. A good way 
to begin is to construct a base 
with a pair of uprights having 
deep 90-degree V's in them; 
this is made so that it can be 
bolted to the drill-press table. The V's should be lined with leather 
or fabric. Discarded clutch or brake linings answer this purpose 

Fig. 50. A Home-Made Wooden Stand to 
Facilitate Drilling Out Pistons 


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very well. To one of the uprights is pivoted a long handle, hav- 
ing a lined V which matches with that of the upright below it, 
and gives a good grip on the piston. 

Drilling Holes. When drilling to save weight, the holes are 
put in close together and in regular form, the idea being to take 
out as much weight of metal as is safe. In doing this, it is well 
to work out a scheme of drilling in advance, to make a heavy 
brown paper template, and fasten to each piston in turn. 

Ring Repairs. When rings are turned- either for reducing 
thickness or for truing up the face, a wooden faceplate should be 
made with a slightly tapered groove for 
the ring to fit into. The ring should be 
pressed into the groove, and its natural 
spring will hold it in place. When work- 
ing on the outer diameter, the face of 
the wood will have to be cut away suffi- 
ciently to allow the ring to project, or, 
instead of a single large central hole, 
an annular ring can be turned in the 
wooden faceplate, the ring being fitted 
over the outside of it. ^ 6L Method of Groovi and 

Curing Excessive Lubrication. Holes Dr i£e^^^ 
in Pistons. WTien it comes to drilling 

holes to provide an outlet for the excess oil in the cylinders and so 
to reduce smoking, small holes, J-inch for example, are sufficient. 
They may be drilled in on any spiral plan by simply beginning near 
the bottom and working up close to the piston-pin bosses along a 
spiral track. The advantage of the spiral arrangement is that no 
hole is above another; the dripping from each hole is therefore 
distinct, and the quantity which runs down is greater. 

Grooving Pistons. Another method of curing the excessive lubrica- 
tion to which the older cars — particularly those with splash lubrication 
— are subject is to turn a deep groove in the bottom of the piston, 
about like a piston-ring groove but with a lower edge beveled off. 
When this is done, about as shown in Fig. 51, a series of small holes 
— made with a No. 30 drill — are put in at the angle of the bevel; 
six or eight holes, equally distributed around the circumference, 
are probably enough. The sharp upper edge acts as a wiper and 

201 Digitized by G00gle 



Head 5 lock 


removes the oil from the cylinder walls into the groove, whence it 
passes through the holes to the piston interior and there drops back 
into the crankcase. No ring is placed in the slot as it would prevent 
the free passage of the oil. This device stops the smoking immediately. 

Loose Pistons. Many times the pistons will wear just enough so 
that they are loose in the cylinder all the way around. This causes 
leakage of gas, piston slaps, and other similar troubles. If the owner 
of the car does not care to buy new pistons, or if the car is an 
"orphan", or if, for other reasons, pistons cannot be obtained, the 
clever repair man can remedy the trouble at small expense. The 
process consists in heating and expanding the old pistons. The 
heating is done in charcoal and must be done very carefully and 
slowly. After the pistons become red hot the fire is allowed to go out 
slowly, so that the piston is 
cooled in its charcoal bed. 
Sometimes as much as io 4 oo 
of an inch can be gained in 
this way. When the pistons 
are so far gone that they 
cannot be handled in this 
way, they must be replaced 
with new ones. 

Mounting Pistons on Lathes. It is difficult to handle a piston 
in the lathe, or machine the outside in any manner, as a chuck does 
not get enough of a hold on it, and is likely to mark the surface. 
When work on it is necessary, the piston can be handled effectively 
by using a small rod with an eye at one end. This is made to fit the 
piston pin in the case of an old piston. The rod is run through the 
hollow spindle and bolted at the outer end. The tightening of the nut 
on it pulls the piston up against the face plate as Fig. 52 shows. 
This same method can be used when making a new piston. In the 
latter case, it is held in the chuck to finish the outside and inside, then 
the wrist-pin hole is drilled, bored, and reamed, and the wrist pin fitted. 
Finally, the finishing cut, or grinding of the outside, is completed. 

Fig. 52. Rigging for Holding Piston against Face 
Plate of Lathe 


Design Characteristics. HSection Form. Established prac- 
tice in connecting-rod design is almost all in favor of the common 


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H-section rod, usually with two bolts to attach the cap. In some 
cases four bolts are used, since with four bolts a flaw or crack in one 
is less likely to cause damage than is the case when only two are used. 
The did scheme of hinging the cap at one side is now practically 
obsolete, having been discarded because it made accurate adjustment 
of the bearing surfaces almost impossible. 

Tendency- to Lighten Rods. The modern tendency toward 
lightening the weight has extended to the connecting rods, since a 
portion of the rod is considered as reciprocating. This lightening 

has been accomplished by 
external machining. Thus, 
in the typical connecting rod 
of forged alloy steel, shown in 
Fig. 53, the form at the left is 
that formerly used, while that 
at the right is its present 
shape. Note how the round- 
ing sides of the H-part, nec- 
essary in forging, have been 
machined off; how the fillets 
at big end and piston end 
have been machined down; 
how the upper end has also 
had its central rounding part 
machined off; and the whole, 
file finished. Another excel- 
lent feature of the work done 
to lighten the rods in this 
way is that ' they can b« 
brought to an absolute stand- 
ard of weight, so that ever> 
rod weighs exactly -the same as every other. This was not pos< 
sible previously, as the variation of the exterior surfaces, due to 
differences in forging, made considerable difference in weight. In 
both, the bushings are in place. 

Tubular Rods. Tubular rods, in place of the H-section, are 
giving good service in several of the long-stroke foreign motors, and 
it is difficult to see why this form is not superior to that in common use* 

Fig. 63. Old and New Connecting Rods Showing Hqw 

They Can Be Lightened 

Courtesy of the Locomobile Company of America, 

Bridgeport, Connecticut 


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The question of cost, however, is a consideration, since it is necessary 
to bore the hole through the inside of the rod, whereas a forged rod 
of H-section requires no machining except at the end. 

The wonderful progress in welding, however, has made it possible 
to construct a tubular connecting rod at a very low expense, and, owing 
to its many advantages, this is finding much favor for small motors. 
The two ends are machined and a section of tubing welded to them. 

One advantage of the tubular rod, in addition to its superiority 
for withstanding the compression load to which a rod is chiefly sub- 

ject, is that it can be used as a pipe to convey oil from the big end 
to the piston-pin bearing. 

Fig. 54 shows an example of a very light-weight, high-quality, 
aviation-motor connecting rod, machined out of a solid bar of 
alloy steel, and provided with four bolts in the cap. 

Connecting=Rod Bearings. Usual Types. Connecting rods have 
two different forms of bearings. This is due to the difference in their 
service. At the upper or piston end, the bearing is usually a high- 
grade bronze tubing, machined all over and pressed in place. When 
in place, it generally has a central oil hole drilled through rod and 
bushing, and then a couple of oil grooves are scraped in by hand to 
start from this hole and distribute the oil outward in both directions 
on its inner surface. 


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At the lower or, as it is usually called, big end, the connecting rod 
must have a better bearing. This end is bolted around the crankshaft 
pin and must sustain high rubbing speed, as well as the load of explo- 
sions. Bolting it on, and the need for removing it occasionally, call 
for a form which is split horizontally. Generally, this bearing is of 
high-grade bronze with a softer, or babbitt, central lining which can 
be replaced easily and quickly. The harder bronze back will sustain 

Fig. 55. Connecting Rods for V-Type Engine, Showing Method of Forking One Rod 
Courtesy of Cadillac Motor Car Company, Detroit, Michigan 

the stresses of bolting up tight and stand up under the constant 
pounding, while the softer and renewable center takes all ordinary 
wear. These bearings are fitted with great care. They are reamed 
by hand after machining, and then hand scraped to a precise fit. 
They are pinned in place, drilled for oil, and grooved to distribute it. 
Eight- and Twelve-V- Types. The eight- and twelve-cylinder 
V-type motors have altered the design of connecting-rod bearings 

205 £/*~ 


somewhat, in that there are two connecting-rod big ends working 
upon one crank pin, that is, an eight-cylinder V-engine uses a four- 
cylinder form of crankshaft with two connecting rods on each pin. 
This modifies what was good connecting rod bearing practice, one of 
two different forms being utilized. When the rods are placed side by 
side with individual bearings, the pins are made very large and as long 
as possible, in prder to give adequate bearing surface. The other 
form is the forked rod in which one rod works within a slot in the 

Fig. 55A. Triple Lite Piston and Connecting Rod Manufactured by the 
Laurels Motor Company, Anderson, Indiana 

other. In this type, a split bearing of the usual form is placed in the 
forked or long rod, and the outer surface of the central part of this 
prepared as a pin surface for the other or central rod. The requisite 
area of the smaller rod bearing is made up by its larger diameter. 
This is well shown in Fig. 55, where the rods and bearing are shown 
assembled, and the separate big-end bearing is shown at the right. 
In another type of V-motor connecting-rod bearing, the larger bearing 
is slotted for the central rod and its bearing, the slot being made large 
enough to permit a rotation, which never exceeds a quarter of a turn. 
This arrangement is more complicated to install and repair than the 
form shown. 



Aluminum Connecting Rods. A number of manufacturers are 
now developing aluminum connecting rods as this metal is very 
light and will combine very readily with other metals, thus form- 
ing an alloy of great strength. The lighter the reciprocating 
weight, such as the piston and connecting rod, the greater will be 
the efficiency, power, and speed of the motor. It is for this reason 
that the engineers desire to develop a much lighter rod. While 
it is true that the entire rod does not act as reciprocating weight, 
in general practice, the upper half of the rod is considered recipro- 
cating while the lower half is rotating weight. 

The Triple Lite connecting rods — an alloy with aluminum as 
its base — shown in Fig. 55a are constructed with a section some- 
what different from the ordinary drop forged connecting rod. A 
comparison with Fig. 55 shows that the H section in the Triple 
Lite connecting rod has its flange between the bearing pins while 
the flange in the drop forged steel rod is at the side of the bearing 
pins. The Triple Lite is also used as a bearing making it unneces- 
sary to equip these rods with a babbitt bearing face. This rod 
weighs but 14 ounces. 

Connecting Rod Troubles and Repairs 

Classification of Troubles. In general, all connecting-rod 
troubles come under one of four headings: straight rod, proper bear- 
ing adjustment, mechanical work (scraping bearings, straightening rod, 
or other work), and special equipment for doing connecting-rod work. 

Straightening Bent Rod. The need for a straight and true 
rod is apparent, but it is surprising how many rods are not straight, 
particularly in old motors 
Many erratic and bad- 
sounding motors have all 
their trouble caused by a 
bent rod. A connecting r M Mt , , , T . « . . w , 

° Fig. 56. Method of Testing Connecting Rods 

rod can be bent either of ™ th two M » ndr eis 

two ways, and one gives as much trouble as the other. If bent in 
the plane of rotation, the rod will simply be shortened, the piston will 
not go as high as it should, and it will go down a little lower than 
normal. Moreover, the bend will press it with unusual force on the 
cylinder wall on one side and cause it to wear more than the other. 

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The combination will soon result in trouble. When bent in a longi- 
tudinal direction, that is, fore and aft, the upper end of the rod will 
run against one side of the piston or perhaps only knock against it 
on each stroke. At any rate, this too, will give trouble. 

Methods of Testing Straightness of Rods. The first thing to do 
when a connecting rod is suspected is to take it out and test it. One 
way of doing this is to attach the lower end to a mandrel, which 
can be bolted into a drill-press table, as shown in Fig. 56. Before 
doing this, the small end is also fitted with a mandrel, the lower part 
of which is of considerable length aiid has two short vertical pegs. 
When the big end is bolted down, if both the small pegs on the other 
end touch, it proves at least that the two holes (big end and small 
end) are parallel. If one of these pegs is off the table as shown, 

Fig. 57. Complete Connecting-Rod Testing Fixture 

it proves that the two holes are not parallel. In the latter case, the 
rod would need to be straightened, as nothing but the bending of the 
rod would throw the holes out of parallel when they were bored 

Another method, which is very similar, consists in forcing two 
mandrels of equal length into the two holes, until each is centered in 
the rod. Then, if the rod be placed on supports on the surface plate, 
or other similar true surface, so that one mandrel is horizontal, the 
surface gage will show at once if the other end is also horizontal, 
and thus, if the rod is straight and true. It will also show how much 
it is twisted, if out of true. If the mandrels are made long enough, 
ordinary calipers can be substituted for the surface gage with equally 
accurate results. 

A method almost the same as that just described is utilized in 
the testing fixture shown in Fig. 57. The advantage of such a fixture 


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Fig. 58. Connecting - Rod Straightener Constructed 
from Three-Quarter-Inch Bar Stock 

is that it always works the same, while the use of surface gages 

and calipers varies from one workman to another, and even with the 

same man, from day to day, according to his moods and feelings. 

As the sketch shows, there is a mandrel for each end of the rod, that 

for the big end being pivoted in the fixture. When the rod is forced 

into this, and the other 

mandrel put in place in the 

piston end, if rotated down 

to a flat position (as shown), 

the small end mandrel 

should touch both of the 

fixture stops. If badly 

twisted, it will not be able 

to go down on one side. 

Straightening Jigs. 
When it has been proved 
that the rod is not straight, it is necessary to have a device for apply- 
ing pressure in order to straighten it. The simplest way is an ordinary 
straightening press consisting of a pair of ways with V-blocks upon 
which the work is supported and a lever or screw to apply the pressure 
in the middle. The work is supported on the V-blocks, the distance 
apart varying with the amount it is to be bent — far apart for a 
big bend, close together 
for a small one. For as 
short a member as a con- 
necting rod, however, 
this is not sufficiently 
accurate, and besides, the 
form of the rod does not 
suit it to good results by 
this method. 

A simple fixture for 
bending a rod, shown in 
Fig. 58, consists of a pair of hooks for holding it and a central 
screw for applying power. The rod is slid into place inside the 
hooks and the screw turned until the rod is straightened. Then to 
prevent its springing back when the pressure is released, it is peened 
on the side opposite the screw. The advantage of this method is 

Fig. 59. Box Type of Connecting-Rod Straightener 


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that it throws all stresses upon the rod itself and none on the bearing 
surfaces. The hooks are forged from high-carbon steel of f -inch square 
section. The screw should be not less than f 
inch to f inch in diameter and fine threaded. 
Another fixture is on the box order, 
shown in Fig. 59. This has a pair of end 
clips which hold the rod tight by means of 
wedges which are driven into place. When 
this has been done, the rod is straightened 
by means of the central screw. As will be 
noted, the principal difference between the 
two forms, Figs. 58 and 59, is in the holding 
method. There are other forms, as well as 
forms of mandrels for lapping in big-end 
bearings, which are so constructed as to give 
a check on straightness and to allow of 
remedying the situation if the rod is not 
%odV^nfHow°B2ar- ting straight. Some of these will be described. 
ings wear Offsetting Causes Trouble. Many motors 

have been constructed with offset connecting rods, that is, the 
perpendicular center line of the wristpin, located in the piston, 
where the pressure is applied, is not upon the center line of the 
bottom end. This resultant wear on the bearings is exaggerated 
in Fig. 60, which indicates also how this situation causes wear on 

the upper left end and lower right 
end of both bearings. The sketch 
also shows how this unequal wear 
i3 greater on the crank end, which 
is offset, than upon the piston 
end. The cause of this wear is 
simple, the pressure is unbalanced 
on the left side, so a downward 
push on that side is taken up by 
extra wear there, and on an 
upward push, as on the compres- 
sion stroke when the flywheel is 
driving the pistons, the extra resistance of the left side causes unusual 
upward pressure on the right side. So the ends continue to wear, until 

Fig. 61. Wooden Core for Babbitting 
Connecting-Rod Bearings 


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a rocking motion of the pins results, and this causes a noise. New 
bearings help temporarily, but a stiffer connecting rod will often 
remedy it more or less permanently. 

Adjustment of Connecting-Rod Bearings. Babbitting Bearings. 
As has been stated, the majority of connecting-rod and crankshaft 
bearings are bronze shells or backs, lined or faced with babbitt as a 
wearing metal. The bronze provides the stiffness and long life, the 
babbitt, the softer wearing face which is easily and cheaply replaced. 
In this replacement, a form or jig to simulate the crankpin and 
approximate its size must be used for a center. A form made of 
wood is shown in Fig. 61. This is simply a round member of hard 
wood, turned up slightly smaller than the actual crankpin at the 
upper end, while the lower end is left large to form an under surface 
for the metal. Next, the upper part is split or rather has a cut taken- 
across it, equal in thickness to the shim to be used when the bearing is 

Fig. 62. Home-Made Creeper 

assembled in place. Then, when the babbitt is poured in, a metal 
member is set across the rod to form the shim, which is shown in the 
smaller sketch at the right. 

This method has the advantage over that of using the pin when 
pouring the metal in position, because it gives a little surplus to 
machine off, and thus makes the surface more accurate before it is 
scraped. If broaching to harden the surface of the metal is resorted 
to, it gives a little metal to broach down. Moreover, by making it 
so simple and easy to handle, the work of babbitting is made easy. 
This cannot be said of trying to babbitt in place. The core need not 
necessarily be of wood; it can be of metal or of anything else desired. 
But the wood has the advantage of being easily worked, or of being 
cheap and quickly obtained. 

Kinks in Adjusting Bearings. Usually, crankshaft and connect- 
ing-rod bearing adjustment is a difficult job. , This is particularly 

211 Digitized by G00gle 


true when the engine is not removed from the chassis. The con- 
necting-rod bolts are tight and hard to reach, and the operator, who 
is lying on his back, has all dislodged dirt or oil dropping in his face. 
Work like this calls for an easy means of getting under the engine and 
out again. For this, a form of creeper is necessary. There are many 
forms made and sold, but a simple one which any repair man can 
construct for himself is shown in Fig. 62. This consists of a wood 
frame with casters at the four corners and longitudinal slats for the 
floor. By making the ends concave, the surface is made concave. 
With a pillow or other head rest, it is more comfortable to use. 
Another way in which this work may be facilitated is to make a 
special socket wrench for connecting-rod nuts and to make it deep 

enough to hold four nuts, one 
over the other. Then with a 
spring-stop arrangement, Fig. 63, 
the nuts from two rods can be 
taken off without stopping; or if 
lock nuts are used, the nuts and 
lock nuts may be removed from 
one rod. This is accomplished 
by means of four spring-operated 
pins. When the first nut is 
removed, it sticks in the end of 
the tool, but pushing this into the 

Fig. 63. Spring Clips on Socket Wrench for Second One moves the first nut On 
Use in Inaccessible Places . , . , , . T , 

up inside the socket. In replace- 
ment, when the upper pins are pulled, a nut drops down and is held 
by the lower pins enough to start it on the bolt end. When tightened, 
the socket can be pulled off, and the next nut dropped down and fixed 
in place by hand. The four pins have hardened ends, and the springs 
are old clock springs to which the upper pair of pins are brazed. 
The lower pins can be free. This form of socket wrench can be used 
with equal advantage in many other inaccessible places. Its single 
drawback is that it can only be of one size; and a set of them have 
to be constructed to take care of all needs. 

In ordinary bearing adjustment, the nuts are taken off, the 
connecting-rod cap removed, and the shims taken out; say, a shim 
of .001-inch thickness for very small wear, .002 inch for considerable 

212 • Digitized by G00gk 



wear, and .003 inch for severe wear. If more than this has been 
worn off the bearings, they need re-scraping, as this is about the 
maximum that can be taken out without scraping. Usually, when 

Position of Wrench 
When fldjusling Searing 

Position of Wrench When 
Locking D earing 

Fig. 64. Connecting Rod and Main Bearings Constructed without Shims 
Courtesy of Reo Motor Car Company, Lansing, Michigan 

the bearings have been taken up in this way, the caps are put back 
on pretty tight, a little bit tighter than they were previously. Then 
they are flooded with oil and run in this condition. The combina- 
tion of excess oil and tight 
caps soon gives the entire bear- 
ing surface a fine polish which 
will last for many miles. 

Special Sleeve Replaces 
Shims. In one motor (Reo), 
the shim is replaced by an 
ingenious arrangement of a 
threaded sleeve around the 
bearing bolts. This is shown 
in Fig. 64 in which the sleeves 
are marked A and the bolts 
B. It will be noted that the 

Fig. 65. Standard Mandrel Method of Lapping 
Big-End Bearings of Connecting Rods 

sleeves rest against the upper part of the bearing and have a head 
against which the bolts rest, so that the latter can be tightened only 
as far as the sleeves allow. With this construction, when it is desired 
to tighten a bearing, the socket wrench is slid on so as to hold the 
heads of both bolt and sleeve, and then turned to unscrew both. 


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Then the socket is drawn off the sleeve head, in the position shown 
at the left, and the bolt screwed back to pinch the bearing together 
and lock it. As will be noted, the two halves of the bearing metal 
are separated a considerable distance so that this arrangement is 
good for many thousand miles. Two years' running will usually 
exhaust the possibilities of the original bearing and its shims, which 
calls for re-babbitting, re-scraping, new shims, or for an entirely new 
bearing. This form of construction could be used anywhere that 
the bearings are likely to need frequent readjustment. 

Mandrel for Lapping. In order to give the connecting-rod 
bearings the best possible surface, a mandrel should be used to lap 
them in. This is the equivalent of running in. The rod, with bear- 
ings in place, is put on the mandrel, and the bolts tightened a little; 
then it is worked back and forth, until the flattening down of the 
surface will allow more tightening of the bolts. This is continued 
until, with a mandrel the exact size of the crankpins, the bolts can 
be pulled up dead tight. Then the rod is removed; it is finished. 
Such a mandrel, shown in Fig. 65, is usually a piece of steel turned up 
on one end to the exact size of the crankpin, with a flat spot machined 
in the other end to allow holding in the vice. By making it perfectly 
straight, a try square against the mandrel will show the correctness 
of the rod. On the other hand, if the outer end be made with a very 
slight taper, it is easier to work the rod on and off and easier to 
inspect the inside surface without unbolting. 

Drilling Thin Shims. When thin brass shims are used, and the 
shape is formed by the workman, it is difficult to get a good true hole 
because of the extreme thinness of the metal. By collecting a num- 
ber of these together and clamping them between two blocks of 
wood, a straight true hole can be bored through wood and brass with 
an ordinary bit and brace. The use of laminated shims avoids all 
this, as they come in the required thickness and are drilled to size. 
With these, adjustment is simply a matter of peeling off one of the 


Material. The crankshaft in all but heavy slow-running motors 
should be made of the finest alloy steel obtainable, for it carries the 
practical equivalent of thousands upon thousands of heavy blows. 

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Variation of Design. The 

greatest variations in auto- 
mobile crankshaft design* aside 
from those permitted or made 
necessary by differences in the 
quality of material, are due 
to the conditions involved in 
the different combinations of 
cylinders that can be utilized. 
Thus the number of crank 
throws, as well as their posi- 
tion, varies with the type of 

As the repair man knows 
crankshafts today, they are of 
two kinds. The first is the 
four-cylinder form, in which 
all throws are in a single plane. 
This type of shaft has four 
pins, one for each connecting- 
rod big-end bearing. It may 
have either three bearings, as 
shown in Fig. 66, or five bear- 
ings. The second type, which 
the repair man is likely to 
meet, is the six-cylinder shaft, 
which will have six pins for 
connecting rods; these are 
grouped in pairs, and each pair 
in a different plane, the angle 
between them being 120 de- 
grees. This type of shaft may 
have either f our or seven bear- 
ings. In the four-bearing 
form, there is a bearing at each 
end, and another between each 
pair of cylinders, as shown in 
Fig. 67, with pistons and con- 


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necting rods attached. In the seven-bearing form, there is a bearing 
on each side of each connecting rod. These are the modern types, 
but older shafts may be encountered occasionally, in the way of 
four-cylinder shafts with two bearings, one at each end only; also with 

Fig. 67. Six-Cylinder Four-Bearing Crankshaft with Pistons and Connecting Rods Assembled 
Courtesy of Nordyke <fc Marmon Company, Indianapolis, Indiana 

four bearings, the latter having the usual center bearing eliminated. 
The modern tendency is toward simplification, compactness, and low- 
ered first cost; and the shafts with the fewer number of bearings are 
on the increase. 

Fig. 68. Typical Drop-Forged-Balanced Crankshaft 
Courtesy of Park Drop Forge Company, Cleveland, Ohio 

Crankshafts may be found which are drilled out for lubricant pas- 
sages. In such cases, the repair man must look for attachments which 
feed the oil into the hollow interior. Also, he may meet a ball- 
bearing form of shaft which has been built up to allow the bearings 
to be assembled. Such a shaft should be handled with extreme care. 



Eight-cylinder engines generally use a four-cylinder form of shaft, 
with two connecting rods on each of the four pins. This is explained 
previously under connecting rods. Similarly, twelve-cylinder motors 
have a typical six-cylinder crankshaft, with two rods on each of the 
six pins. 

Balanced Crankshafts. While not an assembled shaft in the 
sense just referred to, the balanced form is meeting with great favor, 
and is being widely adopted. This will be met by the repair man 
in two forms. One is like Fig. 66, except that the weights are 
machined to fit on the crank cheeks and bolted there. The repair 
man should not remove these unless it is absolutely necessary, as 
they vary in size and weight. They are fitted in place with extreme 
care and fastened extremely well. The other type — the kind being 
introduced into the latest models — has its counterweights forged as a 
part of the crankshaft, Fig. 68. In this type, the weights are adjusted 
to make the proper balance when the shaft is being machined. 

Crankshaft Bearings. The bearings of the crankshaft in the 
crankcase do not differ materially from the connecting-rod bearings 
just shown and described. They may be a little longer, but the type 
is the same. They are pinned or otherwise fastened in the crankcase so 
as not to rotate, while the connecting-rod bearings are fastened in the 
connecting rods so as to rotate with them. A few shafts will be met 
which have ball or roller bearings, but the great majority have the split 
bronze-backed, babbitt-faced bearing described for connecting rods. 

Crankshaft and Connecting=Rod Bearing Shims. Practically all 
split or two-piece bearings for either crankshafts or connecting rods 
are assembled in place with shims. These are very thin flat pieces 
of metal set between the two halves of the bearing when it is 
assembled new to spread it apart. The shaft bearings are scraped to 
an exact fit on the pins with these shims or expanders in place. Then 
when wear occurs in the bearing, so that its inside diameter is enlarged, 
the bolts may be taken out, a shim or shims of the required thickness 
removed, and the bolts put back and tightened. This removal 
reduces the diameter of the inside of the bearing. To facilitate this 
action, the shims are generally put in, in such a way as to allow taking 
out a number of thousandths of an inch, there being two shims of 
io x jo , two or more of iooo , possibly one of io 5 oo , and a thicker one, or 
more of the very thin ones. These shims enable the taking-up of wear 

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amounting to -nnnr of an inch, when one of the thinnest shims is 
removed; nnnr by removing one of that thickness; io 8 oo by removing 
a io*oo and a io 2 oo; io 4 oo by taking two 2's, etc. 

Of course, a crankshaft bearing or a connecting rod-bearing will 
not wear entirely round, but the work of adjusting either bearing is 
reduced to a minimum by the use of shims. When the wear is very 
bad, the bearings should be re-fitted and the shims left out. 

An entirely new form is the laminated shim. The total thickness 
required is built up of very thin laminations, either one or two 
thousandths of an inch thick, so that in adjusting a bearing as many 
laminations are peeled off as are necessary to take up the wear, then 
the original shim, slightly lessened in thickness is replaced. 

In Fig. 66, the end view shows both connecting-rod and crank- 
shaft bearing shims in place, and indicates how they perform their 
function of holding the halves of the bearing apart when the bearing 
is being fitted. 

Crankshaft and Bearing Troubles, and Remedies 

Bearings. Bearings of the two-piece, or split, type give the 
auto repair man fully as much trouble as anything, in fact, the 
crankshaft bearings should not be tackled until considerable repair 
experience has been had. In general, wear on the bearings is due 
to one of two causes: either to a soft metal which has caused vertical 
wear on the inside or outside of the lower half of the bushing, or to a 
vibrating shaft which has worn an oval hole somewhere in the length 
of the shaft, as at the inner or outer end. 

In the former case, the height of the worn half must be reduced. 
This is usually done by taking as much metal from the upper face as 
is necessary. When this has been done — either by filing or by 
rubbing across emery cloth wet with oil — the two halves of the bushing 
will approach so close together that the hole will be smaller than the 
shaft. This will necessitate scraping out, or reboring, according to the 
amount which has been taken off. In the case of very small amounts, 
this wear can be taken up by removing shims, as mentioned above. 

When the second form of wear is found, that is, when the bush- 
ing is worn oval by a wobbling shaft end, the only remedy is to bring " 
the bearing halves together as before and re-bore. It may be that 
this operation robs the bearing plates of so much metal that they 

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will not fit the holes in the case; 1 or 
possibly the wear may have com- 
municated itself to the case, so 
that the hole there is out of true. 
If this be slight, refilling the cases 
with babbitt metal or building-up 
may be resorted to, but if the wear 
is considerable, a new set of bear- 
ings is the only remedy. In build- 
ing up the bearing, strips of soft 
metal are placed in the worn spots, 
after cutting or filing them to fit 
as closely as possible, and the bear- 
ing driven down upon them as firmly 
as possible. In this way, it is often 
possible to build up a worn crank- 
case to answer for many thousand 
more miles running. 

Bearing Wear. In this connec- 
tion, it is important to know how 
and why bearings wear. Normally, 
between the crankshaft bearing and 
the pin, there is a space of perhaps 
.002 inch divided into .001 inch all 
around, and this space is occupied 
by a film of lubricant. So long as 
this is the case, if the metal remains 
hard and does not give under the 
constant pounding, and the film of 
lubricant stays unbroken, it remains 
a perfect bearing. But the film does 
get broken or reduced, and the softer 
metal does give, so we have a con- 
dition shown at A, Fig. 69. Instead 
of a cylindrical pin centered in a 
cylindrical hole, one or the other is 
worn oval. This is usually the 
bearing, for the weight of the 


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shaft, coupled with the pressure on it, keeps it at the bottom of 
the hole. The tendency, then, is to increase this eccentricity. 
In this condition, the pin is running against the bearing metal at 
only one very limited surface, so all the pressure and all the wear are 
concentrated there. If the bearing is hard, or if a hard spot develops, 
the pin is likely to wear flat on the bottom side, as shown at B. When 
the bearing is fitted to the case, great care and accuracy are required. 
If care is not taken, an incorrect fitting, shown at C, results. Here 
the shim does not entirely fill the opening for it, and the bearing metal 
rests on the case at one point; on the shim at another; and does not 
touch either at a third. This is remedied by scraping both bearing 
and case, as shown at D, or the shim alone as seen at E. In the former 
it will be noted how the full shim has raised the bearing so that its 

points project into the pin, 
where scraping will be needed. 
In the latter case, also, scrap- 
ing the bottom of the bearing 
will be necessary, for using a 
fully fitted shim has raised the 
center more than the sides. 

Crankshaft Pounding. 
When the dull throbbing noise 
is found to come from within 
the crankcase, possibly be- 
tween two of the bearings, 
this indicates a crankshaft or a connecting-rod pound. That is 
to say, either the rod is loose on the shaft or the shaft is loose in one 
of its bearings. Whenever the force of an explosion comes on the 
piston and drives it down, this looseness is taken up quickly, and the 
dull pounding noise is made. This is a serious trouble and, if long 
continued, may wreck the engine. That is, the loose rod may become 
entirely loose and free so as to thrash around and, in so doing, wreck 
the crankcase; or, if the pound comes from the shaft, the bearing 
may continue to loosen and finally that part of the shaft become 
entirely free to thrash around. Both these troubles can be overcome 
by tightening of the bearing caps. 

Test for Tightness. When a connecting rod has been fitted to 
a crankpin and is ready for use, a simple test of correct tightness is 

Fig. 70. Holding Fixture for Crankshaft 
Bearing Caps 


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this: If the rod is placed vertical, it will stay there, but if pulled 
over past 20 degrees from a vertical, it will swing down, of itself, 
to the bottom position and stop there 
without continuing to swing. If it 
will do this, it is just tight enough. If 
it will not swing down at all or con- 
tinues swinging, it is either too tight 
or too loose. To a certain extent, 
crankshaft bearings are delicate, and 
they can be ruined by having the 
big ends too tight. 

Holder for Bearing Caps. When 
a number of bearing caps have to be 
scraped, or filed down, it is worth 
while to make a holder for them. A 
plain form is shown in Fig. 70. This 
consists of a semicircular piece of 
metal which fit3 into the hollow part 
of the bearing, with each end pivoted 
on two L-shaped members. The mem- 
bers are held tightly in the vise, and the tighter they are gripped the 
tighter the bearing cap is held. This jig holds the cap with the desired 


Fig. 71. Semi-Socket Wrench for Crank- 
shaft Bearing Nuts 

Fig. 72. Set-Up for Supporting Crankshafts Out of Motor 

firmness, yet it leaves the whole upper surface free and clear so the 
workman can work at it readily and do a neat quick job of filing. 


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The same layout is suitable for connecting-rod caps, except where they 
have an oil scoop or other central projection which interferes. 

Another Handy Wrench. The form of the crankshaft-bearing 
cap and also of the connecting-rod bearing cap are such that no space 
is wasted. Very often the nut is so close to the cap that it is difficult 
to turn, unless the cap is taken out of the motor where the wrench can 
be applied at right angles. The use of the socket form of wrench, 

Fig. 73. Dogs for Use in Turning Four-Cylinder Crankshafts 

however, does not make it necessary to take the cap out of the motor. 
Aside from the socket wrench it is hard to get any other form of 
wrench to use on these nuts that is not so small and thin that it 
has no particular strength. In Fig. 71, however, a form is shown 
which has all the strength of the very stiffest forms, and yet it can be 
applied to these inaccessible nuts with ease. Moreover, its con- 
struction is such that it can be applied and used readily. It consists, 
as the sketch shows, of a solid socket wrench, as distinguished from 

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the form made of tubing, and has part of one side of the socket cut 
away. This makes its quick application to the nuts easy, although 
it also limits the amount of turn possible. Generally the case nuts 
are different in size from the connecting-rod nuts; so it is advisable to 
make the wrench double endeC with a size at one end for the rods, 
and one at the other end for the case. 

Holding the Crankshaft* When the shaft has been removed from 
the engine, and work is to be done upon it, it is an awkward thing to 
handle. It is just delicate enough so that it cannot be handled care- 
lessly, yet its size and weight make it difficult to move around. 
Thus, in lapping the shaft pins, in fitting connecting-rod bearings, or 
doing other work upon it, a sup- 
port which is simple, easily moved 
around, yet adequate, is needed. 
Ordinarily a shaft is clamped in a 
vise, but this is not always satis- 
factory when working on an end 
bearing. The method shown in 
Fig. 72 has many advantages. 
This ccftisists of a special bench 
fixture and a notched board. The 
latter should be at least 1-inch 
stock, that is, it should be f-inch 
when dressed on both sides. The 
former is simply a metal angle with 
a series of radial slots to take the 
flywheel bolts, with a central hole 
for the shaft to rest in. The metal 

Fig. 74. 

Fixture and Lathe Jig for Turning 
Six-Cylinder Crankshafts 


above the hole is well 
away to facilitate putting the shaft in and taking it out. 

Handling Shaft in Machines. When the crankshaft is to be 
machined, no matter what the form of lathe, grinder, or other machine, 
the fact that the pins are eccentric necessitates a special dog or jig 
for holding it. If an ordinary flange is bolted on the end, the oain 
pins can be turned, smoothed down, or ground, but the crankpins 
cannot. What these latter need is a form of flange or plate with two 
exact centers on either JAe of the central one at distances exactly 
equal to the crank throw. One is shown in Fig. 73, which is attached 
to a four-cylinder shaft all ready for the machine. Above will be 


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seen another shaft without machining flanges. The bolts which 
attach the flanges to the shaft can be seen beyond the right-hand 
flange and at the far end. The rack in the background, on which 
these shafts are placed, is of interest also, forming, as it does, a simple 
and efficient means of holding the shafts, yet it is convertible for 
holding other parts or units. It is simply a stout form of horse, 
rather high, £nd with three legs instead of the usual two. The braces 
are all put on the inside to leave the surface clear, while the support- 
ing pins differ only in length. In this case they have been made 

Fig. 75. Dogs with Adjustable Centers for Handling Crankshafts 

long enough and strong enough to hold two or three shafts at once. 
In this way, the one horse can hold some 48 shafts at once. 

Handling Three-Throw Shafts. The rigging just described is 
for four-cylinder shafts only, as these have the throws all in one 
plane, so that, although three different centers are required, they lie 
in one straight line, and the flange can be very simple for this reason. 
With a six-cylinder shaft, on the other hand, this is not the case; 
and a much larger flange is needed, for the three pin centers are 
spread out fan-like around the main bearing center. A form is 
shown in Fig. 74, which can be used for a shaft of this general type, 
although the one shown in the lathe provides for two pins only, not for 
three. For a six-cylinder engine of ordinary crankshaft construction, 
this would have to be like the triangular sketch at the lower right, if 
it is carried out on the same plan; or with the same bearing and pin 
centers, and a round outline as shown by the dotted line, if there was 
no necessity for saving metal. 


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Fig. 76. 

Lapping Fixture of Simple Construction 
for Crankshaft Pins 

Adjustable Crankshaft Flanges. In the small shop the general 
run of work varies so much that the principal difficulty lies in having 
flanges, dogs, or fixtures for handling the variety of crankshafts that 
come in. Diameters vary so much that a wide range of central holes 
is needed, because throws 
are all different. This 
gives a different center 
to center distance; then, 
too, there are still one- 
and two-throw, and 
other old forms of shafts 
in use, which come in 
occasionally for repairs. For these reasons, it is not wise for the small 
shop to go too far into special crankshaft fixtures; it should stick to 
simple dogs, with adjustable center distances, like the three shown in 
Fig. 75. While the shaft indicated is a single-cylinder form, dogs of this 
type can be used on other forms. This constitutes their biggest advan- 
tage. The variation in the three is self-explanatory to any machinist. 

Crankshaft Lapping. The pins of a crankshaft need lapping 
the same as other pins where a grinding machine is not available. 
There are two ways of doing this: by hand, which is slower but more 
simple so far as apparatus is concerned; and by machine, which 
requires special fittings for this purpose. In the sketch, Fig. 76, a 
form of hand lapper is shown. This consists of a pair of hinged 
members, with a central 
hole large enough to 
take various sizes of 
bushings, such as would 
be required on different 
shafts. A long handle 
is provided; also a bolt 
to hold the two halves 
together when the bush- 
ing has been inserted. 
The babbitt bushing must be split and have end flanges to hold 
the halves in place sideways. The handle gives leverage for work- 
ing the tool, which is made effective by the application of fine emery 
and oil on the pins to be lapped. In the same way, the pins are pol- 

Fig. 77. Lathe Set-Up for Lapping Crankshaft Pins 


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ished by means of a pair of long wooden clamps, shown below, and 
made in somewhat the same way. There is a hinge at the back; and 
the abrasive used is fine emery cloth, which is flooded with oil. 

The throws on the crankshaft can be lapped in the lathe by 
putting it between centers for the main bearings and by using a 
special flange for the other pins. A method which can be used is 
shown in Fig. 77. This consists of a special fixture, made from a 
large casting with a base to fasten to the face plate; a long extension 
arm, having a split end for attaching and detaching, to encircle the 
throw to be lapped. When this is used, the shaft is supported in 
V-blocks, somewhat flexibly it is true, but sufficiently. 

Welding Shafts and Cases. The welding of broken crankshafts 
and crankcases, such as central breaks, breaks around the cylinder 
supporting surface, bearing supports, and supporting arms will be 
found fully discussed under the subject of welding, with full direc- 
tions as to the preparation of the work, the materials, and other details. 


Function of Crankcase. The lower part of the motor ear, truck, 
or tractor engine is generally enclosed for the purpose of assisting the 
circulation of the lubricant, and for keeping the dirt and dust out. 
This enclosure is called the crankcase, and covers the crankshaft, 
the connecting rods, the bearings for both, and the lubricating system 
and lubricant reservoir. In general, the crankcase forms the support 
for the entire engine, as arms extend from it for this purpose. It 
also supports the cylinders upon its upper face or faces, and the 
crankshaft bearings upon inner integrally cast bosses. This is worded 
in this way, for formerly many marine engine cylinders, and even 
today, all high-powered marine engine cylinders are set upon posts 
and the sides between the cylinders and crankshaft left entirely open. 

Crankcase Construction. Most crankcases are split longitudi- 
nally along the center line of the crankshaft. The upper half sup- 
ports the cylinder and crankshaft and the weight of the engine on the 
chassis frame, and also has proper provision for the support of the 
various accessories upon it. The lower half, in such cases, is formed 
as a simple enclosing pan, with oil reservoir in the bottom. When 
the lubricant is circulated by pump, this is generally attached to 
the lower half of the crankcase, either inside or outside. 


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A section through a modern crankcase is shown in Fig. 78, which 
illustrates a twelve-cylinder motor. Note the inclined upper sur- 
faces of the upper half to which the cylinders are bolted and the 
stiffening rib at the center line where the two halves meet. Note 
also how the lower half is simply an enclosure, carrying only the oil 
strainer (shown) and the oil pump (not shown) . It has cooling fins cast 
on its lower surface to keep the temperature of the oil down. The 
shelf, which is cast on the upper half to close the space between the 

Fig. 78. Section through Crankcase of Box Type for Twelve-Cylinder 
V-Type Packard Motor 

sides of the crankcase and the chassis frame, serves the double purpose 
of a protecting pan to keep out road dirt and water and of a supporting 
shelf for accessories. Fig. 79 shows the same engine from the front. 

Crankcases are made mostly in two forms: the box type, which 
has more or less straight sides, with a flat top and bottpm; and the 
barrel type, which is round or a modified round with a flat bottom and 
top. The one shown is of the box type; the barrel type is generally 
not split along the center line, but it has removable end plates which 
allow the insertion of the crankshaft and a very simple bottom plate 
which carries the oil supply. The one-piece type is supposed to give 
greater rigidity, but this is at the expense of accessibility. 

Modern Tendencies in Design. There are two modern ten- 
dencies shaping toward a modification of, or the entire elimination of, 


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the lower half of the crankcase as it is now known. One is the mini- 
mizing of its functions, so it can be made of pressed steel, when it 
becomes a cover only, and the oiling system is made such that the 
supply is carried elsewhere. The other is the casting of parts of 
the crankcase integrally with the cylinders. This has been done 
successfully with the Marmon, the Ford, and with others, in which the 
cylinder block and the upper half of the crankcase are cast as one. If 

Fig. 79. Assembled Motor Shown in Section in Fig. 78 
Courtesy of Packard Motor Car Company, Detroit, Michigan 

this casting is considered as a cylinder unit, there is no upper half of 
crankcase. By extending this practice a little further, the lower half 
may be combined with cylinder block and upper half, so that the 
crankcase as we know it now would cease to exist. 

All these combinations save weight and reduce cost. They also 
reduce the number of parts and make the car as a whole more simple. 
In some cases they go hand in hand with large production, as the 
pressed steel lower half of the crankcase calls for a big expenditure 
for dies. On the other hand, they may make the repair man's work 
greater. As, for instance, when the cylinders are combined with the 


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crankcase, it is an all day's job to take out a piston and replace it. 
When the cylinders are separate, cast in pairs, or bolted on, a piston 
can be taken out and replaced in a couple of hours. 

Crankcase Materials. It is important that the repair man 
should know the materials of which both upper and lower halves of 
the crankcase and the gear cover are composed, for these may need 
repairing. In general, crankcases are of aluminum alloy, the exact 
composition varying. When this is the material, the gear cover is 
of aluminum alloy also. A few crankcases are made of cast iron, on 
very low priced cars. Others have the pressed-steel oil pan, pre- 
viously mentioned. A few high-grade cars have bronze crankcases; 
these are either government bronze or vanadium bronze. 

Crankcase Arms and Engine Supports. The engine is generally 
supported by crankcase arms extended from the sides or ends of the 
upper half of the crankcase and cast integrally. However, this is not 
always the case. In many unit power plants, the rear pair of sup- 
porting arms may be fixed to the flywheel housing or to the transmis- 
sion case. Moreover, separate supporting members bolted or hinged 
in place may be used. These are heavy steel forgings, stout bronze 
castings, or heavy gage steel tubing. This may be done to allow 
the engine freedom of slight rotation and relieve it of twisting due to 
road inequalities; it may be done because of lack of confidence in the 
strength of the crankcase material as an engine support; it may be 
done to facilitate foundry work on the crankcase, and thus reduce its 
cost; or for other reasons. In taking out an engine, the repair man 
should find out about this, as it may simplify or complicate the removal. 

Gear Cases, or Gear Covers. At the front end of the great 
majority of engines, the gears which determine the working of the 
engine and its accessories are placed. These may include the crank- 
shaft driving gear and any or all of the following driven gears : camshaft 
gear, magneto gear, water-pump gear, lighting-generator gear, oil- 
pump gear, and sometimes fan gear and air-pump gear. These may 
be driven directly by gear contact or by means of silent chains. In 
either case the gears are enclosed by a case or cover, variously called 
the gear case, gear cover, or cam-gear cover. This housing is generally 
of as simple a shape as possible, and is bolted in place with as few 
bolts as possible in the lower half of the crankcase, so as to facilitate 
its removal for crankshaft or other bearing inspection or for repair. 


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Other details of the crankcase parts, not previously discussed, 
will be taken up under the groups in which they belong; for instance, 
camshafts and cams with valves and valve parts; lubricating parts, 
drilling in crankshafts for lubricating purposes, oil passages in the 
crankcase, etc., under lubrication; and others under their respective 

Crankcase Troubles and Remedies 

General Nature of Troubles. The most general crankcase 
trouble, aside from bearing trouble, is breakage. The usual bearing 
troubles previously outlined occur as well with main crankcase 
bearings. These require similar attention, and in their handling 
much special apparatus, such as stands, jigs, fixtures, and tools, can 
be developed by the ingenious repair man. Worn main bearings 
cause a knock. If this comes from any one bearing, it can usually 
be traced quickly. The use of the stethoscope is recommended for 
any crankcase or gear-cover noises or troubles. A squeak from any 
part of the crankcase usually means a lack of oil or the rubbing of 
parts which should not rub. 

Mending Breaks. If the case is of aluminum, it should be 
watched carefully for breaks or cracks. If a crack develops, it should 
be drilled, plugged, and welded, as cylinder water jackets. This will 
prevent the crack from spreading. Any fairly large break means 
either undue stress or a weakness in the metal. The latter can be 
remedied by patching, by building up in the welding operation, or by 
the use of a new part. The repair man who is in doubt about his 
ability to repair a break or crack should always consult a welding 
expert, for welding can be done, and is being done daily, which would 
astonish those unfamiliar with the scope of the process. Moreover, 
* it is relatively inexpensive. Quite often, a weld which would not cost 
more than $4 or $5, can be made the same day even by a fairly busy 
shop; otherwise it would mean a new case at a cost of perhaps 10 or 
12 times as much, two weeks' delay or longer for delivery of the order, 
and the additional time and delay of detaching all the old accessories 
and fittings from the old case, and re-attaching them to the new case. 

Cleaning Aluminum. Aluminum can be cleaned, externally, by 
means of a weak sulphuric-acid solution, say not more than 10 per 
cent sulphuric acid. This should be well scrubbed into the surface 
with a stiff brush, then washed off with water. Care should be taken 


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to wash well enough and long enough to remove all the acid. 
Moreover, it should be kept from clothes or from any wood parts, as 
it is strong enough to attack fabrics and wood. 

The aluminum oil pan should be cleaned out at least once a 
season, for the strainer will separate a lot of dirt and dust, as well as 
other foreign matter, from the oil in the course of 8 or 9 months. 
This will be found in the bottom of the oil pump or beneath the oil 
proper, as a kind of slush or sludge. Sometimes it is thick enough 
to need scraping, particularly in sandy country where the car gets 
little or no care. Generally, a kerosene bath will clean it out. This 
is followed by a "once-over" with gasoline to clean off the kerosene 

Kg. 80. Method of Boring Crankcase Bearings with Special Boring Bar 
_ Courtesy of Pierce- Arrow Motor Car Company, Buffalo, New York 

and the last of the dirt. If any gasoline remains, it will evaporate 
and leave a crankcase which actually is clean. The porosity of 
aluminum emphasizes this need for a thorough cleaning, which is not 
needed so badly with pressed-steel oil pans. 

Machining Crankcases. Generally speaking, the repair man 
will not be called upon to do any machining on crankcases, beyond 
something like chipping or filing, or in the case of a break, patching 
or welding. But in case such a job should come along, it is important 
to know how to handle it, for there is no more important crankcase 
job than the machining of the main bearings. The necessity here 
is to keep them in perfect alignment, and this necessitates machin- 

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ing all of them at once with a long boring bar, as shown in Fig. 80. 
The method of support upon the flat upper, or cylinder, face will be 
noted, also the holding down blocks bolted to the table of the machine, 
after being bolted to the cylinder studs. The provision for lubricant 
on each one of the boring cutters will be seen in the small copper pipes 
above and at the back. As the average shop does not have a boring 
tool of this kind, this work will have to be approximated. It could be 
done by hand, using the now well-known Martell aligning reamer, 
to ream the bearings out and put in new and larger bushings. This 
also has a series of cutters, much like the boring bar shown, and is 
actuated by hand. So the principal requisite would be a large flat 
surface on which to work. Possibly this will be found at the drill- 
press platen, the planer table, or the working table of whatever large 
machine tool the shop possesses. In this job, the workmen should 
remember that unless the case is held firmly throughout, it is likely* 
to give or spring, and this will spoil the whole job, no matter how good 
it may be otherwise. 

In all crankcase repairs, the repair man should remember that 
the case is really the foundation of the engine, and if it is not firm 
of itself and firmly supported, the action of the engine cannot be 
positive nor continuous. Consequently the case should be handled 
with unusual care. Gear-cover troubles are few and far between, 
consisting mostly of breaks or trouble inside the cover with gears or 
driving chains. These will be discussed elsewhere. Usually, too, 
gear-coyer lubrication is automatic, that is, one end of the crankshaft 
and crankcase-bearing lubrication system is continued forward to the 
gear cover, so that it gets all the surplus oil. In this way lubrication is 
cared for automatically, but the repair man should take no chances 
on this with cars under his care. He should remove the gear cover 
occasionally for inspection. Gear noises, too, emanate from the timing 
gears and are often due to a lack of lubricant there, or, to not enough 
thick lubricant to deaden the sound. Sometimes the construction of 
a gear causes a ringing noise, according to the form of construction 
•used. Often whirring noises from the gear case are caused by burred 
teeth. The repair man can remove the burr with a file. Sometimes 
a chip of metal will get in between two gears and be pressed into the 
softer of the two; from that time on, it will cause noise continuously, 
and will also cut the other gear. 

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Q. Into how many main groups can the mechanical parts of the 
car be divided? 

A. Practically all motor cars can be divided into six general 
groups as follows: (1) engine, or power-producing, group; (2) clutch, 
or engine connecting and disconnecting, group; (3) transmission, or 
speed-varying, group; (4) final-drive group including rear wheels; 
(5) steering group for controlling the direction of the car and including 
front wheels and axle; (6) frame upon which all other groups except 
wheels are hung. The body makes a seventh group, but strictly 
speaking it is not mechanical. 

Q. How many sub-groups are there pertaining to the 

A. According to their functions, the parts and accessories of 
the engine may be subdivided into 10 groups: (1) cylinders, pistons, 
connecting rods, crankshaft, and other basic parts; (2) carburetion 
sub-group through which the mixture is supplied which enables the 
engine to run; (3) valve group through which the mixture is allowed 
to enter and leave the cylinders at the correct time; (4) exhausting 
system through which the burned gases are led away from the motor; 
(5) ignition system by means of which the mixture in the cylinders is 
ignited at the proper time; (6) cooling system by means of which the 
temperature of the motor is kept down to a point at which it can 
operate safely and continuously; (7) lubrication sub-group by means 
of which the rotating, or rubbing, parts are kept lubricated so as to 
run without friction or heat; (8) starting sub-group by means of which 
the motor is started; (9) lighting sub-group through which the car is 
lighted, not strictly an engine part but closely allied with starting 
and ignition, and because of its drive from the engine and general 
location of its parts on it, it is classed as an engine sub-group; (10) 
flywheel sub-group. The last is really a single unit but its size, 
weight, shape, location, attachment, and other points are becoming 
so important as to warrant separate consideration. 

Q. Why is it necessary to consider each of these separately? 

A. Because their functions all differ. The very things which 
make each group best fitted to its work make it more widely different 
from each of the others. Some groups are so very different as to 
warrant separate consideration, almost as extended as the balance of 




the motor group, as, for instance, ignition, starting, and lighting, 
which naturally group together. 

Q. What are the most popular cylinder forms? 

A. Automobile engine cylinders are mainly of the following 
forms: (1) cast in pairs; (2) cast in block; (3) cast in threes, in the case 
of six-cylinder motors. The last is really a modification of the first. 

Q. What are the advantages of each of these? 

A. The cast-in-pairs form can be removed by one man and 
replaced by two, if it is broken, cracked, or damaged; replacement 
is less expensive; the casting is less complicated, consequently there is 
less waste in the foundry; they are easier to machine, store, ship, 
handle; they also have other advantages. All these apply to the 
cast-in-threes modification. The cast-in-block form makes a more 
simple looking engine, a shorter and more compact one, and renders 
alignment and spacing more accurate and permanent. Furthermore, 
all water, inlet, exhaust, and other connections may be cast integral, 
which is not possible with the cast-in-pairs or cast-in-threes forms. 
Similarly, the crankcase may be cast integral if desired. 

Q. How is the weight of reciprocating parts lessened? 

A. In the case of pistons, this may be done in one of three ways : 
(1) the form, shape, size, and material may remain unchanged, while 
the walls are machined thinner, or ribs are eliminated; (2) the material 
may be changed to a steel which can be machined thinner and smaller 
everywhere, thus saving a material amount; or (3) the material may 
be changed to an aluminum alloy which is lighter throughout, is 
strong to stand machining very thin in some places, and is so ribbed 
as to stand casting very thin in others. The first assumes that cast 
iron is retained; the second calls for a high quality of forged steel and 
is most expensive, so that it is used only on racing cars or cars of 
unusually high prices. The last is fast becoming the general 

Q. What is the modern tendency in piston rings? 

A. The experiences of aircraft engines and those in racing cars 
have taught that two well-made and well-fitted rings are sufficient. 
This is being applied rapidly to all motor-car engines by the removal 
of the extra and superfluous rings. Many motors had this number 
previously with an oil ring at the bottom, but it has been found that 
the removal of this makes little difference. 

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Q. Is there a noticeable tendency toward simplicity in connect- 
ing-rod constructions? 

A. Yes, the same as in pistons and rings, toward simplification 
&nd lightening of the weight, with the removal of all superfluous 
parts. Two bolts are becoming the standard for the big end. The 
H-section machined all over is almost universal, smaller sections being 
used than formerly. Pressed-in wrist-pin bearings of comparatively 
thin walls are being used and a better class of material generally, 
which allows lighter weight and smaller sizes for equal or greater 
strength. Lubrication scoops are being machined-in in the forms of 
holds, and a simple projecting lip instead of former brass tubes, 
which were added. 

Q. What is the accepted type of connecting-rod big-end 

A. The split, or two-piece, form with a shell or backing of 
bronze and a facing, or wearing surface, of babbitt with oil holes 
drilled through and the interior surfaces oil-grooved to and from these 
to distribute the oil evenly. 

Q. Why is this the accepted form? 

A. The bronze backing or shell gives the desired stiffness and 
permanence, also machines well and resists overheating well. The 
babbitt facing, when worn, is easily replaced by any repair man, and 
it will melt out in case of lubrication neglect so little harm is done, 
yet when well-fitted it gives a fine bearing surface. The system of 
drilling and grooving supplies a film of oil at all times. These 
materials and this arrangement supply an almost ideal combination 
when well-made and fitted, hence their wide acceptance. 

Q. What difference is noted in V-type engine bearings? 

A. When the two rods of a V-type engine act upon a single 
pin, the arrangement of the bearings must be such that one must be 
notched out, or divided, to make room for the second, or else the 
exterior of the first must be formed as a bearing surface for the second. 
In the former case, the one bearing is practically in four parts; in the 
latter, the exterior of the inner bearing becomes as important as its 
interior surface, since it acts as the bearing pin for the outer rod. 

Q. Name two general forms of crankshaft today. 

A. The single-plane type and the multi-plane type. In the 
former, as used on four- and eight-cylinder engines, all pins, bearings, 

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and webs are in one plane. In the latter, as used on six- and twelve- 
cylinder engines, the pins are in three planes set at an angle of 120 
degrees with each other. 

Q. How many different forms of four-cylinder shafts are 

A. There are but three radically different forms of four- 
cylinder crankshafts, depending upon the bearings. These are: 
(1) The shaft in which there is a bearing on each side of each appli- 
cation of power, or five bearings in all; (2) the form in which there is a 
bearing at each end and one in the middle, or three bearings in all; 
(3) the form in which there are no center bearings, but only the 
two end bearings. The first is used on the highest-priced four- 
cylinder cars, because it is expensive of itself and has a similar 
influence on other parts, notably bearings, crankcase, etc. The 
second is in wide use; being the most popular form. The last 
is used only when extreme compactness is desired. There is an 
odd form of shaft in which four bearings are used, but only one 
maker ever used it. 

Q. What is the difference in the average of six-cylinder crank- 

A. Six-cylinder crankshafts differ about the same as fours, 
according to the number of bearings. There are the same number 
of different forms as follows: (1) with seven bearings, or one on each 
side of each application of power; (2) with four bearings, or one at 
each end and one between each pair of cylinders; (3) with three 
bearings, one at each end and one in the middle, used only with block- 
cast cylinders. 

Q. What can you say of eight-cylinder crankshafts? 

A. These vary the same as fours in general, the eight-cylinder 
motor having a four-cylinder shaft with perhaps slightly longer pins 
and of slightly larger diameter throughout. 

Q. How do twelve-cylinder shafts vary? 

A. They are the same as six-cylinder shafts, with the same 
variations as to bearings; in fact, all twelves have six-cylinder shafts 
with slightly longer and larger pins. 

Q. Does counterbalancing effect the shaft? 

A. No, except in outward appearance. The counterbalanced 
shaft is just the same as the shaft without counterbalancing masses. 


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The general type is the same, also the number of bearings. This 
applies to fours, sixes, eights, twelves, or to any form. 

Q. What are shims, and for what are they used? 

A. Shims are very thin pieces of metal placed between the 
two halves of bearing caps for the purpose of giving a quick, simple, 
easy adjustment when the bearing wears. In theory, this works as 
follows: When a bearing has worn down nnnr inch, the cap is un- 
screwed and removed, and shims of a thickness of nnnr inch are taken 
out on each side. Then the cap is replaced and tightened, and the 
bearing is as good as new. In actual practice, the removal of the 
shims creates a shape of bearing which is not an exact circle, so that 
some slight scraping with very little wear, is necessary, as illustrated 
above, and a great deal of rescraping and refitting (in addition to 
shim removal) with greater wear. 

Q. For what is a crankcase used? 

A. The crankcase is used to support the cylinders and the 
crankshaft; to act as a housing to keep out dust and dirt and as a 
retainer and reservoir to hold the oil in. 

Q. What is its general shape? 

A. Generally, crankcases are either of the box shape or of 
the round, or barrel, type. The first named is generally split 
horizontally along the crankshaft center line; has a flat top and bot- 
tom, with vertical sides; has the bearings supported in the top half 
only, the bottom acting simply as an oil pan. The second form is 
generally in one piece with removable ends in which two of the shaft 
bearings are located; has a rounded bottom in which tb^ oil is held; 
has a flat top but founded sides. 

Q. Of what material is the crankcase constructed generally? 

A. Aluminum and aluminum alloys are most widely used, 
although there are a number of motors with cast iron, some with a 
cast-iron upper half and a pressed-steel or aluminum lower half , and a 
few of bronze. The latter is expensive and is losing ground. Pressed 
steel is suitable only for quantity production, while cast iron is losing 
ground except in those up-to-date designs in which the upper half 
of the case is combined with the cylinder block. 

Q. How are crankcases supported on the frames? 

A. The most general method on pleasure cars is the casting 
of arms, generally four, integral with the crankcase, these extending 



out to and resting upon the frame, to and through which they are 
fastened. Generally, too, a thin web is cast between the front and 
the rear arm on each side, extending out horizontally from the sides 
of the case to the frame. This serves the double purpose of replacing 
the underpan and of acting as a stiffener for both arms and case. 
On a few cars and on quite a few trucks, a pivoted cross-arm 
is used at the front and a bolt cross-arm at the rear (or vice 
versa), these being forged members. In this way a three-point 
support is obtained, which yields as the frame is twisted or raised 

Q. What is the gear cover and what are its functions? 

A. It is the removable cover at the front end of the engine, 
which covers and protects the camshaft and other gears or silent- 
chain drives. In addition to keeping out dust and dirt from these, 
it minimizes the unavoidable noises which they make and retains 
the lubricant. It is generally a light aluminum shell held on by a 
dozen or less bolts. 

Q. What is the general method of lifting an engine out of the 

A. By a rope or a chain sling, hoisted from above by a chain 
hoist, block and tackle, overhead crane, or movable floor crane. 
The latter are of recent introduction but have the advantage over the 
overhead form that they can be rolled around the garage or repair 
shop to any needed point, while the overhead form is useful only 
under its track or runway. In addition, they can be put into use 
more quickly on a rush job, take up little room, and cost no more than 
the overhead built-in form. 

Q. How are engine stands useful? 

A. They hold the engine in a convenient place and at a reason- 
able working height. They hold it firmly so that pressure can be 
exerted if necessary or hammering can be done. Moreover, if rightly 
constructed, they allow rotating the engine to do work upon the sides 
or bottom. In these and other ways they save much time and 
trouble, hasten the work, and thus cut the cost. In addition, their 
convenience allows of doing better work.* 

Q. Is there any best method of removing carbon from cylinders? 

A. The method depends upon the design and the construction 
of the motor, the quantity and the hardness of the carbon and its 

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location in the cylinder, and, in part, upon the facilities which the 
shop possesses. The best method varies with almost every case. 

Q. What is the most rapid method? 

A. Probably burning out with oxygen is the quickest method, 
when the shop possesses an oxygen-burning outfit. The spark 
plugs are removed and their holes plugged, one or more valve caps 
are removed to allow working, the gas is turned on and lighted, when 
the workman can do a cylinder thoroughly in three or four minutes. 
This means that the entire process of doing an engine will not take 
over twenty-five to thirty minutes. Any other process will take twice 
as long as this. 

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CO £ 







Function of the Carburetor. As has been pointed out in the 
general outline of the motor car, the first and most important thing 
in the engine cycle is to get the fuel into the cylinders. This is done 
through the medium of the carburetion system, the principal unit 
in which is the carburetor. The function of this is to convert a 
liquid (gasoline) into gas (gasoline vapor) measure this, and add 
to it the right quantity of air to give proper and complete combustion. 
If this be not done, power is lost, either through the use of too much 
or too little air. In the latter case, not all the fuel is vaporized, hence 
some of it is wasted. 

This sounds like a simple proposition, yet its very simplicity has 
been the undoing of many automobile experts. The vaporizer 
becomes more and more complex each year, constant additions and 
changes are being made in the other parts of the system, and in other 
ways the carburetion system shows a constant change. Despite all 
this, few fundamental laws have been found to be in error, and few 
new ones have been discovered or developed. 

Effect of Heavier Fuels. For some years past there has been 
under way a subtle change in the character of the fuel — the gasoline 
used for the propulsion of automobiles. The small production and 
the increasing demand have combined to render almost unpurchas- 
able, except at high prices and then from large dealers, the lighter 
and more volatile gasolines of some years ago. In the place of them 
there have been quietly introduced much heavier petroleum dis- 
tillates, which evaporate less readily — though they are actually of 
higher value in terms of power units. This condition has compelled 
several changes in the carburetor problem. 

In addition jto the foregoing, in some parts of the world there 
have been serious efforts made to utilize in automobile motors 

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alcohol and benzene (not benzine), which, with proper provision for 
their carburetion, constitute excellent fuels. 

The most important of the changes dictated by this development 
in the fuel situation is the now general practice of heating the float 
chambers of carburetors, either by water from the circulating system 
or by exhaust gases. An alternative scheme is that of drawing of the 
air for the carburetor from a point adjacent to the exhaust piping, so 
that this air is sufficiently warmed to readily take up the gasoline 
necessary to constitute a proper explosive mixture. 

Jacketed Manifolds. A subsequent and very successful method of 
handling the heavier fuels is that of jacketing the upper portion of the 
inlet manifold, and the circulating of the hot water in the cylinder- 
cooling system through this. By having this jacket close to the point 
where the gaseous mixture enters the cylinder, any remaining particles 
of liquid fuel are vaporized before entering the cylinders. In a few 
instances, the same effect is obtained by incorporating the carburetor 
in the cylinder water-jacket casting. In still others, where the car- 
buretor is placed on one side and the inlet valves on the other, there is 
a cored inlet passage through the cylinder block between the cylinders 
which heats the mixture, with the same result as stated above. 

Fuel Injection. Systems of fuel feeding by direct injection of 
minute quantities of the combustible liquid into the cylinders or 
into the intake piping have been advocated or experimented witii 
for many years, and have found very successful application in station- 
ary and flight engineering, though as yet not one of these sytems has 
successfully competed with the carburetor in automobile service, 
where the conditions of power variation are such that fuel injection 
has not seemed readily applicable. 

Nevertheless, there are many engineers who adhere to the view 
that sooner or later fuel injection will supplant present systems of 
carburetion, and progress made recently with aviation motors of fuel- 
injection types may seem in some measure to justify this view. 

Despite the success of this system on aeroplane and stationary 
engines — notably on the Antoinette and the Diesel, respectively — 
there is not, to the writer's knowledge, a single American motor-car 
manufacturer now using or experimenting with fuel injection. A few 
years ago a motor car brought out in the Middle West used it, but 
this was short-lived. Since then, nothing has been done. 


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More Valves vs. Forced Induction. The present-day tendency 
toward the use of many valves, four per cylinder, seems to indicate 
a necessity for getting more gas into the cylinders in order to get 
more power and speed from the same size of motor. This would 
seem to lead back to the subject, agitated a few years ago and dropped 
for lack of interest, of the need for forced induction. This will 
introduce a greater quantity of gas into the cylinders without resort- 
ing to the complications and trouble-breeding possibilities of four 
valves per cylinder. It differs widely from fuel injection, consisting 
in its simplest form of a special form of fan or blower to drive the 
vaporized fuel into the cylinders. 

Classification of Carburetors. Carburetors, as a whole, may be 
divided into three classes: the surface form, in which the air « 
passing over the surface of the fuel picks up some of it, mixes with it, 
and produces an explosive vapor; the ebullition, or filtering, type, in 
which air is forced through a body of fuel from below, absorbing 
small particles so that when it reaches the top and is drawn off, it is 
suitable for use in the cylinders; and the float-feed, or spraying, type, 
under which head nearly all modern devices come. The others have 
gone out of use, as fuels today are too heavy for them to be practicable. 

The original float-feed carburetor consisted of one part besides 
the fuel pipe, float chamber, and passage to cylinder, which made it 
remarkable for its simplicity. It had no adjustments, nor was there 
any way of securing an even and continuous flow of fuel or of air, except 
as the engine suction produced these. The need for these qualities 
brought out, one by one, the modifications of the original; and through 
continuous modifications and recombinations of these, all the modern 
devices have been developed. 

Defects in the Original Are Not Found in Modern Types. The 
original carburetor had no adjustment; the opening in the casting 
measured the amount of air, while the size of the nozzle measured the 
amount of the fuel and the fineness of the spray. There was no 
means of regrinding the float valve, and thus no way of assuring 
an even and continuous flow of fuel. The modern adjuncts of the 
original Maybach device consist of remedies for these defects, and, 
in addition, a proper means of balancing and adjusting the float. 

To pick out a modern carburetor at random, take the one shown 
in Fig. 81. Like its ancestor, it has a gasoline chamber into which 

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2 * 


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the fuel is admitted by the action of a float, when it first passes 
through a strainer. From the float chamber the liquid passes up to 
and through the spraying nozzle. The weight of the float is so calcu- 
lated that the level in the final nozzle is just 1 millimeter (0.04 inch) 
below the top. This insures that there will always be fuel there for 
the air suction to draw off. As the physical action of changing a 
substance from a liquid to a gas is usually accompanied by the 
absorption of heat, it is advisable to supply a reasonable amount 
of this, and thus assist the change of form. In the older Maybach, 
this was inadvertently done by placing the whole apparatus in close 
contact with the hot cylinder. In the modern carburetor, placed 
some distance from the heated portions of the engine, this additional 
heat is supplied by the jacket water. An alternate scheme is to 
pre-heat the air supply by a special pipe from the exhaust manifold. 

From this mixing chamber the mixture of air and gasoline vapor 
passes upward into a secondary mixing chamber. This communi- 
cates with the inlet pipe through the medium of the throttle valve. 
The auxiliary air supply, when used, has access into the secondary 
chamber through the auxiliary air valve. This comes into action on 
very high speeds when the engine is pulling very strongly. At this 
time the proportion of gasoline to air is likely to be too large, so 
the auxiliary opens, admits more air, and thus dilutes the mixture. 

Throttle Valves. Bvtterfly Type. Whatever the nature of 
the mixture in the carburetor, it is admitted to the cylinder by the 
throttle valve, which may take the form known as the butterfly. 
This is a flat piece of sheet metal, preferably brass, attached to a 
suitable shaft with an operating lever on the external end. 

Piston Type. Besides the butterfly type there are fully as many 
of the piston type. The sliding form is a cylindrical ring or shell of 
metal, which is free to slide in a corresponding cylindrical chamber. 
In the walls of the latter are a number of apertures or ports which 
the longitudinal movement of the piston either uncovers or covers as 
the case may be. Sometimes, to facilitate this action, the sides of 
the piston are grooved or notched, but this does not alter the prin- 
ciple of sliding a cylinder within another cylinder to cover or uncover 
certain ports in the cylinder walls. 

In addition to the sliding piston, there is the rotating piston, 
working in practically the same manner, that is, its rotation connects 

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openings in the piston walls with the interior of the vaporizing chamber 
on one side and with the inlet manifold on the other, the amount 
of the opening depending upon the distance the piston is rotated. 
Needle Valves. Needle valves — or spray nozzles as they are 
sometimes called because of the function they perform — constitute 
an important part of every carburetor, or liquid-vaporizing device. 
It might be thought that so long as there is a hole by which the fuel 
can enter the vaporizing chamber that is sufficient; yet such is far 
from the case. In addition to the function of an entering hole, the 
needle has the additional duty of breaking the fuel up into a fine 
spray or mist, the particles of which are easily picked up by the 

inrushing air, and as 
easily converted into a 
vapor. Therefore, that 
shape, form, or arrange- 
ment which will divide the 
entering liquid up into 
the finest particles will be 
the most efficient. The 
difference of opinion on 
this latter point has 
produced the large number of shapes of nozzle and needle which are 
now in use. 

Simple Vertical Tube. In general, practically all these can 
be divided into four groups, illustrated in Fig. 82. The one at A 
is a simple round vertical tube with an opening in the top, through 
which the liquid may pass out. It does not alter the type if the 
sides of the opening converge, diverge, or are straight, but it will 
influence the resulting spray somewhat. Of the twelve makes shown 
with this type, practically all indicate the opening as straight, but 
this may be due to the small size of the drawing which does not make 
the taper apparent. 

Internal Needle Type. Type B, Fig. 82, is similar to the first, 
except that an adjustable pointed needle is added on the inside. 
This occupies most of the center space, forcing the liquid to pass out 
in a smaller circular sheet or stream than would be the case with 
Type A, considering equal-sized holes. In addition, the fact that the 
internal needle valve may be raised or lowered allows this stream 

Fig. 82. 

The Four Usual Shapes of Gasoline Needle 
Valves and Spray Nozzles 


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to vary greatly, both as to quantity of fuel flowing, and the extent 
to which it is spread out. When the needle is down very low, only 
its point enters the hole, so that practically the full area of the latter 
is available, the central needle influencing the column of fuel passing 
out only to make it hollow in the center. 

With the needle raised to nearly its maximum height, however, 
the point projects clear through, and the needle shaft almost fills the 
lower part of the hole. This reduces the flow to a very fine hollow 
column of spray, as the shape of the needle and oi the lower edge 
of the hole is such as to force it inward and then outvard so that as it 
leaves the top of the hole it is diverging widely. Thus, the effect 
of the addition of the needle is to allow the use of much smaller 
quantities of liquid with the same-sized hole, of diffusing it more 
widely, and of making it adjustable to varying needs. Despite all 
its advantages, only three of the carburetors and vaporizers shown 
use this type; and of these, one is a combination of this with A. 

External Needle Type. The third type shown at C, Fig. 82, is an 
inversion of B in that the needle is made external and descends from 
above into the hole in the nozzle. In this form, the shape of the 
needle point produces the desired diffusion and spraying effect, which 
accounts for its popularity. Of the models shown herewith, nine are 
of this kind, one being a modified combination of this form and A. 

External Sectional Needle Type. The fourth form, shown at D, 
is like C, except that instead of a needle resting upon the upper 
surface of the hole and allowing a continuous hollow stream of fuel 
to flow, a series of holes break up the column into a number of very 
much smaller columns, each with its own opening. In this form the 
central member may be movable or not, while the holes may be set 
at any angle. Of the examples of this form shown in this article, 
three in all, every one has the holes placed horizontally instead of 
inclined to a vertical, as shown in Fig. 82. Of these, two show a com- 
bination of B and D. This is an effective combination. 

Floats. Another feature of the earlier forms of carburetors, 
which was soon found to be in need of a change, was the arrange- 
ment of the float. In Maybach's original vaporizer, there was no 
means of balancing the float; consequently, there was no way of 
preventing wrenching and breaking of the needle-valve spindle. As 
this disarranged the gasoline supply, it made a change very important; 


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and this problem received early attention. There was also the neces- 
sity for reliable devices to regulate the supply of air and of gasoline 
spray from the nozzle, either by original adjustment, by means of 
a governor, or by effecting a constant variation by hand to meet 
constantly varying conditions of engine demands. 

These additions to the original form caused some trouble. 
The ordinary way of managing the balancing of the float, while it 
may be the cause of trouble at times, is a very simple one. The float 
is of exceeding lightness, whether made of cork or metal. With 
the inflow of gasoline in liquid form this float rises, and in so doing 
it strikes against a pair of small pivoted levers near the top of the 
float chamber. The other ends of the pivoted levers rest upon a 
form of shifting collar on the needle-valve stem. So, when the float 
rises above a certain level, it automatically shuts off the flow of 
gasoline by pressing against the pivoted levers, which, in turn, act 
against the stem and press it down until the flow is cut off. The 
float will stay up until the suction of the engine has lowered the 
gasoline level so that the dropping of the float releases the levers 
which raise the needle valve off its seat. The gasoline flow is thus 
automatically regulated by this balanced-float arrangement. 


Methods of Handling Fuel Spray. Probably no one detail 
of the whole list of carburetor parts has caused, and still does cause, 
more difference of opinion than the source of and adjustment of the 
air supply, and its companion, the adjustment of the gasoline spray. 
The latter drew attention long before the former; in fact, the 
former is more of a modern appliance. The fuel spray was inves- 
tigated long ago; for the gasoline spray had no adjustment, but 
the size and the location of the level of the nozzle were fixed. The 
spray itself, however, received special treatment. It was projected 
against a conical spray deflector which served to break up the 
column into finer and more diffused particles. In this way, greater 
vaporizing action was gained. 

Water=Jacketing. Longuemare was among the first to use a 
water jacket around the vaporizing chamber. The conversion of a 
liquid into a gas is an endothermic reaction and requires heat for its 
completion. If this is not supplied by external means, it will be 



extracted from surrounding objects. This accounts for the frost 
which gathers on the outside of the mixing chambers of carburetors 
which do not have a water jacket or other source of heat supply. 
The heat is abstracted from the air so rapidly that the moisture in 
the air is frozen, appearing as frost on the outside of the carburetor. 

Auxiliary Air Valve. The auxiliary air valve has always caused 
discussion, its opponents claiming that it means extra parts, and 
therefore more adjustments and more sources of trouble; while those 
favoring it say that without some additional means of this sort for 
diluting the mixture at high speeds, it is impossible to run the engine 
fast, as high speed will then mean an over-rich charge. Be that 
as it may, the fact remains that the weight of opinion lies with the 
auxiliary valve. 

Necessity with Heavy Fuels. Practically all the more modern 
vaporizers use an auxiliary air valve, as this is a partial necessity 
with the heavier fuels. That is, it has been found that the heavier 
fuels require more air to vaporize them than can be supplied by the 
primary air inlet. Moreover, these heavy fuels require considerable 
additional heat in order to vaporize, and the auxiliary air inlet has 
been made the vehicle for conveying this. As will be explained in 
detail later on, this is generally connected with the exhaust manifold 
in such a way that the air entering through it is heated to a high 
temperature. Adding this after the fuel has been split up by the 
spraying nozzle and the primary air has proved very successful. 

Usual Forms of Auxiliary Air-Inlet Valve. The auxiliary air 
inlet usually consists of a simple valve, opening inward, held in. its 
place by a spring of a certain known tension. The strength of the 
spring is carefully determined so that at the proper moment — when 
the motor requires more air in proportion to the amount of gasoline 
used — the valve will open just enough to allow the required amount 
of air to enter. It will be seen that the time and the amount of 
opening will be controlled by the speed of the engine, i.e., by the 
amount of suction produced by the movement of the piston in the 
cylinder. Of course, as the engine speeds up, there is a greater 
piston displacement to be filled per minute, and therefore it is neces- 
sary to supply a greater amount of mixture. Upon changing speed 
suddenly from, say, 500 revolutions to 900 or 1000, the carburetor 
which does not have this device will not give a uniform mixture imme- 


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diately ; in fact, it might require a new adjustment of the gasoline flow 
in order to supply the right amount of fuel. What the auxiliary air 
inlet actually does, then, is to control automatically, above a certain 
point, the amount of air admitted, thereby always maintaining a 
homogeneous mixture. In order to prevent any chattering of the 
valve or rapid changes in the air supply, a diaphragm or a dashpot is 
sometimes used in connection with the valve. 

As a substitute for an auxiliary air valve, a number of makers 
have tried the use of steel balls, resting in holes about two-thirds the 
diameter of the ball. By varying the size and weight of the balls, a 
truly progressive action is obtained, for light suction lifts the light 
balls, and strong suction all balls. 

Venturi-Tube Mixing Chamber. Like every other carburetor 
part, the spraying action and the shape or size of the chamber in 
which it takes place have been the subject of much debate. Orig- 
inally, the chamber took any convenient shape and varied all the 
way from a perfectly plain cylindrical shape to an equally perfect 
square, with all the possible variations in between. A few years 
ago, however, scientists began to look into the vaporizing and equally 
important measuring action of carburetors, with the result that a 
new shape came into use, which was based upon a scientific principle. 

This is the principle of the Venturi meter used for measuring 
the flow of water, and from its use the tube, or chamber, having 
this shape has come to be known as a Venturi tube. In form, this 
consists of two cone-shaped tubes diverging in opposite directions 
from a common point, which in the water meter is the point of meas- 
urement and in the carburetor is the point of location of the spray 
nozzle. The principle is that if these two frustrums of cones are of 
the proper shape, i.e., include the proper angle and are correctly set 
with relation to one another, the flow of air and gas will be in correct 
proportions to each other at all speeds, assuming first that the air 
enters at the bottom of the tube having the greater angle. 

As a proof of the soundness of the principle of this type of 
vaporizing chamber, it might be said that the majority of carburetors 
in use today have it incorporated in one form or another. Many make 
the upper tube conical for a very short distance, beyond which it 
assumes a cylindrical form. In the true Venturi shape, the usual 
angle at the bottom is 30 degrees, while that at the top is 5 degrees. 


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In water meters the contracted area is made one-ninth that of the 
pipe. This same relation, although not exact, holds in the case of 
the carburetor. Since the area varies as the square of the diameter, 
this is equivalent to saying that the diameter of the contraction 
should be one-third the diameter of the full-sized pipe. 

Double-Nozzle Type. A distinctive design of two connections 
leading into the vaporization chamber is the Zenith (French) car- 

Fig. 83. Zenith Carburetor, Model "O" 
Courtesy of Zenith Carburetor Company, Detroit, Michigan 

buretor, a diagrammatic sketch being shown in Fig. 83. This is but 
a modification, in a way, of the Venturi plan, for the latter shape 
is actually used for the vaporizing chamber. The new idea consists 
in leading into this mixing chamber, two tubes. Of these, one is the 
ordinary spray nozzle and does not differ from that used on hundreds 


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of other devices. The second, however, is very different. While it 
leads into the same mixing chamber, it does so through the medium 
of a secondary chamber, or standpipe, to which the suction of the 
engine has access. If this suction is strong, more gasoline is drawn 
into the secondary chamber, from which it may enter the spray- 
ing zone. 

The ordinary nozzle is of an exact size and, consequently, can 
pass only a certain amount of fuel, always at the same speed. With 
the additional nozzle, this does not hold; and being of large diameter 
(comparatively), the flow through it depends wholly upon the engine 
suction, which varies at all speeds, often at the same speed upon 
different occasions. 

Use of By-Pass. This matter of two standpipes has a parallel 
in the use of a by-pass, so-called, around the usual mixing chamber. 
On some carburetors this is made so as to allow easy starting, the 
idea being that when suction is applied to the carburetor by cranking, 
with the throttle closed, practically pure gasoline vapor will be drawn 
through the by-pass. This will start the engine after which, as the 
throttle is opened gradually, its movement cuts off the by-pass, until 
at medium speeds it is out of use entirely. The same thing applies to 
the use of a secondary tube or standpipe for low-speed running. 

A by-pass of a separate nature is made use of for starting and 
priming purposes; this consists of a small separate tank of gasoline 
attached to the dashboard under the hood, with a valve running 
through to the driver's side for turning on the supply. This is 
connected into the inlet manifold above the carburetor by means of a 
special pipe tapped into the manifold. When it is desired to start the 
motor, it is primed with this device by simply turning on the supply. 
Some gasoline flows into the manifold, and after a few seconds it 
vaporizes. The motor is than cranked over sharply, and a start is 
almost certain. This has the advantage of simplicity, accessibility, 
and low cost. In addition, it is economical of time as compared with 
lifting the hood to prime each cylinder separately. 

Nature of New Developments. Horizontal Carburetor Outlets. 
Among the newest carburetor features are some which have worked 
themselves out naturally, and others which have been forced by 
changes in engine design, in fuel quality, etc. Thus the tendency 
toward block motors, and with it the tendency toward neat lines and 


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simplicity, has brought forth a general simplification, or elimination 
of inlet pipes, and a fairly wide use of horizontal carburetor outlets. 
The latter has affected carburetors by requiring a shorter and more 
compact instrument, with a side outlet and a vaporizing arrange- 
ment which will produce tolerably complete vaporization in a 
comparatively short distance. To a certain extent, this horizontal- 
carburetor tendency has modified existing practice in nozzles, Venturi 
tubes, interior areas and arrangements, etc. 

Effect of Heavier Fuels. The growing realization by carburetor 
manufacturers that the increased use of heavier fuels is inevitable 
has brought forth much worthy effort in the way of vaporizing them. 
This has temporarily set aside the kerosene and other heavy-fuel 
vaporizers. However, as the fuel is bound to become heavier and 
heavier, on account of the excessive demands for gasoline, it is only 
a question of a year or so before kerosene and distillate vaporizers 
will be agitated again. 

Effect of Vacuum Feeds. The wide use of vacuum feeding 
devices, combined with the tendency mentioned above to clean 
and simplify, has caused a much higher mounting of carburetors. 
This has always been desirable, but hitherto it has not been possible. 
The vacuum feed for the gasoline supply has made this change pos- 
sible, while the cleaning process and simplification actually forced it. 

Effect of Motor Changes. The high-speed form of motor now so 
generally being adopted has had a big influence, as have also the 
multi-cylinder forms, both creating a demand for greater accelera- 
tion. Similarly, starting devices have forced the use of a carburetor 
modification by which instant starting is possible. These require- 
ments have called for new designs, smaller and lighter parts, more 
nearly complete automatic actions to uncover large air ports, as well 
as other improvements. 

Double Carburetors for Multi-Cylinder Motors. While many 
eight- and twelve-cylinder motors have but a larger-sized plain car- 
buretor, the better forms have a double device, each half supplying 
a group of cylinders, and the halves are entirely separate and distinct 
from the other, except for a common fuel-supply pipe. Each set of 
cylinders has its own suction-actuated nozzle and its own independent 
nozzle. This form has shown its worth in actual use, having been 
very successful in aeroplane work on eight-cylinder and twelve- 
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cylinder motors, and also on a number of the better eight- and 
twelve-cylinder motor cars. 

Multiple-Nozzle Carburetors. Another development brought 
about by this demand for rapid acceleration, coupled with great 
maximum capacity, has been the swing toward multiple nozzles. 
As has been pointed out on previous pages, there are a number of 
carburetors now with two nozzles. 

Stromberg Carburetors. Fig. 81 shows a cross-section of the 
Stromberg Model "L." Except that Model "LB," which is shown 
in Fig. 84, has a horizontal outlet which necessitates the air 
entering from the top and downward, instead of the side and 
upward, these two are almost identical, and the general instruc- 
tions which follow will cover both. In general, all the Strom- 
berg carburetors are of the so-called plain tube type, that is, the 
air and gasoline openings are plain tubes and thus fixed in size. 
This construction automatically meters the fuel by the suction 
of air velocity past the jets, and in addition does away with the 
auxiliary air valve, all the air supply being taken in through a 
single pipe which is heated. Thus, the entire air supply is heated, 
this making for more efficient operation with the present heavier fuels. 

The Model "M" is a vertical, and "MB" horizontal form 
which are similar to the "L" and "LB" models except that they 
are made without the economizer attachment. This alters their 
outward appearance, cross sections, and eliminates one adjust- 
ment. That is, the "L" and "LB" have three adjustments, high, 
low, and economizer, while the "M" and "MB" have but two 
adjustments, high and low. To make these points plain in the sub- 
sequent adjustment instructions, Model "MB" is shown in Fig. 85. 

General Instructions. The high speed is controlled by the 
knurled nut "A," which locates the position of the needle "E," 
past whose point all the gasoline is taken at all speeds. Turning 
nut "A" to the right or clockwise raises the needle "E" and gives 
more fuel; turning it to the left or counterclockwise gives less 
fuel on the "L" and "LB" models. On the "M" and "MB" 
the instructions are the same except that turning to the left or 
counterclockwise gives more fuel and to the right less. 

If an entirely new setting becomes necessary, put the econ- 
omizer "L" in the fifth notch (farthest from the float chamber) 


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as an indicator, then turn the nut "A" to the left until the 
needle "E" reaches its seat as shown by the nut not moving 
when the throttle is opened and closed. When the needle "E" 
is in its seat it can be felt to stick slightly when nut "A" is 
lifted with the fingers. Find the adjustment of "A" where it just 
begins to move with the throttle opening, then give it 24 notches to 
the right or clockwise. In this turning the notches can be felt. Then 
move the economizer pointer "L" back to the zero (0) notch, toward 
the float chamber which will give a rich adjustment. Warm the 
motor thoroughly, then thin down the mixture by turning "A" 
counterclockwise until the motor shows the best power with a quick 
opening of the throttle. This will be the desired adjustment. 

The low speed adjustment is made by means of the adjusting 
screw "B," which controls the jet "K." The latter passes the 
gasoline in above the throttle and the movement of "B" pro- 
vides the necessary air dilution. Screwing "B" in clockwise gives 
more fuel on all models; outward, less. The best adjustment is 
usually % to 3 turns outward from a seated position. This, it 
should be noted, is only an idling adjustment and does not affect 
the mixture above a car speed of 8 miles per hour. When the 
motor is idling properly, there should be a steady hiss in the 
carburetor; if there is a leak anywhere, or one cylinder leaks, 
or if the adjustment is entirely too rich, the hissing sound will 
be unsteady. The adjustment process should be continued until 
a steady hissing sound is produced, for best all-around results. 

As pointed out previously, Models "L" and "LB," Figs. 81 
and 84, have an additional adjustment called the economizer. 
This tends to the use of a leaner mixture, that is, economy of 
fuel, hence its name. To give this desired result, high speed 
needle "E" and nut "A" are raised slightly, the amount of move- 
ment being regulated by the pointer "L." After making the high 
speed adjustment for best power with "L" in the zero (0) notch, 
as described previously, place the throttle lever on the steering 
wheel in a position giving about 20 m.p.h. road speed. Then 
move the pointer "L" clockwise or away from the float chamber, 
slowly and one notch at a time, until the motor begins to slow 
down. At this point turn back one notch, that is, the adjust- 
ment should be one notch before the point of slowing down. 

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The amount of this economizer action depends upon the 
quality of fuel, which differs in different parts of the country, 
and also varies with the temperature. Thus, in the Middle West 
the best economizer adjustment will be the third or fourth notch, 
usually. With Pennsylvania gasolines and throughout the South, 
the second notch will prove the best adjustment, while on the 
Pacific Coast no economizer action will be necessary unless dis- 
tillate is used. Fewer notches of economizer action will be needed 
in summer than in winter. 

Model "LS." A sectional view of the Stromberg Model "LS" 
carburetor is shown in Fig. 85a. It is of the plain-tube type because, 
having no air valve or metering needles, both the air passage and the 
gasoline jet are of fixed size for all engine speeds. It has several 

~ interesting features, 

such as a gasoline feed 
above the throttle with 
idling adjustment, an 
accelerating well, which 
gives an extra supply 
of fuel the moment the 
throttle is opened, and 
an economizer, which 
permits the carburetor 
to operate on a very lean 
and economical mixture 
at the closed-throttle, or 
average driving, posi- 
tion. This economizer 
automatically shifts to 
• ^ the richer setting when 

Fig. 85a. Stromberg Carburetor, Model "LS" ^ ^jj pQWer of ^ 

motor is called for and operates on the thinner setting when max- 
imum power from the motor is unnecessary. 

Adjustments. The idling mixture is controlled by the turning 
of the idle adjustment screw A. This regulates the amount of air; 
screwing it in gives a richer mixture, and screwing it out a leaner 
one. Turn screw A out, anti-clockwise, until the motor slows 
down. Then turn in, or clockwise, notch by notch until the 


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motor runs at its greatest speed without missing .or "loping." 
When the motor is idling properly, there should be a steady hiss 
in the carburetor. If there is a weak cylinder or a manifold leak, 
the hiss may be unsteady and the motor is likely to miss if this 
unsteady hiss is allowed to continue. 

After adjusting the low speed, if the motor runs too fast, the 
throttle stop screw M should be turned to the left, or counter- 
clockwise, until the motor runs at the desired speed. If, however, 
the motor idles too slowly and stops, the screw M should be 
turned to the right, or clockwise, until the proper speed is reached. 
Before adjusting the screw M, it will be necessary to loosen the 
lock screw 0. 

The high-speed adjustment is regulated by the high-speed 
needle B. This needle regulates the opening through which the 
fuel flows to the jet. Turning B to the left, or counter-clockwise, 
gives more gasoline; turning it to the right, or clockwise, gives less 
gasoline. In order to make the proper high-speed adjustment, the 
spark lever should be advanced. Set the throttle lever on the 
steering wheel at a position that will give about 25 miles an hour 
car speed on a smooth road. Then adjust the high-speed needle 
to the minimum opening that will give the greatest engine speed 
for that throttle opening. This will give a good average adjust- 
ment, although two or three notches lean will give best economy 
for continuous driving, or touring; two or three notches rich may 
be best for short runs in cold weather, when the motor is not 
operating at the proper temperature. To secure greater economy 
as thin a mixture as possible should be used. 

To prevent the wrong high-speed adjustment from giving a 
harmful rich mixture, the gasoline nozzle reducer is inserted 
beyond the high-speed needle in the base of the discharge jet 
above the plug K. To secure a richer mixture the reducer placed 
in the carburetor at the factory will permit about 20 per cent 
more gas to pass than may be needed. The economizer device D 
operates to automatically thin out the mixture at speeds from 10 
to 45 miles per hour. 

In all cases adjustments should be made when the motor is 
warm and the motometer shows a temperature higher than 140 


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This carburetor is manufactured in sizes suitable for both 
the vertical and horizontal style. It is now used on a large number 
of truck and pleasure car manufacturers, as it is simple and has a 
very wide range of adjustment. There is a dirt trap in this car- 
buretor which collects dirt and sediment, thereby preventing this 
dirt from clogging up the nozzles and causing the motor to miss. 
This strainer is provided in practically all modern carburetors. 
The float is adjusted at the factory and should not be changed only 
in rare instances. 

Zenith Carburetors. The Zenith Model "O" carburetor, shown 
in Fig. 83, enjoys wide use in this country because of its simplicity. 
It has fewer ordinary adjustments than any other carburetor 
This is so constructed that but one adjustment, that for slow 
speed, is provided. However, its makers realize that sometimes 
changes and adjustments are necessary to secure proper results. 
They provide for these by the removal of three internal parts 
and their replacement with simpler parts, but with different work- 
ing orifices, or holes. 

Zenith Adjustments. The three parts mentioned are: choke 
tube, main jet, and compensator. In Fig. 83, the choke tube is 
marked X. This is really an air nozzle of such a stream-line 
shape (approximating the Venturi) as to allow the maximum flow 
of air without eddies and with the least resistance. When the 
pick-up, or acceleration, is defective and slow-speed running is not 
smooth, the choke tube is too large. In this case, it will be found 
that a larger compensator / does not better the situation. Then 
a smaller choke tube is needed. This is held in place by a screw 
Xi in the choke itself with a lock washer to prevent its jarring 
loose. To remove the choke, the butterfly T must first be 
removed. In the horizontal types, the body is in two pieces, which 
are held together by an assembling nut. When this is removed 
and the two pieces taken apart (the bowl from the barrel), the 
choke can easily be slipped out of the barrel. When the motor 
will not take a full charge, that is, when it cannot, with the throt- 
tle fully opened, this indicates the need for a larger choke tube. 
It will be noted that although the pick-up is good, the car will not 
make all the speed of which it is capable. In this case, take out 
the choke tube X, as explained above, and replace with a larger one. 


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Changing the Main Jet. The main jet G, Fig. 83, shows its 
influence mostly at high speeds. When running at high speed on a 
level road, if the indications show a rich mixture, irregular running, 
characteristic smell of over-rich mixture from the exhaust, firing in 
the muffler, sooting up of the spark plugs, and low mileage, the main 
jet is too large and should be replaced by a smaller one. On the 
other hand, when running at high speed, if the indications are that 
the mixture is too lean, if the car will not attain its maximum speed, 
if there is occasional back firing at high speed, then the main jet is too 
small and should be replaced by a larger one. In respect to back 
firing, however, care should be used, as this is more often due to large 
air leaks in the intake or valves or to defects in the gasoline line. 

To Replace Main Jet. When it is necessary to change the main 
jet G, Fig. 83, to a larger or smaller size, the lower plug L is removed 
first. This has a square head and is removed with a wrench. Then 
the main jet is unscrewed from below by means of a screwdriver, a 
notch being cut into its lower part for this purpose. In reassembling 
care should be taken to see that the fiber joint packing is on the jet 
and that the jet is screwed up far enough to compress this. Otherwise 
gasoline may leak around the threads. But one fiber washer should 
be used. Then the lower plug L is replaced, and this also must be 
screwed up tight. 

Changing the Compensator. The third change which can be made 
is in the compensator /, Fig. 83. The opening in this supplies the fuel 
to the secondary well and, if too large or too small, will have a corre- 
sponding influence upon the running of the car. The makers call 
attention to the fact that its influence is most marked at low speeds 
and suggest that when this is suspected, the car should be tried out on 
a hill, regular but long, and of such a slope that the motor will labor 
rather hard to make it on high gear. Under such a test, if the indi- 
cations are of too rich a mixture, that is, the same as for a rich mixture 
at high speed on the level, as previously explained, the compensator 
is too large, and must be replaced with a smaller one. If the indi- 
cations are of a lean mixture, with the motor liable to miss and give 
a jerky action, the compensator is too small and must be replaced with 
a larger one. This is easily removed in the same manner as the main 
jet G, by removing the bottom plug beneath it and then removing J 
with a screwdriver, through the medium of slots for this purpose in its 



lower surface. In connection with this last method of adjustment, 
the makers recommend that the workman should start with the 
setting provided, then proceed to determine first the main jet, then 
the compensator, then the choke. In a sense, this method makes 
double work, for any change in the choke calls for a corresponding 
change in the main jet, but it gives superior results. 

SlotD-Speed Adjustment. The one adjustment in the Zenith 
device which is really an adjustment and not a change is that for slow 
speed. This is preferably made on the garage floor, with the motor 
properly warmed up. When this has been done and it has been 
throttled down to idling speed, any irregularity, such as the lack of 
ability to throttle down to a really slow speed (say 350 or less r.p.m.), 
calls for a change in the adjustment. When the throttle T, Fig. 83, 
is nearly closed, there is considerable suction at the edge, and the tube 
J in the top of the secondary well P terminates in a hole A near the 
edge of the butterfly at which gasoline is picked up. If the motor 
will not throttle down as slowly as it should, the supply of gasoline 
can be reduced by means of the external milled screw 0. When this 
is turned in, the air entrance N is restricted, and consequently a richer 
mixture is drawn in. When it is unscrewed, or turned out, a larger air 
opening is uncovered, and consequently a leaner mixture is drawn in. 

In this connection, many factors other than the correct slow- 
speed adjustment of the carburetor may prevent good idling. Some 
of these are: too light a flywheel, too much spark advance, and air 
leaks created by (1) poor gaskets, (2) loose valve stems, (3) pitted or 
scored valves, (4) leaky valve caps, (5) spark or valve plugs, (6) leaky 
priming cups, and others. Obviously, if any of these faults exist, 
no amount of adjustment of the slow-speed device on the carburetor 
will give good idling. 

Horizontal Type Adjustments and Changes. Everything that has 
been said thus far applies equally well to the horizontal type shown in 
Fig. 86, except for the adjustment of the idling jet. In this form, the 
idling jet P2 is supported by the knurled nut which governs the air 
opening for this jet, and replaces the horizontal milled screw 0. 
If a leaner mixture is desired, this is turned to the right, or clockwise; 
this lowers the jet and increases the size of the available air passage. 
For a rich mixture it is turned the other way, or counter-clockwise, 
reducing the air opening. 



Float Removal. In both models, it will be noted that the float 
cover is held on by the spring catch. This is lifted by means of 
its handle, and swung around out of the way. The float cover 
can then be lifted readily by means of the knurled edge. When this 
is removed it should be lifted up straight. The float is then exposed 

Fig. 86. Zenith Carburetor, Model "HP" 
Courtesy of Zenith Carburetor Company, Detroit, Michigan 

and can be removed easily with a piece of wire bent at the end or with 
a match inserted in the center hole. 

Model "T4" One of the latest developments of the Zenith 
Carburetor Company is the Model "T4" carburetor, which is 
similar in principle to the other Zenith products, the main differ- 
ence being in the refinements and adjusting features. A sectional 
view of this carburetor is shown in Fig. 87. 

Operation. The gasoline from the tank enters the strainer 
body D, passes through filter screw Dl and enters the float 

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chamber bowl through the needle-valve seat S. As soon as the 
fuel reaches a predetermined height — shown by the horizontal 
level line — in the bowl, the float automatically rises, which forces 
the needle down by lifting the needle arms B. The gasoline is 
then fed from this bowl through the nozzles in different quantities, 
which are always in relation to the speed of the engine. 

Adjustments. The sizes of the nozzles have been determined 
at the factory and should not be changed. The only adjustment 
which might be useful is the idling adjustment. When the butter- 
fly throttle valve T is nearly closed and the motor is turned off, a 
strong suction is produced at the edge of the butterfly where the 

idling is located. Under 
this condition, little or 
no fuel is supplied at the 
main jet G or cap jet H . 
Gasoline from compen- 
sating jet / flows into 
the atmospheric well W, 
the suction then lifting 
it through idling jet P, 
which has a calibrated 
measuring hole at its 

Fig. 87. Zenith Carburetor Model "T4" Upper end « Fr0m this 

point, it is carried into 
its idling port J, where it is mixed with the air measured past 
the conical end of the idling jet. It then passes through the 
idling hole into the carburetor manifold and to the motor. Idling 
tube J is screwed into the bottom of the barrel and its position 
is thus fixed. Idling adjusting tube PI, which is permanently 
assembled to idling jet P, screws into the idling tube and is 
screwed up or down to secure the proper adjustment for idling 
the motor. 

Screwing down increases the air passage left between the 
conical upper end of idling jet P and the flared-out lower end of 
idling tube J, thus admitting more air and thinning the mixture. 
Screwing up reduces the air passage and thus enriches the mix- 
ture. The adjustment is locked by the idling spring P2, which 
engages the knurled surface of the idling adjustment 2. As the 


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throttle is opened, the idling jet ceases to function and the gas 
vapor is supplied through the main jet H as in other previous 
Zenith models. The choke Ql is supplied for easy starting. 
This choke cuts off the air supply and is operated from the dash. 
Yl is a revolving air shutter which controls the hot or cold air 
supplied to the carburetor. 

As the adjustment is changed, a difference in the idling should 
be noticed. If the motor begins to run evenly or speeds up, it 
shows that the mixture becomes right in proportion, but that 
there is too much of it. This is remedied by changing the butter- 
fly throttle position slightly, closing it by screwing out the stop 
screw which regulates the closed position for idling. Care should 
be taken to have the butterfly held firmly against this stop at all 
times when idling the motor. The single thing which is radically 
different and must be remembered in this connection is that multi- 
cylinder engines have very light flywheels and reciprocating parts, 
so the motor is extremely sensitive at low speeds to unequal condi- 
tions of ignition, compression, and air leaks. This makes it more 
necessary than with a plain four- or six-cylinder form to have the 
motor in the best possible condition before changing the carburetor 
idling adjustment. 

The Zenith Model "L" is a refinement of Model "O," just 
described, but all adjustments are made in the way described for "O." 

Carburetors on Ford Cars. On the Model "T" Ford car, 
there are two very simple forms of carburetor used. They are 
very much alike in general design and construction, but they are 
made by different firms. The form shown in Fig. 89 is the 
Model "G" Holley, while the other form, shown in Fig. 88, is the 
Kingston. Both forms have been used in about equal quantities 
by the Ford Company from 1909 to date. 

In the Kingston (Fig. 88), "A" is the fuel connection, "B" 
the air valve, "C" the low speed tube, "D" the spray nozzle, 
"E" the choke throttle, "G" the drain cock, "H" the lever oper- 
ating the choke throttle, "J" the needle valve, and "K" the needle 
valve binder nut. To adjust, warm up the motor, retard the 
spark fully, open the throttle five or six notches on the steering 
post quadrant, then loosen the binder nut "K" so the needle 
valve "J" turns easily. Turn this valve down with the dash 

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adjustment, until it seats lightly but do not force it. Then turn 
back away from the seat one complete turn. Let motor run a 
little while, then make the final adjustment. Close the throttle 
until the motor runs at idling speed, which can be controlled by 
adjusting the stop screw in the throttle lever. Adjust the needle 
valve "J" towards its seat slowly until the motor begins to lose 
speed. Stop and adjust the needle valve away from its seat very 
slowly until the motor attains its best and most positive speed. 
Close the throttle until the motor runs slowly, then pull it open 

Fig. 88. Drawings Showing Construction of Kingston Model "L2" Carburetor 
Courtesy Byrne, Kingston and Company, Kokomo, Indiana 

quickly. The motor should respond strongly. If sluggish, a further 
adjustment may be necessary. Tighten the binder nut. 

In the Holley, A is the thumbscrew with an extension to the 
clutch, by means of which the needle valve B is raised or lowered. 
The lower end of this projects down into the spray nozzle C, where 
fuel enters from the float chamber D, reaching it through the gaso- 
line intake E. To draw off sediment and water use the cock F. 

From the nozzle, the fuel passes up through the strangling tube 
G, where it is met by the entering air from the air inlet H, which has 
been deflected downward and toward the center of this circular space 
so as to pick up the spray of fuel at the nozzle and carry it upward 
in the strangling tube. Then it passes into the mixing tube N, 


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thence out to the motor via the mixture outlet 7. In this, its quan- 
tity is governed by the throttle, the lever of which may be seen at 
J. In the air intake, there is a throttle plate K y which deflects a 
large part of the entering air so that it passes to the right (straight in) 
and is added to the mixture in the mixer chamber. This forms 
the auxiliary air valve. The position of this plate, governed by the 
auxiliary throttle lever L, determines the quantity of both the 
primary and auxiliary 
air, since by its position 
it splits the entering air 
into two parts, one of 
which becomes the pri- 
mary air, and the other 
the auxiliary air. For 
low speeds and idling, 
the low-speed tube M 
carries the very rich mix- 
ture up direct to the 
mixing chamber and thus 
into the engine. 

Ford Adjustment 
This Holley model, like 
the Kingston, has but one 
adjustment. The needle 
valve B, which has a pro- 
jecting knurled head A 
for turning it, has a con- 
ical point C which seats 
into the fuel opening. If 

this is Seated, no gasoline ?*'*>' /^ ° R f Holley Carburetor for Ford Cars 

Courtesy of Holley Brothers Company, Detroit Michigan 

can enter, but as it is 

screwed out or up an opening is created and increased, which allows 
fuel to flow. The amount of this determines the amount of mixture 
entering the cylinder combustion chambers. Consequently, the 
primary adjustment with this screw is that of the fuel flow. Air 
enters through the opening H, passes the throttle K, and then mixes 
with the fuel spray, diluting it and carrying it up into the cylinders. 
The amount of the air is governed by the air lever i, its position 

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being adjusted at the factory. The adjustments as recommended 
by the Ford Motor Company are as follows: 

Initial Adjustment. The usual method of regulating the carbu- 
retor is to start the motor, advance the throttle lever (on the steering 
wheel) to about the sixth notch, with the spark lever (also on the 
steering wheel) retarded to about the fourth notch. The flow of 
gasoline should now be cut off by screwing the needle valve down 
(to the right) until the engine begins to misfire; then gradually 
increase the gasoline feed by opening the needle valve until the motor 
picks up and reaches its highest speed and until no trace of black 
smoke comes from the exhaust. Having determined the point where 
the motor runs at its maximum speed, the adjustment should not be 

changed except as indicated below. 

For average results, a lean mixture 

will give better results than a rich one. 

Dash Adjustment. The gasoline 

adjustment is placed on the dash, 

Fig. 90, the milled head shown being 

fastened to a long rod whose lower 

end is attached to the needle valve 

head A, Fig. 89. Any movement 

of the milled head moves the needle 

Fig. go. Dash Adjustment of Ford valve and gives more or less gasoline. 

Courtesy of Ford Motor Company, After the car has been worked in so 

Detroit, Michigan .1 , .. ' • « . .-i ^-i 1 

that it runs satisfactorily, a file mark 
should be made on the face of this milled head to indicate the 
point at which the engine runs most satisfactorily. This is indicated 
by Fig. 90, in which A shows the milled headed rod projecting through 
the dash, and B the mark for satisfactory normal running. In cold 
weather, it will probably be found necessary to turn the finger wheel 
one-quarter turn to the left, or counter-clockwise, as shown at C, 
particularly in starting a cold engine. This movement increases the 
amount of gasoline and makes the mixture richer. In warm weather, 
gasoline vaporizes more readily, and it will be found advisable to 
give the milled head a one-quarter turn to the right, or clockwise, 
about as shown at D. This admits less gasoline and gives a leaner 
mixture. This last adjustment is particularly advisable when taking 
Ions rides at high speed for it increases the mileage per gallon of fuel. 


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Other Ford Models. While the foregoing describes the carbu- 
retors used by the Ford Motor Company, there have been many 
different carburetors developed by other companies intended to 

Fig. 91. End View of the Hudson and Essex Carburetor 

replace the ones just described and supposedly giving better 
results. Practically every large carburetor company has a so-called 
Ford model, while many firms build only carburetors for Fords. 

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z . 

















5 = 




i w 




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Prom which it may be argued backwards that the results obtained 
with the cars as sold are not always entirely satisfactory. A few 
of these carburetors will be described although lack of space pre- 
vents a description of many of them. 

Carburetors on Hudson and Essex Cars. The carburetors 
used on the Hudson and the Essex are identical in principle but a 
little different in detail construction. The gasoline level, Fig. 91, 
is somewhat lower than the top of the gasoline feed regulator. 
This regulator, which is adjustable from the dash, determines the 
amount of gasoline fed at a given altitude or temperature. For 
high altitudes where the pressure of the air is lower than at sea 
level, less gasoline is needed, and the sleeve is moved upward. 

Principle of Operation. When the throttle is open, the air is 
drawn out of the air chamber, Fig. 92, through the pneumatic 
control passage, thus creating. a vacuum in the air chamber which 
allows the piston to be lifted up. As the measuring pin is con- 
nected to the piston, it will also be lifted and will expose a deeper 
portion of the tapered slot on this pin, thus increasing the amount 
of gasoline as the air is increased. The piston also acts as the air 
cutoff and returns to its position slowly after the throttle has 
been closed. 

This action is necessary as a greater amount of air must be 
provided with the greater amount of gasoline in order to obtain 
the same ratio in the result of mixture. A peculiar air intake con- 
struction is provided on both the Hudson and Essex carburetor, 
and the inquisitive mechanic often wonders why this construction 
is used. This air inlet is made in the form of an inverted funnel, 
having the large end toward the carburetor. A butterfly valve 
is located at the small end to shut off the air side when it is neces- 
sary to supply the motor with a rich mixture in starting. This 
style of motor inlet manifold was not used on the first Hudson cars, 
and it was found that a miss was constantly present when the motor 
was in operation. While this noise was not detrimental, it was 
rather annoying, and the Hudson people found that if the air inlet 
was constructed in the form of an inverted funnel that this undesir- 
able miss would be done away with, the manifold acting as a muffler 
just as the muffler that is attached to the exhaust of the tiiotor, 
so that the noise resulting from the escaping gases may be deadened. 

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Other Holley Carburetors. As has been stated, the carburetor 
illustrated in Fig. 89 and just described is a Holley Model "G". 
This firm also markets a Model "K " which is very similar to the "G", 
as will be noted in Fig. 93. The biggest differences between these 
models are: the vertical outlet in place of a horizontal; and the 
placing of the needle valve at the bottom because of this. In this 
latter figure, fuel enters by the gasoline pipe through the strainer A, 
past the float valve B, into the float chamber D, the level being 
regulated by the movements of the cork float C. From there, it 
passes through the opening F into 
the nozzle well E, through the 
hole H past the needle to a level 
in its cup-shaped upper end which 
just submerges the bottom of a 
small tube J, with its outlet at the 
edge of the throttle disc K. When 
the engine is cranked with the 
throttle nearly closed an energetic 
flow of air past this point draws 
liquid fuel which is atomized upon 
its exit from the small opening at 
the throttle edge. 

As the engine rotates, consid- 
erable air is forced to move through 
the conical passage outside of the 
strangling tube L. The shape of _. OQ _ „ _ . 4 _ _ . . UTPn 

00 ^ Fig. 93. Holley Curburetor, Model "K" 

the passage arOUnd the lower end Courtesy of Holley Brothers Company, 

. . Detroit, Michigan 

of this is such that the entering 

air attains its highest velocity, and thus lowest pressure, near the 
upper end of the standpipe M. Consequently, there is a difference 
in pressure between the top and bottom of this pipe, and the air 
flows downward through the series of holes N. At the bottom it 
turns sharply upward, picks up the fuel spray there and passes into 
the main vaporizing chamber above 0, and thence past the opened 
throttle into the inlet manifold at P. 

Adjustment. As will have been noted, there is but one adjust- 
ment, that provided by the movement of the needle valve I. When 
this is screwed to the right, or clockwise, the valve moves upward 


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and reduces the size of the fuel opening. When turned backward 
to the left, or counter-clockwise, it increases the opening and admits 
more fuel. The effect of these changes in its setting are claimed by 
the maker to be manifest equally over the whole range of the motor. 
According to the maker, this desirable feature is the result of utilizing 
in the nozzle action the pressure drop due to velocity of flow rather 


K Cold/lir> 

Fig. 94. Holley Temperature Regulator Attached to Carburetor 

than the pressure drop causing the air to flow. Other Holley models, 
for motorcycles and small cars, are smaller in size, and need not be 
described here. 

Temperature Regulator. This firm recommends a temperature 
regulator for use with its own and other carburetors. This is particu- 
larly important now, with the scarcity of fuel, its consequent low qual- 
ity, and its high price. It is admitted by all that the heat is necessary 
in cold months, but that it is less necessary, although advisable, in 


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warm months. This necessitates a means of varying it. There is no 
better source of heat than the handy exhaust pipe where heat is 
going to waste, so the Holley device, as illustrated in Fig. 94, utilizes 
the exhaust pipe as a source of heat and leads the same to the carbu- 
retor through a flexible tube with a regulating valve at the lower, or 
carburetor end. This is regulated by a simple rod connection with 
a small handle which pro- 
jects through the dash and 
has a dial behind it. This 
can also be used as a strang- 
ling valve to assist starting, 
as shown above at A, for 
hot-air supply in winter, as 
at B, for half cold air in the 
spring arid fall months, and 
for all cold air throughout 
the summer months. 

Kingston Carburetors. 
Enclosed Type. The King- 
ston enclosed type, as shown 
in Fig. 95, differs from the 
type previously shown in 
that the auxiliary air valves 
in the form of various sizes 
of steel balls are used. 
These are normally seated, 
but they are lifted from 
their seats by increased suc- 
tion. The primary air valve 
is not radically different 
from the former model, but the passage of the air is vertical 
rather than at an angle. When the suction lifts the ball valves, more 
air is admitted. This joins the partially vaporized mixture at the top 
of the vaporizing chamber and completes the vaporization and dilution 
before passing the throttle valve on its way to the inlet manifold. Like 
the model previously shown, it has the cup-shaped needle recess, so that 
when the motor is shut off, a pool of fuel collects there; this makes 
starting easy, for this fuel is drawn directly in, almost without dilution. 



Fig. 93. 

Plan and Section of Kingston Enclosed 

Courtesy of Byrne, Kingston and Company, 
Kokomo, Indiana 


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Adjustments. If the float is found to be too high or too low, it 
can be adjusted readily by bending the float lever to which it is at- 
tached. The only other adjustments are: the setting of the throttle 
which governs the lowest speed, this being accomplished by the screw 
shown on the throttle-lever arm projection at the left; and the setting 
of the needle valve for satisfactory high speeds. This is accomplished 
by unscrewing the cap to which the needle is attached and allowing 
more fuel to flow. Continue until the highest speed is reached and 
passed, then turn back until the maximum speed is reached. 

Fig. 96. Part Section of Kingston Dual Form of Carburetor 
Court. »y of Byrne, Kingston and Company, Kokomo, Indiana 

Kingston Dual Form. This form, as shown in Fig. 96, is really 
two of the enclosed models, just described, attached to a common 
outlet and with a single throttle valve. It is intended for use with 
heavy fuels; one side is connected up for gasoline, which is used in 
starting and for exceptionally slow speeds long continued, while the 
other side is set for heavy fuel, such as kerosene, distillate, etc., and is 
used as soon as the engine running on gasoline has heated up suffi- 
ciently. It will be noted that one-half of this device is fitted with a 
water valve, which is placed on the heavy fuel side. It is a gravity 
valve seated by its own weight at low speeds and lifted progressively 
at higher speeds until wide open. In continuous running on heavy 

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fuels, it has been found that after a certain time the engine begins to 
pound, but that if cooling water be introduced with the mixture, the 
engine will run cooler, and this pound will disappear. To remedy 
this is the function of the water valve. 

Adjustments. Adjustments and repairs for this model will be 
exactly the same as with the previously described enclosed model, 
since it is simply two of these joined together. As has been stated, 
the added water valve works automatically. 

Kingston Model "L." The last Kingston model shown, that of 
Fig. 97, is very similar to the Ford model, except that it is formed 
with a vertical outlet, and 
the air valve B added in the 
vaporizing chamber so formed. 
This is hinged at the side so as 
to be swung upward by the 
suction of the motor, thus 
uncovering a larger and larger 
orifice. It is weighted and 
acts automatically. It will be 
noted also that the shape of the 
nozzle has been altered slightly, 
that on the Ford model being 
perfectly straight. Near its 
lower end, it passes through 
the low-speed tube C, which 
has a series of holes around 
the bottom and an annular 
space around the body of the needle. Through this space the fuel 
and a very little air are drawn for starting, as, at that low suction, 
the valve B would be entirely seated. 

Adjustments. After retarding the spark, opening the throttle, 
loosening the needle, and starting the motor, let it run at a fair speed 
long enough to warm up. Then adjust the needle valve. Close the 
throttle by adjusting the stop screw in the throttle lever until the 
motor runs at the desired idling speed. Adjust the needle valve towards 
the seat slowly until the motor begins to lose speed, which indicates a 
weak mixture. Now adjust the needle valve away from its seat until 
the motor attains its best and most positive speed. This should 

Fig. 97. Section of Kingston Model "L" Carburetor 
irne, Kingston an 
okomo, Indiana 

Courtesy of Byrne, Kingston and Company, 

Ko: ' " 


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complete the adjustment. Close the throttle and let the motor 
idle, then jerk it open rapidly. The motor should respond readily. 
If it does not respond, a slight further adjustment may be necessary. 
When the adjustment has been made, lock it. Float 'troubles m§ 
be remedied in the same way as for the enclosed model. 

Master Carburetor. The Master is called a carburetor with- 
out an adjustment. It was originally developed in Los Angeles 
for the purpose of using the heavy oil, called distillate, which is 
available there. This, as shown in Fig. 98, is a design of remark- 
able individuality. Except for the float chamber, it does not 
resemble any other carburetor. In design it consists of a float 
chamber to which the fuel enters from below through a round 
pan-like screen which filters it. From the float chamber the fuel 
passes through another cylinder-like screen which filters it again. 
Then it passes to one end of a long fuel passage, from which lead 
a series of vertical passages, each ending in a nozzle. These pas- 
sages discharge the fuel into a cylindrical throttle chamber within 
which is placed a rotary throttle valve. This has a peculiar spiral- 
shaped edge, so that one tube — the end one shown on the right- 
hand edge slightly separated from the others— alone communicates 
with the vaporizing space. This is the starting and idling tube, 
or, nozzle. As the throttle is revolved, the spiral edge brings the 
other tubes into play, one at a time, until the whole number is 
engaged. When the throttle is revolved to the full opening, its 
central portion, as shown in the left-hand figure, is seen to be 
somewhat restricted at the center and flared at the ends to pro- 
duce a slightly modified Venturi shape. The passage above the 
throttle leading to the inlet manifold, and the shape of the passage 
below it through which the air enters, both contribute to this effect. 

The air enters from the right, Fig. 98, and the shape of this 
passage, to match the general shape of the carburetor, is low but 
wide. This has led to the development of a variable method of 
furnishing the air; for a division in the end of the passage allows 
of having all cold air, half cold and half hot, or all hot, as desired. 
For the heavy fuel conditions under which the device was devel- 
oped, the all-hot air arrangement was used. Except in the hot 
summer months this would be most desirable, but there are con- 
ditions under which the semi-hot air arrangement would be best. 

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Adjustment. While it is said not to have any adjustment, 
there is a variation which corresponds to the adjustment in many 
carburetors. This is the air damper, which is a long, rigid, flat 
plate extending across the incoming air passage parallel to the 
distributor and is connected by means of a Bowden wire mechan- 
ism to an operating lever on the steering post in the position 
where the usual carburetor adjustment is located. When this is 
moved, the air damper is swung over toward, or away from, the 
distributor. This movement restricts or increases the air passage 
at the jets. When the damper is moved so as to restrict the 
passage of air, its velocity is increased, and the greater suction 
carries up more fuel from the jets, and thereby produces a richer 
mixture. On the other hand, when the damper is moved to 
enlarge the area, there is less suction; consequently less fuel is 
drawn up, and the mixture is leaner. In the sense that the 
operator can change nozzles or modify the maximum or minimum 
amount of air or fuel entering the carburetor, this device has no 
adjustments. The nozzles cannot be changed in any way, and the 
amount of air can be varied only in a wholesale way, i.e., by 
changing from lean to rich through the whole range between these 
two. This device has been used four years as regular equipment 
on Moreland trucks which are built to use distillate selling at 6 
cents a gallon, in barrel lots. This fuel has a specific gravity of 
51 at 60° F. 

When made for Ford cars, this device has only 11 nozzles. 
On the larger sizes from 14 to 19 are employed. The use of this 
device, with its vertical opening, necessitates a special inlet mani- 
fold to replace that on the Ford which provides for a horizontal 
carburetor outlet. 

. Miller Racing Carburetor. A carburetting device very similar 
to the Master is that shown in Fig. 99, this being the Miller car- 
buretor. Proof of its efficiency is shown by its very wide use on 
the highest powered engines, such as the King-Bugatti 16-cylinder 
aeronautic engine, the Duesenberg line of racing and airplane 
engines, and on the majority of recent racing cars. 

As will be noted in the figure (this showing the carburetor as 
used on the King-Bugatti 400-horsepower engine), a number of 
screwed-in jets are used, in the case of this particular engine, the 




number being seven, while the number of carburetors used was 
four, one for each four cylinders. In ordinary racing practice one 
or two of the seven-jet carburetors are used. 

Fig. 99. Miller Multi-Jet Carburetor and Altitude Valve Details 
Courtesy H. A. Miller Manufacturing Company, Los Angeles, California 

As the general view and detail indicate, gasoline is drawn into 
each one of the jets through the small hole in the bottom of the 


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threaded end, mixing with a certain amount of air sucked in 
through the four small holes at A drilled in the barrel of the jet 
just above the threaded portion. This air is taken from the out- 
side through the upper ^-inch hole B in the jet holder, and 
passes down around the outside of the jet to the four small holes 
mentioned. The major portion of the air enters the carburetor 
through the lower end C of the Venturi, which is 3 inches in 
diameter, passes up around the jet bar holder, combining above 
this with the rich mixture from the seven jets to form the proper 
mixture for combustion. 

This particular instrument being for airplane use, an altitude 
adjustment is necessary, and the details of this are shown in the 
illustration. It operates by turning the lever, and has two open- 
ings in its seat which when open register with similar holes in the 
cover giving the free passages to the atmosphere. The float 
chamber is in direct connection with the Venturi through the 
drilled hole D ■& inch in diameter, this being well above the fuel 
level. When the altitude control valve is opened, by this means, 
the vacuum in the float chamber is decreased, thus increasing the 
flow of fuel through the jets. 

Like the Master, this has no adjustment, changes in per- 
formance being produced by replacing the jets with different ones. 

Webber Automatic Carburetor. The Webber carburetor has 
been produced to meet the need for a very finely and carefully made 
instrument. It is an instrument of precision and is priced accord- 
ingly. Two models are made, namely, Model "C," which has a 
vertical outlet and water jacket; and Model "E," which has a horizon- 
tal outlet and no water jacket and is therefore smaller and more com- 
pact. With these exceptions, the two are very similar in construction, 
as well as in adjustment. For this reason only the Model "C" will 
be shown. This will be seen in Fig. 100, which shows a longitudinal 
section along the center line of the two chambers. It will be 
noted that this device has a concentric float 37 in which the 
spray nozzle 35 is located. The needle point 32 is controlled through 
the needle-point lever 13 which works down onto it from above. 
The nozzle is placed in the center of the modified Venturi cham- 
ber 7, the top outlet of which consists of a series of 10 tapered 
holes. As the fuel mixed with the hot air entering through the air 


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horn 9 reaches the vaporizing chamber, the auxiliary air enters from 
the side. Because of the shape of the cylindrical vaporizing chamber 

Fig. 100. Section through Webber Automatic Carburetor 
Courtesy of Webber Manufacturing Company, Boston, Massachusetts 

51 and the distance which this chamber extends downward, the 
auxiliary air is forced to turn at right angles and also to pass through 
a restricted area, thus giving it an increased velocity where it picks 


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up the partly vaporized fuel. In this upper cylindrical vaporizing 
chamber 51 the throttle valve 18 of the simple butterfly type is 

The auxiliary air enters through the holes 50 below the dashpot 
chamber 3 in which the piston 5 is located. This is attached to the 
upper end of the auxiliary air-valve stem, its lower part having a 
conical extended shape so as to spread out the air. The dashpot 
prevents fluttering while the downward movement of the air valve 
is resisted by the spring &£• The tension of the spring is adjustable 

Fig. 101. External View of Webber Carburetor, Showing Adjustments 

by means of the milled thimble 28 and the locking plunger 30. The 
air- valve lever 11 is interconnected with the needle- valve lever 13, 
so that any movement which increases the air opening automatically 
increases the fuel flow also, and vice versa. 

Adjusting the Webber. There are two adjustments, aside from 
the setting of the air valve and the determination of the proper needle 
valve and its correctly proportioned spring. These are for low speed, 
or idling, and for high speed, or maximum power. Assuming that 
the carburetor has been installed correctly and the fuel turned on, 


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the makers recommend turning the air- valve adjusting-spring thimble 
C, Fig. 101, up or down until the air valve upon being pressed down 
and released returns lightly but positively to its seat. Next turn 
the low-speed adjusting screw A down (right handed, or clockwise) as 
far as it will go without resistance, then turn it up, or back, about 
three-fourths turn. Turn the high-speed adjusting screw B to the 
right or left ijntil the fulcrum block E is approximately in the center 
of its travel. Be sure that when the lever of the steering-post control 
(handle operating Bowden wire) is moved down to the lean position, 
the lever F on the carburetor is pressed forward firmly against its stop. 
Low-Speed Adjustment. Move the lever of the steering control 
to the rich position, open the throttle about one-quarter, then start 
the motor. Now move the lever on the steering-column control down 
to the lean position and allow the motor to run idle until thoroughly 
warmed up. If it does not idle properly, turn the low-speed adjusting 
screw A up or down until it runs smoothly with the throttle closed 
against the stop screw D. The latter, after being adjusted properly, 
should be fastened by setting up the clamp screw provided for this 
purpose. This adjustment is for idling only. 

* High-Speed Adjustment. The high-speed adjustment is made 
by turning the screw B to the left or right. This moves the fulcrum 
block E in or out; moving it in gives less gasoline at high speed, and 
moving it out gives more gasoline at high speed. This adjustment 
can be made with the motor standing and continued until what seems 
to be the best position is reached; but the final high-speed adjust- 
ment should be made on a long hill. On this, start up at the bottom 
at about 20 miles per hour, open the throttle wide, and note the speed 
at the top. Now go down the hill. After moving the fulcrum block 
E out about yg inch, try the hill a second time, starting from the bot- 
tom at the same speed as before and noting particularly the speed 
which results at the top. If this shows a gain, move the fulcrum 
block out another y& i ncn an d try again. If it shows a loss, move the 
fulcrum block in and then try the hill. Continue until the maximum 
speed at the top of the hill is obtained, then lock the adjustment. 
This means but a few trips up and down the hill and results in a 
setting which is permanent and gives maximum power at all times. 
This adjustment is for maximum power only and has no effect upon 
the idling adjustment made previously^ Be careful also not to pass 


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the point of maximum power; as this point means maximum speed, 
flexibility, and acceleration.. 

Starting Adjustment. The makers claim that it is unnecessary 
when the proper adjustments have been made to wait for the motor 
to warm up before starting away; simply move the steering-column 
control to the rich position, start the motor, and drive off, then, as the 
motor warms up, move this control lever down toward the lean posi- 
tion, running normally with this as far down toward lean as it will go. 

Fig. 102. Section of Rayfield Carburetor, Model "G" 
Courtesy of Findeiaen and Kropf Manufacturing Company, Chicago 

Except that some of these adjusting screws are located differently, 
the adjustment of the Model "E" is the same as that of Model "C", 
as is also that of the Model "EH" a modification of the "E" adapted 
particularly to the Hupmobile. 

Rayfield Carburetor. The Rayfield carburetor, Model "G", as 
shown in Fig. 102, is of the double-needle type, with three air-inlet 
openings and an eccentric float chamber. The latter is shown at the 
left, with fuel entering from below through a strainer. Communi- 
cating directly with this float chamber is the passage in which the 
low-speed nozzle (marked spray nozzle) is situated; this consists of a 
hollow member with the actual needle point coming down vertically 


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from outside and above, similar to C, Fig. 82. Communicating with 
the float chamber is a passage, or well, through which fuel flows across 
to the bottom of the high-speed well. In tkis passage is located a 
hollow metering-pin nozzle; and in the upper part of it is the meter- 
ing pin. The upper end, through which the fuel flows, is located in 
one end of the elongated vaporizing chamber, while the upper auto- 
matic air valve has access to the top of it and furnishes the air supply. 

At the other end of the vaporizing chamber the idling needle is 
located, and directly beyond it is the constant air opening, a simple 
round hole communicating with the atmosphere. This end is short 
and close to the central portion of the chamber, which is approxi- 
mately cylindrical. The lower air valve is at the bottom, while the 
vertical connection to the inlet manifold and the butterfly throttle are 
at the top. The lower air valve and the upper automatic air valve are 
linked together so as to operate simultaneously. The movement of 
the upper automatic air valve downward actuates the metering pin, 
moving it downward; this tends to allow fuel to flow out around the 
pin. At the same time, the stem of this valve is connected at the 
bottom with a piston working in the dashpot which is filled with fuel, 
so that any sudden tendency for the air valve to open is checked by 
this dashpot. At the same time, this piston communicates with the 
hollow metering-pin nozzle, so that the downward movement of the 
piston forces an extra supply of fuel into the nozzle and enriches the 
mixture. Thus,- the opening of the throttle automatically produces 
a rich mixture for starting, as the slow movement of the air valve in 
opening against the drag of the dashpot causes a relatively stronger 
suction on the nozzles. This arrangement eliminates the necessity 
for an air-valve adjustment, that is, an adjustment which owner or 
repair man is supposed to use. As a matter of fact the carburetor is 
made with an adjusting ring, which, after setting at the factory, is 
locked by means of a set screw and is not supposed to be touched. 

Adjustments. Referring to Fig. 103, there are but two simple 
adjustments on the Rayfield; both are made by means of external 
milled head screws. Before making any adjustments, be sure there 
are no obstructions in the gasoline line, that all manifold connections 
are tight and free from air leaks, that valves and ignition are correctly 
timed, and that there is good compression and a hot spark in all 
cylinders. These carburetors are generally fitted with dash control. 

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Always adjust the carburetor with this dash control down. The 
low-speed adjustment should be made first. To make this, close the 
throttle and let the dash control down, then close the nozzle needle 
by turning the low-speed adjustment, Fig. 103, to the left until the 
block U leaves contact with the cam M slightly. Then turn to the 
right about three full turns. Start the motor and allow it to run 
until warmed up, then push the dash control all the way down, retard 
the spark, close the throttle until the motor runs slowly without 
stopping. Now make the final adjustment by turning the low-speed 
screw to the left until the motor slows down. Next, turn to the right, 

Fig. 103. External View of Rayfield Carburetor, Model "G", Showing Adjustments 

one notch at a time, until the motor idles smoothly. If the motor 
does not throttle low enough, turn the stop-arm screw on the main 
throttle-valve shaft to the left until the motor does run at the mini- 
mum speed desired. 

High-Speed Adjustment. Advance the spark about one-quarter 
with the motor running, then open the throttle quickly. Should the 
motor back-fire, it indicates a lean mixture. Correct this by turning 
the high-speed adjusting screw, Fig. 103, to the right, about one notch 
at a time, until the throttle can be opened quickly without back-firing. 
If loading, or choking, is experienced when the motor is running under 

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heavy load with the throttle wide open, it indicates too rich a mixture. 
This can be overcome by turning the high-speed adjustment to the 
left. Adjustments made for high speed will not affect low speed. 
Low-speed adjustments must not be used to get a correct mixture 
at high speed. Both adjustments are positively locked. 

Changing Nozzles. "Never, under any circumstances, change 
nozzles in the Models "G" and "L" carburetor," say the manufacturers. 
Neither should the float level be changed, as they say this is correctly 
set at the factory and should not be touched. For use with a pres- 
sure system, two pounds pressure is advised. The plugs S, Y, and X 


1 1 -v-i — U 
! ! X 

1 1 


Ftxsitton of Plunger Jt' 
with Dash ffdj. ,%' 
all way up 


Closed Position of Plunger 
'with Dash ffdj.Down. 

Note Suction of AYofor is 3hul 
of f with Plunger in Closed 

V>—. . 

Note Liquid Fuel Drawn 
Direct from Float Chamber to 
Manifold by Suction of Motor: 

r== ^"-TCLv-L 


_ ^^^Pll&JL L *?$¥Q- _ _ . I 

Fuel hole Below 
^Gasoline Leyel 


Fig. 104. Sketch of Starting Primer Attached to Model "N" Rayfield Carburetor 

are for cleaning and draining purposes. In the bottom of the float 
chamber there is a strainer trap, which can be cleaned by shutting 
off the gasoline supply and removing the nut S. The dashpot is 
drained by opening the drain cock X; it is advisable to do this occa- 
sionally to remove any sediment that may have accumulated there. 
The float chamber should also be drained occasionally by removing 
the plug Y. When this is replaced, it should be tightened very care- 
fully; and when the strainer trap is removed and cleaned, care should 
be taken in replacing it to put the gaskets back in place as well as to 
tighten the nut adequately. 

The Model "L" is the same as Model "G" without the water 
jacket. It is adjusted in the same manner, and all that has been 


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said above on the subject of adjusting the "G" applies with equal 
force to the "L". 

Adjusting Model "M". The Rayfield firm makes another model, 
known as Model "M", which is similar to the Model "L", except 
that it has a side, or horizontal, outlet. It has the same two adjust- 
ments, made in the same way, but the shape of the carburetor locates 
these in a different place. The low-speed adjusting screw is on the 
extreme top of the carburetor, and the high-speed adjusting screw 
is also on the top, but it is made accessible by removing the hot-air 
elbow from the main air valve. This model is fitted with a starting 
primer incorporated in the device itself and operated through the 
medium of a dash lever. In the sketch, Fig. 104, which is self- 
explanatory, the construction and operation of this are shown. When 
pressure feed is used, not more than one pound is recommended for 
Model "M". When the starting primer is to be attached, the following 
method should be used: Locate the position on the dash desired for 
the push button and drill a f-inch hole at the proper angle. Attach 
the adjustment and run the tubing to the bracket on the carburetor, 
avoiding sharp bends. Cut off the tubing so it will extend beyond 
the bracket not more than \ inch. Remove the temporary wire 
from the carburetor, insert the tubing and secure permanently by 
tightening the clamp screw. Run the dash adjustment wire through 
the hole in the binding post on the eccentric lever. Then, with the 
push button down, place the eccentric arm in position so that the 
line on the eccentric just comes in contact with the adjusting screw. 
Tighten the screw in the binding post, cut off the surplus wire, and, 
without changing the position of the push button, make the carburetor 
adjustment, as previously described. 

Ball and Ball Carburetor. The Ball and Ball device has been 
developed by Frank H. and Frederick O. Ball and is named after 
them, but it is manufactured and sold by the Penberthy Injector 
Company. In all its forms, as used on a number of different cars, 
whether single or double, horizontal or vertical, it is a two-stage 
instrument. These two stages are called the primary and the 
secondary. As shown in Fig. 105, the primary stage corresponds to 
the usual simple air-valve carburetor. This consists of nozzle, or 
jet, 3, located in the fixed air passage, or Venturi, 2. In the passage 
above this, it receives its air for complete vaporization from the 


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valve 4- Some air is, of course, admitted around the nozzle 8 below the 
Venturi 2, otherwise the fuel would not be drawn up. This nozzle 
receives its fuel from the float chamber 14, which is supplied through 
a strainer in the usual manner from the gasoline pipe 18. The con- 
nection from the float chamber to the jet extends first to the well 16, 
thence across the horizontal passage 17, from which the nozzle 8 
draws its supply. 

Now, to this simple carburetor add another which consists of the 
nozzle 6 and of the air supply 5, which is normally closed by the 

Fig. 105. Section through Ball and Ball Two-Stage Carburettor 
Courtesy of Penberthy Injector^Company, Detroit, Michigan 

butterfly throttle 7; this latter, when closed by a spring, covers the 
top of the jet 6 so that it cannot function. It is obvious that the 
primary stage is constructed for low speed, idling, and for the lower 
range of driving, and is very economical. As this lower range covers 
perhaps 85 to 90 per cent of ordinary driving, this would be a desir- 
able feature. 

As the drawing shows, the opening of the second throttle valve 
7 allows additional air to enter and, at the same time, uncovers the 


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second jet 6, so that this starts to function by drawing its gasoline 
from the same horizontal passage 17 as does the primary jet. 
If this throttle be connected up to the other throttle in such a way 
that, when approaching the maximum opening of the main throttle, 
the secondary throttle begins to open, we have, in effect, two carbu- 
retors, one working over the lower range, which gives good idling 
and splendid economy, and another high-speed and high-power device 
adding its total effect to that of the primary. The two contradictory 
and opposed qualities of highest power and highest economy are 
thus produced by what is, in effect, a double carburetor. This, 
with variations for various sizes and types of cars, constitutes the Ball 
and Ball device, shown in section in Fig. 105. 

Pick -Up Device. This carburetor has a pick-up device which 
produces remarkable acceleration. This consists of the plunger 8 
having a smaller sized upper end 9. It is loosely fitted in the cham- 
ber 15, the bottom of which communicates with the float chamber, 
and is thus kept full of gasoline. At the top, a small hole 10 commu- 
nicates with the manifold above the throttle, while 11 is an opening 
to the atmosphere, and 12 is an opening to the mixing chamber. 
When the throttle is nearly closed, the vacuum in the manifold 
raises the plunger, and the space below it fills with gasoline. In this 
position it is ready to act. When the throttle is opened suddenly, 
the vacuum is broken, and the plunger drops of its own weight, forcing 
the gasoline up where it is swept into the mixing chamber by 
the air entering through the passages 11 and 12. This is repeated as 
often as the throttle is suddenly opened from a nearly closed position. 

Adjustments. The primary stage must be adjusted as a whole 
to give the best idling and slow speeds; this consists of the adjustment 
of the air-valve spring, the arrangement of the hot-air passage leading 
to it, or, if these prove insufficient, the changing of the primary 
nozzle. The last change is opposed by the makers. 

Beyond this, the only adjustment possible lies in the hot-air 
choke valve which can be moved or altered from the dash to give 
more or less hot air. The partial closing of this valve makes starting 
easier and helps the running of the motor until it gets warmed up, 
but in normal running its manipulation has little effect. In going 
farther than this, the only possibility lies in altering the design by 
varying the connection between the two throttles, so the second stage 



cuts in sooner or later, but this might impair the usefulness of the 
instrument. The same is true if the secondary nozzle is changed. 
The device, then, is really lacking in adjustments in the ordinary 
sense, except for the initial setting of the primary-stage air valve. 

Newcomb Carburetor. The Newcomb carburetor is made by the 
Holtzer-Cabot Electric Company and is a constant vacuum type 
having a single nozzle and an eccentric float chamber. It is a high- 
grade instrument and is used only on the highest-priced cars. As 

Fig. 106. Section through Newcomb Carburetor 
Courtesy of Holtzer-Cabot Electric Company, Boston, Massachusetts 

shown in Fig. 106, the hot-water-jacketed vaporizing chamber will be 
noted at the left. In the center of it is the hollow plunger 69, which 
works up and down in the plunger chamber 68. The top portion of 
the plunger has the needle holder 73 held in place by the lock nut 74- 
The hollow plunger 69 surrounds a tube at the top of which the fuel 
nozzle 72 is located. The fuel controlling needle 71 is fixed in the 
needle holder 73 and projects through this nozzle down into the 
central fuel well. This is connected by a horizontal passage at the 
bottom to the lower part of the float chamber, seen at the right, 


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which is of normal, or usual, construction, except for the regulating 
cap 77 on the top of the central opening above the float needle 85. 

Around the bottom edge of the plunger 69 a large number of 
holes of small size are drilled, and these are arranged to register with 
an equal number of relatively narrow air slots cut in the bottom of the 
plunger chamber walls. These distribute the fuel after it has passed 
up the central well, issued from the nozzle, and been drawn within 
the plunger. The plunger when at rest is seated on the collar 70, 
which is threaded into the bottom of the plunger chamber and is used 
as a means of adjustment, as will be explained later. This collar is so 
set as to raise the plunger slightly, thus opening the fuel nozzle without 
uncovering the air slots in the plunger chamber. In this way, the fuel 
port is given a lead with respect to the air ports, so that a rich mixture 
is delivered when the plunger is raised a little, as in starting or idling. 

When air is drawn through the carburetor by the motor suction, 
the plunger lifts in proportion to the amount of air entering. This 
lifts the needle and, at the same time, releases the exact amount of 
fuel needed to charge the entering air correctly and thoroughly. The 
higher the plunger is lifted, the greater the air and fuel openings. 
The effective areas of these air and fuel ports are so proportioned as 
to be correct at all positions. The slots in the plunger chamber walls 
being small, the jets of air coming through them have a high velocity, 
S3 that the fuel is atomized as it issues at these points. Any unatom- 
ized or unvaporized fuel is thrown against the heated walls of the 
vaporizing chamber, which are made greatest in area in this region. 
This produces a dry gas and high fuel economy. The gas passes 
around the outside of the plunger chamber, through the main throttle 
valve, and thence goes into the inlet manifold. 

Starting Device. The small pipe shown at 101 is a starting device 
and consists of a pipe connection from the lower part of the float 
chamber into the gas outlet passage above the throttle valve. When 
about to start, the throttle is thrown over to a position in which the 
opening of this pipe is included in the manifold above it. It is then 
susceptible to the partial vacuum existing there, and pure fuel in a 
very fine spray is drawn directly into the manifold. Under normal 
running conditions, its operation is negligible. 

The Dashpot. This device has a solid head to the plunger 69 
and also to the plunger chamber 68 in which it works. Between the 

293 Digitized by G00gle 



two there is a considerable space, and, as the plunger is a fairly close 
fit in the chamber, this acts as a dashpot and retards the speed of the 
plunger when the motor is accelerating, or when the throttle is opened 
suddenly. By retarding the speed of the plunger, a richer mixture 
is obtained at the precise time when it is needed, in fact, demanded, 
by the motor. And yet when the plunger rises and stops rising, the 
mixture again becomes normal. This arrangement, therefore, does 
not need an extra rich setting in order to obtain good acceleration, 
for the engine can run on a lean mixture with a rapid pick-up. 

Mixture Indicating Pointer. The top of the float chamber carries 
a name plate 88 on which a graduated arc varying from 1 to 9 is 

etched; the 1 end being marked 
poor, and the 9 end rich, as shown 
in Fig. 107. On the top center 
of the float chamber is a regulating 
cap 77, Fig. 106; attached to the 
top of it is the regulating pointer 
78, which traverses the arc shown 
and in this way indicates the 
quality of the mixture being 
formed with that setting. This 
pointer, shown as straight, but 
having two bends, from a hori- 
zontal to a vertical and back to a 
horizontal at the scale, has a small 
hole at one end to which a dashboard controlling lever can be 
attached, thus a quick and easy adjustment can be obtained. This 
pointer, which carries with it the regulating cap 77, Fig. 106, adjusts 
the degree of vacuum above the gasoline in the float chamber and 
this holds back or partially restrains the flow of fuel to the nozzle. 
When turned to poor, the vacuum is increased, and the flow of fuel 
is reduced, giving a weaker, or leaner, mixture. When turned to rich, 
the vacuum is reduced so the fuel flow is increased and results in a 
richer mixture. This effect is felt throughout the range of throttle 
opening and thus throughout the speed range. It is used also to 
compensate for changes in temperature, altitude, and varying fuel 
densities. This vacuum arrangement replaces the usual change of 
area of the fuel opening in other carburetors. 

Fig. 107. 

Sketch of Regulating Pointer on 
Newcpmb Carburetor 


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Adjustments. There are but two adjustments: the load- 
carrying adjustment controlled by the pointer 78 and cap 77 just 
described; and the idling adjustment controlled by the regulating 
collar 70, mentioned previously, and shown in Fig. 106. Contrary to 
the usual method, the load-carrying adjustment is made first, and the 
low-speed, or idling, adjustment is made last. To make the load- 
carrying adjustment, set the throttle in the special starting position 
as described, turn the regulating pointer to the rich position on the 
dial, then screw the slow-speed ring, or regulating collar, 70 as far up 
as it will go. This is the rich position of the ring for starting only. 
Flood the carburetor by means of the tickler 94 until gasoline appears 
on top of the float chamber. Then start the motor and immediately 
move the throttle to a running position, otherwise the motor will stall. 

With the motor running normally, move the regulating pointer 
78 to about 5 on the dial; this gives an average setting, but different 
points should be tried and the poor-mixture, or lean-mixture, side 
should be favored always. To obtain the best setting, move the 
pointer half a point at a time, and try out the setting each time on 
the road. When the best setting has been found for some one condi- 
tion of motor speed and load, the mixture will be found correct under 
all conditions except idling. 

Idling and Low-Speed Adjustment. Now that the load-carry- 
ing adjustment has been made, the ring 70 which adjusts the mixture 
for idling should be unscrewed to weaken the mixture until the motor 
throttles evenly, without loading or popping when accelerated. 
Possibly the best combination of slow running and quick smooth 
acceleration may call for a slightly richer mixture than that on which 
the motor idles best and slowest. After this setting has been made, 
to see if the ring is screwed up too far and is giving a richer mixture 
than is necessary, move the regulating pointer 78 slowly from the 
No. 5 point toward poor. If the motor speeds up, the mixture is 
too rich, and the ring 70 should be unscrewed until the motor idles 
correctly with the pointer in the position found to be correct for the 
load-carrying mixture. After the correct idling position has been 
found, all variations for atmosphere, temperature, and fuel conditions 
should be made by changing the pointer only. 

Newcomb Air-heated Model. In addition to Model "B" just 
shown and described, the Newcomb is made in an air-heated form 




shown in Fig. 108. This is known as Model "E," and differs from 
Model "B" mainly in the method of heating (air instead of water), 
the slow speed adjustment, and the arrangement of the high speed 

In place of the adjusting ring 70 which raises or lowers the 
plunger in Model "B," spray nozzle is raised or lowered by means 
of an adjusting thumb nut at the bottom of the carburetor and 
outside. This is seen at the bottom of Fig. 108, which shows 
also how this nozzle would be withdrawn from the metering 
needle or raised to it by such movement. The high speed adjust- 

ftoat _ 

7humb Afut ~" 

3ti<fifi0 A/ozxJe 
Stuffing 3oX 

Fig. 108. Section tKrough Newcomb Model "E" Air-Heated Type Carburetor 
Courtesy Holtzer-Cabot Electric Company, Boston, Massachusetts 

ment is much the same in principle, but instead of the pointer on 
top of the float chamber a lever hung in a vertical plane works 
upon a pin "A" between the float chamber and body, this by its 
position governing the amount of vacuum above the fuel, and 
thus, its flow. The starting device is similar to the pipe 101, 
Fig. 106, but the fuel is broken up by the knurled edge of a pul- 
verizing ring in the throat above the throttle, the knurling doing 
the actual work of pulverization. 

Marvel Carburetor. The Marvel carburetor, Model "E," 
shown in section in Fig. 109, is notable for using the exhaust gases 


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directly for heating the vaporizing chamber, as well as for pre-heating 
the air used for vaporizing the fuel. The latter is common enough, 
but in the usual case where heating is thought necessary, hot water 
from the motor's water-circulating system is used. Another novelty 
in this design is the inclined hinged form of air valve set across the 
lower part of the vaporizing chamber. The float chamber A is 
eccentric to the central vaporizing chamber B, but is set very close to 
it, so the ends of the cylindrical float C have to be cut off for clearance. 

Fig. 109. Section through Marvel Carburetor, Model "E" 
Courtesy of Marvel Carburetor Company, Flint, Michigan 

Fuel enters from below. It enters the gasoline passage from above, 
as this is horizontal. The primary, or low-speed, nozzle D, which is 
adjustable, takes off from this about midway of its length, and the 
high-speed nozzle E from the end. The former operates within a 
Venturi tube which is supplied with air from below. Above this, the 
chamber broadens out through the zone in which the high-speed nozzle 
contributes, but above that it narrows down again before meeting the 
outlet, the last few inches having exhaust heat applied around it. 

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These exhaust gases pass downward through an external cylin- 
drical passage and, after warming the Venturi and primary nozzle 
region, escape t6 the atmosphere. This gas is obtained by tapping 
into the exhaust manifold within a few inches of the last cylinder out- 
let (4 inches are recommended). As the motor demand rises beyond 
the ability of the primary nozzle, the inclined air valve is drawn 
toward the vertical position, and, as soon as it leaves the cylinder wall, 
the high-speed nozzle is uncovered and starts to contribute. The air 
is supplied from the same air inlet, but it rises more directly. A 
throttle is placed in the air inlet to facilitate starting; closing this 
cuts off the air, so that a richer mixture is supplied. There is a 
damper, or throttle, F in the exhaust gas-inlet passage. It is inter- 
connected with the main throttle G in such a way that it is opened 
when the latter is closed and closed when the latter is opened. The 
idea is to furnish a great quantity of heat when the throttle is nearly 
closed, and to gradually diminish the supply as the throttle is 
opened and the motor warms up. 

Adjustments. There are two adjustments: the gasoline adjust- 
ment H, so-called by the maker, and the air adjustment I. The gaso- 
line adjustment operates the primary nozzle. These preliminary 
adjustments can be made on the instrument as received by closing 
the gasoline needle valve H by turning it gently to the right until 
seated, then opening it by turning to the left f turn. The air- 
adjusting screw I should be turned until the end of the screw is about 
even with the edge of the spring ratchet J provided to hold it when 
set. After starting, close the throttle to produce a moderate speed. 
Then close the gasoline needle Ha, very little at a time until the motor 
runs smoothly. Allow the motor to get thoroughly warmed up, 
though, before making the final adjustment. 

Next, adjust the air valve. Turn the adjusting screw I to the left 
to back it out and release the air spring about one-eighth of a turn at 
a time until the motor begins to slow down. This indicates that the 
screw is too loose, so turn back slowly, one-eighth of a turn at a time, 
until it runs smoothly again. Next, advance the spark two-thirds of 
its travel and open the throttle quickly. The motor should speed up 
promptly and quickly. If it hesitates or pops back a little more 
gasoline should be released at the needle valve H by turning it to 
the left a very little at a time. It may also be necessary to tighten 


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the air screw I a little more. Now, wait for the motor to settle down 
to this new adjustment, then open the throttle again quickly. Con- 
tinue this sudden throttle opening and subsequent adjustment until 
the point is reached where the motor will respond in a satisfactory 
manner to a sudden throttle opening. The highest economy is 
obtained by turning the air screw to the left and the gasoline needle H 
to the right, closing it as nearly as possible and still obtain the desired 

Fuel Supply. When the carburetor is fed by gravity, the bottom 
of the bowl should be at least eight inches below the bottom of the 
gasoline tank. When it is fed by pressure, one pound is sufficient, 
and two pounds should never be exceeded. 

The Marvel Carburetor Company also makes a Model "N", 
designed for Ford cars to which it can be attached without change of 
manifold, levers, or other fittings. It is built on the same general 
plan as the Model "E" previously illustrated and described. 

Schebler Carburetors. The Schebler carburetor is one of the 
simplest complete carburetors made. In general, all Scheblers have 
a concentric float; a single needle valve, the position of which can 
be adjusted to suit varying needs; and an auxiliary air valve which is 
also adjustable. In all these models, too, there is a primary air 
orifice of unvarying section. In the later models, the needle valve, 
or metering pin, as it is more correctly called, is interconnected with 
the air valve so that operation of the latter varies the former. Many 
models are made and all are still in use, but space forbids descrip- 
tion of more than four: the widely used "L"; its successor, the 
"R"; and the latest form, the "A," made with vertical outlet and 
horizontal air inlet, much like the Zenith "L," which it resembles. 

Adjustment of Model U L" It will be noted in Model "L," shown 
in Fig. 110, that the needle valve sets at an angle in the mixing cham- 
ber. The upper expansion of this chamber forms the vaporizing 
chamber of long rectangular shape with rounded ends and has the 
auxiliary air valve located at the other end of it. The vaporized 
mixture passes upward, by the throttle, and into the manifold. To 
adjust this model, turn the screw A down to make sure the air valve 
seats firmly, then close the needle valve by turning the adjusting 
screw B to the right until it stops; but do not apply pressure. Then 
turn it to the left four or five complete turns and prime, or flush, the 


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carburetor by means of the priming lever C, holding this up about 
five seconds. Open the throttle one-third and start the motor, then 
close the throttle slightly and retard the spark. Next, adjust the 
throttle-lever screw F and needle-valve adjusting screw B until the 
motor runs at the desired speed, smoothly and evenly on all cylinders. 
Then make the high-speed adjustment on the dials D and E. Turn 
the pointer on the dial D from 1 toward 3, about half way. Advance 
the spark and open the throttle so the roller on the track running 
below the dials is in line with the first dial. If the motor back-fires, 
turn the indicator a little more toward 3, or, if the mixture is too rich, 
turn the indicator back toward 1 until it runs properly. Now open 

Fig. 110. Section through Schebler Carburetor, Model "L" 
Courtesy of Wheeler and Schebler Company, Indianapolis, Indiana 

the throttle wide and make the adjustment on dial E for the high 
speed in the manner just completed on D for intermediate. As lean 
a mixture as the motor will stand is advised. 

This model is also made with a dash-control air valve, as shown 
separately at the left of Fig. 110. Otherwise the carburetor and 
adjustment are exactly the same, except that where the directions 
previously given above have read A, those dealing with the dashboard 
connection should read A x . As will be noted, the movement of this 
lever rotates a small gear which engages with a rack formed in the air- 
valve stem, so that movement of tlje lever gives the same result as 
turning the screw A. 


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Adjustment of Model "R". Model "R", as Fig. 111. shows, is 
very similar, the most noticeable change being the vertical setting 
of the needle valve (here marked E). Its movement is adjusted by 
an internal lever connected to the air- valve cap A. The air inlet 
group has been raised to correspond with the longer Venturi, and its 
main opening is on top, with the adjusting screw F on the bottom. 
To adjust this model, see that lever B is attached to the steering- 
column control or dash control in such a way that the boss D is 
against the stop C when the lever on the steering column or dash 
registers lean, or air. This is the proper running position. To adjust, 

turn the air-valve cap A 
clockwise, or to the right, 
until it stops, then turn to 
the left, or counter-clock- 
wise, one full turn. Open 
the throttle one-eighth to 
one-quarter, start the 
motor, let it warm up, 
then turn the air-valve 
cap A to left, or counter- 
clockwise, until the engine 
hits perfectly. Advance 
the spark three-quarters, 
and if the engine back-fires 
on quick acceleration, turn 
the adjusting screw F up 
until acceleration is satis- 
factory. This increases the 
tension on the air- valve spring. Turning the air- valve cap to the right, 
or clockwise, lifts the needle valve E out of the nozzle and enriches 
the mixture. Turning it counter-clockwise lowers it and makes the 
mixture lean. When the motor is cold or the car has been standing, 
move the steering-column or dash-control lever toward the gas, or 
rich, position. This lifts the needle E out of the nozzle and makes a 
rich mixture for starting. As the motor warms up, move the lever 
back toward the air, position to obtain the best running position 

Adjustments of Model "A." The newest form, Model "A," is 
made in both the vertical and horizontal forms. Only the former 

Fig. 111. Schebler Carburetor, Model "R" 
Courtesy of Wheeler and Schebler, Indianapolis, Indiana 


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will be illustrated here, this being shown in Fig. 112, which pre- 
sents a vertical section. This is built aroundf the principle of the 
"Pitot" tube, utilizing the differential head created by an . up- 
stream and down-stream pitot tube to control the fuel delivery 
into the Venturi-shaped vaporizing chamber, to which the air has 
access from below. This arrangement gives a fuel flow exactly 
proportioned and controlled by the air. In the figure, E indicates 
the up-stream opening and F the down-stream nozzle of this 
arrangement, with air entering at the lower left through the pas- 
sage there, which is controlled by the starting shutter C. The 
high speed adjustment is simple, and is made through the needle 



\ / 


Jig. 112. Schebler Model "A" Carburetor, a Single Tube Device 
Courtesy Wheeler and Schebler Company, Indianapolis, Indiana 

B. The low speed or idling device delivers fuel and air at the 
low edge of the throttle disc in its closed position, this being 
adjusted through needle A and the passages in the body of the 
carburetor, shown adjacent to A. 

Adjustment of Model "A" With the lever D set to give a 
rich mixture, and air choker C set to cut off all the air, both fuel 
nozzles A and B are opened 3 or 4 complete turns from the 
closed or seated position. Open throttle, start motor and let it 
warm up. Then with warming-up lever D fully retarded adjust 
A to correct mixture for idling. Open throttle \ and adjust high 
speed mixture with needle B. 

Stewart Carburetor. .The predominating feature of the Stewart 
Model "25" is the automatic- metering valve by which the air 
admitted measures the gasoline used. This valve, which is the only 


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moving part, is drawn upward by the suction of the motor and comes 
back down onto its seat through its own weight when the suction is 
lessened. In Fig. 113, the complete carburetor with the throttle 
open is shown at the right, and the vaporizing chamber only and with 
throttle closed is shown at the left; the float chamber is the same in 
both cases. Gasoline flows in through the strainer to the float 
chamber, thence to the dashpot, filling this and continuing to rise to 
a point about on a line with the top of the tapered metering pin, 
which corresponds to the usual needle valve. 

With the engine at rest, as shown by the left-hand figure, the 
upper end of the metering valve, which has a conical lower surface, 

Fig. 113. Sections Showing Construction of Stewart Carburetor 
Courtesy of Detroit Lubricator Company, Detroit, Michigan 

rests upon the valve seat, thus closing the main air passage. Its 
lower end extends down into the gasoline in the dashpot. Through its 
center is an opening, known as the aspirating tube, into the lower end 
of which extends (from below) the tapered metering pin. As soon as 
the motor starts, or is turned over, so that a partial vacuum is created 
in the mixing chamber, the metering valve is lifted to admit air past the 
valve seat, as shown in the right-hand part of the figure. This vacuum 
is also communicated to the fuel chamber through the aspirating 
tube, drawing gasoline through it and up the central passage; the latter 
is expanded in diameter near the top and is then flared out to a large 
size at the point where the air entering through the vertical holes in 
the metering valve meets the gasoline and picks it up. The purpose 


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of this flare is to spread the fuel out into a thin film, which the high 
velocity primary air picks up readily in minute particles, producing 
thorough atomization. The high velocity of the air is due to the 
constant vacuum, this vacuum being determined by the weight of the 
valve which is always the same. Obviously, atomization is equally 
good at all speeds. 

Starting. This arrangement also makes for easy starting, but 
this is further facilitated by means of a dash control, which is attached 
to the metering pin in such a way that, when the plunger (on the dash) 

is pulled out, the meter- 
ing pin is lowered away 
from the metering valve 
above. This permits 
more gasoline to be 
drawn up through the 
aspirating tube and 
results in a richer mix- 
ture. The dashpot 
arrangement prevents 
rapid fluctuations and 
also makes the metering 
valve slower to respond 
than the fuel valve; in 
this way it produces a 
gasoline lead over the 
air which gives good 

Fig. 1 14. Exterior of Stewart Carburetor, Showing ^ " e ill g* ler tJie 

,„ . r r Adjuat ™ cnt8 n . 1# . L . metering valve lifts in 

Courtesy of Detroit Lubricator Company, Detroit, Michigan ° 

response to engine suc- 
tion, the greater will be the opening around the metering pin, which 
permits more gasoline to be drawn up; therefore, as the suction 
varies and the metering valve moves up and down, the volume of air 
and amount of gasoline must always increase or decrease in the right 
ratio, automatically giving the right proportions in the mixture at 
all speeds. 

Adjustment. The Stewart has but one adjustment. This 
consists of the lowering or raising of the tapered metering pin, thereby 

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increasing or decreasing the relative amount of gasoline admitted to 
the mixing chamber in response to the movement of the metering 
valve. This movement is produced by the rotation of the small gear 
A, which engages with a rack on the lower end of the tapered metering 
pin. This gear is rotated by means of a flexible-wire (Bowden) con- 
nection to the dash control. The limit of this motion, as well as the 
normal position of the gear, is governed by the setting of the adjusting, 
or stop, screw B> shown in the external view, Fig. 114. 

This screw can be turned either way; turning it to the right 
lowers the position of the metering pin, admitting more gasoline; 
and turning it to the left raises it so that less fuel is admitted. A 
wider range of adjustment than this stop screw affords can be had by 
releasing the Clamp C of the pinion-shaft lever D and moving it around 
to a new position on the shaft. This adjustment, however, is not 
recommended except for expert repair men. 

With the motor idling the adjustment should be made by moving 
the screw up and down, that is, out and in until the motor runs 
smoothly. This adjustment must be made with the dash control 
pushed all the way in. When this simple adjustment is made cor- 
rectly, the device is practically automatic from that time on. A stop 
screw E on the throttle lever is movable and affords the equivalent 
of a limited adjustment, for it can be set to give a smaller and smaller 
opening and thus slower and slower idling. It also has an influence 
on the maximum opening which influences the highest speed. 

Johnson Carburetor. The Johnson carburetor, of which a 
section through Model "D" is shown in Fig. 115, is one of the newer 
designs to be placed on the market. It is a simple form, with a con- 
centric type of float chamber A, above which is a simple cylindrical 
mixing chamber B containing the air-regulating device. It is sur- 
rounded by a hot-air jacket C, which warms the mixing chamber and 
furnishes the primary air supply. This is composed of the strangle 
tube D and, air controlling sleeve E, with a lift plate F suspended 
from this sleeve in the strangle tube. 

Operation. Gasoline enters the float chamber from above, in 
the usual way. It enters the spray nozzle through the cross-hole 6?, 
then rises inside this and passes the tip of the needle //, where it con- 
tinues out through the nozzle point into the lower part of the mixing 
chamber. The fuel issues as a fine spray into the strangle tube D, 

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which is conical in shape. In the mixing chamber is a sliding brass 
sleeve E, which moves up and down according to the engine suction 
and carries the lift plate F which is just above the outlet from the 
spraying nozzle. Warm air enters the air inlet I and finds its way 

around the chamber C, some 
of it reaching the passage J 
below the lift plate and stran- 
gle tube. Here it picks up the 
fuel from the nozzle and im- 
pinges it against the lift plate 
to break it up into finer parti- 
cles. In addition, the rising 
air and fuel raise the plate and 
with it the sleeve E, allowing 
more air to enter around the 
bottom of the sleeve. By this 
arrangement, the current of air 
is divided and forms both the 
primary and the auxiliary cur- 
rents. The latter current is 
varied to suit the engine de- 
mands by the rising and falling 
of the sleeve. This move- 
ment of the sleeve automat- 
ically pr6portions the air and 
gas to the demand, for, in 
rising, the lift plate is drawn 
away from the nozzle tip, and 
more fuel is allowed to flow out. 
On top of the strangle 
tube rests a flat choker plate 
K, which is capable of being 
turned around. There are 
holes in this to correspond with the holes in the strangle tube through 
which the primary air passes down to the lower side. In rising again, 
it picks up the fuel spray. A lever L extends through the outside of 
the carburetor and is connected up to the dash control. This lever 
controls the choker plate which can be moved around to cover or 

Fig. 115. Top View and Section of Johnson 
Carburetor, Model "D" 


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uncover the air holes and give more or less primary air as the device 
needs it. Thus, the low-speed screw M, the needle valve, and the 
stop screw N on the throttle shaft constitute the adjustments. 

Adjusting the Johnson. The function of the low-speed screw is 
to admit or to cut off the small amount of air supply to the upper 
part of the mixing chamber as the motor demands; this screw is to be 
adjusted only with a closed throttle, retarded spark, and the motor 
idling. The motor should be hot. This is an idling adjustment, 
designed to supply additional air through the opening 0, the need for 
which is caused by the sleeve E being in its bottom position and thus 
cutting off the supply, which is available later when the sleeve has 
risen and in so doing has formed the annular air passage. 

The spray needle H, adjusted by the external handle, takes care 
of all other throttle positions and speeds by admitting more or less 
fuel. To adjust it, turn the low-speed screw and spray needle to 
their seats and set the throttle-lever stop screw to approximate the 
correct closed position. Open the spray needle one and one-half 
turns. Start thp motor, and when it has warmed up, place the spark 
lever in the fully retarded position; then open the throttle quickly, 
and if the motor does not back-fire, the mixture is slightly rich and 
the spray needle should be closed by turning to the right about one- 
eighth of a turn. Again open the throttle quickly and repeat until the 
motor does back-fire; this will determine a lean mixture. Open the 
needle slightly to correct the mixture, which will give the correct 
adjustment on high and intermediate speed. Adjust the throttle 
stop screw until the desired idling speed, or about 240 r.p.m., is secured. 
If the motor does not fire continuously and run smoothly, the low- 
speed mixture is too rich and is corrected by backing out the low-speed 
screw M until sufficient air is admitted for smooth even firing. Then 
lock it with the lock nut. If this last adjustment has increased the 
speed of the motor, restore the idling speed by unscrewing the throttle 
stop screw N slightly.- If necessary, reset the low-speed screw, as 
both of these have to be adjusted in combination. 

Dash Control. This controls the choker plate, which acts as a 
choke to the nozzle by reducing the supply of primary air. After 
the motor has been warmed up, this should be in the wide-open 
position. The position for a cold motor, approximating the closed 
position, will be determined by experience. It is recommended that 


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the motor be choked, that is, the dash control set in the closed position, 
when stopping. This provides a rich charge for starting. As will 
be seen from this, the choker plate, with its dash control, is primarily 
a starting device. 

Other Models. This carburetor is made in other models, notably 
a small one for the Ford car; the essential difference in this being the 
location of the low-speed screw on top, as it has a horizontal outlet 
on one side and the warm air inlet on the other. Another large size 
for eight-cylinder models has a special accelerating device consisting 
of a fuel plunger operated from the throttle. Still another model is a 

fixed-needle type in which 
the nozzle is calibrated for 
the motor. The adjust- 
ment is practically the 
same for all these. 

Carter Carburetor. 
The Carter carburetor is 
a multiple-jet device in 
which, at slow or idling 
speed, but one jet is fur- 
nishing fuel, while at ex- 
treme high speed eighteen 
are operating. These are 
not jets in the sense that 
the ordinary carburetor 

Fig. 116. Section of Carter Multiple-Jet Carburetor " ftS se P arate Vertical Or 

Courtesy of Carter Carburetor Company, horizontal jetS, aS in the 

St. Louts, Missouri * ' 

Master carburetor, for 
instance, but they consist of a series of holes set spirally around a 
central standpipe of fairly large diameter. The action of the device 
is such that only one is working at low speed, while at high speed 
the great suction is drawing the fuel up so high in the standpipe that 
it is issuing from the entire group of 18 holes. 

A vertical section through the center of this carburetor is shown 
in Fig. 116. As will be noted, the bottom of this rests in a tube, or 
open standpipe, which communicates with the float chamber and is 
kept filled to the float level with fuel. Just at the top of this tube is 
the main air inlet. The air enters around the sides of the standpipe 


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and rises vertically along it. Around the upper part of the standpipe 
is a flaring conical tube, the top of which is closed by a damper. Air 
enters here and is drawn downward, its amount being controlled by the 
damper. At the left will be seen the supplementary air valve, a third 
source of air; this air is also drawn downward, and the amount is 
adjustable. From this it can be seen that the primar^ air and the fuel 
from the first few jets come upward, while the secondary air and the fuel 
from the additional jets go downward, and that the supplementary air 
rushes in at an angle where these two meet at the bottom of the 
U-shaped vaporizing chamber. This produces a constant state of 
turbulence around the standpipe, which facilitates breaking up and 
vaporizing the fuel. The fuel passes a butterfly throttle in its 
passage to the inlet manifold. > 

For easy starting, a tube (marked anti-strangling tube in the cut) 
is by-passed around the vaporizing chamber, taking its fuel directly 
from the well at the left of the float chamber and furnishing it 
directly into the outlet pipe above the throttle. In starting and 
idling on the lowest jet, or hole, of the standpipe, the fuel is drawn 
almost directly from the float chamber. For this reason an unusually 
accurate float arrangement is necessary, and this is provided by the 
metal ball float and the needle arrangement with its ball and spring 
shock absorber. The latter eliminates any possibility of jamming 
and gives accurate control of the fuel level. The action of the device 
is very simple, the engine suction drawing the fuel higher and higher 
in the standpipe as the suction increases, while the same suction draws 
open the intermediate air valve as soon as the required supply exceeds 
the capacity of the main air intake. The high-speed air inlet, oper- 
ated by the damper, is thrown into action from the steering post or 
dash at the will of the operator. 

Adjusting the Carter. By reference to Fig. 116, the adjust- 
ing will be made plain. First set the high-speed adjustment with the 
lever in a vertical position; then turn the knurled button marked low- 
speed adjustment down, or to the right as far as it will go; next back 
it off and turn it to the left three-quarters of a turn. Turn the 
knurled valve ring marked intermediate-speed adjustment to the 
point where the valve seats lightly, then turn the valve down, or 
to the right, from eight to ten notches to increase the spring tension. 
Pull the easy-starting lever, connected with the dash, forward to 

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the position shown in Fig. 119, advance the spark a very little, 
close the throttle, and start the engine. 

Through the medium of the anti-strangling tube, this will 
furnish rich mixture (almost pure fuel) to the inlet manifold and 
result in instantaneous starting. Immediately reverse the easy- 
starting lever which controls the flow of fuel and open the main 
throttle slightly. By means of the two screws A A on either side 
of the throttle lever, set the throttle valve where it gives the 
desired engine speed when idling. Move the low-speed adjust- 
ment to the left, one notch at a time, until the engine slows 
down, noting each setting. Now move it in the opposite direc- 
tion, one notch at a time, until the" engine again slows down. 
Then move the adjustment to a point midway between the two, 
and the low-speed setting will have been finally fixed. This 
should not be changed on account of weather or temperature 

Set the throttle about one-third open and turn the inter- 
mediate adjustment to the left until the engine slows down. 
Move to the right until a similar decrease in speed is noted, then 
set midway between the two. This adjustment, when once 
properly made, should not be changed for weather or temperature 
changes. After this adjustment has been made, connect the high- 
speed adjusting lever to the dash or steering-post control so that 
in the center of its movement the lever on the carburetor is verti- 
cal. Drive the car over a level r6ad at about 20 miles an hour, 
then move the control lever to the point where the engine gives 
the best results at this speed. At low temperatures, or when the 
engine is cold, this control should be moved toward the closed 
position, so as to cut off air and make a richer mixture. At high 
temperatures and with a warm engine, the best results are obtained 
with the control wide open. This is the only adjustment which 
should be varied for weather or temperature variations. 

Newer Carter Models. In addition, this company has two 
newer models, "H" and "L," the principal difference being in the 
outlets, "H" having a vertical and "L" a horizontal outlet. The 
former is shown in Fig. 117, which shows both a vertical section 
and end view. It will be noted that the fuel passes through a 
strainer into the float chamber, then entering below passes through 

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the high speed jet if the throttle is open and through the small 
hole in it, and thence through the low speed jet, up the vertical 
fuel passage, and part passes out into the vaporizing chamber, 
while part continues on up into the inlet manifold above or beyond 
the throttle. The action of these two jets is evident from their 
construction and this description. 

Adjustment of Carter "H" and "L" Models. The adjustment 
of these two models is similar, this being controlled ordinarily by 
setting the throw of the throttle lever in the proper position for 
idle engine speed. This is done by means of an adjusting screw, 

Fig. 117. Carter Model "H" Carburetor with Vertical Outlet 
Courtesy Carter Carburetor Company, St. Louis, Missouri 

which is provided with a lock screw to hold it when adjusted. 
This lever should be so set that with steering wheel quadrant 
lever and accelerator closed, engine will turn over at normal idling 
speed of 250 to 300 r.p.m. Model "L" has an additional idling 
adjustment, consisting of a small screw which controls the amount 
of fuel passing out into the manifold beyond the throttle. The 
only other normal adjustment is the connection of the dash 
control wire to the carburetor choker lever; shortening this will 
cause the air shutter to close more tightly, lengthening it, not as 

Carter Truck Carburetor. A Carter carburetor especially 
designed for truck use is made with extra large bearings for the 

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working parts. The throttle and choke shaft are larger than those 
employed in common practice, and the bearings for these shafts 
are longer. Bronze bushings are used on the throttle shaft where 
the wear is greatest; if these bearings become worn, however, they 
may be replaced. The upper part of the float is reinforced, which 

Fig. 118. Model "M" Carter Carburetor 
List of Parts — Description: 1, body; 2, throttle valve; 3, throttle shaft; 4, throttle lever; 7, 
choker valve; 11, idle well tube; 12, fuel metering jet; 13, choker shaft; 14, choker lever; 17, needle; 
20, main jet and float needle seat plug gasket; 21, float; 22, float lever; 24, float lever pin; 25, float 
needle seat plug; 29 A, strainer cap; 30, strainer gauze; 30 A, idle adjustment screw; 37, gasoline 
connection; 48, float needle adjusting collar; 49, float cover dust cap; 50, float cover; 51, drain plug; 
52, strainer trap screw; 53, idle well plug; 54, jet body plug; 55, nozzle assembly; 59, idle adjust- 
ment screw lock nut; 60, wire clamp; 60A, lower lever; 61, idle adjustment screw body; 63, idle 
well plug gasket. 

eliminates the wearing of holes, for the float is in continuous con- 
tact with the float weights. It will be noted that the idling 
adjusting screw and lock nut are shown in detail in the upper 
half of Fig. 118. 

A sectional view of this carburetor is shown in Fig. 118. This 
is a standard, plain-tube carburetor, idling through the by-pass at 
the throttle and having but one main gasoline passage, through 


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which a metered supply of fuel is admitted to the main nozzle 
from the float chamber. 

The main nozzle is of the air-bleed type, composed of a com- 
bination of passages and ports which admit both air and fuel to 
the mixing chamber. This nozzle, being entirely self-contained, is 
automatic in action, supplying the proper mixture at all speeds. 

There is but one main nonadjustable supply jet, although this 
jet can be changed to a different sized jet when it becomes neces- 
sary to make another adjustment. 

Tillotson Carburetor. In a general way the Tillotson car- 
buretor resembles a long U-shaped tube laid upon its side, with 
the air entering the upper branch, passing around the curve and 
out to the motor at the end of the lower branch. In the latter 
near the delivery end, are placed the two jets, first the secondary, 
next the primary. A pair of flexible reeds are arranged within 
the passage in such a way that they entirely enclose and shut off 
the secondary when they are closed, but do not interfere with the 
primary. The reeds are opened by the suction of the engine, so 

Fig. 119. Tillotson Model "C" Carburetor, lowing Steel Reeds 
Courtesy Tillotson Manufacturing Company, Toledo, Ohio 

that the primary nozzle furnishes fuel at all engine speeds but is 
the only one in operation at the slower speeds, and is the only one 
that is adjustable. The secondary nozzle gives the added fuel 
for high engine speeds and is in operation at these higher speeds 

Not all the Tillotson models have this exact shape, many 
being more of an L shape. The float chamber location varies 
with the different models in some being below the U (or L) tube, 
in others at one side. 


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Adjustment of the Tillotson Carburetor. As has been stated the 
primary nozzle only is adjustable. The company recommends 
that this be done with unusual care, and very slowly. With the 
motor running and well warmed up, turn the adjusting handle up 
to the right until the motor commences to slow down from lack of 
fuel, then turn it back about one-eighth of a turn. Avoid getting 
the mixture too rich. Fig. 119 shows Model "C" 85-6 in partial 
section and the reed action. 

Pierce-Arrow Carburetor. This carburetor utilizes a little 
different principle in the introduction of auxiliary air from most 
other carburetors as the air passes through reeds in somewhat the 
same manner as in the Tillotson carburetor. Fig. 120 shows the 
construction of this carburetor. The gasoline level should be ^ 
inch below the top of the spray nozzle K. The opening of the 
spray nozzle is regulated by a valve H when the throttle is 
practically closed. The air entering the carburetor at R is 
thoroughly mixed with gasoline regulated by the nozzle S. The 
amount of mixture entering the cylinder is regulated by the adjust- 
ing screw E, which is really a throttle for the small passage R. 
The three auxiliary air reed valves are closed. As the throttle B 
opens, the suction is greater through R than through the main 
passage for a short period and then becomes the same in both. 
As the motor speeds up, the light, intermediate, and heavy reeds 
open in succession, admitting more air. In setting the reeds, the 
distance between the reed valves and the supplementary springs 
should be § inch for the light reed and -£? inch for the intermedi- 
ate and heavy reeds. There is a supplementary spray nozzle L, 
provided with the adjustment needle valve J. This spray nozzle 
comes into action when the motor is operating at high speeds and 
the reed valves are open. 

Adjustments. Disconnect the throttle rod from the lever and 
close the main throttle B tight by backing off on screw C. Adjust 
this screw until it touches the lever A. Then screw in from \ to 
f of a turn more and turn lock nut B. Connect the throttle rod, 
adjusting the length so that the throttle just begins to open. 
Turn idle screw E into the shoulder until the head of the screw 
seats, then back out about 1§ turns. Loosen screw F on lever G 
and turn needle H to the left until it is seated, then turn to the 


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right to open f of a turn. Start the motor by priming and allow 
it to run until warm — run on battery with the lever advanced \ 
inch on the quadrant — and then open the throttle so that a motor 
speed of 20 to 30 miles per hour is obtained. Next adjust needle 
H until the motor runs best, set lever G at right angles to center 
line, and tighten screw F. Set the regulator on the steering column 
in center, put the wire in lever 6?, and tighten screw I. This 
should give equal travel to each side of center. Loosen the high- 
speed screw on high-speed needle J and, with the finger, screw 
down until closed, and then turn back or up from f to f of a 
turn. The car should then be tested on the road and should not 
be adjusted to run slower than 5 or 6 miles. Always keep throttle 
screw E closed as much as possible. If the car works best at a 
speed of 20 to 30 miles per hour with the regulator in center 
adjustment on needle H, it can be considered O.K. If it will run 
better at 50 miles with the regulator at the heavy position, the 
high-speed needle must be open more; the reverse is true if it 
runs better with the regulator on the light side. If properly 
adjusted, the motor should run the entire range of speed with the 
regulator in one position. No change is necessary except to take 
care of climatic conditions. 

Packard Carburetor. The carburetor used on the Packard 
twin-six (twelve-cylinder) cars is shown in section in Fig. 123. 
The inlet manifold, or rather the pipe which leads in both direc- 
tions to the manifold proper, is seen at the top at A. It will 
be noted that this is water-jacketed, the water space being at 
the top. The float arrangement is of the usual type, with a 
metal float which supplies fuel to a small well B at the base 
of the single-spray tube G. This has a flared end located in 
the center of the Venturi. When the air from the air horn 
D passes the air shutter E, it picks up the fuel and carries it up 
into the vaporizing chamber F. The primary air shutter is normally 
open but not in use. It is operated by a hand wheel on the control 
board which also operates the auxiliary air valve G. By turning this 
clear over to the position marked choke, the air intake is closed, and a 
rich mixture is drawn in for starting. After that, the hand wheel 
should be set back toward the position marked AIR which opens the 
air intake. 


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The auxiliary air valve is controlled by the springs H and 7. 
These are adjusted so that the valve opens very slightly at low speed, 
but more and more as the speed, and consequently the suction, 
increases. The air enters around the outside of the Venturi, com- 
municating with the mixture only above the top of the latter where 
the real vaporizing chamber commences. The tension of the springs 

Fig. 123. Section through Packard Twin-Six Carburetor 
Courtesy of Packard Motor Car Company, Detroit, Michigan 

is varied by means of the adjusting nuts at the top and by the adjust- 
ing cams «/. The cams are connected up to the air-valve hand wheel 
which is turned toward gas to provide a richer mixture and toward 
air for a leaner mixture. If the wheel is turned too far toward air, 
spitting back may result; and if it is turned too far toward gas, the 
result may be irregular running and overheating. The throttle K 
is of the butterfly type and regulates the quantity of mixture allowed 
to pass out, not its quality. An adjustable stop holds this valve 
open slightly and allows a small amount of mixture to pass, even 
when the hand throttle is entirely closed. * This minimum amount is 

317 '* Digitized by G00gle 


for slowest running, or idling, only. To increase it, loosen the check 
nut L and screw the stop M forward. To decrease the minimum 
speed, screw the stop backward. 

Adjustments. . Aside from those described previously, the 
Packard Company advises against making any adjustments as 
it prefers to have this done by its own men, who have had 
extended experience in adjusting the motor and carburetor com- 

Packard Fuelizer. The Packard fuelizer is an auxiliary car- 
buretor operated by motor suction. This fuelizer, Fig. 123a, is 
connected to a combustion chamber located on the intake manifold, 
the combustion chamber having an ordinary spark plug, igniting 
the incoming gas, which is under atmospheric pressure. As this 
carbureted gas burns, the products of combustion, which are com- 
posed of hot gases, mix through small openings with the cold 
incoming gas vapor from the carburetor as shown in Fig. 123b. 
This heat thoroughly vaporizes the mixture, making it dry — it 
does not condense and does not pass the piston rings into the 
crankcase. The fuelizer also does away with a great deal of 
carbon on account of better vaporization and of better fuel com- 

With the fuelizer installed and in proper operating condition, 
it is possible, even in cold weather, to operate the car with the 
choke set in normal position after the motor has been running for 
from twenty to thirty seconds. The acceleration, or pick-up, of 
the car is thus greatly improved. On account of the fuel being 
thoroughly vaporized, better combustion takes place, carbon for- 
mation is practically eliminated, and a great deal of spark-plug 
trouble is overcome. Gasoline economy is not effected to a very 
great extent, although in cold weather a little more mileage is 

On the twin six, three sparks per revolution of the engine are 
used at the fuelizer plug. There are two methods of obtaining 
the spark. On new cars, an auxiliary breaker is provided operat- 
ing from the same cam which works the main breakers, this breaker 
being supplied with its own condenser and resistance. An addi- 
tional spark coil located on the dash receives current from the 
ignition current in the same manner as the standard ignition coils. 

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319 Digitized by GoOgle 



A somewhat simpler construction applied to cars in service consists 
of the same coil, the primary of which is wired in series with the 
primary of one of the main coils, Fig. 123c. The extra resistance 
and self-induction of the extra coil in series do not perceptibly 
have any effect on the regular ignition at engine speeds under 
2600 r.p.m. 

Special Suggestions and Precautions. If the inspection glass is 
dirty, it should be cleaned through the spark-plug opening instead 




— * 







Fig. 124b. Simple Illustration Showing the Principle of the Packard Fuelizer 

of removing the glass from the container. If the nut is removed, 
air leaks may be caused in replacing, as the nut may be drawn up 
too tight, which will cause the glass to break when at running 
temperature. If the glass becomes sooted rapidly, it is a sign that 
the mixture is too rich; this should be corrected by raising the 
vaporizer choke and inserting a gasket. The glass may foul up if 
oil or some other substance is mixed with the gasoline. 


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If there is no gas passing through the burner, the spark 
appears purple and stringy. This is due to some obstruction 
which prevents the gasoline vapor from reaching the burner. The 
entire vaporizer equipment may be easily removed. 

To check the gasoline level and to make sure that the gaso- 
line is reaching the vaporizer in proper condition, it is simply 









Fig. 124c. Wiring Connections of the Packard Fuelizer When Installed 
After the Car Leaves the Factory 

necessary to remove the vaporizer and measure the distance from 
the top of the float chamber down to the gasoline level while the 
motor is running. This dimension should be 1^ inches. 

Cadillac Carburetor. A section through the latest Cadillac 
carburetor, which is a very simple device, is shown in Fig. 124. Fuel 
enters through the pipe A at the bottom, passing on to the well B 9 
and thence to the float chamber, through the vertical pipe C and the 
float valve Z>, which are operated by the float E. This float is con- 
centric and is hinged on one side of the float chamber. Below the 
float chamber is another chamber, or well, F which is supplied from it. 
Through the opening in the side of the nozzle G, this well in turn sup- 
plies fuel to the nozzle H, the fuel being drawn out at the top into 
the Venturi chamber /. At the left will be seen the air valve J as well 
as the scoop of shield K, which assists in drawing in the required 


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volume of air. TWsair reaches the passage L, whence a portion is 
drawn downward around the outside of the Venturi J, through the 
passage M, and around the bottom of the tube, then upward. There 
it mixes with the fuel spray, vaporizes it, and carries it up into the 
main vaporizing chamber N, where additional air comes in from L, 

Fig. 124. Section through Cadillac Carburetor Used on Models 53, 55 and 57 
Courtesy of Cadillac Motor Car Company. Detroit, Michigan 

and the mixture passes on up, through the throttle valve 0, into the 
inlet manifold. 

On a lever P attached to the throttle valve shaft is hung the 
connecting rod Q 9 by means of which it is attached at its lower end to 
the piston R. This works up and down in the chamber S. Its lower 
portion, or well, T is full of fuel and communicates through passage U 
with the well F and the nozzle H. When the throttle is opened, the 
plunger is forced into the gasoline in the carburetor bowl, and fuel 
is thus forced through the hole G up to the nozzle H. When the 


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throttle is opened quickly, this acts to supply the needed fuel. When 
the throttle is opened slowly, the plunger has practically no effect. 
This plunger has an influence on starting, as will be explained. 

Adjustments. Carburetors are factory set and should need no 
adjustment ordinarily, but for different atmospheric conditions a 
slight change in the air-valve spring may be needed. In the exterior 
view, Fig. 125, this is altered by turning the screw V. In case the 
carburetor really needs adjustment, proceed as follows: Open the 
throttle lever on the steering wheel about two inches, place the spark 
in the driving range and start the motor; run it until the water jacket 

on the intake pipe is hot; then move the spark lever to the extreme left 
on the sector and the throttle lever to a position which leaves the 
throttle slightly open, and adjust the air-valve screw V to a point 
which produces the highest engine speed. Turning this screw clock- 
wise increases the proportion of gasoline to air in the mixture, that is, 
makes it richer; while turning it counter-clockwise decreases the 
proportion of gasoline, that is, makes it leaner. 

Close the throttle by moving it to the extreme left on the sector, 
and adjust the throttle stop screw W to a point which causes the 
engine to run at a speed of about 300 r.p.m. The spark lever should 

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be at the extreme left when this adjustment is made. With the spark 
and throttle levers in this same position, adjust the air valve screw V 
again to the highest motor speed. Open the throttle until the shutter 
attached to the right-hand end of the throttle shaft just covers the slot 
in the carburetor body (the other side of the carburetor is not shown 
in either view). Then adjust the screw X to the point which pro- 
duces the highest engine speed or to a point where the engine slows 
down slightly from a lean mixture. This screw also works clockwise 
to give a richer mixture and counter-clockwise for a leaner one. 
During very cold weather, it will be found advisable to turn this screw 
farther in a clockwise direction to give a slightly richer mixture. 

The rod Q from throttle arm P to the fuel plunger is adjusted 
closely at the factory and should need no change unless the carbu- 
retor is disassembled. When reassembling, the rod should be ad- 
justed so that its upper end is flush with the upper face of the arm P. 
When the carburetor has been used for a long time, there may be slight 
wear at the point of the inlet or where the float needle D, Fig. 121, 
rests on its seat. If this should occur, the height of the fuel in the 
carburetor bowl will rise. To determine whether the float is set 
properly, remove the carburetor from the engine and the bowl from 
the carburetor. Then measure the distance from the upper surface 
of the float to the metal surface above it, as indicated at Y to Z. 
This is measured best with the carburetor inverted and should be 
exactly \ inch. If more, or less, the setting may be corrected by 
slightly bending the airm to which the float is attached. 

Starting. In cold weather, when the engine will not start imme- 
diately, it is not advisable to continue cranking the engine over and 
over. Instead, open and close the throttle rather quickly once or 
twice, no more, with the throttle lever on the steering wheel or foot 
accelerator. This action raises and lowers the throttle pump at- 
tached to the throttle-shaft arm, as previously explained, thus raising 
the level of the fuel in the float chamber so that it is more easily 
drawn up. If pumped more than once or twice, too much fuel will 
be forced up, and this is just as bad as too little. 

Oxygen-Adding Devices. There are now upon the market a 
number of devices for assisting carburetion by furnishing an 
additional source of oxygen. These are not carburetors in them- 
selves, in that they do not handle any_fuel, consequently they 


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must be used in addition to some standard carburetor, furnished 
with fuel in the regular way. The desired result is obtained in a 
number of different ways, as for instance the direct injection of 
water, which the heat of combustion is supposed to break up into 
its components hydrogen and oxygen. The hydrogen is a fuel 
itself, and the oxygen assists the vaporized gasoline fuel to burn 
better and more completely. Steam is but a variation of this, 
the exhaust heat being used to create this from water furnished 
by a special tank. When equipped with valves to control water 
passage or steam emission, these constitute the only adjustment. 


Need for Heavy Fuel Carburetors. As has been mentioned 
several times previously, and explained elsewhere in detail, the 
lighter, more volatile grades of gaso- 
line are not available in sufficient 
quantities to supply the present de- 
mand. Consequently, the fuel now 
carries a considerable quantity of what 
was formerly sold as kerosene and also 
under other names. At that, the fuel 
sold is still much lighter than kero- 
sene — of which tremendous quantities 
are available — as well as other heavy 
fuels, notably benzol in England, where 
kerosene is called paraffin. To de- 
velop a carburetor which would handle 
these cheaper but heavier and more 
available fuels has been the aim of 
many inventors and a vexing problem 
for carburetor manufacturers. 

Holley Type. A firm, the Holley 
Company, which has devoted much time and study to this problem, 
has developed the device shown in Fig. 125. While this is not 
offered as perfect, even by its maker, who is still working on this 
problem, it has been found to do these things: cut the fuel cost 
over 50 per cent; increase the power 5 to 8 per cent; save almost 
one-half of the engine lubricant; give less spark-plug trouble and 

Fig. 126. Section through the Holley 
Kerosene Carburetor 


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less carbonizing; and give a greater mileage to the gallon. It 
also has these deficiencies: requires the use of gasoline for starting; 
and necessitates a material reduction in compression pressures. 

This device as shown in Fig. 126 has two float chambers, one 
for gasoline used in starting, the other for the kerosene or heavier 
fuel. The shifter valve B determines which fuel flows to the 
adjusting needle valve W and through a jet where a minute 
quantity of the total air needed in the form of an air blast 
atomizes it. Then it is carried up through the tube R situated in 
the exhaust manifold and heated by it. Then it enters the main 
mixing chamber M , where the main air supply enters through U, 
this opening being governed by the suction of the motor and the 
throttle valve opening. From here it is drawn in through the 
intake manifold V in the usual way. 

Adjustment Holley Kerosene Device. In general, the motor is 
always started on gasoline, which is used purely for starting and 
warming up the motor, when the change over to kerosene is made. 
The adjustments should be made on the basis of kerosene, even 
though it seems somewhat rich when running on gasoline. Set screw 
E, which limits the throw of the throttle lever, should be adjusted 
so the motor runs at proper idling speed when the hand throttle 
lever is in the closed position. 

Holley All=Fuel Carburetor. Another Holley device is intended 
for the use of all kinds of fuel, heavier than our so-called gasoline. 
This is shown in Fig. 127, which presents a sectional view and 
explains all the parts as well as the operation. It consists of a 
simple spraying device with an air valve which sprays the heavy 
fuel, adds a very small amount of air to it, and then forces this 
mixture through a vapor tube, consisting of coils of thin-walled 
pipe surrounding the exhaust pipe. The exhaust heats the walls 
enough to completely vaporize any fuel that will evaporate below 
600° F. This heater, rich, dry gas mixture is then returned 
to the main body of the carburetor where additional cold air is 
admitted to convert it into a perfectly combustible mixture. It 
then passes through the throttle and inlet manifold to the engine. 
Like the Holley kerosene carburetor just described, this starts on 
gasoline, and is switched to the heavier fuel as soon as the motor 
is well warmed up and the exhaust heat begins to be available. 


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Aside from the usual throttle and air valve limit stops, there 
really is but one adjustment. 

Adjusting the All-Fuel Carburetor. The principal adjustment 
on this device is the idling. The figure shows this near the bot- 
tom, it consisting of a valve with a milled outside head which 
controls the inflow of air. Sufficient air is drawn past this for 
idling and it lifts to admit more air for higher motor speeds. 
The valve is regulated so that in its lowest position just enough 
air passes to give a satisfactory idling speed. An arrow on the 

Fig. 127. Section Showing Construction of All-Fuel Carburetor 
Courtesy Holley Brothers Company, Detroit, Michigan 

top indicates this. When the valve is entirely closed, as indicated 
by the arrow, the air is practically shut off and the mixture is richest. 

The air intake is fitted with a choke throttle and the tight- 
ness of closing this can be regulated by a stop screw. Similarly, 
the main throttle can be regulated by means of a stop screw, to 
va?y its tightness in the closed position. The only other changes 
or adjustments would be to change the atomizer for one with differ- 
ent sized jet holes at Y and Z as well as the primary air inlet. 

Foreign Kerosene Carburetors. A large number of firms in 
different parts of the world have worked on this problem of kerosene 
vaporization. In Germany, the following have done so, and in 

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solving this each has been obliged to develop his own vaporizer: 
Daimler; Swiderski; Maurer; Adler; Sleipner (boats mostly); Deutz; 
Banki; Neckarsulmer (motorcycle); Koerting (fuel injection); Kam- 
per; Diesel (fuel injection); Capitaine (boats mostly); Gardner; 
Dufaux (Swiss motorcycle); and others. Space prevents a descrip- 
tion of these, the list being given simply to show that kerosene as a 
fuel has attracted wide attention. 

In France the same is true; the Aster device, for instance, having 
been so very successful that it is now made under license in both 
England and Germany. 

In England the Binks, with two jets, is designed to use 20 per 
cent gasoline and 80 per cent kerosene after starting. The Hamilton 
Bi-fuel has two float chambers, two nozzles, and other duplicate 
features. This is designed for a 44 gasoline (petrol) and 56 kerosene 
(paraffin) mixture; on such a mixture, a test of a bus engine showed 
equal (rated) power at 890 r.p.m.; 1 horsepower more at 1050; almost 
3 more at 1275; and at its highest speed 1375 r.p.m., 3 horsepower more, 
maximum output. The Kellaway has two fuel leads, but these use a 
common jet. The Morris uses forced feed with a constant air pressure 
of 4 pounds per square inch on the fuel tank; this is supposed to mini- 
mize variations in fuel flow, and thus, as pointed out in the description 
of the Browne, minimize variations in the output. The Southey 
ignites part of the fuel to create heat with which to vaporize the bal- 
ance, delivering to the cylinders a fixed gas which is heated. The 
Edwards has been described. In the Notax the fuel spray, as it 
enters the vaporizing chamber, is forced to strike the lower hot surface 
of the exhaust-gas passage, which not only encircles the chamber but 
has a passage right through the middle of it. In the G. C. (English 
and American), the vaporizer complete replaces both carburetor and 
muffler. It is constructed to utilize all the heat in the exhaust gases 
for vaporizing the kerosene, which then is led up to the engine, and 
auxiliary air added just before it enters the manifold. This has a 
separate small gasoline carburetor for starting and a special float 
chamber for the kerosene. In America, the Knox employs an 
arrangement in which a gasoline by-pass around the entire carburetor 
is used for starting, while the exhaust heating concerns the fuel at the 
bottom of the device only. The Secor type is used on the Rumely 
tractors. The Hart-Parr Tractor Company and a number of other 


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builders of tractor, marine, and stationary engines have been more or 
less successful in vaporizing kerosene so as to lise it advantageously. 

Master Carburetor. The Master device, previously shown 
and described, was designed primarily for the extra heavy fuels, or 
the residuum in the distilling process called distillate, which is 
heavier than kerosene and has heretofore been considered a waste 
product. The Master has utilized this successfully in actual serv- 
ice for more than four years. In addition, it will handle kerosene, 
alcohol, and other heavy fuels, as well as mixtures of all these 
with one another and with gasoline. 

Like the Master, the Miller also previously described as a 
gasoline device, was designed originally for the extra heavy fuels 
of the coast, so that it must be considered as a heavy fuel car- 
buretor. This is partly true of the "H and N," which was 
designed originally for heavy fuels, the present form embodying 
the most successful details of the heavy-fuel device. 

Bennett Carburetor. The Bennett device, Type "C" which 
is shown in section in Fig. 128, is intended for kerosene, alcohol, 
distillates, or other heavy fuels, but by a simple change of the 
adjustments it can be used for gasoline. For alcohol, however, the 
makers provide a special float, the carburetor remaining the same 
otherwise. It has two needle valves: one projecting downward 
from the top of the device A, called the slow-speed needle; and the 
other, projecting upward from the bottom B, called the high-speed 
needle. The primary air for both enters at C, passes around the 
exhaust heating pipe D, and enters from below. It rises around 
the lower needle and fuel passage into the chamber E, where the 
fuel is picked up and carried up into the main vaporizing chamber 
F. From here it passes up into the passage G, where additional 
air comes in from the air valve H, after passing the air throttle /. 
This dilutes the mixture and completes vaporization, and the mix- 
ture passes the main throttle J into the manifold, or engine. 

The fuel enters the float chamber K, in which the float is indi- 
cated, and passes from this through the horizontal opening L to the 
needles. As there is hot air in the passage just below the opening, 
and exhaust gases in the passage just above it, it is subjected to a 
considerable warming effect. In the center at the bottom, a recess 
forms a dashpot for the lower end of the shaft M , which is connected 


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to the air valve H at its upper end; this prevents rapid fluctuation, 
or fluttering, of this 'valve when there is a sudden opening of the 
throttle after running at slow speed. The extra suction created by 
the sudden opening* of the throttle tends to jerk the auxiliary air 

Fig. 128. Section through Bennett Double-Jet Kerosene Carburetor 
Courtesy of Wilcox- Bennett Carburetor Company, 
Minneapolis, Minnesota 

valve open quickly to its maximum area. Another feature of the 
device is the feeding of small quantities of hot water from the motor 
circulating system through the pipe N; this has an adjustable valve 
(not shown) connected to the dash. The water is sprayed in through 


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the medium of the valve attached to the bottom of the small dash- 
pot and the plunger P which surrounds the bottom of the high-speed 
needle B. An additional feature of the device is an air cleaner Q, 
which is shown at the left in the diagram, Fig. 129. Its function 
is to clean all dust out of the entering air when the carburetor is 
used on a tractor or other unit which must work in the midst of con- 
siderable dust. As this dust is known to filter slowly but surely 
through the carburetor and, in time, reach the pistons, valves, rings, 
and bearings, where it does considerable damage, the utility of this 
simple auxiliary device, which has no moving parts, is evident. 

Installation. Whenever it is possible to use the air cleaner, 
install the carburetor with the hood of the air intake facing away from 

Fig. 129. Diagram Showing Method of Connecting and Adjusting Bennett Carburetor 

the fan so as to prevent dirt from being blown into it. Connect the 
exhaust manifold to the carburetor, using the three-way valve or 
damper in such a way that the amount of gas can be regulated. When- 
ever possible the exhaust connection should enter the larger end, 
because the cored passage for heating the primary air is there. Screw 
an elbow in at the other end, and, if required, a short piece of pipe, 
to carry the used exhaust gases away from the carburetor. Connect 
the water jet near the bottom with the water jacket or a small 
auxiliary water tank. This water jet and its regulating needle can be 
moved to any desired position by means of the large nut R. The 
needle is connected to the dash so as to be operated by the driver. 
Two fuel tanks are needed, one for gasoline to be used for starting, 

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and the other for kerosene to be used in regular running; they should 
be connected to the float chamber at the bottom by means of a three- 
way valve or a siamesed pipe, with a shut-off cock in each line above 
the T-connection. 

Adjustment. There are but two adjustments, so-called: the 
high-speed fuel needle for full load; and the slow-speed fuel needle for 
slow speeds and idling. Both are made by knurled nuts, which are 
turned clockwise to close and counter-clockwise to open. In the 
process of adjusting, close the exhaust damper S, so as to throw the 
exhaust gases through the carburetor and furnish the needed heat. 
Then close the air-choke valve /, to make a rich mixture for starting 
purposes. Before turning on the gasoline, open the high-speed needle 
B about two turns. Then start the motor and immediately open the 
air choke valve I. If it fires unevenly after running a little while, 
close the slow-speed needle A by turning the knurled nut T to the 
right, one notch at a time, until the motor fires and runs evenly when 
throttled down to the slowest speed. If the motor hesitates and stops 
when the air choke valve is opened, open the slow-speed adjustment, 
one notch at a time, until the point is reached at which the motor 
will just run and fire evenly when throttled down. 

Regulate the high-speed needle until the motor will respond when 
the throttle is opened quickly, by speeding it up to its maximum 
number of revolutions without missing. If the motor misses when 
the throttle is jerked open, close the needle slowly, one notch at a 
time, until the missing ceases and the motor responds to the quick 
opening smoothly. On the other hand, if the motor back-fires when 
the throttle is suddenly opened wide, open the needle slowly until it 
will speed up without missing or popping back. As soon as motor and 
carburetor have become thoroughly heated, turn on the kerosene 
and shut off the gasoline. 

Kerosene Modified Adjustments. The use of the kerosene may 
change the adjustments slightly. Thus the slow-speed needle adjust- 
ment may have to be opened one or two notches more for kerosene 
than for gasoline. Similarly, the high-speed needle adjustment will 
have to be opened two or three notches more. If the motor becomes 
so hot when running on kerosene that pre-ignition occurs — and this is 
likely because the whole device is designed to use the maximum pos-* 
sible amount of heat — the water-needle connection to the operator 

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should be opened. Thispre- 
ignition can be detected as 
a sharp metallic knock in 
the cylinder. Only enough 
water should be used to stop 
the knock; the carburetor 
should not be flooded with 
it. The cap at the bottom, 
or inlet, of the air cleaner 
Q should be kept tight. The 
air cleaner should be emp- 
tied once a day, but it should 
not be removed while the 
engine is running. 

Bennett Air Washer. 
The wider use of tractors 
and also of cars and trucks 
in the country, over dusty 
roads, and in the dust-laden 
fields which are being 
plowed, harrowed or other- 
wise worked, has forced the 
use of devices for removing 
the dust from the entering 
air. The device indicated 
at Q is one of these and is 
shown in detail in Fig. 130. 
Its interior consists of a 
series of spiral passages. 
The air enters one of these 
at A and is forced to pass 
through the water. Then 
it passes upward and out 
along the other spirals C, C. 
The air is doubly purified, 
first by passing through the 
• water, second in the removal 
of dirt by centrifugal action. 



Fig. 130. Bennett Air Washer, Indicating Operation 

Courtesy Wilcox- Bennett Company, Minneapolis, 


Fig. 131. Parrett Air Cleaner for Removing 

Dust and Dirt 

Courtesy Ro$8~Wortham Company, Chicago 


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Parrett Air Cleaner. A similar device working on a different 
principle is the Parrett air cleaner shown in Fig. 131. Air enters 
at the top and is drawn downward through the central tube, the 
lower part of which is flared out and is supported on a metal 
float smaller than the bottom of the bell. The air passes between 
the two, through a very narrow opening, at high velocity. Large 

air bubbles can not form, 
and because of the high 
velocity all heavy dust par- 
ticles are thrown directly 
into the water. The ris- 
ing purified air and mois- 
ture are separated by a 
series of baffle plates so the 
air finally passing to the 
carburetor is completely 
cleaned of dirt or dust. 

Deppe Qas Generator. 
Although not called a car- 
buretor by its maker, the 
Depp6 gas generator re- 
places the ordinary car- 
buretor for the purpose 
of vaporizing kerosene. In 
appearance and in sec- 
tional drawing, as shown 
in Fig. 132, it is not unlike 
an ordinary carburetor 
with an extra-special some- 
what globular chamber 

Fig. 132. Section of Depp6 Gas Generator, above it, and below it the 

Showing Construction 1 . • 1 < • e 1 1 

courtesy of w. p. Depp*, New York city ordinary inlet manifold, 

which is exhaust heated. 
Some of the things claimed for it, when it is attached to ordinary 
cars with no change except in the vaporizer, are: perfect gas at all 
speeds; superior acceleration; no loading; increased high speed; lower 
slow speed on high gear; much greater fuel efficiency expressed in 
miles per gallon; handles all ordinary hydrocarbon liquids — gasoline, 



kerosene, naphtha, etc., and mixtures of these; fixed metering adjust- 
ment which is not affected by altitude, temperature, or location; easy 
starting; less vibration of engine; and others. 

In Fig. 132, the fuel enters the float chamber A from below and 
passes through a horizontal passage B from which the two nozzles 
lead upward. The low-speed nozzle C draws its heated air through 
the primary intake D and mingles with this in the modified Venturi E. 
When the engine demands more fuel, it is supplied by the high-speed 
nozzle F, which gets its air from the auxiliary air valve G; this air and 
fuel mixture combine with the other in the chamber H, just above 
the Venturi and just below the center-opening throttle /. Up to 
this point it is not radically different from the average two-jet car- 
buretor with the auxiliary air valve. 

However, in the chamber just above this a mechanical atomizer, 
or rotating mixer on ball bearings J, is inserted. The idea is to com- 
bine the air and fuel particles more intimately through the rotation 
of this mixer within the zone of vaporization. The actual vaporizing 
chamber K is next above this. It is an annular passage around the 
highly heated exhaust gas chamber L, but inside of the outer exhaust 
chamber. This insures the absolute completion of the gasification 
started in other chambers, so that the mixture passing into the gasi- 
fication chamber M at the top and thence into the inlet manifolds 
and cylinders is sure to be a pure dry gas. 

Starting. To assist in starting, the primary-air passage is fitted 
with a choke valve of the butterfly type, which closes off this passage 
entirely so as to produce a rich mixture. Across the middle of the 
lower vaporizing chamber H, an electric resistance wire or heating 
coil is strung. The coil is connected to the starting battery. The 
connection is made so that the current passes through this heating 
coil as soon as it is turned on. This supplies the cold carburetor with 
the equivalent of the exhaust gas heat, which is available shortly 
after the engine has been started. 

Adjustments. As will be seen from the illustration, the low-speed 
nozzle and air opening are fixed, the only possible adjustment, setting, 
or change being in the alteration of the nozzle or in the quantity of 
primary air admitted. The high-speed nozzle is fixed similarly so 
that it cannot be adjusted, the high-speed air valve G furnish- 
ing the only adjustment 1 . The adjustment of this is very simple; 

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with the engine running, advance the spark pretty well to the 
limit, open the throttle lever to its maximum, and then vary the 
position of the nut N which governs the tension of the spring 
to the point where the maximum speed of rotation is obtained. 
This setting should be checked against actual high-speed running 
on the road, as there is usually a difference between the best road 
high-speed setting and the best engine-speed setting, with the car 
standing on the garage floor. 

Ensign Heavy Fuel Carburetors. A section through a new 
device recently perfected on the Pacific Coast, the Ensign car- 
buretor, is shown in Fig. 132 A, while Fig. 132 B is a horizontal 
section of the vortex mixing chamber which forms an important 
part of this. This device was designed to handle heavy fuels, but 
that shown in Fig. 132 A can be used for gasoline. As the figure 
shows the fuel enters a float chamber, thence into the bottom of a 
standpipe H, within which a suction tube A is set with its top 
opening slightly above the fuel level so that fuel must be drawn 
up by the air suction. . This air enters at B and passing around 
the vortex, of which Fig. 132 B shows a better view, acquires a 
high velocity. Thus a considerable suction is exerted on the fuel 
which passes out through holes D into the whirling air stream, 
which vaporizes it. Should any fuel moisture remain the centri- 
fugal action of the air stream throws it against the walls whence 
it drips down through holes J into the mixture which passes 
through the narrowed throat K, thence makes a sharp bend to a 
horizontal direction, and another to a vertical flow entering the 
inlet pipe V on its way past the throttle M to the cylinders. 
The nature of this vortex chamber thins the mixture as it is pro- 
duced at D, and with increasing demands, and thus increasing air 
velocity, continues to thin it, so the vortex chamber automatically 
delivers a thinner and thinner mixture as the engine speeds up. 

Adjusting the Ensign Type G. This model has two adjust- 
ments, air at A and fuel at G, Screw both of these clockwise to a 
closed position; then open G one and a half turns, and A one- 
fourth turn for four-cylinder motors, one-eighth turn for six or more 
cylinders. Start the motor and warm it up. Open the throttle 
to high speed and use G as a needle valve, adjusting to get the 
highest motor speed. Then refine this by adjusting A, one notch 

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Fig. 132 A. Ensign Carburetor, Model "G" 

Courtesy Ensign Carburetor Company, Los 

Angeles, California 

at a time. To start cold, open throttle M to slightly more than 
an idling position, and pull primer Y heavily before cranking. 

Ensign Fuel Converter. This 
company's Model "N" device is 
intended to handle the very 
heaviest fuels, up to a dry boil- 
ing point of 600° F. It con- 
sists of three elements, the car- 
buretor proper, the gas producer 
and the temperature regulator. 
Fig. 132 C shows that the first 
is almost identical with the car- 
buretor shown in Fig. 132 A. 
To this is added the gas pro- 
ducer which consists of the fire 
screen U to which the heavy 
unvaporized fuel flows, the com- 
bustion chamber Q and the spark- 
ing element A which ignites it. 
This heats up screen U and the 
plate C below it so that these 
subsequently vaporize a larger 
portion of the fuel, and less of 

•it passes down into Chamber Q Fig. 132 B. Horizontal Section of Ensign Car- 
, . . t , , . buretor Showing Vortex Mixing Chamber 

to be ignited and thus vaporized. 
That is, this part of the device 
is self-regulating as to tempera- 
ture. The idling temperature is 
controlled by thermostat capsule 
N, operating temperature con- 
trol plug M . This is half full 
of alcohol, and its chamber is 
provided with means for cir- 
culating the hot mixture. As I 
the mixture approaches 210° F. 
the capsule pushes the plug 
outward and closes the port 
reducing the draft and thus controlling the temperature, 

Fig. 132 C. 

Section through Ensign Fuel 


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Adjustment of Ensign Fuel Converter. Adjustment of this 
device is the same as the carburetor previously described, except 
for starting and with the addition of the spark plug care. In 
starting G is opened 1 turn, then E is filled with gasoline to fill the 
fire bowl up to the overflow F. If motor and converter are hot, 
prime very little; if motor has stopped but a few minutes, prime 
with Y on top of the flat bowl and start directly on the heavy 
fuel. With spark retarded adjust 6? to maximum engine speed. 
After engine has been running some time check this adjustment. 


Engine Should Start on the First Turn. In starting a car or 
any engine, whether located in a car or not, everything should be 
inspected so as to know if all is right before attempting a start. 
With the novice, this is somewhat of a task, but to the old hand 
it is so much of a routine task that he does it unconsciously. If 
all conditions are right, the carburetor is primed and the engine 
will start on the first turn of the crank. If it does not do so, 
there is a source of trouble which must be remedied first, and it is 
useless to continue cranking. The trouble may lie in the fuel 
system itself, but exterior to the vaporizer, or it may be in the 
ignition apparatus. It is well in a case of this sort to start with 
the gasoline tank and follow the fuel through each step until it 
apparently reaches the combustion chamber in the form of a 
properly proportioned mixture of gasoline and air. 

To start with the tank — is there enough fuel in it not only for 
starting purposes, but enough to allow of making the proposed 
trip? This is readily ascertained by unscrewing the filler cap and 
inserting a measuring stick. For the purpose a graduated rule is 
good, but not necessary; any stick or small branch of a tree will 
answer, or, lacking all these, a piece of wire can be used. 

Having verified the presence of fuel, the next question is: 
Does it reach the vaporizer as it should? Nearly all carburetors 
have a drain cock at the lowest point. Open this, and if fuel 
flows out in a steady stream, you may be sure that the pipe from 
the tank up to this point is not clogged. 

In either case, if there is no sign of gasoline when the tank 
contains plenty, it is apparent that the feed pipe is clogged. To 

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remedy this, the method of procedure is as follows: Shut off the cock 
below the tank so that none of the previous liquid can escape, then 
drain off the carburetor and pipe into a handy pail. Next, open the 
union below the cock in the feed line and the one at the other end of 
the same pipe. At both places look for obstruction. Then clean the 
pipe out thoroughly, using flowing water, a piece of wire, or other 
means which are available at the time. 

Gasoline Strainer a Source of Trouble. If you find nothing here, 
look in the strainer of the carburetor to make sure that the flow is not 
stopped there by the accumulation of dirt and grit, filtered out of the 
fuel. The strainer should be cleaned often, but, like many other dirty 
jobs, it is postponed from time to time. 

Should this source of trouble prove "not guilty" the carburetor 
itself becomes an object of suspicion. Is the float jammed down 
upon its seat, or are there obstructions which prevent the flow of fluid? 
Is the float punctured, or has one of the soldered joints, if a metal one, 
opened, or is it fuel-soaked, if cork? 

Bent Needle Valve-Stem. To attend to this sort of trouble, 
disconnect the priming arrangement, take the cover off the float 
chamber (it usually is screwed on with a 
right-hand thread) and take the float out. 
An examination of the float, Fig. 133, 
will disclose whether it is at fault in any 
of the above-mentioned ways, all of which 
are comparatively easy to fix. If the float 
was jammed down, perhaps by priming, 
the act of taking it out will loosen it, 
provided that the stem of the float is not 
bent, and the needle valve or its seat is 
not injured. If the seat is scored, it should 
be ground-in just like any other valve, 

., , n APi ii Fig. 133. Bent Needle Valve 

using oil and nne emery. A fuel-soaked 

cork should be thrown away if another is at hand to replace it, but if 
not, the cork float should be moved in its position on the stem so that 
it sets higher in the liquid. In other words, move the cork up suffi- 
ciently to compensate for its loss of buoyancy. 

In case of a punctured metal float or of loose solder, the only 
real remedy in either case is to resolder. It usually happens that a 

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soldering outfit is not available out on the road, and some form of 
makeshift will be necessary in order to reach a place where one may 
be had. If the puncture is on the bottom, it is sometimes possible 
to accomplish this by inverting the float so that the hole comes at the 
top where the gasoline seldom reaches it. If the flow be reduced to 
make sure that the float will not fill up, it is possible to reach a place 
where a soldering iron may be procured. 

A remedy which might be tried in an extreme case of this sort is 
to fill the float to make it heavy, so that it will have a tendency to 
sink. Then take a spring of small diameter, cut off a short piece and 
place it in the float chamber so that it opposes the sinking action 
of the now heavy float. By carefully determining the length and 
the strength of this spring, the same action is obtained as if the float 
were working all right. If the entrance of the liquid fuel is such that 
the sinking of the heavy float tends to close rather than open the gaso- 
line inlet, the spring would have to be on the bottom and fairly strong 
so as to oppose the action of gravity. But if the float works down- 
ward to open the gasoline passage, the spring will be at the bottom 
and very weak being there simply to prevent an excessive flow. 

Throttle Loose on Shaft. Now the carburetor trouble has been 
reduced to a minimum. The remaining troubles might be centered 
in a clogged spraying nozzle. But this nozzle is readily removed, 
and with it the trouble, if that be the offending member. If the 
spray is proven O. K., the throttle is ready for attention. If of the 
butterfly type, it may have become loose on its shaft, or, what is 
the same thing, the operating lever may be loose. In either case the 
shape and weight are such that it would swing into such a position 
as to cut off the entrance of gas to the inlet pipe and thus to the 
cylinder. If the throttle is of the circular sliding or piston form, it 
may not be connected to the throttle rod, but is stuck in such a 
position as to prevent the passage of gas. This sometimes happens 
when running, and then, apparently, closing the throttle does not 
stop the engine. The writer had this happen to him once at a time 
when it was absolutely necessary to stop. The only way that trouble 
was averted was by the instantaneous closing of the switch and 
the hasty application of the brakes. 

The last hope of finding trouble in the carburetor system rests 
with the inlet pipe. If the source of the trouble is not found else- 


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where, take this off in search of misplaced waste or similar sub- 
stances. The size of the pipe is such that anything in it large enough 
to cause trouble may be instantly seen and removed. The only 
exception to this is a small hole in the inlet-pipe casting, which, if 
clogged even with a grain of sand or other material, will not only 
cause trouble with the mixture at all times, but will also be very 
hard to find, particularly if it happens to be of very small' diameter. 

The valve, or cock, controlling the flow of liquid from the tank 
should be examined frequently and care be taken to keep it in good 
shape. It must act hard and must be tight, so that no gasoline flows 
when it is supposed to be shut off. If this valve does not act hard it 
is likely to jiggle shut during a long run and stop the engine by 
shutting off the gas supply from the tank. A method of fixing it — 
which, in general, is not to be recommended — is to open the cock and 
then hammer the handle so as to jam it tight against the seat, but in 
the open position. This makeshift will answer until a place is reached 
where the taper seat can be reground or tightened in place, if that is 
what it needs. In case the driver does not wish to do this, and the 
cock is of the two-way type — open when the handle is parallel to the 
axis of the pipe — it may be tied in the open position by passing a cord 
around the cock and pipe. 

Carburetor Adjustment. In adjusting the carburetor the 
worker should remember that the correct proportion varies from 11 
to 14 parts of air to 1 of gasoline vapor. It is not always possible 
to measure the two in just this way, but the adjustment is provided 
for in the carburetor. The tendency in carburetor construction is 
toward simplification and fewer adjustments. In making carburetor 
adjustments, always remember to make them with the motor hot. 
A good plan is not to make any adjustments of this kind until after 
the motor has been running for an hour. 

Tool for Carburetor Nozzles. Many carburetor nozzles are made 
with a screwdriver slot to facilitate their removal. It will soon be 
found, however, that the screwdriver is not so easy to use on these 
as a home-made tool. One useful form consists of a bar of f-inch 
steel-bar stock bent into the form of an L, the short end being flat- 
tened down into a screwdriver thickness and hardened. 

Starving at High Speeds. Many times, a motorist will experience 
the phenomenon known as starving at high speeds, that is, bis 

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motor will give better power and run faster with the throttle partly 
closed than when wide open. This happens when the auxiliary air 
valve does not open sufficiently to admit the large quantity of air 
needed at the widest throttle opening. The mixture, therefore, 
becomes too rich, and the motor starves. The auxiliary air valve 
usually has an outside spring, the tension of which is controlled by a 
milled nut, also on the outside. Then, when it is desired to make a 
change in the mixture, the nut is turned, altering the tension of the 
spring and thus altering the lift of the air valve; in this way the 
proper amount of air is admitted. To admit more air, the nut is 
backed off in order to weaken the tension and thus allow the air valve 
to open wider. To admit less air, the spring tension must be increased 
so that the air valve cannot open quite so far or stay open so long. 

Adjustments for Heating Water and Air Supply. On a large 
number of carburetors there are two more adjustments: those for 
heating the water and those for heating the air. The general run of 
carburetors are now water-jacketed to help vaporize the heavy fuels; 
during warm weather this may supply too much heat. For this 
reason, a cock is generally fitted to the hot-water line, which will allow 
partial as well as total closure. 

Similarly, hot air is supplied to almost all carburetors to vapor- 
ize the heavy fuels more quickly, a necessity if rapid acceleration, 
quick getaways, and other present-day demands are satisfied. In 
order to vary the hot air according to the weather or to cut it off 
entirely, some kind of a shutter is provided which can be locked in 
any position. When the days begin to grow warm late in the spring, 
the shutter is partly closed; during the heat of mid-summer, it is 
closed completely, and sometimes the connection with the exhaust 
manifold for heating the air is entirely removed from the car; when 
the temperatures begin to go down, the shutter is opened again, and 
in cold weather it is entirely open, and as much heat as possible is 
supplied the carburetor. 

Adjustment of the Nozzle. Nozzle Too High. A rather common 

trouble is failure to start readily. One puzzled driver described his 

case as follows: 

The engine starts hard, necessitates priming, and the primer must be 
held down for a long time. When this is done, it will start and run for a short 
distance, when it will stop and the same proceeding must be repeated. On 
taking the carburetor apart, everything was clean and apparently all right. 

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If you are ever bothered in this way, you may be sure, granting 
that the spark is good, that the trouble lies in the fuel system. From 
the description of the trouble, it appears as if conditions were such 
as to starve the engine, although this was doubtless done uncon- 
sciously. This action is due to the fact that the gasoline level has been 
lowered so far that the suction of the engine does not draw up sufficient 
fuel for running. The fact that you have to prime to start and then 
prime to keep going, even this priming failing to work sometimes, 
would seem to prove that the engine is not getting enough fuel. The 
trouble is that the spray nozzle has been raised too high, so that the 
gasoline level is four or five times as far below the nozzle as it should 
be. The engine suction must raise the gasoline this distance before 

Fig. 134. Section of Carburetor Showing Variation of Nozzle Level. First Figure, Correct; 
Second, Too Low— Engine Will Flood; Third, Too High— Engine Will Starve 

any of the fuel will get into the cylinder, and if the distance exceeds the 
height to which the suction can raise the fuel, none will pass over. In 
a case of this sort, priming only helps temporarily. 

Cleaning the Carburetor. Cleaning the carburetor, then, 
should be done very carefully, until one becomes quite familiar 
with it and with the influence which movement of the various 
parts will have. In Fig. 135, a foreign carburetor partly taken 
down shows how the top part of the float chamber should be 
removed in order not to damage the delicate needle point at the 
bottom of the float by which the latter governs the fuel supply. 
The cover should be loosened and then lifted straight up until 
clear of all remaining parts. With the cover off, the float may 
readily be removed in the same way, the only care being in start- 
ing it. As the amount, or length, of the needle point within the 
tapered seat is small, the float need be raised but a small amount. 

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Pre-Heating the Air. One thing that gives a lot of trouble is 
the heavier fuel now supplied. It can be used successfully only by 
adding heat, the application of which may take one of two forms: 
a water or exhaust-gas jacket around the carburetor or an arrange- 
ment pre-heating the air supply. The former cannot be added, 
but the latter can very easily. This is done by running to the 
inlet for the carburetor a flexible metal pipe from a collector 
fastened to the exhaust manifold. This tubing can be obtained at 
any well-equipped automobile supply house, as can also the 
various fittings for the exhaust pipes. In some cases, these firms 
carry the carburetor hot-air attachments also, but, if not, the 

Fig. 137. Method of Adding a Hot-Air Connection to Improve Carburetion 

maker of the carburetor can supply them at low prices. By the 
use of this attachment, the air drawn in through the carburetor 
passes around the very hot exhaust pipe, hence it is heated a 
gre&t deal. 

With the present grade of fuel, it is necessary to supply a great 
deal of extra heat in order to properly vaporize the fuel, especially 
during the winter months. It is sometimes advisable to remove 
the hot air pipe during the summer, as there is danger of too much 

Practically all late-model cars are equipped with a carburetor 
having a hot-water jacket and a special pipe for leading heated air to 


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the carburetor. In Fig. 138 is an English example of this, showing 
the carburetor connections on the four-cylinder Belsize. The pipe 
at the left is the inlet manifold and the one at the right, the hot-air 
pipe from exhaust manifold down to air inlet. In all cases this 
hot-air connection is made as short as possible. 

Causes of Misfiring. There are a number of vexatious things to 
make the novice and prospective driver peevish. Chief among these 
is the trouble known as misfiring. This may be described as a failure 
of the mixture to fire in any one cylinder. It is usually due to igni- 
tion, so that the term, as used now, means a failure to fire a charge due 
to an electrical cause. However, there are many common misfires 
which are due equally as much to a failure in the fuel-supply system, 
so that the latter meaning attached to the word is a misnomer. 

Among the causes which contribute to misfiring may be men- 
tioned ignition troubles, such as short-circuit in wires, exhausted 
battery, pitted or improperly adjusted vibrators of the coil, sooty 
or cracked plugs, loose connections or switch, dirty timer or com- 
mutator, punctured condenser, moisture in coil, wet wires or cables, 
water on distributing plate, dirt or wear on contacts in distributor, 
or dirt or wear in timer. 

Then, there are the misfires due in part or wholly to the fuel or 
carburetion system. These may be grouped or listed as follows : 

Carburetion and Fuel. Faulty mixture, sediment, or water in 
the carburetor, clogged gasoline strainer, leaky float, clogged spraying 
nozzle, bent float-valve spindle, stale gasoline, partial stoppage of 
fuel-supply pipe, hole or obstruction in intake pipe or manifold — 
these are not all the things that might happen, but are the principal 
ones which the writer's experience has suggested as most likely to 
occur to cars in general. 

Foremost among the several difficulties which may- be called 
common misfires is the lack of a proper mixture. A rich mixture 
containing a relatively large proportion of gasoline in proportion to 
air is never desirable, inasmuch as it deposits considerable soot upon 
the piston, cylinder walls, and valves, and is, moreover, a waste of 
fuel. The motor will seldom run well on a very rich mixture, and 
the carburetor should be so adjusted that no more gasoline is fed to 
the mixing chamber than is sufficient for the motor to develop its 
full power. The exact mixture may be found by experiment. 

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A very rich mixture will cause misfiring; the motor will have a 
tendency to choke at other than high speeds and is likely to overheat. 
A lean or too thin mixture will, on the other hand, lower the efficiency 
of the motor, giving it a marked tendency to miss at high speeds, 
and is also accompanied by a popping sound in the carburetor. In 
this case, the needle valve should be adjusted to admit more gasoline, 
or, if due to an excessive supply of air, the auxiliary air valve should be 
adjusted to admit less air. 

Bent Float Spindle. A bent float spindle will cause missing in 
one or more cylinders. The float spindle may become bent or it 
may become jammed into its seat by too vigorous priming. This 
may be discovered by unscrewing the cover and lifting out the float. 
Considerable care should be taken in straightening out a bent spindle, 
and the metal should be placed upon a block of hard wood, another 
block interposed, and the spindle gently tapped with a hammer. 

Leaky Float. A leaking metal float or a fuel-logged cork will 
cause missing, owing to its uncertain and erratic action. A cork float 
should be thoroughly dried out and then given a couple of coats of 
shellac to prevent it from absorbing the gasoline. As a new float 
is not at all expensive, the driver will probably find it more convenient 
to put in a new one. A metal float must be soldered when it leaks. 
As the copper is thin and easily damaged, only a very little solder 
need be used. Precaution should be- taken to keep the hot soldering 
bit away from the metal. 

A clogged gasoline strainer is often the cause of trouble, and 
this is about the first thing that the autoist should examine when 
the misfiring is apparently in the fuel-supply system. The brass 
gauze strainer should be frequently taken out and cleaned of any 
dirt that may have been filtered out of the gasoline. 

Obstructed Spraying Nozzle. Owing to the small needle-like 
opening in the spraying jet, it is not uncommon for a particle of grit 
to lodge in the orifice and partially stop the flow of gasoline. The 
obstruction will not always interfere with starting, but as soon as 
the motor speeds up, the amount of gasoline sucked through the nozzle 
will not be sufficient for the motor at higher speeds, and it will soon 
begin to misfire until the motor slows down to first speed. A leak 
in the intake manifold will cause misfiring and is often mistaken for 
ignition trouble. The cause may be due to loosening up of the bolts. 

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Summary of Gasoline System Troubles 

y Carburetors should be among the last things to change in case of 
trouble. A black smoke from the exhaust will indicate too rich a 
mixture. Too thin a mixture may cause back-firing through the 

Flooding of Carburetor. This may be due to the failure of the 
needle valve to seat properly, which may be corrected by grinding 
the valve; or to a punctured float which must be removed and the hole 
carefully soldered. It may also be due to the spraying nozzle being 
so adjusted that the opening is below the gasoline level. To remedy, 
raise the nozzle by easy steps until the correct level is obtained. 

Filling of Gasoline Tank. This should never be done by lamp 
or lantern light. 

Leaks in Gasoline Line. These must be repaired as soon as 
discovered. They may result in fire, destroying the car and endanger- 
ing the lives of its occupants. 

Filler Cap. The filler cap should uncover an opening in which 
is a strainer of gauze wire which should not be taken out, or, if broken, 
it should be replaced promptly. As an additional protection against 
small foreign particles getting into the gasoline system a funnel 
with a chamois skin through which the gasoline may be poured 
should be used. 

Grade of Gasoline. For ordinary use, gasoline from 56 to 68 
degrees test is most satisfactory. The former, called also stove 
gasoline, is the only kind qbtainable now. 

Obstruction in Needle Valve in Carburetor. In searching for 
a clogged gasoline line, it is well to unscrew the needle of the jieedle 
valve and then blow, through Ihe valve. This will remove particles 
of dirt that may 'be there. 


Changes in Manifold with Engine Developments. Notwith- 
standing the parked attention paid to minor details of design in the 
last three or four years, manufacturers have had no greater problem 
than that of vaporizing the fuel properly, quickly, and efficiently; 
this has led to considerable attention being given to inlet-manifold 
design. In the beginning, the inlet was a plain straight piece of 

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Fig. 139. Different Types of Inlet Manifolds for Four-Cylinder Engines 
Courtesy of N. W. Henley Publishing Company, New York City 

Fig. 140. Exterior of Studebaker Six Motor, Showing Particular Form of Inlet Manifold 
Courtesy of Studebaker Corporation, Detroit, Michigan 


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tubing from what corresponded to the carburetor to the hole in the 
cylinder leading to the combustion chamber via th§ inlet valve. 
With the development of the four-cylinder motor, the majority of 
these were cast in pairs, and the pipe assumed a plain or modified 
Y-shape. Even at that, there was considerable chance for variety, 
as will be noted in the nine dif- 
ferent forms shown in Fig. 139. 

Changes from Fours to 
Sixes. With the coming into 
popularity of the six-cylinder 
form of motor, the inlet mani- 
fold received renewed atten- 
tion; for now there were more 
variables, and it was a question 
of the best combination of 
them. One solution of this, as 
seen on a medium sized block 
six, is illustrated in Fig. 140. 
Here, the distance which the 
fuel must travel to the two 
central cylinders (cylinders 3 
and 4) is so much less than the 
distance which the gases must 
travel to either 1 and 2 at the 
front or 5 and 6 at the rear 
that there was the possibility 
of these four cylinders being 
somewhat starved. To com- 
pensate for this, the central 
part of the manifold where the 
three pipes to the cylinders join 
that from the carburetor was 
made much larger, with the 
idea of providing a well, or reservoir, for gaseous mixture large 
enough so the two central cylinders could not use all its contents. 

The majority of designers, however, preferred to make the dis- 
tance for the gases the same in each case, which led to some of the 
shapes seen in Fig. 141. Here it will be noted that a central loop is 

Fig. 141. 

Variety of Inlet Manifolds Used on Six- 
Cylinder Engines 

Courtesy of N. W. Henley J 3 ubli thing Company, 
New York City 


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used to make these distances come out equal in all but one case; in 
that, the cylinders are cast in threes with a single inlet for each group. 
Changes for Eights and Twelves. The coming of the V-type 
motors, both eights and twelves, has had another influence; for they 
came at the time when fuel was getting heavier and heavier. 
Designers were beginning to recognize the difficulty of vaporizing all 
the heavy fuel before it reached the cylinders, and, to assist in this, 
they began utilizing the manifold. Consequently, the majority, 
if not all, the eight- and twelve-cylinder engines have manifolds of the 

Fig. 142. View of National Twelve-Cylinder Motor from Above, Showing Inlet Manifold 
Courtesy of National Motor Vehicle Company, Indianapolis, Indiana 

loop type shown in Fig. 142. The unusual diameter of this is due 
to the water jacket around it; the water inlet is seen at A and the 
outlet to the carburetor water jacket at B. In this form, the unusual 
height is due to two things: the necessity of getting the carburetor 
between it and the cylinders, yet not too close for accessibility; and 
of having a sufficient volume to act as a storage reservoir, . since 
each side of this (each half of the loop) serves six cylinders (four 
in the case of the eight-cylinder engine). This is a typical eight- and 
twelve-cylinder manifold, except that many of them have a pair of 
pet cocks let into it for priming or cylinder testing purposes. 


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Heating the Charge. 

taken a number of forms. 

The method of heating the charge has 
In a simple four-cylinder motor of the 

Fig. 143. Type of Combination Inlet and Exhaust Manifold Which Improves Vaporisation 

L-head type, like the Ford, it has been possible to develop a combina- 
tion inlet and exhaust manifold (a single casting which would replace 
both of the former manifolds) which would give the heating effect 
desired in the inlet portion. Fig. 143 shows one way in which this 
is done and shows the central plate, or rib, between the two manifolds, 
which is heated to a high temperature by the exhaust gases, and thus 

Fig. 144. Form of Water- Jacketed Inlet Manifold Used on Marmon Motor 
Courtesy of Nor dyke & Marmon Company, Indianapolis, Indiana 

has a large influence on the final vaporization of the inflowing gases 
on the other side of it. It is claimed for this form that it will save 


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from 25 to 40 per cent of the fuel used, and, even though this 
claim is not borne out in all cases, the fact that there is a saving 
shows that this is a correct method. Many of the more modern 
motors are not only incorporating this as a method of saving fuel 
and increasing the motor's efficiency, but also of reducing the 
number of parts in the machine, the opportunities for trouble, and 
possibly of reducing weight. 

Another way in which the ordinary four- and six-cylinder 
inlet manifold has been altered is by the addition of the water 
jacket, previously mentioned. A typical example of this is seen in 
Fig. 144, which shows a water-jacketed inlet manifold on a six- 
cylinder motor, although the water-pipe connections are not visible. 

Changes in Construction of Manifold. In addition to the 
design, the constnjction of inlet manifolds has been of marked 
influence. Thus a manifold of aluminum, iron, or other cast 
metal is usually quite different from what a manifold for the same 
engine would be if made from copper or steel tubing. In addition 
to the limitations of the process of production, there would be the 
changes which the surface produced would have. Thus, a casting 
would have a more or less rough surface, while a drawn tube 
would be perfectly smooth. This allows the use of a slightly 
smaller diameter and more abrupt bends with the latter than with 
the former. Similarly, the fastening means have had an influence. 
On a number of block-cast motors, the manifolds have been cast 
integral with the cylinders, thus taking further advantage of the 
heat generated within the motor, for fuel vaporizing purposes. It 
is for this type of motor that the horizontal-outlet type of carbu- 
retor has been developed. In this type the volume of vaporizing 
space beyond the spray nozzle is at a minimum, that is, they have 
been designed simply to mix the fuel spray and air, while the 
highly heated inlet passages do the actual vaporizing. 

Hot Spots in Manifolds. A later trend in inlet manifold has 
to do with easier vaporization of the heavier fuels of today. Due 
to the high boiling point an external source of heat has been 
found necessary in this, and one of the ways in which this has 
been done is by means of the "hot-spot" manifold. To explain 
this simply, the inlet manifold is so constructed that a portion of 
it consisting of solid metal is in constant contact with the exhaust 

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manifold so that in continuous running this solid metal in the 
intake manifold becomes heated, perhaps to a high degree. Further- 
more, this "hot-spot" is so located in the inlet passages that all 
fuel must pass over it before passing to the cylinders, that is the 
last thing before passing in. A sharp bend in the inlet passage at 
this point does it, with the result that any unvaporized particles 
remaining in the fuel gas at this point are thrown against this 
highly heated spot and vaporized there, instead of being carried 
into the cylinders as liquid particles, as would be the case without 
this heated spot. One of these using the Stromberg "L" car- 

Fig. 144 A. Chalmers Hot-Spot Inlet Manifold 
Courtesy Automotive Industries, New York 

buretor is that of the Chalmers, shown in Fig. 144 A, said to pro- 
duce more power, greater economy, and more rapid acceleration. 

Another similar arrangement is used on the Hinkley truck 
engine as shown in Fig. 144 B. This engine is really a modifica- 
tion of the Class B Government engine and resembles it very 
closely. As will be noted in the drawing, this arrangement is 
very similar to the Chalmers, the exhaust and inlet being slightly 
different to facilitate easy and quick removal and replacement. 

As has been stated frequently, much heavy fuel is available 
on the Pacific Coast and at low prices, so out there considerable 


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effort has been expended on using these cheaper but heavier fuels. 
A modification of the hot-spot arrangement, designed to be used 
on Ford cars is shown in sketch form in Fig. 144 C. Here the hot 


Fig. 144 B. Hot Spot Manifold Arrangement on Hinkley Truck Engine 
Courtesy Hinkley Motors Corporation, Detroit, Michigan 

spot projecting into the exhaust manifold is not alone made very 
large but the outer or heating surface is increased by the addition 
of fins similar to an air-cooled engine. This adds metal to heat 
up and hold the heat, which is what the heavier fuels like distil- 
late must have. In addition, as will be noted, the carburetor is so 
constructed as to spray all the fuel oil directly into the interior of 
this highly heated mass of metal, the gasified parts coming down 
into the intake manifold. This heated mass of metal is thus the 
entire dependence for vaporization in this case, the actual car- 
buretor part of the device having been eliminated. It would seem 
that this carries the hot-spot or hot surface plan almost too far, 


Fig. 144 C. 

Far- Western Carburetor Which Is All 
Hot Spot 

its original intention having been for use as an auxiliary solely, 
the hot surface vaporizing only those heavy globules of the liquid 
which the spraying and atomizing and air mixing did not or could 


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not break up and vaporize. In short it was intended originally 
only as a clean-up device, following and wholly dependent upon 
the carburetor. The device in Fig. 144 C aims to make the hot 
surface become hot surface, vaporizer and clean-up device all in one. 
Another version of the heated manifold surface is shown in 
Fig. 144 D, the manifolds of the Velie tractor. Here the first 
part of the inlet manifold is highly heated by constructing the 
two manifolds as one, the inlet consisting of a straight vertical 
passage through the center of the exhaust passages, just as the 
detail at the left shows. This would give the high heat necessary 
for the original vaporization or cracking up of all the fuel, but to 
insure continuation of this condition, that is, to prevent any of 
the mixture condensing out into liquid again, the second portion 

Fig. 144 D. Combined Inlet and Exhaust Manifold of Velie Tractor 
Courtesy Velie Motors Corporation, Moline, Illinois 

across the top of the cylinders is water cooled. In this condition, 
the gas would be too hot to enter the cylinders, hence it is cooled 
by means of air-cooling fins or ribs along the last portion of its 
length. As a permanent gas has been produced by the previous 
steps, this carries with it small possibility of any condensation. 

The real flaw in the hot surface method is that it is of no 
help whatever in starting, since it does not begin to work until 
after the engine has run for some time, and heated up. And poor 
starting is really more drawback than running on heavier fuels. 

Inlet Manifold Troubles. The principal inlet manifold troubles 
are air leaks, which dilute the mixture beyond the carburetor, making 
it and its many elaborate adjustments more or less useless. These 
leaks may be due to leaks around joints, connections, or gaskets or to 
porous castings. If the inlet manifold is of copper or steel tubing, the 


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idea of a leak can be dismissed, but, otherwise, a porous pipe can be 
discovered at idling speeds by squirting gasoline upon the suspected 
surface of the manifold and noting if the motor speeds up. If it does, 
this is a sign that some of the gasoline has been drawn through the 
holes in the manifold, enriching the mixture. 

The leaks around joints, connections, or gaskets can be found in 
much the same way. When the leak is found, the joint should be 
tightened if possible, or a new gasket should be put in, or both. In 
the case of the porous manifold casting, it can be painted with a fairly 
heavy paint while hot so that the pores of the metal are well opened. 
Then, after this has dried in thoroughly, another coat will probably 
finish the job. If this does not prove to be the case, special cement 
for filling porous castings can be purchased and applied; or, best 
of all, if the case is a bad one, an entirely new manifold should 
be put in. 


For storage of the fuel required for the propulsion of a car and for 
feeding the fuel to the carburetor, many different systems are in use. 

Tank Placing. In automobiles, the gasoline tanks are generally 
placed under the front or rear seats, or under the frame at the rear. 
In many types of runabouts and roadsters, the tank is placed above 
the frame at the rear. 

Fuel Feeding. When the tank is at the rear, or when it is under 
the front or rear seat, no special provision is necessary, under ordinary 
circumstances, to insure a positive flow of the liquid fuel to the 

Gravity. With the tanks placed high, the gasoline can be 
depended upon to run down to the float chamber by gravity. In 
mountainous districts it is sometimes found, in climbing very steep 
hills, that the angle becomes such that the fuel will not flow, especially 
when the tanks are under or back of the rear seat, or when they are 
nearly empty. 

A means of getting around this difficulty is to place an auxiliary 
tank of one or two gallons capacity on the front of the dashboard, 
behind the^ engine and under the bonnet, and run a pipe direct from it 
to the carburetor. When the car is in a level position, this auxiliary 
tank fills automatically from the main tank, but a simple valve pre- 

356 s~> 

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vents the contents of the auxiliary tank from running back when the 
machine is tilted up. In this way a sufficient supply for 15 or 20 
miles running is placed in a position to reach the carburetor under 
any possible road condition. 

Air Pressure. With the tanks placed low, whether under the 
frame or above it, it is necessary to feed the fuel to the carburetor 
by more positive means than gravity. One of the commonest sys- 
tems involves pumping a low air pressure into 
the tank above the fuel, so that this pressure 
forces the liquid out regardless of the relative 
heights of tank and carburetor. Ordinarily, 
a small hand pump is sufficient to provide 
such air pressure, though in modern auto- 
mobiles equipped with compressed-air starting 
devices, or compressed-air tanks for filling the 
tires, provisions can be readily made for sup- 
plying the tanks with air from these sources 
for the purpose of feeding the fuel. 

Exhaust Pressure. A system that is 
much used for providing pressure in the fuel 
tanks, though not so highly regarded as in the 
past, is to tap the exhaust piping and to take 
from the connection a pipe line that permits 
the entry of a certain amount of the exhaust 
gases into the fuel tank. A simple automatic 
valve controls the pressure and shuts off the 
admission of gas when the pressure rises above 
the very low maximum required^ In a sys- 
« iak a „*• *u v*v tern of this character there is no possible 

Fig. 145. Section through the r 

Stewart vacmun GasoUne danger of fire, not only because the exhaust 
gas is very quickly cooled in passing through 
a length of small piping, but also because the contents of a gaso- 
line tank is ordinarily not ignitiable, because of the lack of any air 
to support the combustion. 

Sooting up of the automatic valve is the commonest trouble 
with this system. 

New Vacuum Feed Device. The many troubles incident to the 
use of the near tank location with pressure feed have brought about 



the production of a new device, which is called the Stewart vacuum 
feed* This is a small compact circular unit, which is placed on the 
dash under the hood for use with a rear tank and, when so used, 
eliminates the pressure feed. A sectional drawing of this is shown in 
Fig. 145. It may be described as follows: There are three connec- 
tions at the top, one to the gasoline tank, one to the intake mani- 
fold, and one to the air vent. Through the medium of the intake- 
manifold connection, the motor suction is communicated to the 
tank, for that is what the device amounts to. This produces a 
vacuum and opens the valve connecting with the gasoline tank. 
That, as well as the connecting-pipe line, being air tight, gasoline 
is drawn in to fill the vacuum, flowing into the upper chamber 
with which the gasoline tank communicates. 

This has a valve connection to the lower chamber, operated 
by means of a float; it, in turn, is controlled by the intake mani- 
fold suction, through the medium of the system of levers. By it 
the lower chamber is kept filled to a fairly high level, whence feed 
to the carburetor is by gravity. This method thus does away 
with all the troubles of the pressure system, at the same time 
allowing the accessible and advantageous rear-tank location. It is 
placed as high as possible on the inside of the dash under the 
hood, hence there is never any trouble with the gravity feed even 
on the steepest hill. In one test, this vacuum-feed device increased 
the mileage of the car per gallon of fuel by more than 22 per cent. 

Stromberg Fuel Pump. The Stromberg Fuel Pump operates 
on the pulsating principle. It consists of a pulsator and pump 
connected by a tube. The pulsator is a part of the engine and 
consists of ' a cylinder and reciprocating piston. There are no 
ports or valves and this pulsator is driven from the camshaft and 
is lubricated by the emulsion from the crankcase. The fuel 
pump is placed in the main line between the tank and the car- 
buretor. This pump consists of a float chamber, an inlet chamber 
which is also a sediment trap, and an outlet chamber, which is 
also an air-cushion chamber. The inlet chamber is connected to 
the float chamber through a gravity valve, and, in turn, the float 
chamber is connected to the outlet chamber by a similar valve, 
which, is closed by a spring. This construction is shown in 
Fig. 146. 


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Connections. As a guard against breakage and to allow altera- 
tions in the relative positions of different parts, due either to the 
straining of the machine while it is in use or to a change of adjust- 
ments when it is disassembled or reassembled, loops or coils in the 
soft brass or copper pipe line are of great advantage. 

Stop cocks close to the tanks are an excellent safeguard against 
fire, since they permit the shutting off of the fuel supply in the case of 
any breaks in the line. Such safeguards should always be provided. 

With reference to the pressure system of fuel feed, there is hardly 
any limit to the precautions which must be taken to avoid leaks. The 
smallest leak puts the system out of commission as soon as the pressure 
leaks down to a point where the fuel will not rise to the carburetor. 
When this occurs, the engine cannot be operated until the leak is 
found and fixed. To avoid leaks, many drivers go over all joints 
frequently and likewise replace all old packing. In addition, they 
wipe the joints with soap to prevent leakage and then cover them on 
the outside with tire tape or similar flexible material which can be 
wound on in such a way as to stay permanently. The rapid adoption 
of the Stewart device, since it was brought out in 1914, shows better 
than anything else how troublesome was the pressure-feed system. 
Statistics for 1914 cars showed that in" 237 different models, 109 had 
the gravity tank under the seat, and 31 in the cowl, this making 140 
with gravity feed, leaving 97 with the rear-pressure tank location. 
Similar statistics for 1915 show 52 per cent in favor of the rear tank 
location, while 1916 shows almost 66 per cent with rear location, and 
34 per cent vacuum fed. 

Reserve Tanks. To guard against the annoying mishap of 
having the gasoline give out while an automobile is in use, perhaps 
remote from any source of supply, many cars are now provided with 
reserve tanks which hold back one or two gallons of gasoline. This 
reserve cannot be used except when it is fed into the system through 
the deliberate intent of the operator. 

In its simplest and one of its best forms, a reserve tank takes 
the shape of a partitioned-off portion of the main tank, into which 
the gasoline automatically flows through an opening at the top when 
the tank is filled. It cannot pass to the carburetor until a special 
valve in the bottom is opened and the fuel allowed to flow back into 
the main tank. 


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A later and even more simple provision is the use for the gasoline 
tank of a three-way outlet cock which has a'fairly long extension up 
into the tank. The extension tube is open at the top and has a hole 
near the bottom of the tank which communicates through a branch 
tube with the third way of the cock. When the outlet cock is set for 
normal flow, the fuel feeds until the level reaches the top of the exten- 
sion; at that point it stops flowing. This is the warning to the driver 
that his fuel is low. Then all he has to do is to turn the outlet cock 
to the other position, thus allowing the fuel to feed from the bottom 
hole of the extension tube. The remainder of the fuel, that is, the 
amount represented by the difference in level between the top and 
bottom of the extension tube, will carry the car to the next fuel station. 

Fuel Gages, The development of depth and quantity indicators 
has received much attention in the last few years, with the result that 
practically all new cars have some form of gage on, or in, the fuel 
system. On rear-pressure tanks, it is usually located on the tank, so 
the driver must go to the rear of the car to see how much fuel he has 
left, but on cowl tanks or those located under the seat, it is possible 
to have the gage set on the instrument board or the dash, as the case 
may be, so that it is in plain sight. Practically all the gages give 
indications in gallons and fractions, so that with the gasoline gage and 
odometer in front of him, and knowing how many miles he averages 
to the gallon of fuel, no driver need worry about having gas. He can 
readily figure ahead and keep sufficient on hand for his needs. A 
device has been produced to give dashboard indication of rear-tank 
capacities, but this is so complicated and expensive that it is little used. 


Failure of Fuel to Flow from Full Gravity Tank. Many times 
the fuel will not flow from a gravity tank which is full. This may be 
because the air holes in the filler have been stopped up so that no air 
can enter. By cleaning out the holes, if there are any, drilling some 
if there are not, or by loosening the filler, this can be remedied. For 
this reason, it is well not to use a gasket or washer on a gravity tank. 
On a pressure tank, just the reverse situation exists, and it is advisable 
to use a rubber or leather washer at the filler cap. 

Fuel Line Obstructed. Many times an obstruction in the fuel 
line will be found at a very low point or sharp bend, where dirt in 

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the fuel has gradually collected until there was enough to cut off 
the flow. A good way Out of such a difficulty is to close connections 
at the tank and at the carburetor, take the entire fuel line off and 
blow it out with compressed air. This will clean it thoroughly. 

Lock on Fuel Line. The garage or repair man can insert a very 
efficient lock on any car by putting into the fuel line at a convenient 
point a shut-off cock which works with a removable key. These are 
readily obtained, and any good workman can install one in a couple 
of hours. Many owners of cars would be glad of an efficient lock 
and would be willing to pay well for one. This one has the advantage 
of being simple, cheap, and effective. 


Q. What is a carburetor? 

A. A carburetor is a device for vaporizing liquid fuels, and for 
adding to them, when vaporized, the proper amount of air for imme- 
diate and complete combustion. 

Q, How many types of carburetors are there? 

A. Three: the surface form, now out of date; the filtering type, 
no longer used, except on one or two English cars; and the spraying 
type, to which all modern devices belong. The first was useful only 
with the very light and extremely volatile fuels of ten and twenty 
years ago. 

Q. What are the essential units of a spraying type of carburetor? 

A. The essential parts of a spraying type of carburetor are: 
a float chamber with a float arranged to regulate the level of the 
inflowing fuel; a needle and nozzle, or spraying device, which should 
preferably be adjustable; an air opening, which may be variable or 
not, which may be in multiple form or not, which may have automatic 
valves to regulate its size or not; and a throttle valve to control the 
quantity of fixture passed into the cylinders. As an important 
auxiliary, the needle, nozzle, or spraying device, whatever its form, 
should be placed in a special vaporizing chamber, of a size and shape 
to give the best results. 

Q. Do all these appear in all modern carburetors? 

A. Practically all, in one form or another, and also a consider- 
able number of additional parts. Thus many carburetors have two 
or more nozzles, or spraying devices; quite a few have two air openings, 


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one of which is controlled by an automatic valve, some have three air 
openings; many, in fact most, of the modern devices have a method 
of heating the vaporizing chamber, or the space immediately above or 
below it, so as to facilitate complete vaporization, as well as to quicken 
the action; some have air valves in the form of steel balls; others 
have pistons and dash pots to eliminate sudden movements or changes 
in operation; many have auxiliary devices intended to give a special 
starting mixture; practically all have removable strainers for cleaning 
the fuel, some having two different forms of strainer. 

Q. What is the generally accepted form of needle valve, or 
spraying nozzle? 

A. There is no one accepted form, although the majority of 
carburetors have spraying nozzles, or needle valves, which come into 
one of four classifications. These are: the hollow nozzle with an 
opening at the top, slightly smaller in inside diameter than in outside, 
so that the spray of fuel is opened out in a fan-like form; the same form 
with an internal needle having a long tapered point and screwing up 
into it from below, this giving a means of adjustment which the plain 
hole does not; the same plain tube and hole, with an external needle 
having a tapered point and screwing down into it from above (in 
this, the body of the needle divides the spray of fuel) ; and the form 
of hollow nozzle in which the fuel is forced to flow outward through a 
series of holes, then upward to an outlet which consists either of an 
additional series of holes or a very fine annular ring. Either form 
gives the same result, a very fine and somewhat extended spray of 
fuel. The last form is sometimes modified to the extent that this 
annular ring of fuel, where it emerges into the vaporizing chamber, is 
as much as 3 or 4 inches in diameter. 

Q. What is the purpose of the auxiliary air valve? 

A. To supply additional or auxiliary air at the higher and 
highest speeds. Without this, the heavy suction of high speeds or 
hard pulling is very likely to produce too rich a mixture, that is, a 
mixture with too much fuel and too little air. 

Q. Is there any disadvantage in this? 

A. Yes. It has been found by experience that a motor will not 
operate well or give its extreme power or greatest speed on a rich 
mixture. Rather, at its highest output, the mixture should tend 
toward leanness. 


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Q. How does the auxiliary air valve remedy this? 

A. By adding air when the motor suction gets strong enough to 
open the auxiliary air valve, the amount added being in direct propor- 
tion to the strength of the suction. 

Q. What other disadvantage is there in over rich mixtures for 
high speeds? 

A. An over rich mixture at high speeds shows a noticeable lack 
of economy, as at these speeds a great amount of gas is being used, 
and, if too rich, the gasoline fuel is being used up very rapidly. The 
makers of practically any carburetor equipped with an auxiliary air 
valve will guarantee a saving of 20 per cent in fuel consumption when 
it replaces a carburetor which has no auxiliary air valve. 

Q. Why are some carburetors water-jacketed? 

A. The conversion of a liquid like gasoline into a vapor is a 
chemical action which needs heat to complete it. If no heat is sup- 
plied, it will be taken from surrounding objects, or else the vaporiza- 
tion will not be completed. This abstraction of heat from the sur- 
roundings can be noticed in unjacketed carburetors in the form of frost 
or snow forming on the outside of the vaporizing chamber. The 
water-jacketed carburetor has the hot water of the engine system 
circulated through it to supply the needed heat, and thus assist and 
complete the vaporizing of the fuel. 

Q. Why are some carburetors supplied with hot air? 

A. This is done for the same reason. The pre-heated air is 
supplied to vaporize the fuel, instead of using cold air and supplying 
heat from other sources. In principle, it is practically the same as 
the other. 

Q. When hot air is supplied, how is this heated? 

A. Generally a stove, or a hollow member around the heated 
exhaust pipe, is connected by metal tubing to the air inlet of the car- 
buretor; in this way all of the air drawn in is forced to pass around the 
exhaust pipe, which heats it. This is not always the case, some 
makers using air sucked in from around the heated cylinders. Still 
others use an exhaust jacket on the carburetor, and draw the cold 
air supply in around this, so that it is heated. 

Q. What difference does the fuel make in this heating method? 

A. On the heavier fuels, such as kerosene, alcohol, distillate, and 
mixtures of these with gasoline, a great quantity of heat is necessary, 

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as these heavier fuels are more difficult to vaporize and are also slower 
to start vaporizing. This means an extra supply of heat at starting 
time, and more than the usual supply at all times. It works out, in 
the direct use of exhaust gases, through a small pipe tapped into the 
exhaust manifold, thus giving the highest available temperature. 
This is used through the carburetor jackets, but, in addition, the air 
supply to vaporize the fuel is heated. Another vaporizer of heavy 
fuels, which has been quite successful, places heavy metal weights 
inside the carburetor in the upper part of the vaporizing chamber and 
then forces the exhaust gases through hollow passages in these. In 
this way, the weights are heated up, and this heat is transmitted to 
the gas and air; the size and nature of the metal gives an equable 
supply of heat, regardless of the exhaust gases. 

Q, What is the throttle valve? 

A. A valve placed in the pipe between carburetor and cylinders 
to vary (or throttle) the quantity of mixture flowing to the latter. This 
is generally connected to the throttle lever on thq steering wheel, and 
to the accelerator pedal. General practice in driving, after the initial 
stages of learning, is to set the hand throttle at some medium poftit, 
and thereafter to vary the speed of the motor by means of the foot. 

Q. What is the general form of this throttle valve? 

A. The butterfly throttle is used more than any other form, 
although the piston valve is considerably used. The butterfly is the 
simplest form possible, consisting of a thin circular disc the size of the 
interior diameter of the inlet pipe, fastened at the middle to a round 
shaft which extends across the pipe, and has a lever fastened on the 
outside extension. When this lever is turned so that the disc lies at 
right angles to the pipe, the passage will be shut off; when it is turned 
up parallel to the pipe, the passage will be wide open, for the disc is so 
thin as to offer practically no resistance to the gases. The piston type 
of throttle may be arranged so as to rotate or to slide. When it 
rotates, it is generally constructed with holes in its walls which register 
with the opening in the pipe, according to its position. When it 
slides, these holes are generally continuous at one end, this being 
moved along so as to register with the opening in the pipe. Another 
type of throttle is the swinging, or flap valve. This is so shaped 
as to swing from side to side, closing the passage entirely in one 
position, and leaving it entirely open in another. 


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Q. What is a Venturi tube? 

A. This is the essential principle of the inner member of the 
Venturi meter, invented for measuring the flow of water. It consists 
of two cone-shaped tubes diverging in opposite directions, with the 
proper relation of angles to one another and to the diameter of the 
smallest point, or meeting point, of the two tubes. The larger angle 
should be at the bottom, or entering end for the gases; the nozzle, 
or needle, should be just at or just below the smallest diameter; and 
the gases should flow through from end to end, that is, air in at one 
end, gas in at the middle, mixture out at the other end. In the true 
Venturi tube, the bottom angle is 30 degrees, the top angle 5 degrees. 

Q. When more than one nozzle is used, how are they connected? 

A. In practically all multiple-nozzle forms, the arrangement is 
such that the second (and later) nozzles are brought into action by 
increased demand from the engine, that is, automatically. In one 
case, a flap valve covers the second nozzle; but, as the suction increases 
this is drawn up and the nozzle is uncovered; having its own air 
supply, the nozzle begins to function as soon as it is uncovered, the 
amount of gas supplied by it depending upon the extent to which it is 
uncovered by the suction. In another, the first nozzle passes a fixed 
amount of fuel, as the engine demands rise; this suction is communi- 
cated to the second nozzle and the fuel standpipe from which it draws; 
it is put into action, but varies its supply always according to demand. 
The combination of fixed and variable nozzles gives reasonably 
good vaporization at all possible speeds and under all variations of 

Q. What is a horizontal=outlet carburetor? 

A. The first carburetors were all connected to the engine cylin- 
ders through the intermediary of an inlet manifold. The latter con- 
nected up to the cylinder horizontal face at a number of points, and 
was carried down to a single flange for the carburetor connection. 
While the surface of this flange was horizontal, the outlet on the car- 
buretor, that is, the passage to this, was vertical. Consequently, 
carburetors made to fit this arrangement are said to have vertical 
outlets. With the principle of block casting, it is usual to incorporate 
the inlet manifold in the cylinder casting and have a single carburetor 
opening and place for attaching, this being a vertical face. As the 
face, or carburetor flange, is at right angles to the body of the carbu- 

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retor outlets, this brought about a horizontal outlet. A carburetor 
with this form of outlet, and intended to bolt directly upon the cylin- 
der casting in the manner just described, is called a horizontal- 
outlet carburetor or a horizontal carburetor. 

Q. What is a double carburetor? 

A. A double carburetor is one made for a V-type of motor in 
which a common float chamber supplies fuel to two separate and 
distinct groups of vaporizing chamber, fuel nozzle and needle, air 
inlet, etc., each half supplying one of the blocks of cylinders. That 
is to say, it is a double carburetor, or two carburetors, if that is easier 
to understand, each one of which supplies one-half of the engine's 
cylinders, but has nothing to do with the other half. It has been 
found that better results can be obtained in this way than in any other. 

Q. What has been the effect of vacuum feeds? 

A. The principal effect has been to raise the carburetor. For- 
merly, the carburetor had to be set low so the fuel could flow to it, and 
even when pressure became general, the carburetors were still set very 
low. Now, with auxiliary tank feeding, it is possible to raise the 
carburetor from two to six inches, and practically all designers have 
taken advantage of this. It makes the carburetor easier to adjust, 
easier to prime when priming is necessary, less likely to be stopped or 
clogged by road dirt or water, because it is farther away from the road 
and better protected, also, the car can go through deeper water with- 
out stopping. Another effect has been to produce a steadier and more 
even flow of fuel at all times and under all circumstances. In one 
way, this gave better power, in another, it benefited by giving better 

Q. What is the vacuum feed? 

A. It is an auxiliary gasoline tank which draws the fuel from 
the main gasoline tank at the rear of the chassis (or elsewhere). It 
does this and maintains itself filled automatically, the vacuum being 
used to raise the fuel from the main tank to the auxiliary, which is 
usually about a foot higher. The tank can be placed anywhere, but 
the two usual mountings are on the inside of the bonnet, either on the 
engine or on the dash. 

Q. What other methods are there of fuel supply? 

A. The original method was by gravity, from a tank under the 
front seat. This necessitated having the carburetor so low that the 



fuel would flow to it on the steepest hill. The substitute for this was 
pressure, but this necessitated much apparatus, and the system had to 
be kept air tight or it was useless. In this form an air pump forced 
air through a regulator into the air-tight tank, this pressure forcing 
the fuel out and to the carburetor. 

Q. How does the Stromberg fuel pump differ from the 
Stewart vacuum feed? 

A. The Stromberg fuel pump operates on the pulsating 
principle, this pulsating being produced by a small pump, while 
the Stewart vacuum feed operates on the vacuum principle, the 
fuel being lifted by means of a vacuum created in the intake mani- 
fold. The Stromberg fuel pump draws a supply into an auxiliary 
float chamber, from which it is forced into the float chamber of 
the carburetor by the action of the pulsator. 

Q. What is the Packard fuelizer? 

A. The Packard fuelizer is an instrument which produces 
heat by means of a small gas torch. This heat goes into the 
intake manifold, vaporizing the mixture. 

Q. When no fuel flows, yet the tank is filled, what is the 

A. If the tank is full and no fuel flows, there must be an obstruc- 
tion in the line somewhere. Try the gasoline pipe line first for a bend 
or kink. If none is found, try the carburetor connection. Failing 
that, remove the strainer and inspect it. Then look into the float and 
float chamber, float valve and outlet to vaporizing chamber. Some 
one of these is sure to be at fault. 

Q. How can a punctured float be managed, so as to get home? 

A. Let the float sink, but oppose this sinking by means of a 
spring, carefully cut to the right length to give the same effect as if the 
float were O. K. This will carry the car to the nearest repair shop, or 
lacking that, will take it home. A punctured metal float can readily 
be soldered, but should be dried out very carefully first, this being done 
primarily to make sure there is no more gasoline inside, nor any vapor 
to condense. 

Study Questions for Home Work 

1. What are the general rules for adjusting Stromberg carbu- 
retors, Models L, LB, M and MB? If an entirely new setting is neces- 
sary on Model MB, what is the correct procedure? 


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2. What is the purpose of the economizer adjustment on the 
Stromberg Model L? 

3. Tell how the main jet is replaced on the Zenith. 

4. A car equipped with a Zenith Model O carburetor does not 
accelerate well and slow speed running is pot smooth. What is the 
trouble? What is the remedy when this car will not develop full 

5. Give the method of making a slow-speed adjustment on 
the Ford car. 

6. Describe the construction of the Master carburetor 

7. Explain the action of the air damper on the Master car- 

8. How is the Miller carburetor adjusted for altitude? 

9. Mention in detail the process of starting adjustment of 
the Webber. 

10. How many adjustments has the Rayfield? Describe them. 

11. What is the mixture-indicating pointer on the Newcomb? 
What are its advantages? 

12. How would you adjust a new Schebler Model "L"? 

13. What is the predominating feature of the Stewart car- 

14. How is the Johnson carburetor adjusted? 

15. What are the salient features of the Packard carburetor? 

16. Describe the adjustment of the Cadillac, (a) low speed, 
(b) starting, (c) high speed. 

17. Select and describe the working of a heavy fuel carburetor. 

18. Describe in detail the workings of the Carter auxiliary tank. 

19. It is desired to burn distillate in a truck. What carburetor 
would you select? 

20. What is the difference between an oxygen-adding device 
and a regular carburetor? 

21. Describe the construction of the Bennett air washer and of 
the Parrett air cleaner. Where are such devices necessary? 

22. Describe the construction and operation of the Toquet 

23. Describe the construction and operation of the Ensign 
fuel converter. How is alcohol used in this instrument? 


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24. How is vaporization obtained in the "Nitro?" How many 
adjustments are possible? 

25. What is the purpose of the flexible reeds in the Tillotson 
carburetor? How are they operated? 

26. How is a mechanical subdivision of the fuel obtained in 
the Shakespeare carburetor? How is this carburetor adjusted? 

27. Trace the fuel through the Holley "all fuel" carburetor. 

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Sectional View of the LaFayette Eight-Cylinder Motor Showing the Valves 
Set at an Angle to the Cylinders 

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Importance of Valves. Probably the most important thing 
about a four-cycle gasoline engine is the valve, or, more correctly, are 
the valves, for the usual number is two per cylinder. The opening 
and closing of these control the functions of the engine; for if the valve 
does not open and allow a charge of gas to enter, how can the piston 
compress, and the ignition system fire, a charge? Similarly, if the 
exhaust valve is not opened and the burned gases allowed to escape, 
they will mingle with and dilute the fresh, incoming charge, possibly to 
the extent of making the latter into a non-combustible gas. This 
is purposely stated in this way because both methods mentioned 
have been utilized for governing the engine speed, although not to 
any great extent in automobile work. 

Summary of Valve Features. In the valves and valve mech- 
anisms of modern gasoline engines there have been and are impending 
more interesting changes than seem in prospect in any other portion of 
the mechanism of the modern automobile. Particularly is this the 
case with reference to the present tendency to discard the poppet 
valve with its many objectionable features. Even where there is no 
tendency toward the use of a sleeve-valve or slide-valve form of 
motor, much experimenting has been done with increasing the number 
and changing the position of the valves. 

Poppet Valves. Though the very first internal-combustion 
engines ever made were operated with slide valves, the poppet valve 
was introduced very early in the history of this art, and has reigned 
supreme in practically all types of gas and gasoline engines. 

The chief advantage of the poppet valve is its capacity for con- 
tinuous operation at excessively high temperatures, but since the 
cooling of engines has progressed to the status of high reliability, 



this advantage is of less importance than formerly. And the dis- 
advantages of poppet valves — the small openings that they afford, 
the noisy and hammering action they involve, their tendency to leak 
and in other ways give out, and the necessity for frequently regrinding 
them — are objections so serious that it is no wonder the prospect of 
their elimination is so widely welcomed. 

About the only recent improvement that has been made in 
poppet valves is in the quality of material used in them. Many 
valves now used have cast-iron and nickel heads, which offer a max- 
imum resistance to warping from the heat to which they are subjected. 
These are fitted with carbon-steel stems, which are superior in their 
wearing qualities. More use has been made recently of tungsten 
as a material for valves. Steel containing this is even harder than 
nickel steel, and experiments have shown that it does not warp as 
much. In practice, the objection found to cast-iron heads was that 
the fastenings to the carbon-steel stem were not sufficiently strong 
to withstand the constant pulling and pushing to which a valve was 
subjected. As a result they separated, causing trouble. 

In the operation of poppet valves, the cams become an important 
factor. These are the parts which, in revolving, raise the valves so 
that they open at the proper time. In addition, the cams are so shaped 
as to hold the valves open for just the right length of time and allow 
them to close, through the medium of the valve-spring pressure, at 
the proper point in the cycle. The importance of this can be seen, 
if we consider that opening the slightest fraction of a second too late 
will reduce the amount of the charge very much, and thus lessen the 
power developed by the motor. 

Enclosures. The use of casings to enclose the valve stems, 
springs, and push rods, so as to keep these elements from exposure 
to dirt, and at the same time silence, in a large degree, the noise the^ 
make, is also becoming usual. 

Many excellent examples of this may be seen in modern motors. 
The whole side of the motor where the valve mechanism is located is 
covered with a long removable plate, keeping in noise and lubricant 
and keeping out dirt. Usually, however, on a six-cylinder motor the 
valve enclosure is made in two parts, one half enclosing the mechanism 
of the valves in the first three cylinders, the other half, those in the 
last three. This is, of course, the preferred construction on those six- 



cylinder engines which have the cylinders cast in threes, instead of in 
a block, as the one referred to. On some motors where this construc- 
tion has not found favor, the designers have followed the plan of 
enclosing the individual valve mechanisms. While more expensive, 
this method is equally as efficient. On the other hand, it adds to the 
parts, and the whole modern l^pdency has been to reduce the number 
of parts. "■'"$ 

Sleeve Valves. This type of valve, while not at all new, has only 
within the past few years come into considerable prominence, chiefly 
as a result of the truly remarkable performances of the Knight motor, 
which is equipped with the most advanced examples of this type 
of valve. 

Contrary to past opinion, it has been conclusively demonstrated 
that sleeve valves do not, to any perceptible degree, increase the 
tendency of a motor to overheat, nor do they wear at any very meas- 
urable rate. They afford, moreover, in the best constructions, a much 
higher thermal and mechanical efficiency than it is possible to secure 
from the average poppet-valve motor, this improvement being due to 
the better-shaped combustion chamber that can be used and the 
greater areas of valve opening, which facilitate the ingress and egress 
of the charges. 

Another advantage in favor of the sleeve valve is that its timing 
is permanent and unchangeable and does not alter materially with 
wear. Not the least of the merits of the sleeve valve is found in 
the fact that it lends itself to positive operation by eccentric mech- 
anisms, which are in every way greatly superior to the non-positive 
cam mechanisms universally used to actuate poppet valves. 

A very good example of this latest type of Knight motor is 
illustrated in Fig. 149, showing the intake side of the Moline-Knight 
four-cylinder motor. 

Sliding^ Valves. Sliding valves of other than the sleeve type, 
embracing a considerable variety of piston valves and valves similar to 
those employed in steam engines, have not found as much favor with 
designers of automobile engines as have other types herein referred to. 

One exception is the successful use of a "split-ring" valve sliding 
up and down in the cylinder head just above the piston, which has 
found successful application in a few motors recently built by the 
Renault Company, of France. 



Rotating Valves. A number of engines with rotating valves have 
been built from time to time, but none of these seem to have survived 
the test of time, for not one which was in evidence two years ago is 
being made now. A case in point is the Speedwell car with the Mead 
rotating- valve motor. The motor was excellent but is no longer made. 

Half- Time Shafts. For the actuation of the valve mechanism 
of any four-cycle motor, it is necessary to have a shaft (or in the case 

Fig. 149. Intake Side of Moline-Knight 50-Horaepower Motor 
Courtesy of Moline Automobile Company, East Moline, Illinois 

of rotary valves, to run the valve itself as a shaft) turning at one-half 
the speed of the crankshaft through a two-to-one gear ratio. 

Ordinarily the half-time shaft is the camshaft, but in motors 
of the Knight type it is, of course, an eccentric shaft. Camshafts, par- 
ticularly, call for good workmanship and high-grade materials, as well 
as sound design, since the constant pounding of the valve stems 
or push rods on the cams is a prolific source of trouble, if anything 
but the soundest of sound construction be employed. 


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The most important recent innovation in this detail of auto- 
mobile mechanism is the driving of half-time shafts by silent chains 
in place of the long-used gearing of spur and helical type. By this 
improvement the noise of the gears is eliminated. 

A typical silent-chain installation, driving half-time shaft and 
other shafts as well, is seen in Fig. 150, which presents the King eight- 

Fig. 150. Front of King Eight with Cover Removed to Show Use of Silent Chain 
Courtesy of King Motor Car Company, Detroit, Michigan 

cylinder motor with the chain cover removed. These occupy the 
compartment formerly called the gear case, or gear cover, when all 
driving was done by gears. Here it will be noted that there are two 
sprockets on the crankshaft; one driving the camshaft through the 
medium of a third sprocket which serves a double purpose, as a chain 

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tightener and as a drive for the pressure oil pump; while the other 
sprocket, through a second silent chain, drives the electric generator 
at the right, no tightener being needed as the generator can be 
moved sufficiently to care for this. 

In the Cadillac motor, shown in Fig. 2, Part I, a pair of gears is 
used, one driving the camshaft from the crankshaft, while the other 
drives the auxiliary shaft from the camshaft. In the American form 
of Knight sliding sleeve-valve motors, shown in Fig. 149, a pair of 
silent chains is used for the eccentric shaft on one side and the electric 
generator on the other. These are driven from a pair of sprockets 
set side by side on an extension of the crankshaft. 

A point that should be brought out in connection with silent- 
chain camshaft driving is that the use of the chain allows the shafts 
to be placed anywhere desired and thus, to a certain extent, frees 
the designer from the former restriction of a two-to-one reduction 
ratio in the gears, which rather fixed the size and, consequently, the 
position of the gears. This restriction had an influence also upon 
cylinder design, as the center of the camshaft fixed the center of all the 
valves, that is, their distance from the center line of the motor. 



Function. Granting the necessity for proper means to regulate 
the inflow and outgo of the charge and consequent products of 
combustion, as exemplified by the valves, the next most important 
part is the one which controls the movement of the valve, and is, 
therefore, essential to the success of the latter. This is what is known 
as a cam and in the usual case amounts to an extension of, or pro- 
jection from, the so-called camshaft. In as much as the valve func- 
tions only come into play upon every other stroke of the crankshaft, 
this camshaft is gear-driven from the crankshaft, so as to rotate at 
half the speed of the latter. This is very simply effected by having 
the cam gear twice as large as the crankshaft gear. As the same valve 
is never used for both the inlet and the exhaust, so the cams are seldom 
made to do more than the one thing, namely, operate one set of the 
valves. From this has grown the custom of referring to them accord- 
ing to the function of the valve which they operate — inlet cam, 
exhaust cam, etc. 

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In laying out or designing a set of cams for a gasoline engine, 
such as is used on an automobile, it is first necessary to decide 

Valve Timing of a Number of American Cars 

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upon the exact cycle upon which to operate the engine. By this 
is meant the exact length of time, as referred to the stroke, in 
which the valve action will take place. Upon this subject, 
designers all over the world differ, and no wonder, as this cycle 
can but be judged by results, for it is impossible to watch it as it 
operates. Deductions differ, therefore, as to what happens and, 
consequently, as to the effect of various angles of beginning and 
ending the valve actions. 

Valve Timing. Table I shows the valve setting of a number 
of standard 1920 cars of American manufacture. From this table 
it may be seen that the time of opening the exhaust valve has a 
range of from 35 degrees on the Maxwell to 71 degrees on the 
Stutz. The valve opens much earlier on the Stutz, so that plenty 
of time will be allowed to get rid of the burnt gases, as this motor 
operates at a fairly high rate of speed. The general average of the 
opening of this valve, however, is about 50 degrees before lower 
dead center. On the Mercer the valve opens at 70 degrees for the 
same reason as on the Stutz. The closing of the exhaust valve 
varies between 10 degrees before dead center on the Dorris and 25 
degrees after dead center on the Franklin. This is considered a 
very wide range for the closing of the exhaust valve — much wider 
than in former practice. The Cadillac closes its exhaust valve at 
upper dead center. The Maxwell does likewise, while the others 
have this valve closing at an average of about 10 degrees past 
upper dead center. 

The opening of the inlet valve also has a very wide range. 
The Franklin inlet opens 5 degrees before upper dead center, 
while the Chandler opens its* intake valve 18 degrees 16 minutes 
after upper dead center. Both the Cadillac and the Chalmers open 
the intake valve at upper dead center. The King eight also has this 
opening. The average intake opening of the other motors is about 
12 degrees past upper dead center. There are a few motors that 
have the positive timing; that is, the inlet opens at the same time 
that the exhaust closes. Examples will be found on the Stutz, 
National, Chevrolet, and Cadillac. 

The closing of the inlet valve varies between 35 degrees and 
57 degrees past lower dead center; 35 degrees is a very common 
position of this valve, while a few cars have their inlet valve clos- 


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ing at or above 50 degrees, such as the Stutz, National, Mercer, 
Franklin, Chalmers, Willys-Knight, Cameron, and Chevrolet. 
The closing of this inlet valve is made late on these models as the 
speed of the motor is generally high and this timing will allow a 
greater volumetric efficiency* which naturally increases the possible 
power output of the motor. 

The late valve timing of the foreign motors is not available at 
this time. The earliest exhaust opening of the 1908 French cars 
was on the Mutel, the valve opening at 62 degrees before lower 
dead center. Referring to Table I, it will be noted that the earliest 
exhaust opening of the late American cars is on the Stutz, the valve 
opening at 71 degrees before lower dead center, while the average 
opening of the late American cars is 50 degrees before lower dead 
center, and the average opening of the exhaust in the 1908 French 
cars was 46 degrees and 20 minutes before lower dead center. This 
setting is similar. The inlet valve of the Unic (French) opens 40 
degrees after lower dead center, while the inlet of the Peugeot 
closes 58 degrees past lower dead center. This closing position is 
rather extreme, although the Stutz inlet valve closes at 57 degrees 
past lower dead center, comparing very favorably with the Peugeot 

The late American motors operate at a higher rate of speed 
than in the early part of the industry and it has, therefore, been 
necessary to use a valve timing that would allow a greater amount 
of gas to be taken in and expelled in order to obtain a satisfactory 
volumetric efficiency. Foreign motors have been built with a 
small bore and a long stroke, producing a very high speed for years. 
This accounts for the rather fast valve timing of these cars. The 
present tendency is toward small higher speed motors, as they are 
more economical to operate. 

Timing Any Motor. Many automobile mechanics believe that 
gas engines cannot be timed unless the exact timing for the par- 
ticular motor is known. This is true to a certain extent; yet it 
does not hold good throughout as the engine can be set at an 
average setting and give good results. The pitch of the timing 
gears is generally coarse enough to allow only one proper setting. 
When this position is almost reached the teeth of the camshaft 
gear, which mesh between the two correct teeth on the crankshaft 


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gear, will be so close to the correct setting that less than the width 
of one tooth will be between that setting and the exact valve 

The average setting taken from 146 cars, which include a 
number of prominent 1920 types, is: intake opens 10 degrees past 
upper dead center; intake closes 43 degrees past lower dead 
center; exhaust opens 50 degrees before upper dead center; exhaust 
closes 8 degrees after upper dead center. It will be noticed that 
the intake opens about 2 degrees after the exhaust valve has 

If the motor is of L-head construction, it will be necessary to 
follow only one mark, either that of the intake opening or of the 
exhaust closing. The other settings will naturally take care of 
themselves. In any case, however, the valves should be timed by 
the intake opening or the exhaust closing, as these two points 
vary the least. 

Typical Valve Actions. Figs. 151 and 152 illustrate the complete 
valve action very well; the former, that of the Locomobile Company 
of America, Bridgeport, Connecticut, showing the form in which the 
cam works against a roller in the bottom of the push rod. This works 
upward in the push-rod guide and has a dirt excluding arrangement 
at the top. The top of the push rod bears against the bottom of the 
valve stem with an adjustable hardened screw forming the contact. 
The valve is held down on its seat in the cylinder by means of a strong 
spring, which the upward movement of the push rod opposes. The 
valve is guided in and has its bearing in the valve guide, which is 
made long to give large bearing surface. As the Locomobile motor 
is of the T-head type, the exhaust and inlet valves are on opposite 
sides of the cylinders and are operated by separate camshafts. The 
valve mechanism is completely enclosed. 

The second figure shows the valve action used on Haynes cars, 
made by the Haynes Automobile Company, Kokomo, Indiana. 
The difference is in the elimination of the roller at the bottom of the 
push rod which forms the poir / of contact with the cam. In this 
form, a flat hardened surface makes the push rod more simple and 
reduces the number of parts. It has been said against this form 
that the cam scrapes across the push-rod face and thus wears it, 
but in actual use it has been found that the push rod rotates and 


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in this way the wear is distributed over the whole flat face, which 
in this construction can be made much larger than can the face of 
the roller. The push rods are of the "mushroom" type and are 

Fig. 151. Complete Valve 

Motion with Roller Push Rod 

Courtesy of Locomobile Company 

of America, Bridgeport, 


Fig. 152. Complete Valve Motion 

wi hout Roller in Push Rod 

Courtesy of Haynes Automobile 

Company, Kokomo, Indiana 

made of nickel steel. The push-rod adjustments are completely 
enclosed but may be readily reached without disturbing any other 
unit. They may be removed and replaced without removing the 
valve springs or valves. 


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Neither of these systems is in decided favor, designers being 
about equally divided between them. 

The construction and operation of the cam mechanism is the 
same whether used in connection with an exhaust or an inlet valve; 
as the same line of reasoning and the same method of procedure, 
in both cases, would lead to the same result! 

It has many times been tried and still more often urged that 
the straight surface of the side of the cam is not conducive to the 
best results, because of the fact that when the first straight portion 
of the cam surface strikes the cam roller it does so with so much 
force that it tends to wear the latter in that direction. As for the 
receding face, it has been urged that the ordinary closing of the 
valve is too slow and that the straight surface can be altered so as to 
allow of speeding up the downward movement of the valve. This idea 

works out into a curve; 
the back of the surface is 
hollowed out so that as 
soon as the cam roller 
passes the center it drops 
vertically, owing to the 
tension of the spring. 
This method has been 
tried, but without suc- 

What Good Modern 

Fig. 163. Power Curve of an American Engine with Practice SHOWS. A TTinrp 

Superior Cams and Balancing 

modern way, which is 
fast becoming universal, is to use straight sides for the cams and 
take advantage of rapid closing in another way, the benefits of 
which more than offset the benefits of the old way and have no corre- 
sponding disadvantages. In the ordinary automobile engine running 
at 1000 revolutions per minute, the gases are traveling into the cylin- 
der at the rate of 5000 to 6000 feet per minute, and traveling out at 
from 7000 to 10,000 feet per minute. At this tremendous speed, the 
gas inertia is very high, and experiments go to show that the gases by 
means of this inertia will continue to force their way into the cylinder 
even against the return motion of the piston. So it is now common 
practice to hold the inlet valve open about 30 degrees on the upstroke 

384 Digitized by G00gle 


of the piston, which results in a much larger piston charge. The same 
practice is carried out with the exhaust, but as the pressure is higher, 
so large an angle is not necessary. These actions take place on 
the back — flat side — of the cam surface and have given to the high- 
speed automobile engine a larger charge and a more complete 
scavenging effect, resulting in more power and speed from the same 
size of cylinder. 

As proof of this statement, the power curve of an engine of 
but 3£-inch diameter of cylinder is shown in Fig. 153. This size of 
six-cylinder engine would be rated by any formula at about 29 
horsepower at the maximum speed, and a commercially obtainable 
type in this size would doubtless be guaranteed to deliver between 
20 and 25 horsepower. This engine, which is not built for racing 
purposes, displays a power curve which continuously rises; a speed at 
which it would turn downward has not been obtainable in the tests. 
This curve shows also that the maximum power obtained was over 
80, which is nearly three times the power of the ordinary engine of 
this same size. This result is ascribable to superior valves and 
superior attention to the valve angles as governed by the cams; 

Number of Valves per Cylinder. Three Valves per Cylinder. 
When it was stated that but two valves per cylinder were ordi- 
narily used, with one cam for each, the majority case was spoken of. 
But, as it is a fact that there are other cases which differ from this, 
it would not be fair to close the subject without mentioning them. 
The most prominent advocate of air cooling in this country and the 
world, the H. H. Franklin Manufacturing Company, used three 
valves, and consequently three cams, per cylinder. These three were 
the ordinary inlet; the usual exhaust; and the additional auxiliary 
exhaust. By re-designing later, this complication was avoided and 
the third valve eliminated. 

. The Wisconsin Motor Company has developed another motor 
with four valves per cylinder and, after a notable racing success, 
has placed it upon the market. Any maker desiring to do so, may 
purchase this and incorporate it in his chassis. This emphasizes the 
distance which the sixteen-valve four-cylinder motor has progreseed 
in the space of a year or so. A section through this motor, both side 
elevation and end view, showing all the details of the construction, is 
shown in Fig. 154. The exhaust of the Stutz motor is given in Fig. 155. 

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Four Valves per Cylinder. The very latest practice in the 
way of multiple valves is the use of four valves per cylinder — two 
inlets and two exhausts. There are a number of reasons why this 
construction is a good one. The area through which the gases 
enter and leave the cylinders is made greater, thus giving the same 
or greater supply of gas more quickly and a better scavenging 

The volumetric efficiency of the cylinder is greatly increased 
in this way, giving more power and speed from the same size of 
cylinders — so much more as to give a four-cylinder engine with 

Fig. 155. Exhaust Side of the 1920 Stutz Sixteen-Valve Motor 

sixteen valves as great a flexibility as that of a six-cylinder with 
but twelve valves. Another big advantage claimed for the 
smaller lighter valves of this construction is that very much lighter 
valve springs can be used. This advantage was discovered by 
using sixteen valves on a four-cylinder racing engine where the 
compression and other pressures were enormous. The valve springs 
for the ordinary eight-valve engine had to be very stiff and, con- 
sequently, gave much cam trouble. The stiff springs dug out the 
sides of the cams very rapidly and also failed rapidly themselves. 



With the lighter springs which can be used with sixteen valves, 
these troubles are eliminated. 

In the 23 cars starting in the 1920 Indianapolis Derby, 13 
were of the four-cylinder forms and the remaining 10 were seven- 
cylinder cars. The four-cylinder cars had sixteen valves with 
exception of 3, these having twenty valves. The fights were con- 
structed with all cylinders in line and four valves to each cylinder. 
In the sixteen-valve motor developed by the Stutz Motor Car Com- 
pany, the engine has the outward appearance of any other T-head 
form, for the use of double the usual number of valves does not 
change the exterior at all. 

Fig. 156. Carburetor Side of the Monroe Racing Type Engine. 
(Winner of the 1920 Indianapolis Race) 

In the majority of V-type motors, both eights and twelves, 
the valves are in side pockets; the cylinders are of the L-type, and 
thus there is no radical innovation except the inclined push rods 
and valve systems. In a few of these motors, however, a follower 
is used between the cams and the push rods because of some 
other structural reasons. 

When any kind of a cam follower differing from the usual direct- 
lift push rod is used, this may or may not affect the shape of the cam. 
Usually it does not, so that the shape does not have to be taken into 
account. Ordinarily these followers are used to prevent side thrust 
on the push-rod guide, the follower itself taking all the thrust and 

388 Digitized by G00gle 



being so designed as to be readily removable or adjustable, to take 
care of this. In cases where this does not obtain, the object usually 
sought is the removal of noise. The two objects may be combined, as 

in the case shown in Fig. 158. This 
represents an enlarged view of the 
cam mechanism of the famous one- 
cylinder French car, Peugeot. It 
will be clear that the action is that 
of one cam operating both the 
exhaust arid the inlet valves through 
the medium of a pair of levers, upon 
which the cam works alternately. 
A cam follower of somewhat 
different form, but one achieving the 
same results, will be noted in the 
Cadillac eight-cylinder motor, shown 
in Fig. 164, where attention has been called to these, and also in the 
Chalmers six-cylinder motor with overhead valves, shown in Fig. 156. 
Difficulties in Making Cams. There was a time when the pro- 
duction of a good, accurate camshaft was a big job in any machine 
shop, well-equipped or otherwise, and represented the expenditure of 
much money in jigs, tools, and fixtures. Now, however, the machine- 
tool builder has come to the rescue of the automobile manufacturer, 
and special tools have made the work easy. So it was with the pro- 
duction of the shaft with integral cams; this used to be a big 

Fig. 158. Cam Mechanism of Peugeot 
Single-Cylinder Engine 

Fig. 159. Cams Integral with Shaft— Milling Machine Job 

Fig. 160. Ar. other Camshaft with Integral Cams 

undertaking, but today special machinery has made it an easy matter. 
The illustrations, Figs. 159 and 160, show some of the product of a 
cam milling machine. This is now the favored way of putting out 
engines, for the integral cams and shaft have the advantage of much 
lower first cost and, with proper hardening, will last fully as long as 
those made by mounting the separate cams directly on the shaft. 


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Grinding Increases Accuracy. An even later improvement in 
the way of a machine for producing cams on an integral shaft is 
the grinding machine which has been developed for this purpose. 
This works to what is called a master camshaft, that is, a larger 
size of shaft which has been very accurately finished. This master 
shaft is placed in the grinding machine, the construction of which 
is such that the grinding wheel follows the contour of the very accu- 
rate master shaft and produces a duplicate of it, only reduced in size, 
a reducing motion being used between master shaft and grinder- 
wheel shaft. 

The result of this arrangement is a machine which is almost 
human in its action, for it moves outward for the high points on the 
cams and inward for the low 
spots on the shaft. Moreover, it 
has the further advantage that 
all shafts turned out are abso- 
lutely alike and thus accurately 
interchangeable. It allows also 
of another arrangement of the 
work, the drop forging of the 
shafts within a few thousandths 
of an inch in size; the surface of 
skin is easily ground off in one 
operation, then the hardening is 
done, and the final grinding to 
size is quickly accomplished. In this way, the shafts may be 
produced more cheaply than was formerly the case and have, in 
addition, the merits brought out above, namely, greater accuracy, 
superior interchangeability, and quicker production. 

The same process is applicable to, and is used for, other parts of 
the modern motor car; thus crankshafts are ground, pump and mag- 
neto shafts are finished by grinding, and many other applications of 
this process are utilized. The process can be extended indefinitely, 
the only drawback being that a master shaft is very expensive. 

Old Way Required More Accurate Inspection. With the old 
method of making the cams and shaft separate, the amount of 
inspection work was very great and represented a large total expense 
in the cost of the car. Thus, it was necessary to prove up every cam 

Fig. 161. Useful Form of Gage for Separate Cams 


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separately, as well as every shaft, and, later, the cams and shaft 
assembled. One of the forms of gages used for inspecting cams 
is shown in Fig. 161. It is in two pieces, dovetailed together. This 
allows of the testing of many shapes of cam with but one base piece 
and a number of upper, or profile, pieces equal to the number of differ- 
ent cams to be tested. To test, the cam is slipped into the opening, 
and if small, the set screw forces it up into the formed part of the 
gage, showing its deficiencies; while if large, it will not enter the form. 

Valve Timing 

This increase of speed without material alteration in the engine is 
what every repair man aims to get when he goes over the timing of the 

motor. Valve timing has been 
called an art, but it is not; it is 

PEAD CENTER u.\z°^j 

only the application of common 
sense and the known valve dia- 
gram to the motor in an attempt 
to get the best all-around results. 
These, as might be expected, are 
a compromise, and that repair 
man does the best timing, who 
realizes this and, instead of 
attempting the impossible, sim- 
ply produces the most desirable 
all-around compromise. 

Flywheel Markings. Nearly 
all motors now have the timing 
marked upon the rim or face of the flywheel, so that it is unnecessary 
to bother with the crankshaft and pistons. This has been found by 
experience to be the best and handiest way, for the flywheel is gen- 
erally accessible without removing many other parts. The same is 
true with the valves. This is not the case with pistons and crank- 
shaft; moreover, with these it is difficult to determine the exact upper 
and lower dead centers, and still more difficult to work to angles. 

To use these settings marked on the flywheel, a stationary pointer 
on the upper surface of the crankcase hangs over the flywheel surface 
as closely as possible and indicates the reading. The flywheel is 
turned by hand or by means of the crank at the front of the engine 

Fig. 162. Overland Four Valve Timing 


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until a mark or the desired mark is brought up to the pointer. Thus, 
the cylinders are marked from front to back always, that nearest the 
radiator being 1, the next 2, then 3, and the last, in the case of a 
four-cylinder motor, 4. In a six-cylinder motor the method is the 
same with the addition of two cylinders, the one nearest the dash 
being, of course, 6. The flywheel sometimes has the position? marked 
on its surface, as well as the valve operations. Referring to Fig. 162, 
this shows the valve-timing diagram of the Overland Four, 1920 
model. Notice in this that none of the valve operations begin 
or end on a dead center point so that even if the centers are marked 
on the flywheel (as they are in this case) this is of little benefit except 
as will be pointed out. The marks on the flywheel are as follows, 
this showing also what they indicate. In referring to these it will be 
remembered that on a four-cylinder crankshaft the first and fourth 
crankpins are up (or down) together, while the second and third are 
down (or up) together: 

1-4 UP Means that pistons in cylinders 1 and 4 are in 
their uppermost position, or at upper dead center. 

2-3 UP Means that pistons in cylinders 2 and 3 are in 
their uppermost position, or at upper dead center. 

1-4 1-0 Means that inlet valve of cylinder 1 or 4 (not both) 

1-4 I-C Means inlet valve of cylinder 1 or 4 closes. 

1-4 E-0 Means exhaust valve of cylinder 1 or 4 opens. 

1-4 E-C Means exhaust valve of cylinder 1 or 4 closes. 

2-3 1-0 Means inlet of cylinder 2 or 3 opens. 

2-3 I-C Means inlet of cylinder 2 or 3 closes. 

2-3 E-0 Means exhaust of cylinder 2 or 3 opens. 

2-3 E-C Means exhaust of cylinder 2 or 3 closes. 

The firing order of the cylinders is 1- 3- 4- 2. To apply this 
knowledge, open the pet cocks so the motor will turn over easily; 
selecting cylinder 1 to start with, turn the flywheel until the mark 
1-4 UP comes to the pointer at the top. Now continue turning 
to the left (at the rear end) about an inch more when the mark 1-4 1-0 
will be seen. Bring this slowly up to the pointer, when the inlet 
valve should just begin to open. This can be noted by feeling the 
stem, or by placing a wire upon the top of the valve and noting when 
it begins to be pushed upward by the valve movement. If this should 


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happen in cylinder 4 instead of 1, turn the flywheel one complete 
revolution, bringing the same point to the top. If this is entirely 
correct, the flywheel can be turned in the same direction about 5 to 6 
inches more than half a turn, when the mark 1-4 I-C will appear. 
Turn slowly until it reaches the pointer, when the valve in cylinder 1 
should be completely closed. This can be determined again by 
feeling of the valve stem which should come down to its lowest 
position, or by the wire on the top of the valve. At this point the 
valve-tappet clearance comes in. When the valve tappet has reached 
its lowest point, and the valve has been allowed to seat, the tappet 
should go down slightly farther than the valve, leaving a very small 
space between the two. This is the clearance and it varies in normal 
engines from .002 inch to .012 inch. In the motor which is being 
described it is .012 inch. The closest approximation to this is an 
ordinary visiting card, which is about .012 inch thick; when a motor 
is handled which has less, very much less, this can be approximated 
by means of cigarette papers which are very close to .003 inch thick. 
These are used in the absence of precise metal thickness gages, 
or feelers, as they are called. 

Valve-Stem Clearance. This clearance is necessary to compensate 
for the expansion of the valve stem when it becomes highly heated 
during the operation of the engine; the tappet or push rod does not 
become heated, consequently it does not expand. Practically all 
motors are made with an adjustment here in the form of a screw with 
a hexagon head which is hardened where it strikes the valve stem or 
it is recessed out for a piece of hard fiber to deaden the noise, Fig. 151, 
and the fiber is locked in the desired position by means of a lock 
nut. If the clearance is less than the required amount or greater 
so that the motor is very noisy, the lock nut is loosened, and the screw 
gradually turned upward until it just begins to grip the visiting card. 
This should be done very carefully, for if the clearance is made too 
small, the valve will not seat fully when the motor is hot and the valve 
has expanded; on the other hand, if the clearance is made too large, 
the push rod will come up against the valve end each time with a bang, 
and eight of these repeated a thousand times a minute make a great 
deal of disagreeable and useless noise. In the modern motor, the 
cams are made an integral part of the camshaft. If the driving gear 
for the camshaft is in its right place, and the camshaft bearings are 


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all in good shape, this push rod adjustment is the only valve adjust- 
ment possible. If the timing is not correct, that is, if none of the valve 
operations correspond with the marks on the flywheel and the maker's 
instructions, then the cam gear has been misplaced. 

Exhaust-Valve Setting. The same procedure is followed through 
for the exhaust valve of the same cylinder, continuing past the 1-4 UP 
mark to the mark 1-4 E-O. At this point the exhaust valve of 
cylinder 1 should just begin to open. Then continue around to the 






exhaust closes s° 
past upper dead 



Z AND 5 

Fig. 163. Valve Timing Diagram for Hudson Super-Six Motor, Showing All Cylinders 

1-4 E-C point where the exhaust valve of cylinder 1 is just complet- 
ing its downward, or closing, movement. If there should be any need 
for adjustment here, as described previously, this should be made 
before proceeding to the other cylinders. It should be stated that 
many makers give the exhaust- valve stems slightly greater clearance 
than the inlets, on the assumption that they work with hotter 
gases, are subjected to more heat, and should therefore expand 
more. The make being described has the same clearance for both 
valves; .004-inch clearance on the intake and .005 to .006-inch on 
the exhaust are recommended. 

Relation of Settings in Each Cylinder. Now, having checked up 
and adjusted both valves for cylinder 1, follow through the same 


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process for cylinder 4, and, after that, of cylinder 2, then 3. The dia- 
gram, Fig. 162, shows but the cycle in each cylinder, while the descrip- 
tion above simply listed the markings to be found on the flywheel, 
so the additional diagram, Fig. 163, is given to show the relation of 
these marks to one another. This diagram refers to a different motor, 
a Hudson Super-Six model, and the timing is indicated on the face, 
but the repair man will understand that this is done simply for con- 
venience, and that these marks are actually found on the rim. So, 
too, the lines drawn down to the center are simply shown for conven- 
ience in indicating the angles and do not appear on the flywheel. 

Fig. 164. Section through Cadillac Eight, Showing Camshaft and Valve Mechanism 
Courtesy of Cadillac Motor Car Company, Detroit, Michigan 

In this a different timing will be noted, in that the inlet opens later and 
closes earlier, while the exhaust opens earlier and closes earlier. 

System Applies to All Types of Motors. As has been stated pre- 
viously, discussed, and shown in Table I, there is now, and 
always has been, a wide divergence among designers on the subject 
of valve timing, so that the repair man must look for a different 
setting with each different make, and often a different setting with 
each different model of the same make. All that can be used for all 
cars is the general method. The general method, however, is appli- 
cable whether the valves are all on one side (L-head cylinders), half 


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on each side (T-head cylinders), all in the head or half on one side and 
the other half in the head, in short, regardless of the valve position. 
Similarly with regard to numbers, the method holds good regardless 
of the number of valves per cylinder. Moreover, it applies regardless 
of the number and arrangement of the cylinders, as it is just as good 
for eights and twelves as for the four described. On V-type motors 
there is a close relation between the opposing cylinders, right- 
hand No. 1 and left-hand No. 1, and this must be taken into 
account. In some motors there is a cam for each valve, in which case 
no trouble would ensue; but in others there are but eight cams for 
the sixteen valves (of an eight-cylinder motor). This type of shaft 
will influence the timing diagram, and in setting, the repair man will 
have to concern himself with the same cam for two different valves — 

Fig. 165. Cadillac Camshaft, Cam Followers, and Covers Removed from Motor 

one in a cylinder of the right-hand group and one in a cylinder of 
the left-hand group. 

This statement will be more plain perhaps if reference is made to 
Fig. 164, which shows a section through the Cadillac eight for 1917, 
and indicates how the one cam operates two valves through the hinged 
rocker arms A on the left-hand cylinder and B on the right for the 
right-hand cylinder. By comparison, see also Fig. 165, which shows 
the plate C in Fig. 164 removed and turned upside down, with the 
camshaft and rockers complete. Not all eights and twelves are like 
this, nor do all have a single camshaft set in the middle of the V; 
on the contrary, one well-known twelve-cylinder motor, the Na- 
tional, has the valves on the outside of the two groups of cylinders, 
and thus has two camshafts. In such a case, the timing method just 
described would be followed through for all the cylinders on one block, 
then the same system would be followed through on the other side 
of the engine, one cylinder after another, on that block. 


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Repairing Poppet Valves and Valve Parts 

The interest of the repair man in all these valve-motion parts is 
quite different from that of the designer, for he cares not so much 
how they are made as how they are taken out, repaired, and put back, 
when accident or wear make this work necessary. To the repair man 
suitable tools for doing this kind of work are also of interest, particu- 
larly those for reaching inaccessible parts or for doing things which 
without the tools could not be done. 

Curing a Noisy Tappet. Valve springs and the valves them- 
selves, either at the seat end or at the tappet end, give the most 
trouble. For example, when the clearance between the end of the 
tappet and the end of the valve (usually from .003 to .008 inch) is 
too great, a metallic click results. Often this noise from the tappet 

is mistaken for a motor 
knock; but the skilled 
repair man has little 
trouble in finding and 
remedying it, for, even 
if he cannot measure in 
thousandths of an inch, 
he knows, for instance, 
that the ordinary cigar- 
ette paper is about .003 
inch in thickness, and 
from this he can estimate 
.003, .006, or .009 inch. Ordinary thin wrapping paper is well 
known to be about .005 inch; with this alone, or in combination 
with cigarette papers, he can obtain .005, .008, .010, and .011 inch, 
practically all the variation he is likely to need. 

Removing Valve. Getting the valve out frequently gives much 
trouble; the valve is often found frozen to its seat or to the stem 
gummed in its guide. A tool to meet this difficulty is a plain bar 
or round iron about £ inch in diameter, Fig. 166, with one end, for a 
distance of perhaps 2 or 2\ inches, bent up at an angle of about 120 
degrees. To use the tool, insert the short bent end in the exhaust 
or the inlet opening, according to which valve is stuck, until the end 
touches the under side of the valve head, then lower the outer end 
until the bottom of the bent part or point at which the bend occurs 

Fig. 166. Bent Tool Which Facilitates Removal 
of Stuck Valves 


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Fig. 167. Easily Made Tool for Removing 

rests against solid metal. The outer end can now be pressed down, 
and, with the inner end acting as a lever, the valve can be pressed off 
its seat and oiit very quickly. 

To make this clearer, the rod, Fig. 166, is indicated at A, while 
the dotted line shows how it is pressed down and the valve forced out. 
The garage man can elaborate upon the tool when making it for 
himself by using square stock; 
it has the inner end forked so 
as to bear on each side of the 
valve. The form pointed out 
above is the simplest, cheap- 
est, and easiest to make. 

Removing Valve Spring. 
Taking out the valve spring 
is frequently difficult for 
various reasons; perhaps the 

springs are very stiff, or they Valve Spring 

may have rusted to the valve cups at the bottom, or the design 
may not allow room enough to work, etc. At any rate the 
removal is difficult, and a tool which will help in this and which 
is simple and cheap, is in demand. Many motor cylinders are cast 
with a slight projection, or shelf, opposite the valve-spring positions, 
so that one only needs a tool that will encircle the lower end of the 
valve spring and rest upon this ledge and give an outer leverage. 

Types of Valve Removers. 


In working on cylinders that 
do not have this cast pro- 
jection, a tool like that shown 
in Fig. 167 is useful. It con- 
sists of a yoke for encircling 
the lower end of valve spring 
and cup, with a long outer 
arm for prying, and a slot into which a drilled bar is set. This 
bar is placed in various positions according to the kind of motor 
which is being worked on; when removing a valve-spring key, the 
lower end of the bar rests upon the crankcase upper surface, or 
upon the push-rod upper surface if that is extended. After slipping 
the grooved yoke under the spring cup, a simple pressure on the outer 

Fig. 168. Type of Valve-Spring Tool Which 
Leaves the Hands Free 


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end raises the valve so the key can be withdrawn. Then the removal 
of the tool allows the valve spring to drop down, and the valve is free 

The valve spring may be 
removed in two other ways by 
the use of the two tools shown in 
Figs. 168 and 169. In the former, 
the idea is to compress the spring 
only, no other part being touched. 
This tool, once set, will continue 
to hold the spring compressed, 
leaving the hands free — a decided 
advantage over the tool shown in 
Fig. 167. This device consists, as 
the illustration shows, of a pair 
of arms with forked inner ends 
and with outer ends joined by a 
pin. A bent-handled screw draws 
the ends together or separates 
them, according to which way it 
is turned. 

The simplest tool of all is the 
one shown in Fig. 169. It is a 
formed piece of stiff sheet 
metal which is set into 
place when the valve is 
open, and when the valve 
is closed by turning the 
motor, the sheet-metal 
piece holds the spring up 
in its compressed position. 
There are almost as 
many different valve and 
valve-spring removers as 
there are different cars or 
different motors. How- 
ever, the simple makeshift 
shown in Fig. 170 is worthy of mention. Lacking a form of valve- 
or spring-removing tool, this repair man simply supported a plain 


Fig. 169. Substitute for a Valve Spring 

Remover Which Pushes Spring away 

as Motor is Turned 

Method of Compressing Valve Spring without 
Special Tool 
Courtesy of "Motor World" 


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double-ended wrench by means of a wire attached to the water 
pipe on top of the motor; adjusting the length of it so that the 
end of the wrench would just slip under the valve key, he was 
able to remove the pin, which freed the spring and thus the 
valve. Practically the same thing was evolved by another repair 
man who took a wrench of this type and drilled a hole through the 
center of the handle which was first twisted through a right angle. 
Then he bent a piece of stout wire into the form of a hook, one end 
through the wrench, the other over some projection on the engine. 
With the hook removed, the wrench was not radically different from 
any other and could* be used as freely; with the hook in, he had a 
simple valve-spring removing tool. 

Fig. 171. Method of Compressing All Twenty-Four Packard Valve Springs at Once 
Courtesy of "Motor World" 

Twelve-Cylinder Valve Remover. One of the objections raised to 
the twelve-cylinder motor is the trouble of removing and grinding all 
the valves. The Philadelphia Branch of the Packard Company has 
overcome this disadvantage by constructing the special tool shown in 
Fig. 171. This lifts the whole 24 valves at once. It consists of the 
central stand, which rests on the flat top of the crankcase, having a 
long arm and connected levers at the bottom to work the spring com- 
pressors. These, as will be seen at A and B, are really the special 
feature of the outfit, as they are specially constructed to fit around the 
valves in sets of 12 each. A ratchet holds the device locked, so that 
after it is applied and fitted to all the valves, they can be forced up 
and locked; then the matter of valve removal, regrinding, and replace- 


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ment can be handled for the whole 24. At its conclusion, the rigging 
can be unlocked and all 24 valves freed at once. 

Holding Valve Springs Compressed. Many times there is a 
need for holding the spring in its compressed form, as, for instance, 
when the valve is removed with the positive certainty that it will be 
replaced within four or five minutes. In such a case a clamp which 
will hold it in compression is very useful, for it saves both time and 
work. These may be made to the form shown in Fig. 172 in a few 
.minutes' time, for they consist simply of a pair of sheet-metal strips 
with the ends bent over to form a very wide U-shape. A pair of 
these is made for each separate make of valve spring, because of the 

varying lengths, but they are so 
easily and quickly made that 
this is no disadvantage. 

In many shops, after getting 
in the habit of making these 
clamps, the workmen take this 
way of replacing the spring in 
preference to all others. After 
removal of the valve, the spring 
may be compressed in a vise and 
a pair of the clamps put on. 
Then when the valve is ready to 
go back in, the spring is as easy 
This is especially true when replacing 

Fig. 172. 

Spring Clamp, Which Is Easily Made 
kves Much Work and Trouble 

to handle as any other part, 
the spring retainer and its lock. 

Stretching and Tempering Valve Springs. Many times when 
valve springs become weakened, they can be stretched to their former 
length, so that their original strength is restored. This can be done 
by removing them and stretching each individual coil, taking care 
to do it as evenly as possible. When well stretched, it is advisable 
to leave the coils that way for several days. This method will not, 
of course, restore the strength permanently; it is at best a makeshift, 
for in the course of a few thousand miles the springs will be as bad 
as before. 

Sometimes weakened valve springs may be renewed by retem- 
pering, on the theory that the original temper was not good or they 
would not have broken down in use. The tempering is done by 


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heating to a blood-red color and quenching in whale oil. If this 
is not successful, new springs are advised. 

Adjusting Tension of Valves. Unless all the valves on a motor 
agree, it will run irregularly, that is, all the exhausts must be of 
the same tension, and all the inlets must agree among themselves, 
though not necessarily with the exhausts. Many times irregular 
running of this kind, called galloping, is more difficult to trace 
and remove than missing or some other form of more serious trouble, 
and it is fully as annoying to the owner as missing would be. 

To be certain of finding this 
trouble, the repair man . should 
have a means of testing the 
strength of springs; a simple device 
for this purpose is shown in Fig. 
173. As will be seen, this consists 
of sheet-metal strips and connect- 
ing rods of light stock, with a hook 
at the top for a spring balance and 
a connection at the bottom to a 
pivoted hand lever for compress- 
ing the spring. By means of the 
center rod at R and the thumb 
screw at the bottom, the exact 
pressure required to compress the 
spring to a certain size may be 
determined. Suppose the spring 
should compress from 4 inches to 
3| inches under 50 pounds. By compressing it in the center portion 
of the device, so that the distance between the two adjacent strips of 
metal indicated by S is just 3§ inches, the spring balance should show 
just 50 pounds. If it shows any less, the spring is too weak and 
should be discarded; if it shows any more, it is stronger than normal 
— which is desirable if all the other springs on the same engine are 
also stronger. 

If only a quick comparison of four springs is desired, the device 
can be made without the bottom lever, as the setting of S at a definite 
figure — say to a template of exact length — would call for a certain 
reading of the scale of the spring balance. 

Fig. 173 

Simple Rigging for Testing Valve- 
Spring Pressure and Strength 


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Cutting Valve-Key Slots. Cutting valve-key slots in valve 
stems is another mean job which the repair man frequently meets. 
He runs across this in repairing old cars for which he has to make 
new valves; and at other times for other repairs. The best plan is to 
make a simple jig which will hold, guide, and measure all these things 
at once, as all are important. Such a jig is shown in Fig. 174. It con- 
sists of a piece of round or other bar stock, in which a central longi- 
tudinal hole is drilled to fit the valve stem, one end being threaded for 
a set screw. Near the other end of the jig, three holes, of such a 
diameter as to correspond with the width of key slot desired, are 
drilled in from the side. These are so placed that the length from 
the top of the upper hole to the bottom of the lower gives the length 
of key seat desired. Opposite the three drilled holes and at right 
angles to them, another hole is drilled and tapped for a set screw. 

To use the device, slip the 
valve in place and set the bottom 
screw of the jig so as to bring the 
three drilled holes at the correct 
height for the location of the key 

Fig. 174. Cheap Jig for Slotting Valve Stems , m, ,1,1 1 1 

seat. Then the three holes are 
drilled, and the valve is moved upward so that the space between 
the holes is opposite a guide hole, and two more holes are drilled to 
take out the metal between. The five holes will give a fairly clean 
slot, which needs a little cleaning out with a file before using. 

Grinding the Valves. The new driver must learn when to grind 
his valves, that is, how often, and he must also learn to do the 
work properly. There is no hard and fast rule which can be given 
aside from grinding when it is necessary. A careful driver may get 
four to five thousand miles out of his valves with one grinding, while 
another may get only one or two thousand miles with the selfsame 
car and engine. There are many factors which enter into the life 
of a valve seat, and, in the frequency of grinding, all of these have 
to be taken into account. Some of these are: imperfect cooling of 
the seats; too strong springs, which cause hammering and thus wear 
out the seats prematurely; over-lubricating, which causes spitting 
and sooting, both of which reduce the active life of the valve seat. 

Another cause for frequent grinding is contributory negligence 
on the part of the driver. He does not examine them as often as he 




should, and the result is failure to discover something in the way of 
soot or dust caught in between the valve and seat, which is being 
gradually pressed into the seat. 

Regrinding Process. When either the valve head or seat has 
become worn or pitted, it must be reground as follows: Secure a small 
amount of flour of emery, the finer the better, and mix this into a thin 
paste using cylinder oil, or graphite, or both. Loosen the valve, dis- 
connect all attachments, remove the valve cap above, and free the valve 
in a vertical direction. Now lift it out, place a daub of the emery 
paste on the seat, and replace the valve. With a large screwdriver 

Fig. 175. Two methods of Grinding-In Valves: (A) by Hand, Using a Screwdriver; 
(B) with Brace, Screwdriver and Bit 

press the valve firmly in place, at the same time rotating it about 
one-fourth of a turn to the right and then the same amount to the left. 
This is shown in Fig. 175-A, in which S is the screwdriver, V 
the valve, and VS the valve seat. Note how the right hand presses 
down on the screwdriver and turns it at the same time. While this 
is being done, the left hand should be held right below the valve 
stem with one finger just touching it. After moving back and forth 
about eight or ten times, lift the valve off its seat with the finger, 
turn it through a quarter-turn, and drop it back into place. Then 
repeat the grinding until the whole circle has been covered several 
times. Then remove the valve and clean off both moving member 
and seat with gasoline. Mark the seat on the valve with a slight 


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touch of Prussian blue, replace the valve, and twirl it around 
several times so as to distribute the color. Remove the valve 
without touching the seat portion on it or in the cylinder, and 
examine both. If the grinding process has been complete and 
accurate, the color will have been distributed in a continuous 
band of equal width all around the surface. If not continuous, or 
not of equal width all around, the task is but partially completed 
and must be continued until the full streak results. On the first 
attempt at this rather delicate piece of work, it is well to call in 
an expert repair man to examine and pass upon the job. 

In Fig. 175B the same process is shown, but a brace, screw- 
driver, and bit are used in place of the slower screwdriver. This 
method would hardly be advocated for an amateur attempting his 
first job of valve grinding, but as soon as some proficiency has 
been attained, it is the best, quickest, and most thorough method. 

There are, of course, a number of tools now on the market 
for grinding valves; some of these are constructed in such a man- 
ner as to do all the work, namely, the partial turn and reverse on 
the grinding stroke, then the lift and partial revolution, then drop- 
ping the valve down on the seat again, and repeat. The use of 
one of these tools reduces the act of valve grinding to a matter of 
knowing how to apply the emery and when and how to stop. 

Noisy Valves. Sometimes the valves get very noisy and 
bother the driver a great deal in this way, that is, the wear in the 
valve-operating system becomes so considerable as to make a 
noise every time a valve is opened or closed. With the engine 
running at slow speeds, each one of these is heard as a separate 
small noise and not much is thought of it, but when the motor is 
speeded up, the noises all increase and become continuous and 
very noticeable. This may be remedied by taking up the valve 
tappets which usually are made adjustable for this purpose. 
They should be taken up until there is but a few thousandths of 
an inch between the valve tappet and the lower end of the valve 
stem. A good way to measure this is to adjust until one thickness 
of tissue paper will just pass between the two; then there is approxi- 
mately 0.003 inch between them. 

The clearance between the end of the valve stems varies a 
great deal in different motors. This depends mainly upon the cam 




Com, Shaft 

clearance, the length of the valve stems and the cooling of the stems. 
A variable thickness gauge may be had from any supply house. 
Troubles with Inlet Valve. The inlet valve is often the seat of the 
trouble, and missing here is generally caused by a weak or broken 
spring, a bent stem, or a carbonized valve. If the valve spring has 
lost its temper and broken down, the tension will be insufficient to 
properly hold the valve on its seat, and the gas will partially escape 
and so cause missing. The insertion of an iron washer or two will 
increase the tension of the defective spring and serve as a temporary 
road repair. A broken spring may be similarly repaired by placing a 

washer between the broken ends. 
A bent valve stem should be 
taken out and carefully straight- 
ened by laying it upon a billet of 
wood with another block inter- 
posed between it and the ham- 
mer. Only a very little force is 
needed, and the stem should be 
repeatedly tried until it slides 
freely in its guide. 

Valve Timing Gears. As has 
been stated, the camshaft is gen- 
erally gear-driven from a crankshaft by a pair of two-to-one reduc- 
tion gears; these are simple spur gears with straight or spiral teeth. 
As the one gear is keyed to the crankshaft and the other to the cam- 
shaft, it is highly important that these two gears be meshed in an 
exact manner. If one of them is out as little as one tooth, the differ- 
ence in the running of the engine will be very marked. The timing 
previously mentioned under the head of Valve Timing will not be 
obtained; either all operations will occur later than the valve timing 
diagram and instructions call for, or else all these will be earlier. In 
either case, there will be a loss of speed and power, accompanied 
by noise, and the engine will not throttle down or speed. 

To avoid this difficulty for the repair man, all gears are set and 
marked correctly at the factory. The marking is done in several 
ways. One is by lines cut on the gears when correctly meshed, so 
that if the gears are correctly meshed later, the part of a line on one 
gear will be a prolongation of the part on the other. Another way is 

Centre Punch Marks 

Fig. 178. Marking Timing Gears Is a Simple 
Job and Saves Much Time and Trouble 


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to use center punch marks, one mark between the teeth on one and 
on the tooth meshing with these on the other. Then, if a second 
place has to be marked, two prick-punch marks are used in a similar 
manner, and if a third is marked, three punch marks. A third method 
is the use of numbers, the first pair marked being numbered 1 on each 
gear at the point of meshing, the second pair marked 2 on each, etc. 
For the second method, all that is necessary is a prick punch and 
hammer, used in the manner shown in Fig. 178. When there are but 

Fig. 179. Method of Marking Timing Gears by Means of Numbers 

two gears, as in the case shown, it is easy to make one hole between 
two teeth on one gear and another which lines up with it and as close 
to it as possible on the other gear. Where there are three, four, or 
more gears, the usual practice is to make the first and third with two 
prick-punch marks on each, the others with three, four, etc. 

For the third method, or the use of numbers, see the set of gears 
shown in Fig. 179. This figure is that of the engine whose timing 
was described and shown in Fig. 162. It has four gears; from right 

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to left they are camshaft gear, crankshaft gear, idler gear, and magneto 
gear. As will be noted, the crankshaft gear meshes with two others, 
so it must be marked in two places, 1 where it meshes with the cam- 
shaft gear and 2 where it meshes with the idler. A moment's thought 
will show, however, that it could never be replaced in the wrong 
manner, since it is marked only on the outside face, its 1 and # figures 
show where it matches a 1 mark on one gear and a 2 mark on another. 
Chain Driye for Camshafts. The silent chain has gained much 
popularity for camshaft and accessory drives in the last two years for 
a number of reasons. It saves the use of idler gears in such cases as 

Fig. 180. Silent-Chain Drive for Packard Twelve, Showing Method of Marking 

that just illustrated and described; it allows the placing of the cam- 
shaft and other shafts anywhere desired (at least in so far as the gear 
is concerned) ; it is more quiet than the gear drive in the prescribed 
position which the two-to-one reduction necessitates; it is less 
expensive to construct and apply, and it weighs slightly less. The 
teeth on the silent-chain gearing are called sprocket teeth, while those 
on the two-to-one reduction are called gear teeth. 

In the silent-chain drive for camshaft and accessories, which is 
shown in Fig. 180, it will be noted that there is a line scribed vertically 
across both gears and the crankcase, with prick-punch marks on the 
case at A, on the camshaft sprocket at BB, and on the crankshaft 


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sprocket at CC. This makes its correct adjustment easy. A 
straightedge is laid across the case marks, the crankshaft sprocket 
turned to this line, and the chain put in place but not joined; finally 
the camshaft sprocket is turned to the line, the chain moved to hold 
it in this position, and its ends joined. By this method, there would 
be two possible positions for the camshaft sprocket, as compared with 
the crankshaft sprocket and line on the case. These could readily 
be distinguished as correct and in- 
correct as soon as the chain is applied 
and the engine given a couple of 
turns. If incorrect, it is simply a 
matter of lining them up again by 
opening the chain, turning the cam- 
shaft gear through 180 degrees, 
putting the chain back on and join- 
ing its ends a second time. 

Other Parts of Valve System. 
There are a number of other parts in 
the valve group whose names and 
functions should be explained, for 
these $re of interest to both the 
owner and the repair man. The 
repair man should know what work 
they do in order to be able to repair 
them successfully. Fig. 181 shows 
an overhead-valve system in which 
the camshaft is in the usual place 
in thecrankcase; long push rods are 
used with rocker arms, or levers, at 
the top. This is mentioned because 
many, in fact the majority of, motors with overhead valves have 
an overhead camshaft like the Chalmers, Fig. 156. 

In this figure the various parts are named. The rotation of the 
camshaft brings the cam around so that it lifts the roller and plunger 
which has the adjusting screw and its lock nut at the top. The top 
of the roller bears against the bottom of the push rod, and the 
upper end of the push rod operates the valve rocker lever which is held 
in the support. At the other end of the valve rocker lever a roller 


Fig. 181. Typical Overhead- Valve Layout, 
Showing Complete Mechanism 


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presses against the top end of the valve stem and pushes it down from 
off the valve seat against the pressure of the spring, the upper end 
of which is held by the cup and cup pin and the lower end rests 
upon the upper surface of the valve cage. The latter is made so 
that its central upward extension also forms the valve guide. The 
valve cage is screwed down into the cylinder head with packing to 
make a gas-tight joint. It carries the valve seat and is cored out for 
the gas passages through which the gas enters (or leaves). 

- When the valve in pockets is substituted for the long push rod, in 
either the L-head or in the T-head cylinder, the construction is about 
the same as if the upper right-hand valve group were lifted bodily, 
turned upside down, and placed so that the upper end of the valve 
stem, upon which the roller rests, comes into contact with the adjust- 
ing screw. In that case, the 
valve lifter would be called the 
push rod, and the valve cage 
would become a part of the cylin- 
der with an integral or, in some 
cases, a removable valve guide. 
Push Rods and Guides. As 
can be seen from Fig. 181 and 
the explanation accompanying 
it, the push rod and its guide, or 
lifter and guide, become impor- 

Fig. 182. Method of Holding Two Push Rods *"*• The sN* ° f ^ CBm is 
with Yoke and Single Central Nut guch ^ ft deals ^ ^Jfe,. ftnd 

lower end of the push rod, or lifter which holds it, a fairly heavy 
blow sideways each time it comes against it. If the roller and 
rod are not a perfect fit, something will yield each time, and the 
roller will wear oval in a short time. The movement and noise 
will increase rapidly and soon become very objectionable. The only 
remedy is replacement. These guides are held in place in one of two 
ways; either individually by means of a pair of bolts or in pairs by 
means of a yoke and a single central bolt and nut of large diameter. 
The Locomobile, Fig. 151, shows the former method; the Haynes, 
Fig. 152, the latter method. These, however, are end views which do 
not bring out the point as clearly as Fig. 182. Here the arrow points 
to the nut midway between the two push rods, which holds down 


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the yoke that rests upon shoulders on the push rods and holds them in 
place. From a repair man's point of view, the latter construction is 
better, for the push rods can be removed and replaced much more 
easily and quickly. 

Valve Cage Repairs. When the valves are in overhead cages, it 
is highly important that they fit tightly in the cylinder head; they 
must be ground in as carefully and as tightly as the valves are ground 
into their seats. Where a shop handles a good many motors of the 
overhead-valve type, it is desirable to make a rig to do the grinding 
easily. One of these rigs is shown in Fig. 183. It consists of a shaft 
and handle with lock nuts for 
the valve cages used on Buick 
cars. On these cars, it is in two 
parts; the cage proper, and the 
locking member which screws into 
the cylinder. Obviously the cage 
is the one to be ground in. The 
rig shown slides in the central 
opening, that is, fits in the Valve 
guide, and has a lock nut top 
and bottom to fasten it tightly. 
When fitted into place firmly, the 
right-angle bend in the rig gives 
a handle by means of which the 
cage can be lifted in and out and, 
what is more important, rotated 
on its seat. When the cage is 
prepared, the seat is given a little oil and emery or oil and powdered 
glass or prepared valve grinding composition, the cage is set in place 
and ground in the same as a valve, that is, with •one-third to one-half 
rotations in one position, then lift, move around, and repeat in the 
new position, continuing this until the whole surface of the cage in the 
cylinder has been covered twice. This should result in a good seat. 

When the valves in an overhead motor need grinding, the valve 
and cage are taken out completely and held in an inverted position 
in a vise or other clamp, and the valve ground in to the seat in the 
cage in the regular way. It is said this can be done very rapidly and 
well by chucking the valve stem, as it projects from the cage, in a 

Fig. 183. Simple Fixture for Grinding-In 
Overhead Valve Cages 
Courtesy of "Motor World*' 


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Fig. 184. Method of Curing Valve- 
Guide Leak Quickly and Cheaply 

shown in Figs. 184 and 185. 

lathe rotating at a very slow speed, and operating the cage by hand, 
that is, slide the cage back, apply grinding compound, then move the 

cage up to the rotating valve and hold 
it with the hand while the valve is 
turning with the lathe. In holding it 
thus, the pressure endwise should be 
very light. 

Valve Guides. The valve stem 
must be a tight fit in the guide, other- 
wise air will leak through into the 
combustion chamber and dilute the 
mixture, or the compression will leak 
out, or both. Any valve leak will affect 
the running of the motor, so it should 
be stopped at once. Two methods of 
temporarily remedying small leaks are 
A simple leather washer with a small hole 
through the center, which fits tightly over the valve stem, is pressed 
up around the outside of the guides, as shown in Fig. 184. This 
simple repair was very effective, and the leather washers lasted an 

astonishingly long time. The other 
method, Fig. 185, shows practically the 
same result arrived at differently. In 
this case, old spark-plug shells, with con- 
siderable recesses in the center pajt, were 
turned down so as to fit around the bot- 
tom of the guides. These recesses were 
packed with felt or other available pack- 
ing, care being taken to pack the recesses 
tightly. Then the whole thing was held 
up in place by a lighter spring put inside 
the main valve spring. By adding a few 
drops of oil to the packing now and then 
to keep it soft, it lasts almost indefinitely. 
The valve-guide hole in the cylinder 
is generally made as long as possible, 
both to give a straight and true hold on the valve stem and thus 
maintain its straightness in spite of the heat, and to give a long 


Valve Cjuide 

fparh Fluq 
-Shell J 


Valve Stem 

Fig. 185. Remedy for Leaky Valve- 
Stem Guide, Using Old Spark 
Plug and Felt 


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wearing surface. This length and the need for accuracy through- 
out makes the valve-guide hole an awkward surface to repair. 
When worn beyond any hope of simple repair, it is best to ream it out 
and press in a bronze bushing so that the valves can still be used. 
An excellent tool for this purpose, developed for Dodge motors but 
which is usable for almost any motor, is shown in Fig. 186. This con- 
sists of a high threaded bushing which is clamped to two diagonal 
cylinder studs. The thread inside the bushing is very fine. A long 
tube, with the lower end bored out to take a standard reamer, is 
screwed into it. The top is squared and a handle is made to fit it. 
When the handle is turned, the 
tube is gradually screwed down 
into the cylinder, carrying the 
reamer slowly but truly down 
through the valve guide. This 
rigging is simple, easily made, and 
gives accurate results. When 
the valve-guide hole is reamed, 
the bushing can be turned up 
and pressed in with any form of 
shop press. 

Valve Caps. The plug which 
fits into the top opening in the 
cylinder through which the valve 
is put in place and removed is 
called the valve cap. Sometimes 
it has external hexagonal sides 
so it can be easily removed, but 
more often it has an internal hexagon, or internal ribs. The 
latter form can be removed most easily by constructing a special 
tool, consisting of a cylindrical member, with a bottom diameter 
slightly larger than the opening in the valve cap, with four (or 
mbre) teeth, or projections, set into the bottom of this to match the 
ribs inside the cap. A central hole is drilled for a bolt with spark- 
plug threads at the bottom. To use the member, remove the spark 
plug, set the device in place, slip the central bolt in and screw it down 
into the plug to hold the whole thing in place, then apply a 
wrench to its upper square surface and remove the valve, cap and all. 

Fig. 186. 

Rigging for Reaming Out Valve- 
Stem Guide Holes 
Courtesy of "Motor World" 


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Fig. 187. Reamer for Clearing Out 

Threads of Valve Cap 

Courtesy of "Motor World" 

It can be laid aside just as removed, and when the work is concluded, 
the whole thing can be screwed back in, the central screw loosened, 

and the rig removed from the cap. 
SometiHaes the threads in the 
cylinder into which the valve cap 
screws become dirty, slightly cut 
up, or marred so that the cap does 
not screw in or out readily. By 
taking an old valve cap of the same 
motor and same threads and fluting 
these in a milling machine, as indi- 
cated in Fig. 187, a neat tap can 
be made which will clean out the 
threads in a jiffy. It is simple, effec- 
tive, and cheap. 

Cleaping Camshaft Gears. On the majority of engines, the cam- 
shaft and other gears or the silent chain which replaces them, are lubri- 
cated automatically by the running of the engine as they are by-passed 
in on the engine lubricating system. This is an excellent feature, but 
it leads to neglect. These gears or sprockets are sure to wear, and 
the metal worn off remains in the case. Moreover, dust and the 

impurities of the oil are bound 
to get in. The foreign matter 
has a cutting action on gears, 
chains, or bearings, so the 
gear case should be cleaned 
out frequently. This is done 
best by thoroughly flushing 
out the case and the gears, 
or sprockets and chains, as 
the case may be, with kero- 
sene. After using the kero- 
sene, use gasoline along with 
the kerosene to clear away any 
remaining dirt or oil. After 
applying the gasoline, wait long enough for it to evaporate before 
replacing the parts, while it might be considered extravagant to use 
both, it really is economical of time. 

Fig. 188. Checking up Camshaft in Milling 


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Twisted Camshafts. With the present form of camshaft having 
the cams forged integral, troubles and irregularities between one 
cylinder and another, which the repair man finds difficult to trace or 
run down, sometimes develop in the running of the engine. A fairly 
light camshaft will sometimes .become twisted, usually right 
at a cam where the stress is. When trouble of this kind is indi- 
cated, the camshaft should 
be removed and tested. A 
good way to do this is to 
place the shaft in the milling 
machine with the index head 
set so that one revolution of 
the shaft can be divided 
into four equal parts. Place 
a thin disc in the arbor, 
then mount the shaft and 
bring it up to the disc. 
Choose one of the cams and 
set the disc to the exact 
center of the point of it. 
Then, by turning the shaft a 
quarter-turn each time, the 
other cams can be tested with 
their relation to this one. 
Sometimes a difference of f 
inch will be found in this 

Way. The lay-OUt for this is Fig. 189. Section through Ledru (French) 

• T* m 100 Camless Engine. The Rotary Gear- 

Seen in r lg. loo. • Driven Sleeve Displaces All Cams 


A method of avoiding cams, and with them all cam troubles, is 
the use of a sliding sleeve in place of a valve, slots in the sleeve cor- 
responding to the usual valve openings, both as to area and timing. 
The sleeves may be operated by means of eccentrics by various lever 
motions, or by a direct drive by means of agear mounted on a separ- 
ate shaft. f 

Gear Control. An example of the application of a worm and 
gear for this purpose to a French two-cycle engine is shown in 


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Fig. 189, although there is nothing in its construction which would 
prevent its use on the more usual four-cycle engine. 

In this figure, P is the usual crankshaft, Q the large end of the 
connecting rod K, while A is the piston and R the crankcase, no 
one of these differing from those in other engines. On the crankshaft 
there is a large gear F, which drives a smaller gear E, located on a 
longitudinal shaft above and outside of the crankcase. On this shaft 
is located a worm gear D, which meshes with a worm C formed inte- 
gral with the sleeve surrounding the piston B. Aside from this worm 
gear, the sleeve is perfectly cylindrical, being open at both ends. It is 
placed outside of the piston, between that and the cylinder walls. 
At its upper end, it has a number of ports, or slots, cut through it, 
which are correctly located vertically to register, or coincide, with the 
port openings in the cylinder wall when the sleeve is rotated. One 
of these is seen at H; the exhaust, while 90 degrees around from it, 
and hence invisible in this figure, is a similar port for the inlet. As 
the crankshaft rotates, the side shaft carrying the worm is con- 
strained to turn also. This turns the worm which rotates the worm 
wheel on the sleeve. In this way, the openings in the sleeve are 
brought around to the proper openings in the cylinder, and the com- 
bustion chamber is supplied with fresh gas, the burned gases being 
carried away at the correct time in the cycle of operations. 

With a motor of this sort, the greatest question is that of lubri- 
cation. The manner in which it is effected in this case is by means 
of the large wide spiral grooves shown at 00 and the smaller circular 
grooves at the upper end M. Another method which renders this 
problem more easy of solution is by the machining of the sleeve; 
during this operation much metal is cut away along the sides so that 
the sleeve does not bear against the cylinder walls along its whole 
length but only for a short length at the top and a still shorter length 
at the bottom. 

Knight Sleeve Valves. In the last few years, tremendous 
progress has been made here and abroad with the Knight motor, 
named after its Chicago inventor. In many important factories 
this valve has displaced the poppet valve. In a regular four-cylinder 
four-cycle engine, the valves consist of a pair of concentric sleeves, 
the openings in the two sleeves performing the requisite functions of 
valves in the proper order. These sleeves, as Fig. 190 shows, are 


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actuated from a regular camshaft — running at half the crankshaft 
speed and driven by a silent chain — by means of a series of eccentrics 
and connecting rods. In the figure, A is the inner and longer sleeve 
and carries the groove or projection C at its lower end. The collar 
actuating the sleeve is fixed around and into it. This collar is 

Fig. 190. Willys-Knight Engine in Which Eccentrics and Sliding Sleeves Replace 
Cams and Valves 

attached to the eccentric rod E, which is driven by the eccentric shaft 
shown. The collar D performs a similar function for the outer 
sleeve B. 

At the upper ends of both sleeves, slots G are cut through. 
These slots are so sized and located as to be brought into correct 

417 Digitized by G00gle 


Royal Automobile Club's Committee Report on Knight Engine 

Motor horsepower— R. A. C 38 . 4 22 . 85 

Bore and stroke 124 by 130 96 by 130 

Minimum horsepower allowed 60 . 8 35 . 3 

Speed on bench test 1200 r.p.m. 1400 r.p.m. 

Car weight on track .3805 lb. 3332.5 lb. 

Gar weight on road 4085 lb. 3612.5 lb. 

Duration of bench test 134 hours 15 min. 132 hours 58 min. 

Penalized stops None None 

Non-penalized stops Five — 116 min. Two — 17 min. 

Light load periods 19 min. 41 min. 

Average horsepower 54.3 38.83 

Final bench test 5 hours 15 min. 5 hours 2 min. 

Penalized stops None None 

Light load periods 15 min. 1 min. 

Average horsepower 57.25 38.96 

Mileage on track 1930.5 1914.1 

Mileage on road 229 229 

Total time on track 45 hours 32 min. 45 hours 42 min. 

Average track speed 42.4 m. p. h. 41 . 8 m. p. h. 

J First bench .679 pt. .739 pt. 

test 613 lb. .668 lb. 

■ Final bench .599 pt. .749pt. 

I test 5411b. .6771b. 

Car miles per gallon . . . . /On track. . . . 20.57 22.44 

\Onroad 19.48 19.48 

Ton miles per gallon /On track 34.94 33.37 

\Onroad . 35.97 31.19 

relation to one another and to the cylinder ports and the exhaust at 
II and inlet at J, in the course of the stroke. 

It might be thought that the sliding sleeves would eat up more 
power in internal friction than would be gained, but a very severe 
and especially thorough test of an engine of this type, made by the 
Royal Automobile Club of England, an unbiased body, proved that 
for its size the power output was greater than that of many engines 
of the regulation type. Moreover, the amount of lubricating oil 
was small. 

The results of the test are shown in Table II. After the test 
was concluded, both the sleeves, Fig. 191, were found to show still 
the original marks of the lathe tool. This proved conclusively that 
the principle of this type was right, for the tests were equivalent to 
an ordinary season's running. 

The slots which serve as valve ports are at G, Fig. 191. The 
longer sleeve A is the inner one. At the bases of the sleeves are 
the collars and pins D by which the connecting rods are attached. 

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The surfaces of the valves are grooved at J to produce proper distribu- 
tion of oil. 

The Knight type of motor has been adopted by a number of 
well-known firms in America, such as the Stearns, Willys, F. R. P., 
Brewster, and Moline Companies. These engines are noted for 
their silent running and for their efficiency. The Moline-Knight 
motor was subjected to a severe continuous-run test of 337 hours, 
under the auspices of the A. C. A. authorities, in January, 1914. 
During this time the motor developed an average of 38.3 brake horse- 

Fig. 191. Sleeves Which Replaced Valves on Knight Engine, after 
137-Hour Bench Test and 2200 Miles on the Road 

power. During the 337th hour the throttle was opened, the motor 
developed a higher speed and a brake horsepower of 53. After the 
test, the motor parts showed no particular evidence of wear. The test 
gives abundant evidence of the endurance and reliability of the sleeve- 
valve type of motor and of the sterling qualities of the product of 
the American automobile manufacturers. 

In addition to the four-cylinder forms just mentioned, the 
Knight type of motor is also made as a six, and, more recently, as 
a V-type eight. In these forms, the basic principle of sliding sleeves 
and their method of operation and timing is not changed. 

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Originally, the Knight motor was installed only in the highest- 
class cars. The firms in Europe which took it up ranked among 
the very first — notably the Daimler, Panhard, Minerva, etc. — but 
in this country it has made little progress among the better cars. 
It is now assuming the rank of a low- and medium-priced motor, being 
available for about $1000, and as an eight, for approximately $2000. 
Timing the Willys-Knight. While the connection between the 
Knight motor sleeves and eccentric rods, and between the rods and 
the eccentric shaft, is more or less permanent, there is the possibility 
of the shaft being bent or twisted during running or dismounting. 
The repair man should know how the motor is timed, in order to cor- 
peap center \*-is ^ rect any faults. As will be noted 

in the timing diagram shown in 
Fig. 192, this is not radically 
different from the poppet-valve 
type. The inlet opens at 15 
degrees past the upper center and 
closes 50 degrees past the lower 
center, a total opening of 215 
degrees. The exhaust opens 50 
degrees before the lower center 
and closes 8 degrees past the 
upper center, a total opening of 
238 degrees. 

The various positions are clearly 
shown in Fig. 193, and make the 
action of the motor much more clear than the simple timing diagram. 
The figures, reading from the left, are as follows: 1 shows the inlet 
just beginning to open; the inner sleeve is coming up, and the outer 
sleeve is going down, so the port opening is increasing in area with 
unusual rapidity. At 2 the inlet is fully open; the inner sleeve is 
coming up, but the outer has reached the bottom of its travel; the two 
ports are fully open and register exactly with one another and with the 
opening in the cylinder. At 3 the inlet has just closed, the inner sleeve 
is still coming up, while the outer sleeve has come up a considerable 
distance. A slightly further upward movement of both inner and 
outer sleeves shows the motor in 4> the top of the compression stroke, 
with all ports closed. This is the point of explosion. In 5 the exhaust 

Fig. 192. Valve Timing 1920 Willys-Knight 


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Me I Opens 
Position 1 

Inlet Open 
Position £ 

Top of 

Inlet Closes Compression Stroke , 
Position 3 Positions- 

Exhaust Opens Exhaust Open Exhaust CI ose9 

Position 5 Position 6 Position T 

Position i 
Fig. 193. Various Stages in Cycle of Knight Sliding-Sleeve Motor 


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is beginning to open, the inner sleeve has reached the top of its move- 
ment and started down, while the outer is almost at the top. At 6 
the exhaust port is fully open, the slots register exactly with each 
other and with the cylinder outlet, both sleeves are traveling down, 
the outer having reached and passed its highest point. At 7 the 
exhaust has just closed, the inner sleeve has reached its bottom 
position and is about to start up, while the outer sleeve is close to the 
bottom. The cycle of inlet, compression, explosion, and exhaust 
has now been completed and is about to start over. Note that 
position 7 is almost exactly like position 1, but a slight additional 
movement of the sleeves is needed to produce the latter. 

The eccentric rods are very similar to connecting rods, as will be 
noted by referring back to Fig. 191. Here E is the eccentric rod 
operating the inner sleeve C, while D is the eccentric rod which oper- 
ates the outer sleeve B. As will be seen, these have an upper end 
exactly like a piston, or wrist pin, except that no bushing is provided. 
At the lower end, it will be noted that the fastening and arrangement 
is just like the big end of a connecting rod. It should be cared for, 
adjusted, and tightened in just the same way to get the best results. 


Successful Operation Requires Two Valves. In addition to 
rotating and reciprocating sleeves and reciprocating valves, the 
rotating valve has been tried, in common with any number of other 
devices intended to supplant the ordinary poppet valve. This 
arrangement on a multi-cylinder motor consisted of a single valve 
for all the cylinders, which extends along the top or side of the 
cylinder head and is driven by shaft, chain, or otherwise, at one end. 
Naturally, this necessitated having the ports cut very accurately in 
the exterior of the valve, or rather the sleeve — as it usually assumed 
the form of a hollow shell — for not alone did it act as inlet and exhaust 
manifold but also as the timing device. This multiplicity of func- 
tions seems to have been its undoing, for the latest types using 
valves of this form have no longer one shell as at first but a pair, 
one for the exhaust valves and one for the inlet valves. In the 
latter shape these have been more successful, but net sufficiently so 
to bring them into competition with the poppet and Knight sleeve- 
valve forms. 

422 Digitized by G00gle 


Roberts Rotary Valve. A motor — a two-cycle riiotor, by the 
way — which has been very successful in motor-boat and aeroplane 

Fig. 194. Roberts Two-Cycle Motor with Rotating Crankcase Valve 
Courtesy of E. W. Roberts, Sandusky, Ohio 

work, although it is not used for motor cars, is the Roberts, shown 
in Fig. 194, with the valve in Fig. 195. This valve is for the inlet 
ports only and is located inside the crankcase, while the cylinders 

Fig. 195. Rotating Inlet Valve of Roberts Two-Cycle Motor 

exhaust freely into the open air, the exhaust issuing directly from 
the cylinders. 


Importance of Handling Exhaust Qases Properly. In all that 
has been said previously on the subject of valves no mention has been 
made of a specific form of valve, everything applying equally to the 
inlet or the exhaust type. Under the subject of carburetors, the inlet 
manifold has been considered in detail. So far, nothing has been said 
of the exhaust gases and the method of handling them. Generally 
speaking, the matter of handling exhaust gases in the past has been 
done with the smallest possible amount of time, trouble, and thought. 
They had to be go.tten rid of, so it was done as easily and quickly as 


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possible. As engines got larger and larger, and as speeds increased, 
there was more and more gas to handle. The growing cry for a quiet 
or a noiseless car necessitated giving the problem more thought, for 
the simple application of a muffler did not entirely eliminate the noise. 
As fuels grew heavier, heat was required to assist in the process of 
vaporizing. In order to apply heat, many designers began to see 
possible uses for some of the gas pouring out at the rear end of the car. 
Today, the handling of the exhaust gases is probably being given as 
much thought as any part or unit on the entire car. 

Forms of Exhaust Manifolds. Ordinarily the exhaust gasee 
emerge from the cylinders into the exhaust manifold. This is gen- 

Fig. 196. Vhw of National Twelve-Cylinder Motor, Showing Particularly Exhaust Manifold 
Courtesy of National Motor Vehicle Company, Indianapolis, Indiana 

erally a cast-iron member of fairly large size held in position by bolts. 
At its rear end, which is round, it is threaded or flanged for the attach- 
ment of the exhaust pipe. This is shown rather well in the National 
engine in Fig. 196. Although this is a twelve-cylinder motor, it 


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has the outside valves, so the exhaust manifold is located there. It is 
a typical cast-iron manifold, differing from the ordinary manifold 
only in having the outlet at the center instead of the rear end. Six 
bolts hold it in place; four on the upper edge, and two on the lower. 
Its interior structure is evidently the same throughout, and no special 

Fig. 197. Section through Peerless Eight, Showing Ribbed Exhaust Manifold 
Courtesy of Peerless Motor Car and Truck Corporation, Cleveland, Ohio 

provision has been made for reducing gas friction. It has no attach- 
ments of any kind. 

Many exhaust manifolds have been cast integral with the cylin- 
der block; this method is quite popular among small car makers, as it 
is used as much to save the expense of machining and fitting and to 


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reduce the weight and number of parts as for any other reasons. 
In the larger sizes it probably never will become popular, because of 
the difficult core work in the foundry which makes cylinder-casting 
cost prohibitive, and thus more than offsets any other saving. 

A number of manifolds have been cast with cooling fins, or flanges, 
on the outside, the effect being to reduce the exhaust heat immediately 
by dissipation; a secondary idea is that of making the casting stiff er 
and stronger and less liable to loss by breakage. A flanged manifold 

Fig. 198. Three-Quarter Rear View of Cadillac Motor in Chassis, Showing Exhaust Manifold 

and Pipes in Duplicate 

is shown in Fig. 197, which illustrates the Peerless eight-cylinder 
motor; the exhaust manifold is marked at A and B. The section 
taken at A shows the full exterior size; the boss, through which a 
holding bolt passes, is seen in elevation. At B, however, the section 
is taken through a pair of bolts, so the section appears smaller than it 
actually is. 

In the usual eight- and twelve-cylinder motor and in some sixes, 
a pair of manifolds, each with its own exhaust pipe and muffler, are 
used. It has been found by experience that^the tremendous volume 


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of gas to be handled, the speed at which it had to be handled, and the 
necessity for silence called for a separate exhausting system for each 
group of cylinders. These were problems, aside from the fact that it 
was more simple structurally to handle the exhaust in two manifolds. 
A double-manifold construction is shown in the Cadillac, Fig. 198, 
which is a view of the rear end of the engine. The two manifolds 
for the two sides can be seen readily; also the two separate exhaust 
pipes, wrapped with asbestos where they pass the dash and other 
wooden parts. A further view of this car is shown in Fig. 199, the 
chassis from above, in which the two separate systems can be fol- 
lowed back to the mufflers just forward of the rear axle on either side. 

Muffler. The purpose of the muffler is to reduce the pressure of 
the gases by expansion to a point where they will emerge into the 
atmosphere without noise. This is generally done by providing a 
number of concentric chambers; the gas is allowed to expand from the 
first passage into the much larger second one, then into the still larger 
third one, and so on, to the final and largest passage, which is con- 
nected to the pipe leading out into the atmosphere. This is not as 
simple as it sounds, for, if it is not well and wisely done, there will be 
back pressure which will reduce the power and speed of the engine, 
cause heating troubles, and may possibly cause the motor to stop. 

The process of spraying water into the muffler has been tried, 
but on account of its first cost and lack of positive beneficial results, 
it has been abandoned. The actual construction of the muffler, 
however, takes a number of different forms. A number of forms are 
shown in Fig. 200. Baffle plates are used in the form at A, the gases 
being forced by them to expand from one chamber to the next so all 
the speed and pressure is dissipated before the outlet is reached. In the 
form shown at B, the gases are allowed immediate and sudden expan- 
sion from a comparatively small pipe into a large chamber. A series 
of annular chambers of large diameter but small depth forms the 
basis of C; the gas enters each of these chambers from the center 
through small holes, thence exhausting outwards, each chamber hav- 
ing an outlet around its circumference. In the form at D, the gases 
enter the central small pipe, escape through holes at its far end, which 
is blocked off, into the first concentric chamber where they travel 
to the front end where holes allow it to pass out into the second con- 
centric chamber and out into the atmosphere. This is a widely used 


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_Bafr/e Plates 


. ^ 

. -* 

, ~^. ^. ^ 

» > 

» >s 

, ^s 

> ^ 

. S \ "N 










A 1 







C \ 




i i 4 

Cental Pipe' 

V N^ 


Fig. 200. Five of the Many Different Types of Mufflers 
Courtesy of N. W. Henley Publishing Company, New York City 


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type. Cone-shaped baffles which force the gases to expand and then 
pass through very small apertures and expand again form the basis of 
E. This is the so-called ejector type, the passage of the gases from the 
large to the small end of the various cones being supposed to create 
a suction behind it which draws the gas out from the exhaust pipe 

Muffler Troubles. When the engine mysteriously loses power, 
it is well to look at the muffler. A dirty muffler filled up with oil and 
carbon, which results from the use of too much oil in the motor, will 
choke up the passages so that considerable back pressure is created. 
When this is suspected, tap the muffler all over lightly with a wooden 
mallet, and the exhaust gases will blow the sooty accumulations out. 

Cut-Outs. Formerly, the majority of cars were equipped with 
muffler cut-outs. By pressing the foot on the button operating the 
cut-out, the engine was allowed to exhaust directly into the atmos- 
phere, cutting out the muffler. It served as a warning signal; it gave 
a good means of checking up the firing of the various cylinders; and 
several years ago, it was supposed to give greater power. Since its 
use was overdone, many cities and states prohibited such an arrange- 
ment on a car. Furthermore, the power loss has been proved a 
fallacy; consequently, the cut-out has gradually gone out of use. 

On six-cylinder motors, and particularly motors with more than 
six cylinders, the sound of the exhaust is not an accurate guide to the 
firing of the cylinders, except for the expert mechanic with unusually 
keen hearing. The explosions of the six-, eight-, and twelve-cylinder 
engine overlap to such an extent that the weak explosion between two 
healthy ones cannot be detected. A missing cylinder can be found 
in this way, but not one that is simply getting a poor or weak spark. 



Though nearly all successful automobile motors, as well as most 
other internal-combustion engines, are water-cooled, there is so 
much obvious fault to be found with this system of securing a result 
— involving first the generation of heat and then its waste by a com- 
plicated refrigerating system, instead of its utilization by converting 
more of the heat units into useful work — that it is scarcely credible 
that water cooling can persist indefinitely. 


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Water-Jacketing. The first essential in water-cooling a motor 
is to, provide the cylinders with water jackets, through which the 
cooling water is circulated in contact with the outside of the walls 
within which the heat is liberated. 

Water jackets are of two types, integral and built-up. The latter 
system of construction, though adding to complication and conducive 
to leakage, permits of lighter construction, besides diminishing the 
likelihood of hidden flaws in the cylinder castings, which, with cored 
jackets, are not likely to reveal themselves until they cause a break- 
down, perhaps after the engine has been long in use. 

Integral Jackets. With integral jackets, the usual system is to 
form the jackets by cores, in the founding, so that there are no open- 

Fig. 201. Detailed View of Cadillac Cylinder Chassis 

ings in the jackets except those for removing the core sand and wires 
and for connecting the pipes of the circulating system. In many of 
the best examples of motor design, however, the core openings are 
left very large but with plane faces, and are closed by screwed-on or 
clamped-on plates, thus making the construction practically a 
compromise between the completely integral and the completely 
built-on jackets. 

For example, in such modern construction as that shown in 
Fig. 2, a large plate will be noted on the ends of the cylinders. This 
covers a tremendous core hole, by the use of which the internal 
construction of the water jackets is made practically perfect in the 
foundry. This also allows easy inspection and cleaning, the removal 
of the two end plates enabling a person to see right through the water 



jacket from end to end. This latter-day construction overcomes all 
objections previously raised against troubles with complicated water- 
jacket cores. A detail of this cylinder block, showing clearly the 
arrangement of the end plates, the water passages around the cylin- 
der bores, and other points, is presented in Fig. 201. The designers 
of large block castings for cylinders were forced to provide for easy 
inspection of this kind for self-protection, although in this connection, 
it is no more than fair to state that foundry men have made just as 
rapid advances in the art of casting automobile-eng'ne cylinders and 
other complicated parts as the designers of machmes have made in 
every other way. 

Built -On Jackets. There are a number of forms of built-on 
water jackets, but few of these are in use at present. The best of 
these was the old Cadillac jacket, a cylindrical one-piece member with 
a junk ring, top and bottom, to hold tightly against water leakage. 
The form more often used is the applied plate, or sheet, which must be 
held by screws, flanges, or clamps. As these are not really success- 
ful in holding the water continuously, particularly against the com- 
bination of hot water, internal pressure, twisting, and racking action 
which comes from traveling over bad roads at high speeds, they are 
giving way to the older form of jacket. 

An important advantage of applied jackets of the type just 
described is their freedom to yield in case the water freezes in them. 
The danger of cracked cylinders, which not infrequently results 
from exposure to cold weather in ordinary automobile motors having 
jackets integral with the cylinder, is eliminated. 

A particularly neat method of water-jacketing, which has been 
applied with some success abroad, consists in the electro-deposition 
of copper jackets on the cylinders, through the use of wax molds, 
to produce the desired forms. Jackets thus applied, though some- 
what expensive, are said to be practically indestructible and com- 
pletely proof against leakage. 

Welded Applied Jackets. The method of welding by the oxy- 
acetylene process promises to produce a cylinder with a cast-iron 
center and a sheet-metal water-jacket exterior made of pressed steel 
or of flat plates. The designers who consider this combination the 
best in that the thin sheet metal of copper or steel is lighter, radiates 
more heat, and will yield under freezing strains, will now be able to 


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obtain such a combination at a reasonable cost. So far, however, 
it has been restricted to racing cars, in which the lightest possible 
weight is obtained regardless of cost. In a car to sell at an ordinary 
price, the cost might be prohibitive. 

Radiators and Piping. It has often been pointed out that all 
cooling of automobile engines is, in reality, air cooling; the water- 
cooled motor is simply one in which the heat units to be disposed 

Fig. 202. Horizontal Plate Type of Tubular Radiator Used on Studebaker Cars 
Courtesy of Studebaker Corporation, Detroit, Michigan 

of are conveyed from the cylinders to the radiator by the circulating 
water, to be dissipated in the air that passes through it, instead of 
directly lost in air passing over thin flanges cast on the cylinders. 
A water-cooling system therefore constitutes a sort of indirect-air 
cooling. This being the case, the chief justification for water cooling 
consists in the margin it allows for much greater cooling areas in 
contact with air than it is possible to provide by mere extensions of 
the cylinder surfaces themselves. 


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A typical pleasure-car radiator of the tubular type is shown in 
Fig. 202. As will be noted, the flanges have a continuous horizontal 
appearance, but the vertical tubes which carry the water can be seen 
in the background. These actually carry the water; the horizontal 
flanges simply serve as a heat-radiating surface. This type is rapidly 
increasing in popularity for pleasure cars of medium and low price, 
at the expense of all others. 

The total cooling area of the radiators employed in automobiles 
will range all the way from ten to ninety square feet; the latter 

Fig. 203. Vertical Tubular Spiral Fin Type of Riker Truck Radiator with Cast Headers 
Courtesy of Locomobile Company of America, Bridgeport, Connecticut 

surface is not unusual in the best type of honeycomb radiators with 
hexagonal openings and very thin water spaces. 

The smaller areas are found in the cheaper types of radiators 
built up of straight, round, or flat tubes, and provided with fins to 
increase the area exposed to the air. Radiators of these types, unless 
very large, are often inadequate to cool a motor when it is laboring 
under continued heavy usage, as in pulling on the low gear through 
deep sand or mud or up long heavy grades. Under such conditions, 


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a motor that may have run for months without any cooling trouble 
whatever in level country will often boil all the water out of the 
cooling system within a few minutes. 

Types of Cells. In the cellular, or honeycomb, radiator, there are 
three forms of tubing in general use. These forms are: the square, 
with its flat sides set horizontally and vertically; the round, with the 
tubes staggered so as to make the number as large as possible; and 
the hexagon, which is also set staggered so as to use the maximum 
number. The square and hexagon are more used on pleasure cars, 

Fig. 204. Renault Form of Radiator Situated Back of Engine 

while the round form has been used on higher-priced motor trucks. 
A modification of the round-tube form is found in the radiator which 
utilizes the plain copper tubes, bunched and fitted into a header, or 
water tank, at the end, but which are not formed into a composite 
unit. This is used on both pleasure cars and trucks. 

Types of Tubes. In the tubular form, there are two well-known 
types: the round vertical tube with spiral fin, or flange, welded or 
sweated on; and the so-called tube-and-plate construction, shown in 
Fig. 202, in which a set of horizontal plates is pierced with a number 




Water Inlet - 

of holes, tubes set into these, and the whole dip-soldered into a 
unit. The former type is gaining rapidly for truck use on account 
of its freedom from leakage under the severe racking conditions of 
truck use. An example of this type is to be found in Fig. 203, 
which shows a welded tubular radiator. It is of interest to note 
that the welded type replaced a soldered honeycomb unit of the 
highest quality which could not be kept water-tight in war service. 
Modifications of Cellular and Tubular Forms. In addition to 
the types shown in Figs. 202 and 203, there are a number of 
forms which partake somewhat of their characteristics but which 
show a marked individuality. The Renault form, which is placed 
at the dash instead of at the front, is shown in Fig. 204. It has a 

tank at the top and small tanks 
at the bottom and sides, the 
central bottom space being taken 
up by the fan. The tubes are 
of pure copper and are not fas- 
tened together as in the cellular 
radiator, but merely connected 
at the two ends. As compared 
with the average radiator of the 
cellular type of equal cooling 
capacity, this form requires 
greater height, width, and depth. 
Its dash position has the disad- 
vantage of keeping the driver's compartment uncomfortably hot 
in the summer months. 

The piping of automobile cooling systems in a great many 
cars is made too small to afford free circulation, and this mistake 
in design, common in the earlier days of automobile engineering, 
is one that cannot be too carefully avoided. 

In the experience of most automobile designers, the most 
satisfactory method of connecting up the piping of a circulating 
system is found in the use of ordinary steam hose, clamped 
around the ends of the pipe by small metal straps. 

Circulation. An unobstructed and vigorous circulation of 
the water in a cooling system is a great factor in reducing the 
size of radiator required and in preventing overheating. 

Fig. 206. Gear Type of Water Pump of 
Very Simple Construction 


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Pumps. The usual method of circulating the cooling water is 
to use one type or another of small pumps, driven by suitable gearing 
from the engine itself. 

Gear pumps are often used for this purpose because of their extreme 
simplicity, but it is difficult to make them large enough to handle 
as great volumes of water as most designers now regard desirable. 

A good example of the gear form of water pump is shown in 
Fig. 206. This is simply a pair of gears which mesh rather closely; 
the movement of the flat side of the teeth carries or forces the water 

Fig. 207. Centrifugal Type of Water Pump as Used on Reo Care 

forward. In general, the gears are made of small diameter but wide 
face to take advantage of this action. The result is a very compact 
pump. The vane type of pump is really a modification of the gear 
pump in that a rotating member is placed in an eccentric chamber 
with a sliding arm on either side, which is held out into contact with 
the sides of the chamber by a central spring. This double sliding 
arm simulates the effect of the teeth of the gear form. This has small 
capacity and is not widely used on that account. 

The consequence is that the centrifugal pump is now the type 
most preferred. In their best forms, centrifugal pumps consist of 

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simple multi-bladed "impellers" revolving with close clearances in a 

One advantage of the centrifugal pump is that if any small 
object, such as a stick or pebble, should by any chance get into the 
circulating system — though strainers always should be provided to 
prevent this contingency — no serious harm is likely to result, whereas 
with a gear pump breakage is almost certain to ensue. 

The construction of the centrifugal form can be seen in Fig. 207. 
This is not as clear as it might be because the impeller is sectioned at 

Fig. 208. Thermosiphon System of Cooling as Used on Overland Cars 

the point where the water chamber is largest; in short, at the water- 
outlet space. The impeller fits the casing very closely except at 
the water outlet where the water is thrown off by the centrifugal 
force generated in rotation. The centrifugal form of pump is also 
fairly well illustrated in Fig* 210, where it will be noted that two of 
them are used on the two ends of the upper shaft. 

Chiefly in motor-boat motors of the two-cycle types, recipro- 
cating plunger pumps are used to circulate the cooling water. The 
volume of water handled by pumps of this type, of dimensions that 
can be conveniently employed, is not very large, however, and it is 

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From Carburetor 

only the fact that the water is not re-used and is, therefore, cooler 
and of a consequently greater effectiveness that makes possible the 
use of plunger pumps in motor boats. 

Thermosiphon. Circulation of the cooling water by the thermo- 
siphon action, owing to the heated water in the jackets rising and the 
cooled water in the radiator descending, is the practice of an increas- 
ing number of designers, and has been demonstrated to be very 
effective with liberal jacket spaces and large-diameter piping. 

The pioneer, and still the most prominent exponent, of thermo- 
siphon cooling is the Renault Company, of France. A typical 
Renault motor-and-radiator combination with thermosiphon cir- 
culation is illustrated in 
Fig. 204. 

A better example of 
the thermosiphon sys- 
tem, that is, a drawing 
which shows it much 
better is Fig. 208. In 
this the large open pipes 
with few bends, and 
those few very easy so as 
to reduce water friction 
to a minimum, are well 
shown, also the small 
difference in level be- 
tween the top and bottom of the system. Ths difference in tempera- 
ture causes the movement of the water. It is said that the pressure 
which the temperature variation produces is seldom more than a 
small fraction of a pound; for this reason it is necessary to reduce 
surface friction and losses at bends and at other similar points. 

Cadillac System. An entirely new idea in the control of the 
temperature of the cooling water is that used on the new eight- 
cylinder Cadillac motors. Here, each block of four cylinders has its 
own circulating system, with pump and piping, entirely distinct from 
the other. In each one a thermostat, like that shown in Fig. 209, is 
located on top of the pump housing. This controls the movement 
of a valve, which, when shut off, prevents the flow of water to the 
radiator, that is, when the temperature of the water falls below a 


Fig. 209. Thermostatic Device in Latest Cadillac Water- 
Cooling System to Preserve Equilibrium and 
Even Temperature 


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certain figure at which the thermostat is set, it comes into action and 
cuts off the flow of water from the radiator to the pump. The result 
is that the pump can circulate only that part which comes through 
the very small pipe to the inlet manifold and carburetor and from 
there back to the pump. This continues until the water becomes 
heated; the raising of the temperature operates the thermostat which 
opens the valve, and the system is again complete. In the upper 

Fig. 210. Thermostat and Water-Pump Group on Packard Twelve-Cylinder Motor 
Courtesy of Packard Motor Car Company, Detroit, Michigan 

right-hand part of this figure, the circulating system of one block of 
cylinders is shown in outline. 

The method of controlling the temperature of the engine with 
an automatic check valve is receiving much attention; there is even 
talk of extending the same system of control to the exhaust gases and 
all sources of heat, interconnecting them with the fuel vaporizer so 
as to vaporize the maximum amount of fuel in the minimum time with 
the least heat loss. The thermostat and pump combination used on 
the Packard twelve-cylinder motor is shown in Fig. 210, in which it 
will be seen that two pumps are placed on the pump shaft, one at 


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each end so that the thrust of each one balances the other. In the 
Cadillac, the two cylinder groups are separate, each having all the 
units shown in Fig. 209 except the radiator. In both the Cadillac 
and Packard systems, the thermostat is placed at the bottom of the 
system. It has been advocated by engineers for other companies 
that this would do the most good if placed at the top of the system. 

The value of a thermostat may be gained from these figures. 
One particular make of thermostat, as used on a popular make of car, 
was tested out with the following results: Without it, the car did 
14^ miles on a gallon of fuel at 15 m.p.h. and 13? miles at 30 m.p.h. 
At the same speeds and with the thermostat set at 160 degrees, 
the same car under the same circumstances did 16 J miles at 
almost 15 m.p.h. With everything the same but with the device set 
to work at 180 degrees, the car did 19 \ and 16 J miles, respectively. 
The gain at the lowest speed of 15 miles an hour from 14| to 16? and 
then to 19| miles per gallon represents gains of almost 14 and 38 
per cent in economy. 

Fans. In the earlier days of automobile designing it was 
deemed sufficient to secure circulation of air through the radiators 
by the movement of the car alone. This was soon found inadequate, 
however, for often when most cooling was needed, as in hill climbing 
or hard pulling on the level, the car would be moving at its lowest 
speed on low gear, with the result that the air draft through the radi- 
ator was not sufficient to cool the water. 

This condition was remedied by the use of a fan behind the 
radiator, driven by a belt or gearing from the motor so as to draw 
a constant draft through the radiator in proportion to the speed of 
the engine rather than of the car. 

Nowadays, practically all automobile power plants are provided 
with fans, the only exceptions being a few very small motors in which 
the difficulty of cooling is not so great as with the higher powers. 

In some cases, instead of a separate fan, fan blade.s are placed 
on the flywheel, and so made to induce a draft through the bonnet 
that covers the engine, thus avoiding the necessity for the addition 
to the moving parts involved in the usual fan system. Such a fly- 
wheel fan is used in the engine illustrated in Fig. 204. 

A later plan of even greater effectiveness is the housing-in of 
the whole rear end of the radiator, so that what air passes through 


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must pass through the center where the fan is located. This is but 
another way of saying that all air must pass through at a high 
velocity, which insures efficiency. This plan fulfills one requirement 
of air cooling, that is, the large quantity of air which must be used. 

Where this system is used now, the entire engine in front of the 
fan is made air tight. The hood, which has no openings anywhere, is 
set into carefully fitted rubber strips to cut off any possible leakage. 
The same precautions of drawing all the air through the radiator, 
and through that alone, are observed elsewhere. While this method is 
effective, it is a disadvantage in another way, for some direct cooling 
is effected through the cylinder walls, exhaust pipes, etc., in the 
ordinary system by the cold air passing over the radiator, particularly 
the air which comes in from around the hood top and sides. 

Anti-Freezing Solutions. In using automobiles in very cold 
climates during the winter months, there is great danger of the water 
in the cooling system freezing when the car is standing still, or even 
with the motor running slowly if the temperature is very low. The 
result of such freezing is almost certain injury to the cylinders, 
through cracking of the water jackets, as well as the probability of 
bursting out radiator seams, with consequent leakage. 

To avoid these difficulties it is not uncommon to use, instead 
of pure water, one kind or another of anti-freezing solution, usually 
compounded by the mixture of some chemical with water to lower 
its freezing point. Thus, glycerine or alcohol mixed with water will 
keep it from freezing at all ordinary winter temperatures. Glycer- 
ine is somewhat objected to because of its sticky, gummy nature, and 
also because of its deleterious effects upon the rubber hose of the 
piping system. Alcohol, if not replenished from time to time, will 
evaporate out of the water and thus permit it to freeze, or, if mixed in 
too great a quantity, it may introduce a fire risk otherwise avoidable. 

A much favored anti-freezing solution consists of calcium 
chloride dissolved in water, in a quantity proportioned to the tem- 
peratures that it is desired to guard against. 

All anti-freezing solutions are more or less objectionable in that 
they are more likely than pure water to corrode and clog up the cir- 
culating system, and there is no doubt that the elimination of the 
necessity for them by the substitution of air cooling for water 
cooling will mark a great advance in automobile development. 


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Though successfully employed in one or two automobiles and 
remarkably developed in some of its applications to aviation motors, 
air cooling is not considered by most engineers to be successfully 
applicable to the average automobile. That it will become more 
practical in the future, however, is the opinion of many. 

Unfortunately, this is an instance where the better and simpler 
method does not meet with popular approval, that is, the cooling 

Fig. 211. Diagrammatic Illustration Showing System of Air Cooling on Franklin Cars 
Courtesy of H. H. Franklin Manufacturing Company, Syracuse, New York 

of automobile cylinders is one of those cases in which the best in 
theory is not, by any means, accepted practice. The extent to which 
the public has adopted water cooling as compared with air cooling 
may be noted in these figures for 1916: Cooled by air, 1 car; cooled 
by water, 168; total, 169. 

Flanges, or Fins. The usual method of air cooling, successfully 
employed in aviation and motorcycle motors and in a few automo- 
biles, is to provide the cylinders with fins, or flanges, for increasing 
the area of the surface, supplementing this with means for blowing 
large volumes of air over the surfaces thus provided. 

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Air Jackets. Several of the most practical examples of air- 
cooled motors in aviation construction are those which have, in 
addition to the flanges, or fins, on the cylinders, air jackets to concen- 
trate the drafts of air that effect the cooling. 

Blowers and Fans. The most successful air cooling has been 
accomplished by types of blowers capable of inducing much more 
vigorous air currents than are drawn through the radiators of water- 
cooled automobiles by the types of fans commonly used in power 
plants of that character. 

In the Franklin, the most successful air-cooled automobile 
motor, a side view of which can be seen in Fig. 211, the cooling is a 
sort of combination of the flange and the blower method. The fins 
are vertical and radial, with a close-fitting hood connected to an air- 
tight pan. At the only opening in this hood, which is at the rear end, 
is placed the fan (on the flywheel). This draws the air past the 
cylinder walls, where it is needed. 

Internal Cooling and Scavenging. Perhaps more promising as 
a road to final and universal use of air cooling are the systems of 
pumping air through the interiors, instead of blowing it over the 
exteriors, of the cylinders. Such internal cooling, in addition to 
directing the maximum cooling effect where it is most needed on 
the oil-coated surfaces that are exposed to the heat of combustion, 
has the further advantage that it may be made to scavenge out all 
residual exhaust gases, which, besides helping to accumulate heat, 
also act so detrimentally upon the functioning of ordinary motors. 
This is a direct result of the admixture of retained exhaust gases 
with incoming fresh charges. 

Methods of internal cooling and scavenging that appear of 
definite promise are those proposed in various recent schemes for 
pumping air first into the crankcase — either by using the under side 
of the piston as a pump, as in common two-cycle constructions, or 
by applying special pumps to the crankcase for this particular pur- 
pose — then into the cylinders by means of by-passes, with the result 
that it exerts a positive cooling effect inside the cylinder. 

In England, some interesting experiments have been made on a 
theory of internal cooling in which water is introduced into the 
cylinders in the form of a spray, at certain points in the cycle. This 
is said to add power in addition to helping the cooling. 


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Cleaning. It is highly important that the cooling system be 
entirely cleaned out at least once, and preferably twice, a year. When 
this is done, the water jackets and radiator should be flushed out with 
a strong current of water, preferably a hot soda solution. This should 
be forced through in a direction opposite to the usual course of the 
water. Thus, a hose can be put in the radiator filler cap and city 
pressure applied to force the water through; in this radiator, it will be 
made to go from bottom to top instead of the usual top to bottom. 
If this method, which is the usual and easy one, does not remove all 
dirt, sediment, and foreign matter, the radiator can be removed and 
boiled, or at least submerged, in a strong soda solution which will 
clean it out thoroughly. The radiator is the most important member 
of the system. 

Replacements. When this is done, it is advisable also to look 
over all hose and hose connections. Many times the hose will have 
become worn or frayed through and cut or otherwise damaged from 
the outside, or the water may have attacked it from the inside, par- 
ticularly if it has been through a winter when an anti-freezing 
solution was used. It is well, when cleaning the system, to replace all 
hose with new. The clamps are important as they determine the 
water tightness of the -hose, so they should be looked over for missing 
nuts, broken screws, broken clamp ends, as well as to note if each one 
is applied straight and true over the hose and the end of the pipe on 
which it is placed. 

Washing. If the radiator is splashed with mud or dirt, the 
washing should be done from the rear, with the hood removed. This 
method allows free use of the hose, and at the same time it insures 
against getting any water in the ignition system where it would cause 

Adjusting=Fans. Usually, the fan is hung on an eccentric bushing 
held in a clamp. It is important that the fan belt be tight enough so 
that there is no slippage, otherwise the engine will heat up. To 
tighten a belt, loosen the clamping bolt on the fan eccentric, and then 
turn this eccentric so as to move the fan-shaft center away from the 
crankshaft-pulley center. The eccentric may be moved with the 
hands, in some cases; in others, a wrench is provided, and the fan 
eccentric made with surfaces on which the wrench fits; while still 


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others need the application of a pointed tool and hammer to turn 
it. In the latter case, do this very carefully so as not to chip off 
any metal. Occasionally, the fan bearings need adjustment or lubri- 
cation. When they are of the plain type, a grease cup is generally 
provided, and after the engine is stopped, a couple of turns of this 
will be sufficient. If of the ball or roller type, they will be packed in 
grease, and if they show signs of running dry, the fan should be taken 
apart and the grease renewed. Use a good grade of cup grease for 
this purpose, not a hard grease. 

Adjusting Pumps. Generally, the pump is made so as to need no 
adjustment. However, a leak may occur at one of the packing nuts. 
To remedy it, tighten the nut as far as possible, but if this does no 
good, remove the nut and add packing under it. Special packing is 
provided for this purpose, but if no other is available, a thick heavy 
piece of string can be well coated with graphite or a graphite grease 
and wound on as packing. In putting on packing of this kind, it 
should be wound on right handed, or in the same direction as the pack- 
ing nut turn^ to tighten. Otherwise, tightening the nut will loosen 
the packing. 

Summary of Cooling Troubles 

Anti-Freezing Solutions. The following are satisfactory formulas 
for anti-freezing mixtures: 

1 . Mix equal parts of glycerine and water. Replace evaporation 
with clean water. Replace leakage with fresh solution. 

2. Mix equal parts of denatured alcohol and water. Replace 
evaporation with alcohol and replace leakage with solution. 

Radiators. Radiators must be kept well filled. Leaky radiators 
are difficult to repair. This work should be done by an experienced 
radiator man, never by a plumber. 

Soft Water. Soft water should be used for filling tank. It 
should be borne in mind that the circulating water gets pretty hot, 
and that incrustation may result from hard water. 

Engine Heats, Loses Power, and Knocks. These are all symp- 
toms of lack of water circulation. To see if this is the case, look into 
the opening in the top of the radiator and see whether water is flowing 
in from the engine. If not, either the water-piping system is stopped 


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up, which can be checked by disconnecting, or else the circulating 
pump is not working properly. All modern engines are so propor- 
tioned that, in this event, the water continues to circulate by thermo- 
siphon action. Taking off the pump will verify this. 


When the lubrication system is referred to, that of the motor is 
generally meant. Motor lubrication is of the highest importance; 
for the motor must have efficient and continuous lubrication to run 
properly. Taken in its broadest sense, however, the title should refer 
to the entire lubricating means of the car; that is the way it will be 
handled here. The other units and parts of the car may not need as 
efficient or as continuous means of lubrication as the engine, and the 
presence or lack of lubricant is not so tremendously important; but all 
of it is of value and influence in the operation of the car, and should 
be well known. 

Interior and Exterior Demands. The engine of a motor car 
requires two distinct kinds of lubrication. The interior parts, which 
are subjected to the greatest heat, rotate or slide at the highest 
rate of speed,, and generally do the greatest amount of work, must 
have what amounts to a continuous stream of good lubricant. With 
the exterior parts, which do not rotate so fast, do less work, are not 
subjected to much heating, and will be kept cool by the atmosphere, 
there is no need for this continuous stream, nor for such a quantity 
or high quality of lubricant. 

The exterior and interior systems must be considered sepa- 
rately. With reference to the internal oiling, there are two general 
systems in use : the pressure form, and the splash type. A third, which 
is now coming rapidly into use, is a combination of the two, called the 
splash-pressure system. For 1917, the relative popularity of these 
three is as follows: pressure, on 30 per cent; splash, on 35; splash- 
pressure, on 35. 

In the pressure form (or its modification, the splash-pressure), 
the pressure may be produced in a number of ways: by a single large 
pump; by a series of small pumps, one for each bearing lead; or by a 
reservoir, or tank, kept filled by a separate pump (gravity pressure). 

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Splash-Pressure Feeding. One of the best and most successful 
types of lubrication systems is that in which the oil is fed under 
pressure to the different bearings. 

In the splash-pressure system, the oil to all the crankshaft and 
connecting-rod bearings, to the timing gears, and to the upper portion 
of the cylinder walls is supplied through the medium of a gear-oil 
pump driven usually by worm gearing from the camshaft. The other 
bearings within the engine are lubricated by oil spray thrown from 
the crankshaft. Such a system is shown in Fig. 213. 

Overland. The same units are necessary in all splash-pressure 
systems, but they can be and are used in widely different ways. It 

Fig. 213. Pressure-Feed Lubrication System on Pierce- Arrow Cars 
Courtesy of Pierce- Arrow Motor Car Company, Buffalo, New York 

is of interest to the repair man to know the details of a number of 
these methods so as to be able to repair and adjust the mechanisms 
more readily, also to more quickly point out their troubles. One of 
the most simple systems in use is that of the Overland, as shown in Fig. 
214. In this, the oil pump at the bottom of the oil sump A is driven 
from the camshaft rear end. After passing through the strainer B, 
the oil continues through an outside pipe to the sight feed C on the 
dash. This simply indicates that the system is working continuously. 



From here it passes back through the pipe D to the inner distributing 
pipe E; this serves to keep the troughs FF, filled. At the middle part 
of the downward stroke, the scoop on the bottom of each connecting 
rod dips into its own oil reservoir and splashes up a fine spray of oil. 
At high speeds, the four rods fill the whole interior of the crankcase 
and the lower parts of the four cylinders with a mist of oil. This is 
sufficient to lubricate everything thoroughly. In a system of this 

Fig. 214. Constant Level Splash System on Overland, in which Pump Maintains 
Oil Supply at Predetermined Level 

kind, the strainer is of great importance and must be kept clean. 
Similarly, the oil sump should be drained very frequently, at least 
every 1000 miles. 

Studebaker. The Studebaker system is very similar, except that 
the oil pump is outside of the crankcase and set higher up. It is of 
the simple gear type and is not liable to derangement. The system 
is equipped with an oil-level indicator on the side of the case, which 
shows the quantity within the case. 


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Single-Pump Pressure Feeding. The drilled crankshaft, as 
shown in Fig. 213, is a necessity in all pressure systems, as it also is 
in all combination splash-pressure systems. This can be seen, and 
perhaps the whole system explained more clearly, by referring to 
Fig. 215. In this the single pump working direct is used, thus differ- 
ing from the reservoir system explained above. This diagram shows 
also how the oil is forced to flow through the three bearing leads to 

Fig. 215. Lubrication System of Cadillac Eight, Showing Pump and Path of Oil, Also 
Auxilliary Circuit for Crankshaft 

the interior of the crankshaft, whence it follows in to the pins upon 
which the connecting rods work. These rods are drilled, and the oil 
is thrown out by centrifugal force, passing up through the rods to the 
piston, thence onto the cylinder walls. In addition, the latter are 
sure to receive sufficient lubricant, for the rotating shaft and rods 
throw off a good deal in the form of a mist which settles upon the 
cylinder walls. 

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Generally, pockets are provided inside the motor to catch the 
mist and force it to flow to the camshaft and other bearings besides 
the crankshaft, but in this case it will be noted that the camshaft 
bearings have individual supplies through the medium of a camshaft 
oiling pipe. 

Fig. 216. Pressure Lubrication System Used on Steams-Knight Motors 
Courtesy of F. B. Stearns Company, Cleveland, Ohio 

An objection to lubricating systems of this type is that in case 
there are several leads to different bearings one of them may become 
obstructed without anything to indicate this condition or to over- 
come it until the bearing involved becomes overheated and ruined. 
If one lead becomes obstructed, the oil can still continue to feed out 



tlirough the others, thus relieving the pressure in apparently the 
normal manner and failing to reveal a serious derangement. 

Stearns. The Steams-Knight system is shown in Fig. 216. 
The oil is circulated by a pump (not visible in this sketch) at the 
front end of the eccentric shaft D. After passing through a screen 
and the pump, it is forced through a strainer A in the filter E, thence 
through pipes to the pump-shaft bearings, eccentric-shaft chains, 
and main crankshaft bearings. It reaches the crankshaft bearings 
through the oil inlet F, the drilled holes in the crankshaft being indi- 
cated at G. From these holes, it reaches the hollow center of the 
connecting rods H, and thus to the piston pins and piston outer walls. 
At the bottom of each connecting rod, there are three small radial 
holes through which sufficient oil escapes to lubricate the inner and 
outer sleeves which take Ijie place of the valves. A gage on the dash- 
board, or cowlboard, indicates the oil pressure and should read from 
1 to 5 pounds with the throttle closed and the motor idling, and 
from 40 to 60 pounds when the throttle is wide open and the motor 
running normally or at high speed. 

Regulator Connected to Throttle. The variation on this pres- 
sure is controlled entirely by the by-pass in the main oil lead, which 
is connected directly to the throttle-control mechanism. This by- 
pass consists of a body with an oil port and a piston with a series of 
holes. When the throttle is closed, and the motor idling, these holes 
and port register, so oil passes through freely, relieving the pressure 
on the bearings. When the motor is speeded up and more oil is 
needed, the piston is turned by the throttle connection so that the 
holes and ports no longer register and the oil cannot escape as freely and 
must be forced through to the bearings. This by-pass is adjustable 
by means of the small blade B, Fig. 216, which is rotated from the 
center to right or left and locked by the clamp bolt C. The safety 
valve I within the cr^nkcase is set at the factory for the maximum 
pressure to be used in the system. If this is approximated, this valve 
is forced open and the oil escapes back into the crankcase, thus lower- 
ing the pressure. The oil-level indicator J is operated through the 
float K in the oil well and indicates the quantity. In cleaning and 
replacing filter screen A, be sure the holes register. The system used 
on the Stearns-Knight eight-cylinder V-type motor is essentially 
the same, with a few differences of location due to the form of engine. 



On high-speed and multi-cylinder motors (which are almost 
invariably high-speed forms), the lubrication assumes an importance 
not hitherto attached to it. This is responsible for the pressures used 





eS ft 

s i 




and for the wide spread use of mechanically driven positive pumps. 
Formerly, pressures of from a few ounces to 4 or 5 pounds were con- 
sidered sufficient. Now, pressures as high as 60 and 70 pounds are 
not unusual. These tremendous pressures, however, have necessi- 




tated a system much more carefully constructed, assembled, and used 
than was the case previously. 

Mormon. The Marmon system is not radically different from 
that just described, but there are a number of small individual points 
worthy of mention. The filling is not through the usual crankcase 
breather pipe, but through an opening in the top of the cylinder head 
1, Fig. 217. From this opening the oil flows around the valve push 
rods (the motor had overhead valves as will be noted) down into the 

bottom of the oil pan 2. After 
screening at 3, it passes 
through the throttle-controlled 
regulator to the oil pump 4 on 
the rear end of the camshaft. 
The main feed pipe is marked 
5, the pressure gage 6, lead to 
crankshaft bearings 7, hollow 
in crankshaft 8, connecting-rod 
bearing 9, cylinder walls 10, 
ball check valve 11 to govern 
pressure in main feed pipe 
and excess oil through hollow 
rocker-arm shaft 12, connect- 
ing to oil container 13 above 
valve tappets. 

In Fig. 218, a detail of 
the regulator is shown. Oil 
enters the pump body from the 
left through the opening B. 
The passage from B to the gears is controlled by the opening in the 
plunger A, which is operated by the movement of the throttle lever 
through the small tappet seen on top. When the throttle lever is 
depressed, the plunger moves down, and its upper, or piston, portion 
closes off a portion of the oil hole, restricting the supply. The spring 
under its lower extension is used to return it to position. Its shape 
is such that the oil has no tendency to act upon it, either to open or 
close it. In this system, the pressure varies from 12 to 60 pounds. 
Types of Oil Pumps. There are but three or four types of oil 
pumps now in use, these being the gear, plunger, plunger operated by 

Fig. 218. Detail of Throttle-Connected Plunger 
in Marmon Oil Pump 


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CAfcM Vatve 

Fig. 219. Gear Type of Oil Pump of Marked 

a cam, and in a few cases the vane pump. While essentially the same 
as the forms used for pumping water described previously, they are 
smaller in actual size and have some few different details. In the gear 
form, which is shown in 

Fig. 219, one gear is driven ISSL^r-*"*- 

directly from the engine and, 
in turn, drives the other, 
their rotation forcing the oil 
along in the direction of 
rotation. Usually a by-pass 
with a check valve is pro- 
vided, and when the pipe 
is obstructed or the pres- 
sure rises for any other rea- 
son, this opens and the oil passes around the pump at low pressure, 
equalizing the system. 

The cam-operated plunger form is shown in Fig. 220. This is 
the method of drive adopted for mechanical lubricators, but few- 
engines have an individually con- 
structed pump of this type. It is 
simple, easy to regulate, seldom gets 
out of order and can be arranged to 
give a different supply at each plunger 
should the system warrant or necessi- 
tate this. A good example of the 
plunger form is the oil pump on the 
Reo engine, shown in Fig. 221. This 
works as follows: When the pump 
plunger A is moved upward by the 
curved eccentric 5, it draws oil through the ports C and the screen 
D, as the entire lower part is submerged in the oil. When the max- 
imum amount of oil is drawn into the pump chamber in this way, the 
plunger descends, the ball E rises, and the oil flows up inside the 
hollow plunger to the top ports F, through these to the surrounding 
chamber G, and thence to the outlet H and into the oil pipes. This 
form is very accurate and reliable. 

Methods of Driving Pumps. Another point of considerable 
importance to the repair man is the method of driving the pump, 


fttrm Driv* SAa/f 
Jhtet c/teck Ht/i/t 

Fig. 220. Cam- Actuated Plunger 
Form of Oil Pump 


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since this influences its location and its accessibility. There are but 

two general methods of driving. One is by means of a special oil-pump 

shaft, in which the pump will 
quite generally be found in the 
bottom of the oil sump or very 
close to it; the other is from 
some part of a shaft used for 
other purposes, in which case 
the position may vary widely. . 
Examples of the first, or special- 
shaft method, will be seen in 
Overland, Fig. 214, and Cad- 
illac, Fig. 215. Examples of 
the second method are seen in 
Stearns, Fig. 216, and Marmon, 
Fig. 217, in both of which the 
camshaft is used. 

In Fig. 222, a gear is placed 
directly upon the rear end of 
the camshaft meshing, with 
another immediately below it 
which forms the pump. This 
is the Scripps-Booth eight. 
Attention is called to these 
additional points, the hollow 
crankshaft for oil circulation 
at A, the method of carrying 
the oil leads and regulator up 
to a handy point on top of the 
motor at 5, and the air cooling 
flanges on the bottom of the oil 
pan at C. The purpose of the 
latter is to reduce the tem- 
perature of the oil after it has 
been used and returned to the 

oil- supply reservoir and before it has been used a second time. The 

oil pump on the end of the camshaft is marked D. 

In Fig. 223, the oil pump is a simple plunger operated by a cam 

Fig. 221. Typical Plunger Pump 

Courtesy of Reo Motor Car Comjxiny, 

Lansing, Michigan 


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on the camshaft. It projects out at right angles on the side between 
cylinders 2 and 3. It is possible to arrange a system of this kind so 
that an extra cam is not needed, one of the regular valve cams doing 
the work of pumping the oil. This makes a simple and inexpensive 
arrangement. The oil suction pipe is marked B and the pipe carry- 
ing the supply to the bearings is marked C. Attention is called to the 
connecting-rod oil scoops D, the feed adjustment E, the pressure- 
relief valve F, and to the main oil lead G. 

Individual Pump Pressure Feeding. The expedient of feeding 
the oil by individual pumps, independently driven and capable of 
individual adjustment which enables them to feed any desired amount 
of oil to any par- 
ticular bearing re- 
gardless of the 
amount that may 
be fed to any other 
bearing, has been 
widely applied. In 
such a system, if 
obstruction of any 
one of the leads 
should occur, it is 
almost certain to be 

Orcea OUt Dy tne ^ 224 Detroit Eight . Feed Multiple Oiler as Used for Motor 
action Of the pump, Lubrication 

. ii i i . Courtesy of Detroit Lubricator Company, Detroit, Michigan 

which, m all lubri- 
cating systems of established type, is made capable of working against 
enormous pressure. 

One of these lubricators, made for eight feeds, is shown in Fig. 
224. By extending the casing and the longitudinal shaft inside and 
adding more pumps, this type is capable of extension to any desired 
number. The eight-feed form shown allows of one lead to each of the 
three main bearings of a four-cylinder engine, one each to the four 
cylinder walls, with a lead remaining for the gear case at the front 
of the motor. 

Gravity Feeding. Feeding of oil by gravity to one or more bear- 
ings is a method that has been employed with some success, but it is 
now encountered only in rare instances in automobile power plants. 

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Splash Lubrication. The feeding of oil to bearing surfaces by 
the simple expedient of enclosing a quantity of it in a reservoir in 
which the working parts are also contained is a successful and widely 
used scheme in automobile motor construction. 

In the splash lubrication system, as will be shown in detail later, 
the lower ends of the connecting rods "splash" up the oil which is in 
the bottom of the crankcase in the form of a huge puddle. Since this 
method, formerly almost universal, has been criticised as wasteful of 
oil as well as productive of much needless smoke, it has been modified 

Fig. 225. Typical Screw 
Type Grease Cup with 
Wing Handle 
Courtesy of Lunken- Fig. 226. Lunkenheimer Fig. 227. Lunkenheimer 

heimer Company, Grease Cup with Re- Grease Cup with Spring • 

Cincinnati, Ohio movable Barrel Cover for Quick Filling 

by the majority of makers so that the scoops on the ends of the con- 
necting rods dip into small narrow troughs provided for this purpose. 
Another objection to this system is that at high speeds too little oil 
is thrown around the interior of the cylinders and crankcase, since 
the initial rotation of the rods has churned or beaten the entire 
supply into a mist, while at low speeds too much is thrown around 
for the work the engine is doing. 

The latter objection has been overcome in the newer engines by 
making the troughs into which the connecting-rod scoops dip mov" 
able and attached to the throttle lever, so that when the latter is 
opened wide to develop maximum power, the troughs are brought up 
higher, allowing the scoops to dip down deeper and thus supply a 
greater amount of lubricant. 

External Lubrication. In the lubrication of the external parts 
of the motor, such as the pump shaft, magneto shaft, oiler shaft, fan 



shaft, generator shaft, air pump shaft, etc., an entirely different 
method of lubrication is necessary — one that is more simple in every 
respect, allows the use of more simple lubricating devices, and does 
not require anything like the care and adjustment previously pointed 
out for the internal parts. 

Oil and Grease Cups. Chief among the devices used for lubricat- 
ing these outside parts are oil and grease cups, the oil cups being used 
in decreasing quantities and the grease cups in increasing quantities. 
Formerly, oil cups were much used, but they gave poor satisfaction, 
collected dirt, and were unsatisfactory generally. In the use of 
grease cups, there are but three things to observe: They should be 
large enough, accessible, and easy to fill. 

For application to spring eye-bolts there is a particular type 
of grease cup. This grease cup is of the type that feeds by being 
occasionally screwed up a small distance as the bearing uses up the 
lubricant, and its positive action is rendered more certain by the use 
of a detent (not illustrated) that holds the cover in any position in 
which it may be left. The grease is contained in the entire cap which, 
when unscrewed from the lower portion, is readily and conveniently 
filled by scooping up the grease. 

A form quite generally used is the simple cup shown in Fig. 225. 
This is a screw-compression cup from which the lubricant is forced out 
by screwing down on the reservoir. This form is prevented from com- 
ing loose by the compression spring, here shown very much compressed 
below the ratchet, which governs the screwing down of the reservoir. 
To fill the reservoir, the ratchet portion is held down and the top 
screwed off, turning in the reverse of the usual direction. Although 
the top is fitted with a wing handle, it can hardly be considered easy 
to refill. 

Another widely used form is seen in section in Fig. 226. This has 
a larger handle and, in this respect, may be considered easier to fill. 
A type which is rapidly coming into use and has all the advantages of 
the other two, and more, is shown in Fig; 227. This is a plain 
screw type with a large handle, but the cap is of sheet brass and 
is sprung into place. As this is sprung off by the plunger inside 
when screwed away out, filling is reduced to a matter of sec- 
onds. The plunger screws all the way in and affords pressure all 
the way. 


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The simplest form of oil cup has a hole in one side, which is 
covered with a spring-held cover. To use it, the cover is lifted with 
the fingers until the hole is uncovered, then the point of the oil can 
is inserted and the oil forced in. 


Lubricating the Whole Car. It is best for both the private owner 
and the repair man to have a definite regular system for going over 
the grease and oil cups on the chassis. As shown in Fig. 228, there 
are a number of cups varying from 30 to 32 and upward, as well as 
oil holes, which need to be looked after occasionally. The worker 
should get an oiling chart and fix firmly in his mind the requirements 
of % the!various parts to be oiled or greased and should regulate his oil 
andTgrease cups by hand from day to day and week to week so as to 
produce the desired results. 

.Lubrication of Other Parts. The precise lubrication of the 
clutch, transmission, rear axle, and other more important units will 
be found discussed in detail under their respective headings. 

There are signs at present that the lubrication of the motor may 
be controlled through the medium of a thermostat in order to conserve 
every unit of heat needed in the vaporization of the fuel and thus 
increase the efficiency of the engine as a whole. There would be a 
double advantage in this, for lubrication would be placed on a more 
economical basis. In using the thermostat, smoking and carboniza- 
tion would be reduced, and their heat utilized . This process, carried out 
to a logical conclusion, might result in forced lubrication of all points 
on the chassis by means of the oil-pump system. A system of forced 
lubrication somewhat like the above has been produced in the Fergus 
car, but here the idea was to reduce the amount of work in connection 
with lubrication. The number of points outside of the automatic 
oiling system, which required oil or grease application by hand, has 
been reduced in this car from 80 to 11. Some 18 points in the spring- 
ing system have been eliminated entirely by enclosing the springs in 
leather boots, grooving and drilling them, and forcing oil in under 
pressure from the main pump. It is questionable, however, whether 
the results as obtained in this case are worth the cost in money 
and complication, for this system gives a freak appearance to 
the car. 

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Oils and Greases 

Characteristics of Good Oils. The variety of oils and greases 
recommended for automobile use is so extensive, and there are so 
many cheap and worthless lubricating compounds on the market, 
that it is almost impossible for the purchaser without technical knowl- 
edge to discriminate between them. The various tests from time to 
time recommended, whereby the user may ascertain for himself the 
quality of the lubricant he is using, are rarely of positive value, since 
the compounders of the shoddy oils and greases are usually sufficiently 
expert chemists to concoct admixtures that will successfully pass 
such simple tests as are available to the average layman, and will fail 
only under the more critical analysis of a competent chemist, or under 
the severe and more risky practical demonstration that results from 
long use, in the course of which the worthlessness of the lubricant is 
likely to be found out only at the cost of serious injury to the 
mechanism. The consequence is that the only really safe policy to 
follow is the purchase of the highest grades of oils and greases, 
marketed by concerns of established reputation. 

The oils generally found best for gasoline-engine cylinder lubri- 
cation are the mineral oils derived from petroleum, though castor 
oil is found to possess peculiar merits for the lubrication of air-cooled 
motors working at high temperatures in which the friction of steel 
surfaces working over steel surfaces is often involved. This oil is 
exclusively employed in aviation motors, such as the Gnome, which is 
built with steel cylinders and pistons, and it is often utilized in 
racing automobile motors. Its chief merit seems to be that instead 
of withstanding the high temperatures, which is the result sought in 
the use of mineral oils of high fire test, it burns up clean without 
leaving any deposit upon the cylinder walls. It has to be fed in 
excessive quantities, which makes its use a rather expensive method of 
lubrication. But for the peculiar services for which it is adapted, it 
certainly proves most satisfactory. 

In greases and oils used for the lubrication of parts not exposed 
to such high temperatures as prevail in gasoline-engine cylinders, the 
admixture of vegetable and animal greases and oils with mineral oils and 
greases is not objectionable and often may be of considerable benefit. 

Graphite is a solid lubricant and is very advantageous to 
employ in many parts of an automobile. In the deflocculated form, 


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admixed in very small percentages with cylinder oils, gearbox greases, 
etc., there is no question but what it greatly conduces to smooth 
running and to long life of bearings. Its resistance to the very 
highest temperatures makes it constitute a considerable safeguard 
against immediate injury in case of neglect to replenish the lubri- 
cants as often as is properly required. 

Oil Tests. Heat Test. The reaction known as the heat 
test is very easily made with any lubricating oil. There is per- 
haps no other test which indicates so decisively and so quickly 
the purity, the durability, and the degree of refinement of an oil. 

This test consists of heating a sample of oil to a temperature 
of between 300° F. and 500° F. — depending upon the flash point — 
and holding it at this temperature for a period of from ten to 
fifteen minutes. A good quality of oil will show a slight change 
in color, turning to a darker shade, but the oil will remain clear. 

A poorly refined and impure oil will show an immediate 
alteration in color and will change to a dense black. As the heat 
is maintained, a black precipitate settles, the quantity of the pre- 
cipitation depending upon the impurity of the oil. 

Oil will act in just the same way when subjected to the heat- 
of the explosions in the internal-combustion motor, and thus there 
is a continuous precipitation of black sediment if the oil is poor. 
This is what causes the costly wear of all parts in moving contact 
within a short time. 

Emulsion Test. The emulsion test shows the quality of lubri- 
cating oils about as accurately as does the heat test on straight 
or blended hydrocarbon oils, but it is not reliable when animal or 
vegetable oils are present. 

Reclaiming Oil. It is now authentically stated by some scien- 
tists that oil does not wear out and can be reclaimed for motor 
use if the proper equipment and method are used. A number 
of manufacturers and service stations are now reclaiming this oil 
with wonderful success. The government reclaimed cylinder oil 
used in aeroplanes and it is authentically stated that 40 per cent 
of the oil used in the motors was returned to the reclaiming sta- 
tion and that from 50 to 90 per cent of this oil was treated in such 
a manner that it was as good, if not better than, the original oil. 
The cost of the reclaiming was less than 10 cents a gallon. The 


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most generally used process of reclaiming this oil is by heating it 
after it has been emulsified with soda ash and water. When this 
is done, the impurities separate from the oil with the ash. After 
the oil is thus treated it is dumped into the reclaimer. Live steam 
is passed into the oil and a violent agitation is set up. This is done to 
distill off the gasoline that had collected in the oil when it was in use. 

Testing Oils for Acid, Etc. Oils must be purchased with much 
care. Once an oil is found which does the work satisfactorily, it 
should be adhered to consistently. No two oils are exactly alike, and 
for that reason, no two will do the same work under the same condi- 
tions in the same way. So, it is advisable to experiment only until 
an oil is found which will do the work. Thereafter, stick to that 
brand. As an instance of the impurities which may be found in oils, 
acids may be mentioned. These are fatal to delicate and closely 
machined parts, such as ball bearings, cylinder walls, pistons, etc., and 
consequently they should be watched for. 

Pure mineral oils contain little acid, and what they do contain 
is readily determined. Vegetable and animal oils, on the other hand, 
all have acid content and under the action of heat this may be lib- 
erated. A simple home test may be practiced as follows : Secure from 
a druggist a solution of sodium carbonate in an equal weight of water. 
Place this in a small glass bottle or vial. To test an oil, take a small 
quantity of the lubricant and an equal amount of the sodium solu- 
tion. Put both in another bottle, agitate thoroughly, and then allow 
it to stand. If any acid is present, a precipitate will settle to the 
bottom, the amount of the precipitation being a measure of the 
amount of acid present. 

Another method is to allow the acid, if there is any, to attack 
some metal. To do this proceed as follows: Soak a piece of cloth or, 
preferably, wicking in the oil suspected of containing acid. Select a 
piece of steel at random and polish it to a bright surface. Wrap the 
steel in the soaked rag or wicking, and place in the sunlight but 
protect it from wind or weather. Allow it to stand several days, and if 
there is no sign of etching of the surface, repeat with a freshly soaked 
rag, being careful to use the same oil as before. After two trials, 
if no sign of the etching appears, you may consider it free from acid. 

Principles of Effective Lubrication. To render lubrication 
positive and effective there are certain conditions regarding the 


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design of bearings and the feeding of lubricants that must be scru- 
pulously observed. 

The proper application of a lubricant to a revolving shaft 
passing through a bearing requires that definite space be provided 
between shaft and bearing for the lubricating material. The amount 
of this space varies with the size of the shaft, the speed of rotation, 
and other conditions, but in a general way it can be specified that 
the space must be greater as the shaft diameter increases, and greater 
for heavy oils and low speeds than for light oils and high speeds. 
For the crankshafts of automobile engines, to take a specific example, 
it is rarely desirable to have the bearing smaller than from .0005 
to .0015 inch larger than the shaft. The annular space thus pro- 
vided, as suggested at A in the end and sectional views in Fig. 229, is 
occupied by the lubricant, which, contrary to another general impres- 
sion, will not be squeezed out unless the shaft is loaded above its 

Fig. 229. Condition of Bearing for Proper Lubrication 

capacity; this is more likely to occur because the bearing area is too 
small than from any other condition likely to be encountered. 

With the bearing area large enough — which means that the 
specific pressure on its projected area must not be excessive — the 
tendency of the oil to remain in its place by capillary attraction, 
perhaps helped by the pressure under which it is fed into the bearing, 
is much greater than the tendency of the load upon the shaft to force 
it out. 

From the foregoing, it is evident that the condition of effective 
lubrication is that in which the shaft literally floats in an oil film of 
microscopic thickness, this film completely surrounding it and so 
protecting it from any contact whatever, under normal conditions, 
with the bearing surface. The necessity for the accurate fitting of 
bearings is to provide an oil film of uniform thickness. 


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Care of Lubricant in Cold Weather. Nearly everyone realizes 
the amount of care necessary with cooling water in freezing weather, 
but few realize that extreme cold has practically the same effect upon 
lubricants. In the coldest weather, a lighter grade of oil specially 
made to withstand low tempera- 
tures should be used. If a 
special oil cannot be obtained, 
the lighter thinner quality will 
suffice, as even when thickened 
up by the low temperatures this 
oil will flow more readily than 
the thick oils. Sometimes the 
slow circulation of the oil in cold 
weather allows the motor bear- 
ings to rim dry and heat. This 
trouble can be remedied by 
changing to a lighter oil. The 
same is true of the clutch oil 
which is in the multiple disc 
running in oil. Thick oil in this 
in cold weather will often thicken 
up and stick so the clutch will Fig. 230. 
not work well. 

Mammoth Grease Qun. For the average shop which handles a 
good many cars a day, too much time is wasted in using an ordinary 
method of filling a transmission, rear axle, or other large part, with 
grease. A mammoth grease gun can be constructed to do this same 
work in a few seconds. A form operated by compressed air is shown 
in Fig. 230. It consists of a steel cylinder about 8 inches in diameter 
and perhaps 7 feet long mounted vertically on a platform which is set 
on castors so that it can be wheeled around the shop as needed. A free 
piston is placed in the cylinder, above the grease, and air admitted 
through the central opening in the screw top by screwing on a com- 
pressed air hose. The outlet hose at the bottom is made long 
enough to reach any ordinary point on the average car. When a 
transmission is to be filled, the platform is wheeled up to the 
car, the bottom hose put in the transmission, and the cock opened. 

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Mammoth Grease Gun for Garage Use 
Courtesy of "Motor World" 



Then the air hose is connected and the pressure turned on; the 
grease will be forced out in a hurry, filling the case in a few 
minutes regardless of the quantity needed. 

Getting Oil Barrels Out of Sight. The oil barrels around the 
garage are in the way; they collect dirt and spread oil into every- 
thing within reach and take up much valuable space, A good way 

Fis. 232. Method of Elevating Oil Barrels to Save Space 

to get rid of them is to build a rack close to the ceiling, Fig. 232, 
and put them up there. A pipe with a faucet at its lower 
end for drawing oil leads down from each barrel; these pipes 
are grouped over a small pan which catches the drip. Filling 
these barrels is easier than it seems. Connect a pipe from the 
barrel of new oil to the overhead barrel to be filled, apply the 
air pressure at the bung, and the oil will be forced up. 

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Fig. 234. Settling Tank with 

Cocks at Various Levels 

for Saving Oil 

Oil Settling Tanks. If lubricating systems are drained as often 
as both manufacturers and oil people recommend, there is a good deal 
of oil around, which is heavy and of a doubt- 
ful quality. But if this oil can be allowed 
to stand, or can be filtered, a large quantity 
of it can be used for other purposes. If a 
tank of fairly large size is made with a series 
of faucets or cocks at different levels, some- 
what like that shown in Fig. 234, enough of 
the oil can be saved to resell at a good profit, 
or, if there is no idea of selling it, it can be 
used for other machinery or for other pur- 
poses, where the need for high-quality oil is 
not so great. The oil drawn off the crank- 
case is poured in at the top and gradually 
settles, the heavier sediment going to the 
bottom, the thickest oils next, and so on, 
until the top will show a fair quality of light oil, and the layer next 
to it a fair quality of medium oil, and so on down to the bottom. 

Oil Filtering Outfit. 
If one has the apparatus, 
filtering is much superior. 
A simple filtering outfit is 
shown in Fig. 235; this 
consists of the tank with 
provision around the inside 
for supporting a fine brass 
screen and two or more 
funnels, one above the 
other. The mouth of each 
of the funnels is filled with 
cotton waste, and the fun- 
nel set in place, then the 
next one is filled and set 
above it, and finally, the 

Fig. 235. Filter of Simple Construction for Filtering Oil brasg gauze j g j^j across 

at the top. As the oil is drawn off, it is poured in at the top. The 
wire catches any large particles, while the oil in filtering through the 


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The Tubinq is Easily 
' Threaded off 

two or three bunches of waste will lose practically all its impurities, 
coming out perfectly clear. After each use, the waste is removed 
and burned, and new waste put in its place. 

Oil measures, funnels, and other containers should always be kept 
clean. The oil left on them soon collects dust and dirt, and the next 
time some of this old oil will be poured into the engine with the fresh 
oil. All oils do not mix, and chemical action may be set up 
between old oil of one quality on the can and new oil of another 
quality in the can. Kerosene or a little gasoline should be poured 
in the containers or funnels to clean them off. This liquid 
should be rinsed out of the cans and put into a settling or filtering 
tank and practically all of 
it recovered. 

Bending Oil Pipes. 
Frequently an oil pipe 
which has a curve or spiral 
in it, or even a series of 
coils has to be replaced. 
If bent by hand, a kink 
may be made in the pipe 
which will lead to a future 
break. A simple fitting 
for bending these pipes can be made in a few minutes. Take a piece 
of hard wood about 3 inches square and 9 inches long and turn it 
up round in the lathe, then down one end, as shown in Fig. 236, and 
cut the spiral grooves or threads in it. These should be about ^ 
inch in width and cut with a round-nosed tool so as to get a smooth 
bottom to the grooves. When a pipe is to be bent, fill it with resin, 
a fine lead rod, or anything flexible. The wood can be held in the side 
of the vise and the tubing wound onto the threaded end. If the 
pipe is of a heavy gage, anneal it by heating and plunge it into cold 
water before starting to bend it. After bending, melt out the filler. 

Summary of Troubles with Lubrication Systems 

Crankcase Oil. This should be changed about every 500 miles as, 
by this time, the lubricating qualities of the oil are nearly exhausted. 
After draining the oil, wash out the crankcase with kerosene and 
see that the kerosene is removed before putting in fresh oil. 

Fig. 236. Hard Wood Fixture for Bending Oil Pipe 


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Grease Cups. These are usually located on the rear axle, steer- 
ing knuckles, steering-column base, and many other parts. They 
should be kept constantly filled with cup grease. These grease cups 
should not be confused with small oil holes having caps which can be 
raised but not unscrewed. Grease cups should be screwed down 
occasionally in order to force the grease down to the bearing surface. 

Neglect of Lubrication. Neglect of lubrication is responsible 
for many troubles. Any automobile requires careful attention to its 
lubricating system. The owner will find it to his advantage financially 
to see that all necessary parts are properly lubricated. 

Steering Gear. The steering-gear parts require occasional lubri- 
cation. These parts include steering rod; worm, or sector, and gear; 
steering link at both ends; foot-pedal pivot or bearing; and all joints. 

Too Much Oil in Crankcase. Usually drain cocks are provided 
in the crankcase and are so located that when they are opened 
they will drain off only the surplus oil. 

Troubles with Mechanical Lubricator. If one of the sight feeds 
fills with oil, it indicates too rapid feeding of oil. Shut off the valve 
on the top of the lubricator till the glass is clear. If it does not 
clear up shortly, the probability is that it is necessary to clean the 

Mixing Gas-Engine Cylinder Oil with Fuel. This is advocated 
by the makers of a few two-cycle engines, the proportion being one- 
half pint of best gas-engine cylinder oil with every five gallons of 
gasoline. This, however, is not considered good practice. 


Types of Bearings Required for Different Locations. As the 

portion of a mechanism upon which, more than upon any other 
element, its continued operation and long working life depends, the 
bearings of any piece of machinery should be of the most approved 
design and most perfect construction. The crankshaft and connecting- 
rod bearings, which are the most important on the motor, are of 
the plain type on the majority of engines. Of the 1914 cars but six 
different makes had ball bearings for the motors, and, of these, two 
used plain bearings on some models, so that only four makers actually 
believed in ball bearings for engine shafts. For camshafts there is 
more difference of opinion, while on fan shafts almost all makers use 

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ball bearings. The other shafts, as pump, oiler, magneto, air-pump, 
generator, etc., are generally of the plain, solid, round type. 

Engine bearings, however, are generally of the split, or halved, 
type, the upper and lower halves being practically duplicates. A 
reason for this construction appears as soon as one" considers the 
application of the bearings to the shaft. It is granted that a crank- 
shaft must be as firm and solid as possible, and hence it must be made 
in one piece. As ball bearings also are made in one piece, there arises 
at once the difficulty of getting the bearings into place on the one- 
piece shaft. This difficulty has necessitated cutting the shaft or else 
making it especially large and heavy in those cases where balls are 
used. With the split type of bearing there are no troubles of this kind 
and the bearings are adjustable for the inevitable wear. 

Plain Bearings. The conditions that determine the proper 
proportioning and fitting of plain bearings have already been referred 
to in a preceding paragraph. 

The materials of plain bearings are commonly varied to meet 
different conditions. With liberal bearing areas, in situations where 
it is desired to bring about a perfect fit with the minimum amount 
of labor, and to protect the shaft from wear in case there is failure of 
the lubrication, the various types of babbitt metal — which usually 
are alloys of tin and lead, with sometimes some admixture of antimony 
and other alloys — are widely regarded as the most serviceable. Prob- 
ably the greatest advantage of a babbitted bearing is that, if the 
lubrication should fail, the low melting point and the soft material of 
the bearing will insure its fusing out without injury to the more 
expensive and valuable shaft. 

Brass and bronze bearings, particularly the phosphor bronzes 
and the bronzes in which the proportion of tin is high and that of 
copper low, with sometimes the admixture of a proportion of zinc 
or nickel, will allow the use of materially higher pressures per square 
inch than can be safely permitted on babbitted bearings. 

Steel shafts in cast-iron bushings, and even in hardened-steel 
bushings, make much better bearings than one might think, and 
though immediate trouble is to be anticipated with such a bearing 
should its lubrication fail, even momentarily, this trouble is more or 
less true of any bearing that can be devised. Since steel-to-steel and 
steel-to-cast-iron permit much the highest loadings per unit of area 


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that are permissible with any type of metal-to-metal bearing, the 
merits of these materials are perhaps less appreciated than might be 
desirable. Steel pins through steel bushings, however, are not an 
uncommon construction for the piston-pin bearings in high-grade 

One noticeable feature of plain bronze or other plain bearings 
for automobile use is that they are always grooved for oil circulation. 
This is done by easing off the edges, then cutting a spiral groove by 
hand diagonally across to the other edge or to the center point where a 
similar groove from the other side is met. In a solid bearing, the 
groove is generally cut both ways from a centrally drilled oil hole, 
while in split bearings the grooyes in each half usually form a modified 
letter x when viewed in plan, that is, two grooves start spirally inward 
from each edge near the ends, and all four meet in the center. This 
central point may be the spot where the oil enters or where it leaves. 
These grooves are seldom of very great depth, perhaps .008 to .010 
(eight to ten thousandths). 

New Oilless Bearings. A form of bearing that is new to the 
automobile but old in years is now coming into use. This is made of 
special wood which previously has been impregnated with oil. By 
saturating the pores of the wood with oil in this way, it is claimed that 
no lubricant need be used on the bearing for years. They are turned 
and fitted the same as bronze or other bushings. 

Another oilless bearing is made of bronze with graphite inserts; 
this bearing is sufficiently soft to form the lubricant, yet sufficiently 
hard to retain its form and shape. Approximately one-half of the 
inner surface of the bearing is graphite, the two alternating in various 
ways, that is, the graphite is put in in spirals, in circles, in double 
diagonals, in a herringbone pattern, in zigzags, and otherwise. 

Roller Bearings. Roller bearings, constituted by the inter- 
position of a number of small rollers between shafts and casings, 
are a type of bearing widely employed in automobiles. 

A much-favored construction is the tapered roller bearing 
illustrated in Fig. 237. This stands up very well under both thrust 
and radial loads. 

Another type of roller bearing is that illustrated in Fig. 238, 
which is the type used on the Ford rear axle. This is one in which 
the rollers are small flexible coils made of strip steel, finally hardened 


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and ground accurately to size. This type of roller can be depended 
upon to work without breakage or injury even though there be con- 

Fig. 237. Timken Roller Bearing 
Courtesy of Timken Roller Bearing Axle Company 

siderable deflection or inaccuracy in the alignment of shaft or casings, 
the flexibility of the individual rollers taking care of such small errors. 

Fig. 238. Hyatt Flexible Roller Bearing Partly Disassembled to Show Components 
Courtesy of Hyatt Roller Bearing Company, Newark, New Jersey 

It will be noted in Fig. 238 that there is a solid steel shell to go on 
the shaft and fit it tightly, and another to fit into the case or support, 
whatever it may be, perhaps attached there permanently. Between 


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these two comes the cage carrying the flexible rollers. Any load 
imposed upon the shaft is transmitted to the inner sleeve and by 
it to the flexible rollers; these rollers absorb the load so that none of it 
reaches the outer case. Furthermore, shocks coming to the case 
from without are absorbed by the flexibility of the rollers and, vice 
versa, shocks to the shaft do not reach the case. 

Ball Bearings. Probably the best of all bearings, except for 
certain special applications in which it is difficult to utilize them in 
sufficiently large sizes to assure durability, are the annular ball 
bearings of the general type illustrated in Figs. 239 to 243, inclusive. 
The basic feature of the most successful of modern annular ball 

bearings is their non-adjustability, the 
balls being ground very accurately to 
size and closely fitted between the 
inner and outer races so as to allow 
practically no play. 

The reason that the best ball bear- 
ings are not made adjustable is that in 
any conceivable type of ball bearing 
one or the other of the races rotates 

and the other remains in a fixed posi- 
ng. 239. Annular Ball Bearing ^ The ^^ j g ^ ^^ mu§t be 

a loaded side to the race that does not rotate, with the consequence 
that when wear occurs, it wears the ball track deeper at this point 
than on the unloaded side. With the bearings thus worn, it is almost 
impossible to make an adjustment, for the attempt can result only in 

tight and loose positions as the balls come 
out and in of the spot that is more deeply 


Fig. 240. section of Annular This condition has led the designers 

Bail Bearing an( j manufacturers of the various types of 

high-grade annular ball bearings that are now on the market to dis- 
card adjustment as of no value and to substitute in its place quali- 
ties of material and hardness of surface which, in combination with 
the provision of sufficient sizes, are found to reduce wear to so small 
an amount that it is almost inappreciable. A bearing thus made 
can be therefore depended upon to outlive almost any other part of 
the mechanism in which it is placed. 

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The carrying capacities of ball bearings, as compared with those 
of roller bearings, are much greater than a casual consideration might 
lead one to suppose. Theoretically, the contact of a roller bearing — 
between a roller and one of the races — is a line" contact, while that 
between a ball and a ball race is a point. But, practically, since some 
deformation occurs in even the hardest materials under sufficient 
load, the line contact in the roller bearing becomes a rectangle and the 
point contact in the ball bearing becomes a circle. Now the vital 
fact is that the area of the rectangle in the one case is substantially 
equal to that of the circle in the other — with given quality of materials 
and a given loading. So a ball bearing is fully as capable of carrying 
high loads as a roller bearing; besides, it avoids the risk of breakage 

Fig. 241. Ball Cage of Annular Ball Bearing 

that usually exists with rollers because of the impossibility of making 
them perfectly true and cylindrical. 

To assemble ball bearings of the type illustrated in Fig. 240, either 
of two expedients may be adopted. One is to notch one or both of 
the ball races, so that by slightly springing them a full circle of balls 
can be introduced through the notch. The other scheme is to employ 
only enough balls to fill half of the space between the races, which 
permits them to be introduced without any forcing, after which they 
are simply spaced out at equal intervals and thus held by some sort 
of cage, or retainer, such as is illustrated in Fig. 241. 

Ball bearings of the common annular type are quite serviceable 
to sustain end thrust as well as radial loads. For the best results 
under such loads, however, it is essential that the load be distributed 
equally around the entire circle of balls, for which reason the system 


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illustrated in Fig. 242 is a means of avoiding the unequal distribution 
of pressure likely to result from the slightest inaccuracy of fitting. In 

Fig. 242. Bearing Designed 
to Equalize Loads 

Fig. 243. 

Annular Ball Bearing Mounted for 
Thrust Loads 

this construction the outer ball race, shown at A, is provided with 
a spherical outer surface, permitting it to rock slightly in the mount- 
ing C, into the position shown in an exaggerated degree at B. It 
thus floats automatically to a position at exact right angles to the 

shaft upon which it is mounted, 
and so insures even loading of 
the whole ball circle. 

An annular ball bearing 
designed for thrust loads alone 
is illustrated in Fig. 243. In 
this bearing, the lower race A is 
provided with a spherical face, 
described from the radius B, so 
that, as in the case of the bear- 
ing illustrated in Fig. 242, when 
in use it automatically floats 
under the load into such a 
position that all the balls are 
under equal pressure. 

To secure uniformly satis- 
factory results from ball bear- 
ings, it is not only necessary in the first place to have them of the 
best materials, accurately made, and of sufficient sizes, but thereafter 
they must be always protected from dust and grit and from water and 
acids which tend to cause rust. They must also be kept lubricated. 

Fig. 244. Bearing for Combined Radial and 

Thrust Loads 

Courtesy of New Departure Manufacturing 

Company, Bristol, Connecticut 


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Combined Radial and Thrust Bearing. The need for a bearing 
which would take ordinary radial loads well and also sustain thrust 
has led to the development of combined radial and thrust bearings, 
one being illustrated in Fig. 244. This is constructed to take either 
form of load equally well, and for this reason has displaced a pair of 
ball bearings in many circumstances where formerly it was thought 
necessary to use a radial ball bearing to sustain the load and a thrust 
ball bearing to absorb the end thrust. In this way it represents an 
important economy. Furthermore, it is economical of space, as it 
takes less room than the former pair of bearings used for the same 
two purposes. 


Importance of Flywheel. With the growing tendency toward 
smoother and more even running and the demand for lower low 
speeds and higher high speeds, the flywheel, which was looked upon 
as a necessary evil for many years, is now receiving more attention. 
The designers realize that the flywheel plays an important part in 
balancing — that if it is too heavy the engine will be slow to pick up 
speed and will not run very fast, and that if it is too light, the engine 
will be very "touchy" and will not withstand quick variations from 
high to low or low to high speed, nor will it throttle down very slowly. 

Flywheel Characteristics. Weights. With weights being reduced 
to the limit in order to get higher engine speeds, the flywheel has 
received some paring down. Formerly, designers erred if at all 
on the heavy side with flywheels, but when they began changing the 
entire design of the engine to save a few pounds, they did not overlook 
the flywheel. In the flywheel, too, the growing use of counterweights 
has had an influence. 

Sizes. Designers realize, now that the hampering sub-frames are 
out of the way, that the larger the diameter the better the flywheel 
effect for equal or less weight. As a result, many flywheels have been 
increased in diameter as they have been reduced in weight. 

Shapes. Flywheel shapes, that is, sections, used to be rec- 
tangular or almost square, with a solid web or spokes practically in 
the center. Clutches, starter-ring gears on the outer surface, and 
other contributing causes have changed the character of flywheels 
so that few have the rectangular shape or character now. The method 




of using fan blades as flywheel spokes has also fallen into disuse; 
although at one time it was widely tried and appeared to be a means 
of eliminating the fan entirely. 

Something of the present shape of flywheels can be seen by refer- 
ring back tc Figs. 217, 222, and 223. In the first figure, the flywheel 
has a triangular section with a solid web set at an angle so as to bring 
the flywheel nearer the engine; the inner surface is tapered to suit 
the clutch. In Fig. 222, the shape is entirely different and apparently 
much lighter. This is an eight-cylinder engine. Here the flywheel 

Fig. 245. Three Common Methods of Fastening Flywheel: A, Flange and Series of Bolts; 

B, Plain Key; C, Key, Taper and Nut 

Courtesy of N. W. Henley Publishing Company, New York City 

section as a whole has a short U-section, being externally a short 
section of a cylinder. The web, too, is perfectly straight at one end. 
The inside is cut out for the clutch, but with a very slight angle. The 
shape of the flywheel in Fig. 223 is somewhat similar to that of Fig. 
217, but it is wider and not so thick. It shows a larger diameter, too. 
The exterior is plain and straight except at the front edge where the 
starting-ring gear teeth are cut into a raised portion of it. The web is 
straight and solid, close to one end, but not flush with it as in Fig. 222. 


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Methods of Fastening Flywheels. That part of the flywheel 
which is most interesting to the repair man is the method of fastening, 
or rather the inverse of this, the method of removal. There are three 
general methods of fastening flywheels to crankshafts, and these are 
shown in Fig. 245. They are the plain round end with a key, as 
shown at B; the tapered end with key, nut, and lock nut, as shown at 
C; and the method of bolting to a circular flange integral with the 
crankshaft, as indicated at A. The first is widely used for stationary 
gas and marine engines of very low price, but very little, if at all, on 
automobile engines. The second has been used, but is rapidly going 
out, as it is, like the first, a low-priced method which did not prove 
satisfactory. The third method is rapidly becoming universal. 

In use, the flywheel flange on the crankshaft is generally five 
or six inches or a figure between these, in diameter, with six to ten 
bolts. In the form shown at C, Fig. 245, the flange is exterior to the 
flywheel, but in Figs. 217 and 223, the more general method of grooving 
the flywheel hub to receive the flange will be noted. In Fig. 245, 
the bolt shown has a countersunk head let into the flywheel surface; 
in general, the bolt head is either standard or else round and set into a 
countersink. In this case, it is slotted for a screwdriver. Also a 
single nut is shown, whereas a nut and lock nut, or, at least, nut and 
lock washer, are always used. 

Flywheel Markings. As has been noted previously under 
Valves and Valve Timing, the surface or rim of the flywheel generally 
carries upon it marks to indicate to the repair man the timing of the 
motor. Some makers give only one or two marks for a single cylinder, 
reasoning, with some degree of correctness, that if the first cylinder 
is set right, the others must be pretty nearly so, and that more marks 
would only confuse. Others put on their flywheel all the marks for 
all the cylinders. 

Summary of Engine»Group Treatment. In Parts I, II, and III, 
the entire engine group has been discussed in detail. The different 
sections have been handled according to present practice and methods 
of operation. It is easily possible that the near future may bring 
about the elimination of one or more of these groups or its combina- 
tion with some other. 

The engine, too, has been discussed in its present form only, 
although some attempts have been made here and there to indicate 


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the trend of developments. He would be a very foolish man who, 
knowing the past history of the automobile engine, would say that it 
has now reached perfection and will always have its present form. 
On the contrary, there seems every reason to believe that hardly a 
single feature of our present-day engine, at least in its present form, 
will be found in the up-to-date engine of ten or twenty years from 
now. This constant change renders a work of this kind almost 
impossible of absolute up-to-dateness, for changes are actually made 
and put into use while the book is being printed. As far as possible, 
however, the work aims to discuss the modern developments and yet 
to give the repair man, in particular, the information he needs as he 
comes in contact with cars of all classes, ages, and conditions. 

Q, For what purposes are valves used? 

A. Valves are used (1) to admit the mixture created in the 
carburetor into the cylinders at the proper time in the stroke and in 
the proper quantity (called admission or inlet valves) ; and (2) to allow 
the burned gases to be exhausted from the cylinders at the proper 
time in the cycle (called exhaust valves) . At all other times the valves 
remain tightly closed. The valves, closing upon a machined seat 
and opening and closing at precise times and in an exact manner, give a 
control over the operation of the engine which is not possible in any 
other way. 

Q. How are these valves opened and closed? 

A. By means of cams, or projections, upon a rotating shaft 
called the camshaft, these projections raising the valve off its seat, or 
opening it, at the proper time. When the projection allows the 
valve to come down onto its seat, or close, a strong spring comes into 
action, forcing it to do this in a positive manner. 

Q. How is the camshaft operated? 

A. By gears or chains from the crankshaft, these being designed 
and assembled carefully, so that the camshaft will revolve at precisely 
half the speed of the crankshaft. 

Q. Why should the camshaft revolve at half the crankshaft 

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A. Because the operation of opening and closing the valves 
comes on every other stroke only, and the camshaft really works 
twice as slowly as the crankshaft. 

Q. What is the general form of a valve? 

A. The usual form is called a poppet valve, and its section is 
that of a letter T, having a long slender stem at the top of which is a 
large flat head. The lower surface of this head is machined off to 
fit the seat in the cylinder, while the upper surface is rounded up to 
the center, where a slot for a screwdriver is provided. 

Q. Are there other forms of valves? 

A. The piston form of valve is little used, but the sliding-sleeve 
valve is used on all Knight type of engines and some others. In addi- 
tion, a few motors have been built with rotating-disc valves. The 
piston valve is similar to the usual piston, having a reciprocating 
motion in a special round-valve chamber made for this purpose. In its 
movements up and down, it uncovers ports in the walls, thus giving 
the equivalent of the poppet-valve opening. The sliding sleeve is a 
hollow cylindrical member entirely surrounding the piston and recip- 
rocating in the same manner. In its up-and-down motions, ports in it 
register with ports in the cylinder walls at the proper points in the 
cycle, thus corresponding to the opening of the poppet valve. The 
rotating-disc valve acts on the same plan but consists of a flat or 
a conical disc which is gear-driven from the crankshaft. It has a hole, 
or port, in it which registers with other ports in the cylinder at the 
correct time in the cycle. There are other forms of valve but none 
in wide use. 

Q. What are the advantages of the poppet valve? 

A. Its simplicity is its greatest asset. The poppet valve is 
the simplest and most easily understood form of all. In addition, it 
will withstand continuous operation at the highest temperatures. 

Q. What are its disadvantages? 

A. It affords a comparatively small opening, smallest at the 
beginning and ending of the suction stroke, where it should be largest; 
it has a noisy hammering action which makes for rapid wear, constant 
adjustment, and frequent renewal; the actual seat is so small and is 
exposed to such variations of temperature and other severe conditions 
that it tends to wear out and leak very rapidly, thus reducing the 
power and speed, rendering action uncertain and calling for frequent 

484 Digitized by G00gle 


regrinding; finally, the necessity for ready accessibility for adjustment 
allows the driver, or operator, to alter the action with a consequent 
influence upon the output. 

Q. Can any of the disadvantages be overcome? 

A. The opening cannot be changed, but the noise can be reduced 
by enclosing the whole valve action in removable covers. The influ- 
ence of hammering in the way of wear, need for adjustment, renewal, 
leakage, etc., can be minimized by the use of tungsten steel, which is 
harder and wears much more slowly. The use of this material also 
lessens power and speed losses, uncertain action, and frequency of 

Q. Is there any way in which the design can influence these? 

A. Recent tendencies and experiments have shown that with an 
arrangement for positive, or mechanical, closing of the valve, springs 
can be made very small and weak, thus eliminating the cutting 
action of the usual stiff spring on the cams and reducing the ham- 
mering action and the noise. 

Q. Have sleeve valves any springs? 

A. No. They are operated by eccentrics from the eccentric 
shaft, which corresponds to the camshaft in a poppet-valve system. 
These are positive at all times, that is, the sleeves are always mechani- 
cally operated and thus are unvarying. 

Q. What is the general shape of valve enclosures? 

A. As simple as possible. Frequently, all the valve mechanism 
is enclosed by a single rectangular plate. More usually, it consists of 
two such plates. With a single plate, a pair of, or at most three, bolts 
are used to hold it in place; with two plates, these generally have 
two bolts each. 

Valve Timing 

Q. How is the valve timing arranged? 

A. The inlet is allowed to open as soon after the upper dead 
center as the designer considers reasonable, and closes as far past the 
lower dead center as will allow the maximum charge to enter and still 
not let any of it blow out. It should be remembered that when the 
piston passes the lower center, it begins to rise and reduce the volume 
in the cylinder. Similarly as to the exhaust, it is allowed to open as 
much before the lower dead center as will insure full power, and is held 

485 Digitized by G00gle 


open as long as possible, this sometimes overlapping the inlet opening 
and always passing the upper dead center. 

Q. What is the average valve timing? 

A. The timing of fifty-six American motors, including perhaps 
one hundred different models, averaged as follows: inlet opened from 
upper dead center to 21° beyond — average 10° 48'; inlet closed from 
15° to 46° 22' beyond lower dead center — average 35° 7'; exhaust 
opened from 31° to 57° 30' ahead of lower dead center — average 50° 10'; 
exhaust closed from upper dead center to 21° beyond — average 9° 20'. 

Q. How does the repair man know what the correct timing is? 

A. Practically all makers give it in their instruction books and 
other literature as well as marking it upon the flywheel surface. 


Q. How are the cams usually made? 

A. On all modern motors, the cams are formed integral with 
the camshaft, which is machined, hardened, and ground as a unit. 
This keeps the timing always the same, which is sometimes not the 
case when cams are made separate and keyed and pinned in place. 
Moreover, the integral cams are more accurate, because the machines 
which have been developed for this purpose insure absolute accuracy. 

Valve Guides 

Q. What is the valve guide? 

A. That member which forms the bearing as well as the support 
for the valve stem. Its importance can be judged from the fact that 
the guide holds the valve in line with its seat so that it seats itself 

Q. How are valve guides usually made? 

A. Generally, they are of cast iron and removable, being 
screwed into the cylinder from below. The diameter is made as small 
as possible and still give sufficient stiffness and strength; the length is 
made as great as possible, for the entire length of the valve guide 
is bearing surface for the valve stem. 

Exhaust Manifold 

Q. What is the influence of the exhaust manifold? 

A. To remove the exhaust gases from all cylinders as quickly 
and as thoroughly as possible. If this is not done, the burned gases 

486 Digitized by G00gk 


will retard the next outflow of gas, until finally the engine may be 
stopped because it is not receiving rich enough fuel. The best form 
of exhaust manifold is the one which does this work most quickly and 
most thoroughly. 

Q. What is its general form? 

A. A long cast-iron member of round or rectangular section, 
slightly larger at the outlet end, and bolted to the cylinder casting. 

Q. How can this be improved? 

A. Recent experiments have shown that an arrangement of 
shape and size can be effected which will bring about an ejector effect 
immediately back of each exhaust orifice. This will produce a 
slight suction upon each succeeding volume of burned gas, which will 
increase the efficiency of the exhaust and thereby improve the power 
of its motor. 


Q. What is the purpose of the muffler? 

A. To reduce the pressure of the exhaust gases so that when 
emerging into the atmosphere they will do this without noise. As 
they emerge from the cylinders, the pressure is fairly high, and if they 
were allowed to pass immediately into the air, the noise would be 

Q. How is this silencing accomplished? 

A. By successive expansions, each of which reduces the pres- 
sure considerably. The gases come into a small central tube and are 
allowed to expand into another surrounding chamber of perhaps 
double the area, with consequent reduction of pressure. Then they 
are allowed to expand into another chamber, perhaps twice as large 
as this, with further reduction of pressure. This process is continued 
until practically all pressure is eliminated, so that the gases will 
emerge without noise. 


Q. How are explosion motors cooled? 

A. Mainly by the indirect method in which water surrounding 
the cylinders removes their heat and then is itself cooled in the radi- 
ator. The direct, or air-cooling, method is now used by but one 
maker, Franklin. 

Digitized by VjOOQ IC 


Q. What is the general cooling method? 

A. There are two methods in general use, called the natural, 
or thermosiphon, and the pump systems. The former is so-called 
because the natural increase in temperature of the water is used to 
circulate it to the radiator and back. The latter is called a pump 
system, because a pump is used to force the water around. 

Q. Are there other differences between the two? 

A. In the thermosiphon system, the difference in pressure crea- 
ted by the increasing temperature is so slight that all bends must 
be made very easy and all pipes made very large, so the water will 
pass easily. Also the system as a whole must be short and compact 
with radiator close to motor, and with little difference in level between 
the highest and lowest points. The added weight of larger pipes and 
their appearance just about balance the simplicity and smaller number 
of parts. 

Q. What general types of radiators are in use? 

A. The cellular (which may have square, round, or hexagonal 
cells) and the tubular form with horizontal fins sweated on are the 
two forms generally used. 

Q. How does the water circulate in these two forms? 

A. In the cellular form the water is in very thin sheets between 
the cells, with a consequently high ratio of air space to water space. 
The water is forced to follow a zigzag path to add to the cooling effect. 
In the tubular form, the water flows from an upper to a lower tank 
through the vertical tubes, which are of relatively larger diameter as 
compared with the water space in the cellular form — f against -st. 

Q. What is the usual form of pump? 

A. Four forms of pumps are used for water circulation: the 
centrifugal, the gear, the plunger, and the vane. The first two are 
used about equally on the majority of American pleasure cars, the 
last two having but a few adherents. 

Q. What is the latest move to improve water circulation? 

A. The use of a thermostat to control the flow of the water 
according to its temperature. This device holds the water in the 
cylinders until a certain predetermined temperature is reached, when 
it opens and allows the water to flow through the radiator and be 
cooled. By setting this so that this predetermined temperature is 
high, but not so high as to be dangerously close to the boiling point, 

488 Digitized by G00gk 


the efficiency of the engine is increased, for a hot engine works better 
than a cold one and gives more power. 

Q. What is the purpose of the fan? 

A. To increase the efficiency of the radiator by drawing more 
air through it and thus cooling the water more. 

Q. How is the fan generally driven? 

A. The belt drive, using a flat or V-type belt is general because 
of its simplicity, but a few better cars have gear or chain drive; 
the latter method has increased in recent years particularly with the 
V-type motors, for in those it has been found easy to drive the fan from 
a shaft in the immediate vicinity. 
Questions for Home Study 

1 . Describe in detail the timing of the Knight motor. 

2. Tell how to regulate and check up the valve action from the 
flywheel marking. 

3. How are silent-chain camshaft drives adjusted? How are 

4. How is the valve-stem clearance adjusted? 


Q. What is meant when lubrication is referred to? 

A. In general, the lubrication of the engine, because that is so 
much more important than the lubrication of any other part or group 
of parts. If the engine is run without lubricant, even for a very short 
time, it is ruined. On the other hand, many of the car parts can be 
run without lubricant for days and days, yet no damage will result. 

Q. What are the most used systems for the internal oiling of 
the engine? 

A. The most used systems are: the splash, the pressure, and a 
combination of the two, known as the splash-pressure, or constant- 
level, system. The first is simple, oil being provided in troughs into 
which the connecting rods dip, thus spreading the oil all over the 
interior of the motor and lubricating everything. The pressure sys- 
tem forces oil under pressure to all the important bearings and surfaces 
by means of interior-drilled oil leads or special pipes. It requires a 
pump, driven from some engine shaft, one or more strainers (for the 
oil is used over and over), the special drilling or piping, a gage on the 
dash to tell the driver how the system is working, and in some cases 


Digitized by LjOOQIC 


an adjustable pressure valve. The splash-pressure form has the oil 
leads to the important points only. Then the excess runs down into 
the crankcase and fills troughs into which the connecting rods dip. 
In some cases, these troughs are filled by direct individual leads off 
of the main oil pipe. Then when the rods dip into the oil, all benefits 
of the splash system are obtained. The fact that the pump main- 
tains a constant level of oil in the troughs has led to calling this the 
constant-level system. 

Q. What pressure is used in the pressure system? 

A. Prior to the introduction of V-type and high-speed motors, 
a few pounds less than 5 was considered sufficient. Now, many 
motors have a system which works under 40, 50, 60, and even 70 
pounds pressure. The oil leads are smaller, but the amount of lubri- 
cant which the bearing receives is much greater than previously. 

Q. What is the external lubrication of the motor? 

A. The lubrication of the accessories, such as magneto, water 
pump, starting motor, generator, air pump, fan, etc. Practically 
all these have oil holes, oil cups, or grease cups. The last named must 
have a special heavy grease or pure mutton or beef tallow, as a thick 
lubricant is needed to resist the passage of the water and not wash 
away. Otherwise the external lubrication is fairly simple and requires 
little attention. 

Q. What are the most used types of oil pumps? 

A. Like the water pump, all forms are used but the most popu- 
lar are the cam-operated plunger, the gear, and the plunger. 

Q. How are these driven? 

A. By gear from any convenient shaft, as camshaft, crankshaft, 
water-pump shaft, magneto shaft, etc. When the pump is enclosed 
in the crankcase, it is almost invariably driven from one of the 

Q. How are other parts of the car lubricated? 

A. Aside from clutch, transmission, rear axle, and wheels, prac- 
tically all parts are lubricated by means of grease or oil cups or oil 
boles. The latter are rapidly being eliminated for the sake of clean- 

Q. What are possible future developments in oiling? 

A. At present, there are two tendencies noticeable, one being 
the extension of forced lubrication to many parts outside the engine. 


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In the case of the Fergus car, the springs are enclosed in leather boots 
and lubricant supplied from the engine oil pump. Similarly, clutch 
and transmission are oiled from the engine pressure system. The 
1917 Marmon car is claimed to have but four or five lubricant points 
outside of the engine system. Another maker has adopted the 
leather-enclosed and lubricated springs. All these signs point toward 
less lubrication for the driver and owner to do, more points being 
included in the engine system. The other noticeable point mentioned 
has been partially covered; it is the reduction in number of points 
requiring individual attention, by other means than extending the 
engine pressure system to them. 

Q. How should graphite be used? 

A. Graphite should be used very sparingly, for a little of it goes 
a long way. It is not like grease which is used up very quickly, but 
is more or less indestructible. When a combination of graphite and 
grease is used, it will be found to last twice as long at any given point 
as the same quality of grease alone. Graphite in its very finest form, 
when introduced into the engine system, is beneficial as it seems to 
put a kind of polish, or surface finish, on the cylinders, which resists 
wear. After this has been put on, less lubricant, by at least 20 per 
cent, can be used in the engine. It should, however, be used in very 
small quantities, two tablespoonfuls to a gallon of oil being sufficient 

Q. What is its big advantage? 

A. In addition to the fact that it seems to fill up the pores 
and surface scratches of the parts on which it is used so as to give 
them a fine finish, graphite has the advantage of resisting the very 
highest temperatures very well, so that its use constitutes a safe- 
guard against immediate injury in case of neglect. 

Q. What are oilless bearings? 

A. There are two forms of oilless bearings, one of hard wood 
which has been impregnated with lubricant by boiling in oil, or some 
similar impregnation process, and the other is a bronze and graphite 
combination, in which about half the bearing surface consists of plugs 
or strips of pure graphite. These graphite surfaces supply the lubri- 
cant for the entire bearing, which never needs additional lubricant, 
so it is claimed. 
Questions for Home Study 

1. Describe the lubricating system of the Pierce-Arrow car. 

Digitized by LjOOQ IC 


2. How is the Cadillac eight motor oiled? Give details. 

3. What is the usual method of changing thfe amount of oil 
pumped, in a pressure system? 

4. Select some method of driving the oil pump, which seems 
simple to you, and describe it, telling why you selected it. 

5. How would you lubricate spring leaves, with what and how 
often? fan bearings? front wheel bearings? magneto shaft? 

6. How do you select a good engine oil ? 


Q. How does a light flywheel, affect an engine? 

A. The engine will be easy enough to start and stop, but very 
touchy on changing speeds— too quick a change will kill it. More- 
over, it will not run very slowly. 

Q. How do present flywheel sizes compare with those of former, 

A. Present flywheels are larger in diameter but narrower and 
lighter in weight. The increase of diameter made by the elimination 
of subframes allowed cutting down the width and weight because the 
flywheel effect is equal to its mass times its radius, so that by increas- 
ing the radius the mass can be reduced. 

Q. What are the usual methods of flywheel fastening? 

A. The flange forged on the crankshaft and through bolts is 
almost universal. A few motors are still made with a round crank- 
shaft end and a large key; or with a tapered shaft end, and a key, a 
nut, and a lock nut. The latter form is used when the crankcase is of 
the barrel type with removable end plates and is so made as to allow 
removal of the crankcase end plate at the rear. In some few cases 
the flywheel is made this way so as to allow putting on or taking off 
a ball bearing at the rear end of the crankshaft. 

Q. What are the markings on the flywheel rim? 

A. The timing is now generally marked on the surface of the 
flywheel to guide the owner or repair man in making adjustments or 
in assembling the engine correctly. The adjustments vary; some 
makers give the complete timing for a single cylinder, others give a 
few points for all, and still others give all the points for all the cylin- 
ders . The latter is the best way. 


Digitized by VjOOQ IC 


The page numbers of this volume will be found at the bottom of the pages; 
the numbers at the top refer only to the section. 

If you do not find what you want under one heading, stop and think 
what other headings it could be under. 




Aviation motors (continued) 

ABC aviation motor 94 



A.L.A.M. horsepower formula 132,142 



Absolute pressures 66 



Absorption brake 127 

Liberty V type 


Adiabatic compression .68, 70, 73 



Admission stroke 14, 66, 70, 155 



Admission in two-cycle motor 83 

Napier Lion 


Air, mixed with fuel 110, 112, 



119, 248 



Air cooling (see also Aviation 

Aviation motors, general data 


motors) 150, 443 



Air pressures 87 

air-cooled motors 


, 89, 91 

Air-pressure feed 357 

B.R. 1 


Airplane motors (see Aviation 






Alcohol as fuel 111, 113, 114, 



115, 118 



Altitude adjustment of carburetor 281 



American motors, valve timing 

air pressure 


379, 380 

all-in-line motors 

89, 97, 

99, 100 

American Power Boat Association 

altitude adjustment of carbure- 

horsepower formulas 133, 134 



Anti-freezing solutions 114, 442, 446. 

automobile motors, 

comparison 86 

Atmospheric pressure 66 


Atoms 121 

B.R. 1 


Autocar engine 18 



Automobile motors 18, 86 



Automobiles 116, 145 



Auxiliary air valve 249 



Aviation motors 



B.R. 1 and 2 96 



Basse^Selve 97 



Curtis V type 101 



Duesenberg 106 



Frederickson 91 







Aviation motors, general 


Aviation motors, general 





norsepower rating 









carburetor for 








cylinders, number of 




B.R. 1 










nine-cylinder motors 


i, 96 



opposed motors 





power output per cylinder 




B.R. 1 




















Jupiter - 






table showing 




V-type motors 








direct-driven motors 

101, 109 



double motors 


radial motors 

43, 88, 89 















single-crank feature 


Napier Lion 






rating of aviation motors 

eight-cylinder motors 


(see horsepower rating) 

eighteen-cylinder motors 


rotary motors 

88-92, 96 

fan motors 

89, 109 

seven-cylinder motors 




six-cylinder motors 96, 97, 


five-cylinder motors 


sixteen-cylinder motprs 99 



fixed-radial motors 

94, 95, 96 

Sliding Sleeve, Frederickson 

four-cylinder motors 




fourteen-cylinder motors 



horsepower rating 


B.R. 1 


B.R. 1 




B.R. 2 
























Note. — For page numbers see foot of pages. 


Digitized by 



Aviation motors, general data 

King-Bugatti 99 

Liberty 104 

Marlin-Rockwell 93 

Mercury 96 

Wasp 94 

ten-cylinder motors 93 
twelve-cylinder motors 

Curtiss 101 

Fiat 106 

V type 101 

Liberty 104 

Napier Lion 109 

two-cycle motors 91 

two-cylinder motors 93, 101 

types 89 

V-type motors 89, 101 

angles, range of 99, 101 

Curtiss 101 

cylinders, number of 101 

Duesenberg 106 

King-Bugatti 99 

Liberty 104 

relation to W-type motors 109 

vertical motors 89, 97, 99, 100 

W-type motors 89, 109, 110 

water-cooled motors 88, 89, 96 

Bass6-Selve 97 

Curtiss V-type 101 

Duesenberg 106 

Hall-Scott 100 

King-Bugatti 99 

Liberty V-type 104 

Sunbeam-Coatalen 109 

weight of motors 

automobile motors, comparison 87 

B.R. 1 96 

B.R. 2 96 

Basse^Selve 99 

Curtiss 104 

Duesenberg 109 

Frederickson 92 

Hall-Scott 100 

Jupiter 96 

King-Bugatti 99 

Note. — For page numbers see foot of pages. 


Aviation motors, general data 
weight of motors 

Liberty 106 

Marlin-Rockwell 93 

Mercury 96 

Wasp 95 

X-type motors 89 


B.R. 1 and 2 aviation motors 96 

Back-firing 77, 83, 85, 347 

Balanced crankshaft 217 

Ball bearings 477, 478 

Ball and Ball carburetor 289 

Barrel-type crankcase 227 

Bass6-Selve aviation motor 97 

Baume" scale 111 

Bearings 150, 204, 211, 217, 468, 473 
Bennett air washer 333 

Bennett carburetor 329 

Benzene as motor fuel 242 

Benzol 115, 118, 325 

Boiling points of petroleum pro- 
ducts 111, 113-115 
Bore of motor (see also Avia- 
tion motors) 79, 182 
Brake horsepower 12, 125 
formulas 126, 128 
British thermal unit 112 
Butterfly valve 245 

Cadillac cam mechanism 396 

Cadillac carburetor 321 

Cadillac connecting rods 205 

Cadillac cylinder chassis 431 

Cadillac lubrication 451, 457 

Cadillac motor 44, 156, 378, 428 

Cadillac thermostatic device 439 

Cadillac valve mechanism 389 

Cadillac water jacket 432 

California gasoline 110, 258 

Cam 378, 384, 388 

Cam-gear covers 229, 232 

Camless motor 415 

Camshaft 378, 389, 414, 415 


Digitized by 



Carbon deposits 114, 


Ball and Ball 


Bennett air washer 



Leppe" gas generator 


Ensign fuel converter 


Ford types 265, 279, 

Holley 266, 272, 



kerosene types 








Packard fuelizer 

Parrett air cleaner 








Carburetors, general data 


air cleaner 

air-heated type 

air-pressure feed 

air supply, adjustment of 

air washer 

altitude adjustment 

auxiliary air valve 


Chalmers hot-spot manifold 

charge, proportions 

cleaning carburetor 

distillate, carburetor for 

159, 175 

299, 308 
325, 326 
265, 274 
277, 329 
245, 247 
279, 329 
244, 254 
251, 260 
147, 241 


Carburetors, general data (con- 
double carburetors 253, 275 

double-nozzle carburetor 251 

dual carburetor 253, 275 

economizer 257 

enclosed type 274 

exhaust-gas jacket 344 

exhaust-pressure feed 357 

exhaust system 149, 423, 486 

cut-outs 430 

manifolds 149, 424 

munler 428 

summary of instructions 486 

float 247, 263, 339, 346 

float chambers, heating 242 

flooding carburetor 347 

forced induction 243 

Ford cars, carburetors for 

265, 279, 299, 308 

Ford manifolds 

fuel gages 

fuel injection 

fuel pump 

fuel system 

gas generator, Deppe" 



fuel knock 

grade of 


supply of 

351, 354 






12, 110, 111 


110, 120 

110, 111, 258, 347 


116, 117, 248, 298 

gasoline adjustment 248, 268, 298 
gasoline line, leaks in 347 

gasoline-strainer trouble 339 

gasoline tanks 347, 356, 360 

gravity feed 356, 361 

heating the charge 

242, 245, 342, 351 
heavier fuels 113, 241, 249, 253, 325 
Bennett carburetor 329 

Deppe" gas generator 334 

dual carburetor 275 

Ensign carburetor 336 

foreign carburetors 327 

Holley carburetor 325 

hot-spot manifold 352 

Note. — For page numbers see foot of pages. 


Digitized by 




Carburetors, general data (con- 

heavier fuels 

Master carburetor 277, 329 

Miller carburetor 329 

high-speed adjustment 

Bennett 332 

Newcomb 295 

Rayfield 287 

Stromberg 254, 259 

Webber 284 

horizontal carburetors 252 

for block-cast engines 352 

Carter Model "L" 310 
on Ford cars 265, 279, 299, 308 

Rayfield- Model "M" 289 

Schebler Model "A'[ 301 
Stromberg Models "LB," 

"MB," and "LS" 254, 260 

Webber Model "E" 281 

Zenith 262 

hot-spot manifold 352 

idling adjustment 

Holley all-fuel 327 

Johnson 307 

Stromberg 258 

Zenith 264 

inlet manifold 147, 347 

construction 352 

heating the charge 351 

hot-spot type 352 

troubles 355 

types 349, 352 

inlet-pipe trouble 340 

kerosene carburetors ^ 325 

lean mixture, disadvantages 346, 347 

low-speed adjustment 

Bennett 332 

Carter 310 

Newcomb 295 

Rayfield 287 

Stromberg 257 

Webber 284 

Zenith 262 

manifold design 347 

Marmon motor, manifold 351 

metering valve 302, 304 

Note. — For page numbers see foot of pages. 

Carburetors, general data (con- 
misfiring 345 

mixing chamber 250 

mixture, proportions 341 

multiple-nozzle carburetors 254, 

277, 279 
National motor, manifold 350 

needle valve 246, 272, 339, 346 

oxygen-adding devices 324 

Pitot tube 302 

popping in 159 

preheating air 342, 344 

preignition in Bennett carbure- 
tor 332 
pressure feed 357 
pulsator 358 
racing type 279 
rich mixture, disadvantages 345 
spray nozzles (see needle valves) 
starving at high speeds 341 
Stewart vacuum feed 357 
Stromberg fuel pump 358 
Studebaker motor, manifold 348 
summary of instructions 362 
temperature regulator 273 
throttle loose on shaft 340 
throttle valves- 245 
troubles and remedies 159, 338 
truck type 311 
two-stage type 289 
vacuum feeds 253, 357 
vaporizing chamber 250 
Velie tractor hot-spot manifold 355 
Venturi-tube mixing chamber 250 
water-jacketing 242, 248, 342, 

344, 352 
Carpentier manograph 55 

Carter carburetor 308 

Castor oil as lubricant 465 

Centrifugal pump 437 

Chalmers car 23-26, 353, 389 

Chalmers hot-spot manifold 353 

Charge, proportions of 74, 341 

Chemical compound 120 

Chevrolet cylinder assembly 173 

Circulation of cooling water 436, 446 


Digitized by 




Clearance 74, 393, 405 

Combustion, analysis of process 121 

Combustion mixture 112, 119 


amount of 73, 93 

poor 81, 160 

reducing to eliminate knock 122, 123 

Compression gage 178 

Compression line 83 

Compression stroke 14, 68, 72, 155 

Connecting rods 147, 202, 220 

aluminum rods 207 

bearings 204, 211 

H-section form 202 

lightening the rods 203 

Triple Lite rods 207 

troubles and repairs 207, 220 

tubular rods 203 

Continental cylinder 171 

Cooling systems 29, 31, 149, 430 

air cooling 443 

air jackets 444 

anti-freezing solutions 442, 446 

Cadillac car 431, 432, 439 

centrifugal pumps 437 

circulation of cooling water 436, 446 

cleaning cooling system 445 

fans 441, 444, 445 

flanges on cylinders 443 

Franklin air cooling 444 

gear pumps 437 

heating of motor 446 

hose, replacing 445 

impeller 438 

internal cooling and scavenging 444 

knocking of motor 446 

Overland cooling system 438 

Packard thermostatic device 440 

plunger pumps 438 

pumps 437, 446 

radiators 433, 445, 446 

Renault radiator 436 

Reo water pump 437 

Riker truck radiator 434 

Studebaker radiator 433 

summary of instructions 487 

thermosiphon circulation 439 

Note. — For page numbers see foot of pages. 

Cooling systems (continued) 

thermostatic devices 439 

troubles and adjustments 445 

water cooling 430 

water jackets 431, 445 

welded applied water jackets 432 
Cranes 162, 164 

Crank arrangement 34 

Crankcase 20, 103, 226 

arms 229 

barrel type 227 

box type 227 

engine supports 229 

gear cases 229 

materials 229 

oil 472 

troubles and remedies 230 

Crankshafts 147, 166, 214 

balanced form 217 

bearings 217 

four-cylinder form 215 

material 214 

shims 217 

six-cylinder form 215 

troubles and remedies 218 

Creeper 212 

Crosby indicator 54 

Crude oil 111,113 

Crude petroleum, amount pro- 
duced 116 
Curtiss V-type aviation motor 101 
Cymogene 111 
Cylinders 30, 103, 147, 166 
breaks, welding 185 
casting, method of 167-169 
flanges 443 
I-head forms 167, 174 
L-head forms 167, 172 
materials used 166 
number of (see also Aviation 

motors) 156, 253, 388, 454 
repairs 175 

T-head forms 167, 172 


Dead center, effect of 
Dead center indicator 



Digitized by 




Degrees Baume 1 


Delivered horsepower 


Denatured alcohol 


Dendy-Marshall horsepower 




Deppe" gas generator 


Detroit lubrication 


Diagrams (see Indicator 


and Manograph cards) 

Diehl electric dynamometer 





Distillate, carburetor for 


Dorris cylinder 


Double-acting motor 

12, 15 

Double carburetors 



Double-nozzle carburetor 


Double-opposed motor 


Down stroke of two-cycle motor 



Dual carburetor 



Duesenberg aviation motor 





Ebullition carburetor 243 

Economizer 257 

Efficiency 15, 69, 124, 126 

Efficiency formula 126 

Eight-cylinder motors 41, 101, 

157, 217, 253, 350, 388 
Eighteen-cylinder motors 110 

Electrine 115 

En bloc cylinders 167, 169 

Enclosed carburetor 274 

Engine group 147, 155, 159, 283 

Ensign carburetors 336, 337 

Essex carburetor 271 

Ether 110 

Excelsior twin motor 22 

Exhaust in two-cycle motor 83 

Exhaust cam 378 

Exhaust-gas jacket 344 

Exhaust pipe 78 

Exhaust-pressure feed 357 

Exhaust stroke 15, 69, 77, 155 

Exhaust system (see Carburetors) 
Exhaust temperature 150 

Note. — For page numbers see foot of pages. 

Exhaust valves 78, 149, 380 

Expansion line 69, 77, 83 

Explosion line 74, 83 

Explosion motors 11 

aviation motors (see Aviation 

fuels * 110 

horsepower and rating calcula- 
tions (see Horsepower 
and rating calculations) 
indicator cards (see Indicator 

summary of instructions 135 

thermodynamics 51 

two-cycle motors (see Two- 
cycle motors) 
Explosion pressure 76 

Explosion stroke 69 

Explosion temperature 150 

Explosive mixture 110, 112, 119 

Explosive range 112, 119, 120 

External lubrication 448, 461 

Fan 441, 444, 445 

Fan motors 89, 109 

Fergus lubrication 464 

Fiat aviation motor 106 

Filtering carburetor 243 

Firing order 34 

Firing position, finding 176 

Five-cylinder motors 91 

Fixed-radial motors 94-96 

Flame propagation, velocity 119 

Flashing point 112, 115 

Float 242, 247, 263, 339, 346 

Float-feed carburetor 243 

Flywheel 151, 480, 492 

Flywheel markings 391 

Forced induction 243 

Forced lubrication 464 

Ford cars, carburetors for 265, 

279, 299, 308 
Ford crankcase 228 

Ford manifolds 351, 354 

Ford motor 171 

Ford rear-axle bearings 475 


Digitized by 






Galloping of motor 



132, 142 

Gas friction 


brake horsepower 

126, 128 

Gas generator 




Gas oil 


Electric dynamometer 


Gas speeds 


finding specific gravity 


Gasoline (see Carburetors) 

degrees Baume" * 


Gasoline line, leaks in 




Gasoline-strainer trouble 


horsepower 123j 

, 132, 142 

Gasoline tanks 


, 356, 360 

indicated horsepower 

124, 127 

Gear covers 

229, 232 

mechanical efficiency 


Gear pumps 


455, 456 

pressure ratio 


Gear set 


146, 151 

Prony brake 


Gear troubles 



132, 142 





Graphite as lubricant 


relation between pressure 


Gravity feed 

356, 361 

volume of air 


Gravity lubrication 



133, 134 


465, 466 


132, 142 

Grease cups 

462, 473 

thermal efficiency 


Grease gun 



127, 134 

Grinding operations 

183 3 

, 390, 403 

White and Poppe 


Four-cycle diagram 



Four-cycle motor 13, 14, 25, 48, 155 

Half-time shafts 


compared with two-cycle 

86, 134 

Hall-Scott aviation motor 

100, 104 

Four-cylinder crankshaft 

215, 216 

Haynes valve action 


Four-cylinder motors 38, 40, 

, 101, 157 

Heating the charge 242, 


342, 351 

carburetors for 


Heating of motor 


valve timing 

391, 392 

Heating value of fuels 112,114,115,117 

Four valves per cylinder 

243, 385 

Heavier fuels 111, 



Fourteen-cylinder motors 




253, 325 

Fractional distillates of petro- 

Bennett carburetor 



111, 121 

Deppe" gas generator 


Franklin car 19, 88, 

, 150, 444 

dual carburetor 


Frederickson aviation motor 


Ensign carburetors 


Fuel, motor 


foreign carburetors 


Fuel converter, Ensign 


Holley carburetor 


Fuel feeding 


hot-spot manifold 


Fuel gages 


Master carburetor 

277, 329 

Fuel injection 


Miller carburetor 


Fuel knock 


Hinkley truck hot-spot manifold 353 

Fuel pump 




Fuel spray 


Holmes car 


Fuel system 


Holley carburetor 266, 


325, 326 

Fuelizer, Packard 


Horizontal carburetors 





Gage pressures 


Horizontal opposed engine 


Note. — For page numbers see foot of pages. 


Digitized by 




Horsepower and rating calcula- 
tions 123 
A.L.A.M. horsepower formulas 

123, 142 
absorption brake 127 

American Power Boat Associa- 
tion horsepower formu- 
las 133, 134 
brake horsepower 125 
formulas 126, 128 
delivered horsepower 125 
Dendy-Marshall horsepower 

formula 133 

Diehl electric dynamometer 130 
dynamometer 127 

efficiency formula 126 


A.L.A.M. 132, 142 

brake horsepower 126, 128 

Dendy-Marshall 133 

electric dynamometer 128 

horsepower 123, 132, 142 

indicated horsepower 124, 127 
mechanical efficiency 126 

pressure ratio 76 

Prony brake 126 

R.A.C. 132, 142 

racing boat 133 

Roberts 133, 134 

S.A.E. 132, 142 

two-cycle 127, 134 

White and Poppe 133 

four-cycle vs. two-cycle motors 134 
fuel knock 110, 120 

indicated horsepower 123 

formulas ^ 124, 127 

mean effective pressure 124, 127 
mechanical efficiency 124 

formula 126 

motorboat horsepower formulas 133 
planimeter 124 

Prony brake 125 

R.A.C. horsepower formula 132, 142 
racing boat horsepower formu- 
las 133 
rating of motors (see also Avi- 
ation motors) 132 

Note. — For page numbers see foot of pages. 

Horsepower and rating calcula- 
tions (Continued) 
Roberts horsepower formulas 

133, 134 
"running in" motors 134 
S.A.E. horsepower formula 132, 142 
Sprague electric dynamometer 128 
testing motors 125, 127, 129, 

134, 419 
two-cycle motors 127, 134 
White and Poppe horsepower 

formula 133 

Hot-spot manifold 352 

Hudson car 271, 395 

Hyatt roller bearings 476 

I-head cylinder 167, 174 

Idling adjustment of carburetors 

Holley 327 

Johnson 307 

Stromberg 258 

Zenith- 264 

Ignition 28, 31, 49, 75, 149 

Impeller 438 

Indicated horsepower 83, 123 

formula 124, 127 

Indicator 51 

Indicator cards 51 

actual Otto cycle 70, 71 

back-firing 76 

fuel knock 65 

ideal Otto cycle 66, 67 

ideal two-cycle card 83 

negative loop 84 

preignition 76 

pressure-time card 65 

pressure-volume card 65 

rates of combustion 75 

time of ignition 75 

Watt's ideal diagram 52 

Injection of fuel 242 

Inlet cam 378 

Inlet manifold (see Carburetors) 

Inlet-pipe trouble 340 

Inlet valves and ports 78, 81, 

149, 380, 406 


Digitized by 





Inspection of motor 


Internal-combustion motors 


Explosion motors) 

Internal cooling and scavenging 


Internal lubrication 


Isothermal compression 



Jacketed manifolds 


Johnson carburetor 


Jupiter aviation motor 


Lubrication system (continued) 


Kerosene 110, 111, 113 

carburetors for 325 

fuel knock 121 

King-Bugatti aviation motor 99, 279 
King silent-chain installation 377 

Kingston carburetor 265, 274 

Knight motor 157, 375, 378, 416 

Knocking 120, 159, 160, 446 

gear oil pump 
graphite as lubricant 
gravity lubrication 
grease cups 
grease gun 
heat test of oils 
internal lubrication 
Locomobile lubrication 
Marmon lubrication 
mineral oils as lubricants 
motor lubrication 
multi-cylinder motors 

oil cups 
oil pumps 

Overland lubrication 
Pierce- Arrow lubrication 
plunger oil pump 
pressure lubrication 
Scripps-Booth lubrication 
settling tanks 

455, 456 



465, 466 

462, 473 





455, 457 

465, 467 



465, 466, 469 



449, 457 


455, 456 

451, 460 



L-head cylinder 


172, 395 

splash lubrication 


LaFayette motor 


splash-pressure lubrication 


Lapping operations 


214, 225 

Stearns-Knight lubrication 

Lean mixture 


346, 347 

453, 457 

Liberty fuel 


steering gear 


Liberty motor 


104, 106 

Studebaker lubrication 


Locomobile connecting rods 


summary of instructions 


Locomobile cylinder 

167, 168 

thermostatic control 


Locomobile lubrication 


troubles and remedies 


Locomobile pistons 


Locomobile valves 

19, 382 


Lubrication system 

150, 448 

"Make-and-break" igniter 


acid, testing oils for 



199, 214 




Cadillac lubrication 

451, 457 


149, 424 

castor oil as lubricant 




cleaning oil containers 




crankcase oil 

472, 473 

Manograph cards 


Detroit lubrication 


Marlin-Rockwell aviation motor 

excessive lubrication 



external lubrication 

448, 461 

Marmon 1920 chassis 


Fergus lubrication 


Marmon crankcase 


filtering oil 


Marmon cylinders 


forced lubrication 


Marmon lubrication 

455, 457 

Note. — For page numbers see foot of p ages. 


Digitized by 




Marmon manifold 351 

Marmon 1920 motor 144 

Marmon piston 189, 190 

Marvel carburetor 296 

Master camshaft 390 

Master carburetor 277, 329 

Mean effective pressure 124, 127 

Mechanical efficiency 124 

formula 126 

Mercury aviation motor 95, 96 

Midgley indicator 59 

Miller carburetor 279, 329 

Misfiring 345 

Mixing chamber 250 

Mixture, explosive 74, 110, 

112, 119, 341 
Molecule 120 

Moline-Knight motor 375, 419 

Monroe motor 388 

Motor (see also Explosion motors) 

147, 155, 159, 283 
Motor fuels 110,116 

Motor lubrication 448 

Motorboat horsepower formulas 133 
Motorcycle motors 20 

Multi-cylinder motors 156, 253, 

388, 454 
Multiple-nozzle carburetors 254, 

277, 279 
Multiple valves 243, 385 

Napier Lion aviation motor 109 

Naptha 111 

Napthalene 110, 111, 115 

National motor 158, 350, 424 

Needle valves 246, 272, 339, 346, 347 
Newcomb carburetor 292 

Nine-cylinder motors 95, 96 


Offset connecting rod 



465, 466, 


Oil cups 


Oil pumps 



Oilless bearings 


One-cylinder motors 


Note. — For page numbers see 

foot of pages. 

Optical system 60 

Otto four-stroke cycle 12, 66, 70 

Overhead-valve system 409 

Overland car 391, 438, 449, 457 

Oxygen-adding devices 324 

Oxygen process of removing car- 
bon 175 

Packard carburetor 240, 316 

Packard crankcase 227 

Packard fuelizer 318 

Packard motor 45, 104, 106, 228 

Packard silent-chain drive 408 

Packard thermostatic device 440 

Parrett air cleaner 334 

Peerless motor 426 

Pennsylvania gasoline 110, 258 

Petroleum, number of barrels 

produced 116 

Petroleum products 111, 117, 

121, 277 
Peugeot cam mechanism 389 

Photographic system 63 

Pierce- Arrow car 19, 314, 449 

Pierce- Arrow carburetor 314 

Piston and accessories 147, 190 

pins 194, 197 

power exerted against 45 

rings 81, 147, 191, 195, 201 

troubles and repairs 195 

Piston slap 122, 179 

Piston speed 75 

Piston travel 66 

Pitot tube 302 

Plain bearings 474 

Plain-tube carburetors 254 

Planimeter 124 

Plunger pumps 438, 455, 456 

Poppet valves 373, 378 

Ports, size of 78, 81 

Power output 86, 89 

Power stroke 14, 69, 77, 155 

Pre-compression 84 

Preheating air 342, 344 

Preignition 73, 120, 332 

Pressure in cylinder 68, 73, 77 


Digitized by 




Pressure feed 357 

Pressure lubrication * 451, 460 
Pressure ratio 76 

Pressure-time synchronizer 63 

Pressure-volume synchronizer 64 

Prony brake 125 

formula 126 

Pumps 437, 446 

Push rods and guides v 394, 410 


R.A.C. horsepower formula 132, 142 
R.P.M. of motors (see Aviation 

Racing boat horsepower formulas 133 
Racing-type carburetor 279 

Radial motors (see Aviation 

Radiators 150, 433, 445, 446 

Rating of motors (see Horse- 
power and rating cal- 
Rayfield carburetor 15, 285 

Renault radiator 436 

Reocar 36, 213, 437 

Repairs (see Troubles and 

Retarded spark, manograph card 81 
Rhigolene 111 

Rich mixture 119, 345 

Ring gear 34 

Roberts horsepower formulas 133,134 
Roberts motor with rotary 

valve 423 

Roller bearings » 475, 478 

Rotary motors 88-92, 96 

Rotating valves 376, 422 

Royal Automobile Club (Eng- 
land), report on Knight 
engine 418 

"Running in" motors 134 


S.A.E. horsepower formula 132, 142 
S.A.E. standard oversizes 183 

Scavenging 71, 85 

Note. — For page numbers see foot of pages. 

Schebler carburetor 299 

Scripps-Booth lubrication 457 

Semi-socket wrench 221, 222 

Setting of cars 379, 380 

Seven-cylinder motors 94 

Sight feed 150 

Silent-chain drive 377, 408 

Single-acting motors 16 

Six-cylinder crankshaft 215 

Six-cylinder motors 40, 96, 97, 

100, 157 

manifolds for 349 

valve timing 392, 394 

Six-stroke cycle 17 

Sixteen-cylinder motors 43, 99, 

101, 106, 159 
Sleeve-valves 20, 91, 157, 375, 415 
Sliding sleeve 20, 91, 157 

Sliding valves . 375 

Smalley motor 16, 47 

Spark lever 153 

Specific gravity 111, 113, 115, 117 

Specific heat 76 

Splash lubrication 461 

Splash-pressure lubrication 449 

Sprague electric dynamometer 128 
Spray nozzles (see Needle valves) 
Spraying carburetor 243 

Starving at high speeds 341 

Stationary gas engine 46 

Steam-engine-type indicator 51 

Stearns crankshaft 215 

Stearns-Knight lubrication 453,457 
Steams-Knight motor 20, 157 

Steering mechanism 147, 153, 473 

Stethoscope, locating noises by 179 
Stewart carburetor . 302 

Stewart vacuum feed 357 

Stroke of motors (see Aviation 

Stromberg carburetor 244, 254 

Stromberg fuel pump . 358 

Studebaker cylinders 169 

Studebaker lubrication 450 

Studebaker manifold 348 

Studebaker radiator 433 

Stutz motor 19, 387 


Digitized by 




Suction inlet valve, manograph 

card 82 

Suction pressure 72 

Suction stroke 14, 66, 70, 155 

Sunbeam-Coatalen aviation motor 109 
Surface carburetor 243 

T-head cylinder 167, 172, 396 


aviation motors 89 

clearance, effects of 74 

explosion motor fuels 112 

Knight engine, report on 418 

valve timing of American cars 379 

Tailings 113 

Temperature regulator 273 

Temperatures in motor cylinder 

70, 72, 73, 150 
Ten-cylinder motors 93 

Testing motors 125, 127, 129, 

134, 419 

Thermal efticiejacY^ fi& 

Thermodynamics of motors 51 

Thermosiphon circulation 29, 439 

Thermostatic devices 439, 464 

Throttle lever 153 

Throttle valves 245 

Throttling 85 

Throttling governor 51 

Tillotson carburetor 313 

Timing of cars 84, 379, 380, 381, 

391, 420, 482 

Timing gears, marking 406 

Timken roller bearings 476 

Transmission 33, 146, 151 

Trouble finding outfit 130 

Troubles and repairs 

carburetor 338 

connecting rod 207 

cooling system 445 

crankcase 230 

crankshaft 218 

cylinder 175 

engine 159, 160, 402 

inlet manifold 355 

lubrication 469 

Note. — For page numbers see foot of pages. 


Troubles and repairs (continued) 

muffler 430 

pistons 195 

valves 397 

Truck carburetor 311 

Twelve-cylinder motors 42, 101, 

104, 106, 109, 158 

crankshaft 217 

double carburetors 253 

manifolds 350 

valves 388 

Twelve-cylinder valve remover 400 

Two-cycle diagram 83 

Two-cycle motor 14, 16, 46, 83, 

91, 155 

vs. four-cycle motors 134 

indicated horsepower formula 127 

motorboat horsepower formulas 133 

Two-cylinder motors 34, 39, 93, 101 

Two-stage carburetor 289 

Two-unit power plant 154 


Unit power plant 25, 154, 157 

Universal joint 152 

Up stroke of two-cycle motor 17, 156 

V-type motors (see also Aviation 

motors) 18, 43, 157 

connecting-rod bearings 205 

manifolds 350 

valves 388, 396 

Vacuum feeds 253, 357 

Valve 18, 30, 149, 373, 409 

A.C.A. tests of Moline motor 419 
American motors, valve timing 

379, 380 
aviation motors 90 

Cadillac car 378, 389, 396 

cages m > 411 

cam 378, 384, 388 

camless engine 415 

camshaft 378, 389, 414, 415 

casings 374 

Chalmers valve mechanism 389 


Digitized by 




Valve (continued) 
exhaust cam 
exhaust valve, timing 
flywheel markings 
galloping of motor 
gas speeds 
grinding valves 
half-time shafts 
Haynes valve action 


393, 405 

Hudson Super-Six valve timing 395 
inlet cam 378, 380 

inlet valve 380 

integral cams 389 

Knight motor 375, 378, 416 

L-head cylinders 395 

LaFayette motor 372 

Locomobile valve action 382 

master camshaft 390 

Moline-Knight motor 375, 419 

Monroe motor 388 

multiple-cylinder cars 388 

multiple valves 243, 385 

needle 246 

overhead-valve system 409 

Overland valve timing 391 

Peugeot cam mechanism 389 

poppet valves 373, 378 

push rods and guides 394, 410 

repairs (see Troubles and reme- 
Roberts motor 423 

rotating valves 376, 422 

Royal Automobile Club (Eng- 
land), report on Knight 
engine 418 

setting of cars 379, 380 

silent-chain drive 377, 408 

size 78, 81 

sleeve valves 375, 415 

sliding valves 375 

split-ring valve 375 

springs 401, 402 

Stutz motor 387 

summary of instructions 483 

Note. — For page numbers see foot of pages. 

Valve (continued) 
timing of cars 


84, 379, 380, 
381, 391, 420, 482 
timing gears, marking 406 

troubles and remedies 397 

cage repairs 188, 41 1 

camshaft repairs 415 

cap repairs 413 

gears 406, 414 

grinding valves 403 

holding valve springs com- 
pressed 401 
inlet valve 406 
leaks 412 
noisy valves 397, 405 
push rods and guides 410, 412 
valve-key slots 403 
removing valve 397 
silent-chain drive 408 
tension of valves 402 
V-type motors 388, 396 
Willys-Knight motor 417, 420 
Wisconsin motor 385 
Valve-in-head motor 173, 174 
Velie tractor manifold 355 
Venturi-tube mixing chamber 250 
Vertical motors 48, 89, 97, 99, 100, 157 
Volumetric efficiency 79, 387 


Wasp aviation motor 93, 94 

Water cooling (see also Aviation 

motors) 29, 31, 150, 430 

Water jackets 150, 185, 242, 

248, 342, 344, 352, 431, 445 
Watt's diagram of work 52 

Webber carburetor 281 

Welding 185, 226 

White and Poppe formula 133 

Willys-Knight motor 417, 420 

Wisconsin motor 385 

Zenith carburetor 

251, 260 



AY 11 1922 

Digitized by 


Digitized by VjOOQ IC 

Digitized by VjOOQ IC 

Digitized by VjOOQ IC 

Digitized by VjOOQ IC 

Digitized by VjOOQ IC 

Digitized by VjOOQ IC