TM 9-3431-254-14&P
ROTATION
GENERAL INFORMATION AND DESIGN
The rotation of the crankshaft is clockwise when
viewing the flywheel or cranking end of the engine.
These
engines are of the four cycle type, in
This gives counter-clockwise rotation when viewing
which each of the four operations of suction, com-
the power take-off end of the engine. The flywheel
pression, expansion and
exhaust requires a
complete
end of the engine is designated
the front end, and the
stroke. This gives one power stroke per cylinder for
power take-off end,
the rear end he engine.
of t
each two revolutions of the crankshaft.
COOLING
Cooling is accomplished by a flow of air, circulated
over the cylinders and heads of the engine, by a
combination fan-flywheel encased in a sheet metal
shroud. The air is divided and directed by ducts and
baffle plates to insure uniform cooling of all parts.
Never operate an engine with any part of the
shrouding removed, because this will retard the
air cooling.
Periodically, remove the cylinder head shrouding and
clean out all the dust and chaff which may have col-
lected between the fins of the cylinder barrels and
cylinder heads. Dirt deposits between the cooling
fins and in the shrouding will retard the flow of air
HORSEPOWER
and cause the engine to overheat. See Page B-5.
The horsepower given in the above chart is for an
atmospheric temperature of 60 Fahrenheit, at sea
CARBURETOR
level, and at a Barometric pressure of 29.92 inches
The proper combustible mixture of gasoline and air,
of mercury.
is furnished by a balanced carburetor, giving correct
For each inch lower Barometer reading, deduct 3%
fuel to air ratios for all speeds and loads.
from above horsepower.
IGNITION
For each 10 higher temperature, there will be a re-
The spark for ignition of the fuel mixture is directed
from the coil to the spark plugs, at the proper time,
For each 1000 ft. altitude above sea level, there will
by a distributor. Electric starter and generator are
furnished with distributor ignition.
The friction in new engines cannot be reduces to the
Magneto ignition can be furnished in place of distri-
ultimate minimum during the regular block test, but
butor, when specified. The high tension magneto used,
engines will develop at least 85 per cent of maximum
is fitted with an impulse coupling that provides a
power when shipped from the factory. The power will
powerful spark for easy starting.
increase as friction is reduced during a few days of
operation. The engine will develop approximately 95%
of power shown on chart when friction is reduced to
LUBRICATION SYSTEM
a minimum.
A gear type pump provides pressurized lubrication to
For continuous operation, limit to 80% of horsepower
the connecting rod bearings, camshaft bearings, tap-
shown, as a safety factor.
pets, valve train and to an oil spray nozzle in the gear
cover, The spray nozzle lubricates the governor and
gear train. The oil expelled from these areas form a
INSTRUCTIONS FOR
mist which lubricates the cylinder walls and the anti-
STARTING AND OPERATING
LUBRICATION
All of the circulated oil passes thru a full-flow oil
Before starting a new engine, fill crankcase with the
correct grade of lubricating oil, as specified in "Grade
element, thereby minimizing friction and reducing
of Oil" chart. Fill through the breather tube opening
wear to critical moving parts of the engine.
with 6 quarts of oil, and check level by means of the
oil gauge saber. When replacing oil filter, an addi-
tional 1 quart of oil is required.
GOVERNOR
For run-in of new engines, use same oil as recom-
A governor of the centrifugal flyball type controls
mended in Grade of Oil Chart.
the engine speed by varying the throttle opening to
suit the load imposed upon the engine. All engines
The standard oil gauge saber is located on the left
are equipped with either fixed speed governors, a
hand side, below the
oil filler-breather tube. See
variable speed regulator to control the governed
Fig. 1. When specified, a saber can be furnished on
speed of the engine, or an idle control.
the opposite side, behind the starting motor.
B-9