TM 5-3895-359-14&P
Keep the cylinder and head fins free from dirt and
Horsepower
chaff. Improper circulation of cooling air will cause
Horsepower specified in the accompanying chart is for
engine to overheat.
an atmospheric temperature of 60 Fahrenheit at sea
level and at a Barometric pressure of 29.92 inches of
Carburetor
mercury.
The proper combustible mixture of gasoline and air is
furnished by a balanced carburetor, giving correct fuel to
For each inch lower the Barometric pressure drops,
air ratios for all speeds and loads.
there will be a loss in horsepower of 3 1/2%.
Ignition System The spark for ignition of the fuel
For each 10 temperature rise there will be a reduction
mixture is furnished by a high tension magneto driven
in horsepower of 1%.
off the timing gears at crankshaft speed. The magneto
distributor rotor turns at half-engine speed.
The
For each 1000 ft. altitude above sea level there will be
magneto is fitted with an impulse coupling, which makes
a reduction in horsepower of 3 1/2%.
possible a powerful spark for easy starting. Also, the
impulse coupling automatically retards the spark for
The friction in new engines cannot be reduced to the
starting, thus eliminating possible kick back from engine
ultimate minimum during the regular block test, but
while cranking.
engines are guaranteed to develop at least 85 per cent
of maximum power when shipped from the factory. The
Lubrication System
power will increase as friction is reduced during the first
A gear type pump supplies oil to four nozzles which
few days of operation. The engine will develop at least
direct oil streams against fins on the connecting rod
95% of maximum horsepower when friction is reduced
caps. Part of the oil enters the rod bearing through
to a minimum.
holes in the rods, and the balance of the oil forms a
spray or mist which lubricates the cylinder walls and
For continuous operation, allow 20% of horsepower
other internal parts of the engine. An external oil line
shown as a safety factor.
from the oil header tube in the crankcase lubricates the
governor and gear train.
Governor
R.P.M.
HORSEPOWER
A governor of the centrifugal flyweight type maintains
the engine speed by varying the throttle opening to suit
1400
17.2
the load imposed upon the engine. These engines are
1600
20.0
equipped with a variable speed control to regulate the
1800
22.5
governed speed of the engine.
2000
24.7
2200
26.5
Rotation
2400
28.0
The rotation of the crankshaft is clockwise when viewing
2600
29.2
the flywheel or cranking end of the engine. This gives
2800
30.0
counter-clockwise rotation when viewing the power
takeoff end of the crankshaft. The flywheel end of the
engine is designated the front end, and the power take-
off end, the rear end of the engine.
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