CHAPTER 3. REPAIR OF ENGINE

CHAPTER 3

REPAIR OF ENGINE

Section I. GENERAL

will shut off the engine when oil pressure falls below 1

3-1. Introduction

This chapter provides you with instructions relating to

pound per square inch.

c. The engine electrical system has a negative

engine repair and overhaul. It includes information

regarding disassembly, inspection of parts to deter-

ground. A flywheel alternator is used to maintain a

mine if their continued serviceability is possible or if

proper battery charge. The flywheel alternator is a

permanent magnet type and has no brushes, com-

they should be replaced, instructions covering repair

mutator, or adjustments. The stator, comprised of a

techniques such as valve grinding and cylinder honing,

reassembly and tolerance checking to assure proper

series of coils, is mounted on the engine gear cover the

magnetic flux is provided by a permanent magnet in

fits and clearances, and other information relating to

the flywheel which rotates around these stationary

engine overhaul.

coils. A center-tap rectifier arrangement prevents

damage to the alternator system, in the event of incor-

3-2. Description of Engine and Components

rect battery connection. Two ground rods are pro-

a. The engine is a four-cylinder, V-type, air-cooled,

vided to insure proper grounding of the welded frame.

pressure-lubricated, four-stroke-cycle unit with an L-

d. The cooling of the engine is accomplished by a

type head. The engine has a displacement of 148.5

flow of air, circulated over the cylinder blocks by a

cubic inches and develops 36.0 horsepower at 2400

rpm. It uses an electrical starting motor, has magneto

combination fan-flywheel encased in a sheet metal

ignition, and a flywheel alternator to maintain the

shroud. The air is divided and directed by additional

shrouding and baffle plates to insure uniform cooling

charge of the battery. When you view the pump end of

of all parts.

the engine, the crankshaft has a counterclockwise rota-

e. The speed of the engine is controlled by the

tion. The rotating crankshaft not only drives the pump

inter-operation of a fixed speed governor and the car-

but also drives the magneto, oil pump, and camshaft.

buretor. A governor variable speed control regulates

The gear train is enclosed by a gear cover and lubri-

the governed speed of the engine. The centrifugal fly-

cated with oil from the crankshaft.

ball-type governor rotates on a ball-bearing supported

b. A gear-driven oil pump supplies oil to four noz-

shaft and is driven off the camshaft gear. As the engine

zles which direct oil streams against the connecting

speed increases, the governor converts the centrifugal

rod caps. Part of the oil lubricates the rod bearing

force to an axial motion which acts against the gover-

through holes in the rods, and the balance of the oil

nor lever and spring this closes the throttle to a point

forms a spray or mist which lubricates the cylinders

where engine speed will be maintained practically con-

and all other internal parts of the engine. An external

stant under varying load conditions.

oil line from the oil header tube in the engine block

supplies the oil to the oil filter and also to lubricate the

3-3. Engine Fits, Tolerances, and Wear Limits

governor and gear train. At normal operating tempera-

Table 3-1 lists engine fits, tolerances, and wear limits.

tures, the oil pressure is from 4 to 5 pounds per square

Refer to the table to help you determine if parts

inch. A pressure relief valve is provided in the oil

replacement is required or if continued serviceability

pump which limits the maximum oil pressure to 15

of the parts is possible.

pounds per square inch. An oil pressure safety switch

3-1