Connecting Rods

TM 10-3930-634-34

(12) Install breather (TM 10-3930-634-12).

for the hardened, floating piston pin. Each end of the

piston pin is sealed with a piston pin retainer.

(13) Install fuel and hydraulic pump drive (TM

10-3930-634-12).

(d) Each piston is fitted with six piston rings.

Four compression rings are installed above the piston

(14) Install limiting speed governor (para 3-20).

pin and two oil control rings are installed below the

(15) Install engine driven hydraulic pump (TM

piston pin. Eight equally spaced holes are drilled just

10-3930-634-12).

below each oil control ring to permit excess oil to re-

(16) Install fuel pump (TM 10-3930-634-12).

(17) Install oil pan (para 3-26).

turn to the crankcase.

(2) Connecting Rods.

(18) Install engine (para 2-5).

(19) Refill crankcase.

(a) Each connecting rod is made of forged steel.

The rod is drilled to provide lubrication to the piston at

(20) Refill cooling system, if drained.

the upper end and is equipped with an oil spray nozzle

3-34. Pistons and Connecting Rods

for cooling the piston.

a. General.

(b) The connecting rod bearing shells are differ-

(1) Pistons.

ent and not interchangeable.

(a) The truck type malleable iron piston is

(c) A helically-grooved bushing is pressed into

plated with a protective coating of tin which permits

each side of the connecting rod at the upper end. A

cavity of approximately 1/8 inch between the inner ends

close fitting, reduces scuffing and prolongs piston life.

The top of the piston forms the combustion chamber

of the bushings, registering with the drilled oil passage

bowl and is designed to compress the air into proxim-

in the rod, forms a duct around the piston pin for lubri-

ity to the fuel spray.

cation.

(b) The piston is cooled by a spray of lubricating

b. Removal.

oil directed at the underside of the piston head from a

(1) Drain engine oil and remove oil pan (para

nozzle in the top of the connecting rod, by fresh air

3-26).

from the blower to the top of the piston and indirectly

(2) Remove cylinder head (para 3-25).

by the water jacket around the cylinder.

(3) Remove oil inlet tube and screen (para 3-27).

(c) Two bushings with helical grooved oil pas-

(4) Use a suitable reamer and remove carbon from

sages, are pressed into the piston to provide a bearing

the upper, inner surface of the cylinder liner.

3-70