TM 5-4320-218-15
h. Measure the fit of the piston pin in the
matching of the parts. Make sure the numbers
piston. If the clearance exceeds 0.0005 inch,
agree for each rod and cap. Push the piston
use an oversize piston pin and ram the piston
down while rotating the crankshaft to bottom
and piston-pin bushing to fit. If new pistons
dead-center. Position the cap on the rod so
are being used, ream the piston-pin bore in
that its oilhole faces the oil-spray nozzle of the
the piston not to exceed 0.0005-inch clearance.
oil-header in the crankcase. Secure the assem-
i. Check the piston-pin bushing in the con-
bly with the palnuts (23) and tighten each nut
necting rod for wear, scoring, or out-of-round
to 28-32 foot-pounds torque. Install the two
condition. The clearance between the piston
palnuts (23) and tighten with a wrench one-
pin and bushing should not exceed 0.0011
fourth turn beyond finger tight position.
inch. Ream and hone the bushing and piston
c. Using a suitable feeler gage, measure the
to accommodate oversized piston pins (0.005-,
side clearance between the bearing and crank-
0.010-, 0.020-, and 0.030-inch oversized pins
shaft. The clearance should measure at least
are available), or replace the bushings as nec-
0.008 inch and not more than 0.015 inch.
essary. When pressing in new bushings, be care-
d. Install the oil pump as insructed in para-
ful to aline the oilhole in the bushing with the
graph 99f.
oilhole in the connecting rod. Ream and hone
e. Install the cylinder heads as instructed
new bushings to provide a clearance of 0.0001-
in paragraph 101c.
0.0006 inch between the piston pin and bush-
f. Invert the piston and slide it into the cyl-
ing. The bushings are a press fit and in pre-
paring the connecting rod for a new bushing :
inder bore. Check the piston to cylinder clear-
ream the connecting rod 0.0025-0.0055 inch
ance at the piston skirt thrust faces. The clear-
ance should be 0.005 to 0.006 inch. If greater,
smaller than the outside diameter bushing.
replace the piston with an oversized one. Re-
j. Check the connecting rod for twist. Use
bore and hone the cylinder as necessary.
bending bars to straighten twisted rods. Make
g. Measure the piston ring side clearance.
sure that the oilholes in the connecting rods
Replace the piston if the side clearance is not
are open.
k. Inspect the connecting rod bearing halves
within the following tolerances:
Top ring ___ _ __ 0-00202 to 0.004 in.
for wear or scoring. Check the bearing to
2nd ring______ _____ 0.0015 to 0.0035 in.
crank pin clearance; i t should be between
3d and 4th_ ____________ 0.001 to 0.003
0.0015 and 0.003 inches. Replace the bearing
halves if worn beyond this limit.
oil rings
Section XII. CRANKSHAFT AND CAMSHAFT
type with self -locking adjusting screws, and
115. Description
ride in bores in the crankcase.
The crankshaft is supported at both ends by
roller bearings. The outer race or cup of the
116. Crankshaft and Camshaft
bearing at the power-takeoff and of the engine
Removal and Disassembly
is carried in the main bearing plate, which is
secured to the crankcase with cap screws and
a. Crankshaft.
lockwashers. Shims are installed between the
(1) Remove the cylinder heads and valves
bearing plate and crankcase to provide the
(par. 101a).
proper crankshaft end play. The camshaft is
(2) Remove the fuel pump adapter (par
made of Gunite, and the cams and fuel pump
82a).
eccentric integral with the shaft. It operates
(3) Remove the gear cover (par. 106a).
the valve tappets and fuel pump adapter. The
two camshaft journals ride in honed bores in
(4) Remove the idler and camshaft gears
(par. 106b).
the crankshaft. The tappets are the mushroom
