per shell out opposite side of bore in block. If
(42) is a pilot bushing and should never need
crankshaft is scored or worn enough so new
to be removed.
bearings will not fit with required clearance
b. Cleaning. Clean all parts in solvent and
it must be reground. Crankshaft can be re-
dry thoroughly with compressed air. Clean car-
ground maximum of 0.040 inch. Before re-
bon from piston head with scraper, carbon
grinding, crankshaft must be checked for
solvent and wire brush. Clean oil passages
straightness and straightened, if necessary, to
in crankshaft and spurt hole in connecting
within 0.002-inch indicator reading. When re-
rods with stiff wire. Clean gear (7) with wire
ground, fillet radii must be within dimensional
brush and blow off with compressed air.
l i m i t s (fig. 6-16) and must be perfectly
blended into thrust and bearing surfaces. New
40 and 41) for corrosion pitting, and excessive
pistons must be fitted in rebored cylinder
wear. Figure 6-12 shows appearance of bear-
bores. Make certain cylinder walls and pistons
ing surface of good bearing after use. Measure
are perfectly clean and dry and that piston
thickness of bearing shells using ball micro-
and block are both at room temperature (68
meter. If bearing shells are thinner than mini-
mum given in table 5-1, replace all bearings.
stock of same thickness given in table 5-1, as
Inspect crankshaft (43, fig. 6-11 ) journals for
proper clearance. Attach feeler stock to small
scoring and excessive wear. Minimum bearing
spring scale of approximately 15 pounds ca-
journals should be within limits specified in
pacity. Slide piston in inverted position and
feeler stock into bore with feeler stock be-
limits specified in table 5-1. Check crankshaft
tween piston pin bosses where diameter of pis-
for straightness within limits specified in table
ton is greatest. Push piston approximately two
5-1. Inspect connecting rod (21, fig.. 6-11)
inches down in cylinder bore. If piston fit is
bearing surfaces for scoring or excessive wear.
correct, feeler stock can be withdrawn with
Piston pin bushing should be smooth and with-
pull of 5 to 10 pounds indicated on scale. After
in limits specified in table 5-1. Bushing hole
individual pistons are fitted, mark number of
should be within limits specified in table 5-1.
cylinder with chalk on head to enable proper
Check connecting rods with piston pin assem-
reassembly. Replace any other parts which do
bled for twist and squareness on fixture as
not pass inspection.
shown in figures 6-13 and 6-14. Connecting
e. Reassembly and Installation. To reassem-
rod must be within limits specified in table
ble and install crankshaft, flywheel, and piston
assembly, turn cylinder and crankcase assem-
Bend or twist connecting rod to meet specifi-
bly with crankcase side up, and proceed as fol-
cations. Check pistons (27, fig. 6-11) for ex-
lows :
cessive ring groove wear and for piston pin
(1) Dip upper and lower bearing shells
hole diameter. Inspect head of piston for pit-
in lube oil and position upper bearing shells
ting and entire body for cracks. Check piston
(38, 39, 40 and 41) in place in crankcase. In-
rings for excessive wear. Check piston pins
stall crankshaft (43) in crankcase carefully
for excessive wear or scoring (table 5-1). In-
to avaoid displacing bearing shells.
spect crankshaft gear (7, fig. 6-11) and ring
(2) Install dowels (36 and 37) in crank-
gear (10) for excessive wear and broken or
case.
chipped teeth. Inspect bearing caps (28, 29,
(3) Assemble lower bearing shells (38, 39,
30 and 31) for scoring and excessive wear.
40 and 41) in main bearing caps (28, 29, 30
Check pulley (3) for wear and warping.
and 31). Check each bearing, one at a time,
d. Repair. Replace bearing (22, 38, 40 and
for proper clearance using feeler stock as
41) which do not pass inspection. If crankshaft
is not removed from engine, upper bearing
stock of thickness equal to maximum allowable
shells can be removed with pin with angular
clearance lengthwise in bearing shell on film
head as shown in fig. 6-15. Insert pin in
of oil. Assemble bearing caps and tighten
crankshaft oil hole and turn crankshaft in
screws to specified torque. Try to turn crank-
clockwise direction. Head of pin will force up-
shaft by hand (with minimum clearances,
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