TM 55-4920-384-13&P
PISTON, RING AND ROD CLEARANCES CHART
71075C
CRANKSHAFT
To remove the crankshaft, first remove the six cap-
screws in the main bearing plate at the take-off end
of the engine. The plate can then be pried off and
the crankshaft removed from that end of crankcase.
place as these are necessary to give the proper end
play to the tapered roller bearings on the crankshaft.
This end play should be .002 to .004 inch when en-
gine is cold. There is practically no wear in these
bearings so that no readjustment is necessary after
proper assembly.
When reassembling crankshaft, the timing marks on
the crankshaft gear and camshaft gear must match up,
perly, or if timing is off considerably, engine will
not run at all.
Mount main bearing plate in the correct position in
reassembly. The word `TOP' is cast on the outside
of the plate, and should be mounted in this position.
Mounting the main bearing plate upside down would
prevent the main bearing from being properly lubricat-
ed. Tighten main bearing plate capscrews, 25 to 30
foot pounds torque.
CAMSHAFT
Remove all valve tappets and withdraw camshaft from
crankcase. See Fig. 33. When replacing, be sure the
spring and plunger are in place in the end of the cam-
shaft, as these hold the camshaft in position endwise.
Camshaft gear is removed by taking out the three
screws and lockwashers, and then prying the gear off
t h e end of the camshaft. The camgear has offset
m o u n t i n g holes to provide accurate assembly for
valve timing. The gear can only be put on the correct
way for matching up the timing mark with that of the
189221 C
crankshaft. See Gear Train, Fig. 22.
The cylinder blocks have replaceable valve guides.
VALVE TAPPETS - ADJUSTMENT
The valve stems have a clearance of .0025" to .0045"
in the guides. When the clearance becomes .008",
The valve tappets must be pulled out before the
the guides should be driven out and replaced with
camshaft is removed. In reassembly, the tappets can
new guides.
be inserted in proper position in the crankcase after
the camshaft is reassembled. See Fig. 33.
The valves and valve seat inserts are of 'Stellite'
After the cylinder block assemblies have been mount-
material.
ed to the crankcase, the tappets should be adjusted.
D-21
