TM 5-3895-346-14
CAMSHAFT OVERHAUL
ENGINE OVERHAUL
If there is a doubt as to the acceptability of the camshaft for further service, determine the extent of cam lobe
wear as follows:
NOTE
The camshaft can be in or out of the engine during this inspection.
1. With a tapered leaf set of feeler gages (0.0015-0.0100 inch) and a piece of square hard material 1/8 x
3/8 x 1 inch measure the flat on the injector rise side of the cam lobes (Fig. 4).
2. If the flats measure less than 0.003 inch in depth and there are no other defects, the camshaft is satis-
factory for service.
3. A slightly worn lobe still within acceptable limits may be stoned and smoothed over with a fine crocus
cloth.
Check the runout at the center bearing with the camshaft mounted on the end bearing surfaces. Runout should
not exceed 0.002 inch.
Examine both faces of the thrust washers. If either face is scored or if the thrust washers are worn exces-
sively, replace the washers. New thrust washers are 0.208 to 0.210 inch thick.
Figure 4. Checking Cam Lobe Wear
Also, examine the surfaces which the thrust washers contact; if these surfaces are scratched but not severely
scored, smooth them down with an oil stone. If the score marks are too deep to be removed, or if parts are
badly worn, use new parts.
CAUTION
If a new camshaft is to be installed, steam clean it to remove the rust preventive and blow out the oil passages
with compressed air.
The clearance between new shafts and new bearings is 0.0045 to 0.006 inch, or a maximum of 0.008 inch with
worn parts. Excessive clearance between the shafts and the bearings will cause low oil pressure and excessive
backlash between the gears.
Bearings are available in 0.010 inch and 0.020 inch undersize for use with worn or reground shafts.
Oversize camshaft and balance shaft bearings are available in sets, 0.010 inch oversize on the outside
diameter, to permit reuse of a cylinder block having one or more scored block bearing bores. To use the
oversize bearings, the camshaft and balance shaft block bores must be carefully line-bored (machined) to the
dimensions shown in Table 1.
Remove Bearings
The end bearings must be removed prior to removing the intermediate bearings.
CAUTION
When removing the bearings be sure to note the position of the bearings in the bore with respect to the notch in
the bearings. Replacement bearings must be installed in the same position.
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