TM 5-4320-302-14
6-17.
CONNECTING ROD ASSEMBLY (CONT)
Location/Item
Action
Remarks
23. Big-end bearings
a.
Replace if bearings are excessively worn, out-
of-tolerance, out-of-round, or show any scoring,
pitting, flaking, etching, or signs of overheating.
Replace if bearings show any bright spots on the
back or outside surfaces. Replace with nominal
or undersized bore bearings or oversized wall
thickness bearings as appropriate for the size of
the corresponding crankpin on the crankshaft.
b.
Install new big-end bearings in connecting rod
only if necessary. Follow procedure described
in step 13. Tighten and retighten hex bolts in
accordance with procedure described in step 10.
Remeasure bearing bore in accordance with
step 14. Measurements for nominal or under-
sized bore should correspond correctly to those
in the chart on page 6-132. The nominal big-
end bearing bore, for example, should be
2.0488 to 2.0501 inches (52.040 to 52.073 mm).
However, if the bore measures an additional
0.0008 inch (0.020 mm) on either side of
tolerance limits, the connecting rod and big-end
bearing
would
still
be
acceptable
for
reinstallation. The tolerance limits would then
become 2.0480 to 2.0509 inches (52.020 to
52.093 mm) and the connecting rod and big-end
bearing would be acceptable for further use.
This would also apply to any of the undersized
bore bearings where the acceptable tolerance
limits would also be increased by an additional
0.0008 inch (0.020 mm) on either side. If big-
end bearing bore measurements are still outside
the extended tolerance limits, the connecting
rod must be replaced. This would include
replacement of small end bush, big-end bearing,
bearing cap, pin, and hex bolts.
6-137
