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 TM 55-1905-220-14-5
3-97.1. CRANKSHAFT BEARINGS (Cont).
LOCATION
ITEM
ACTION
REMARKS
INSPECTION (Cont)
5. Check the clearance
between the main bearings
and the crankshaft
journals. This
clearance may be
determined with the
crankshaft in place
by means of a soft
plastic measuring
strip which is
squeezed between the
journal and the bearing.
Measure the
outside diameter of
the crankshaft main
bearing journals and
the inside diameter
of the main bearing
shells when installed
in place with the
proper torque on the
bearing cap bolts.
When installed, the
bearing shells are
.001 inch (0.0025 cm)
larger in diameter at
the parting line than
90from the parting
line.
The bearing shells do not form a true circle when not installed. When installed, the bearing shells have a
squeeze fit in the main bearing bore and must be tight when the bearing cap is drawn down. The crush assures
a tight, uniform contact between the bearing shell and bearing seat. Bearing shells that do not have sufficient
crush will not have uniform contact, as shown by shiny spots on the back, and must be replaced. If the
clearance between any crankshaft journal and its bearing shells exceeds .0060 inch (0.0152 cm), all of the
bearing shells must be discarded and replaced. This clearance is .0016 to .0050 inch (0.0041 to 0.0127 cm)
with new parts.
Before installing new replacement bearings, it is very important to thoroughly inspect the crankshaft journals.
Very often, after prolonged engine operation, a ridge is formed on the crankshaft journals in line with the journal
oil holes. If this ridge is not removed before the new bearings are installed, then, during engine operation,
3-1702
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