1.3.4 Main Bearings
DETROIT DIESEL 53
Fig. 5. Comparison of Main Bearing Shells
upper and lower shells. Also, if a new or reground
crankshaft is used, install all new bearing shells.
Measure the crankshaft end play as outlined under
Install Crankshaft in Section 1.3. With new parts, the
Page 4 end play must be within .004" to .011". The
Bearing shells are available in .010", .020" and .030"
maximum allowable end play with used parts is .018".
undersize for service with crankshafts which have been
Replace the thrust washers if necessary.
ground to a smaller journal diameter.
Bearings which are .002" undersize are available to
Inspect the crankshaft thrust surfaces and, if necessary,
compensate for slight journal wear in those cases where
recondition the thrust surfaces as outlined under
it is unnecessary to regrind the crankshaft.
Crankshaft Grinding in Section 1.3. If, after "dressing
up" or grinding the crankshaft, new standard size thrust
washers do not hold the end play within the specified
NOTE: Bearing shells
limits, then oversize thrust washers must be used. If
are NOT reworkable
one of the thrust surfaces of the crankshaft is worn or
from one undersize to
ground considerably more than the other, it may be
necessary to install thrust washers of different thickness
on either side of the main bearing to properly center the
crankshaft main journal on the bearing. The oversize
Table 1 gives the minimum bearing shell thickness for
thrust washers are listed in Table 2.
new standard and various undersize bearings, and gives
the crankshaft main bearing journal diameters
Install Main Bearing Shells (Crankshaft in Place )
corresponding to each bearing size.
Make sure all of the parts are clean. Apply clean engine
Excessive crankshaft end play due to an improper
oil to each crankshaft journal and install the main
flywheel or improper clutch adjustment can contribute to
bearing shells by reversing the sequence of operations
excessive wear or scoring of the crankshaft thrust
given for removal.
1972 General Motors Corp.