454 CID (7.4L) / 502 CID (8.2L)
SERVICE MANUAL NUMBER 23
Page 3A-63
90-861326--1 MARCH 1999
journal is out of round .001 in., interference between the bearing and journal will result in
rapid bearing failure. If the flattened gauging plastic tapers toward the middle or ends, there
is a difference in clearance indicating taper, low spot or other irregularity of the bearing or
journal. Be sure to measure the journal with a micrometer if the flattened gauging plastic
indicates more than .001 in. difference.
6. If the bearing clearance is within specifications, the bearing insert is satisfactory. If the
clearance is not within specifications, replace the insert. Always replace both upper and
lower inserts as a unit.
7. A standard, or .001 in., undersize bearing may produce the proper clearance. If not, it
will be necessary to regrind the crankshaft journal for use with the next undersize
bearing.
After selecting new bearing, recheck clearance.
8. Proceed to the next bearing. After all bearings have been checked, rotate the crankshaft
to see that there is no excessive drag. When checking No. 1 main bearing, loosen acces-
sory drive belts so as to prevent tapered reading with plastic gauge.
9. Measure crankshaft end play (see “Specifications”) by forcing the crankshaft to the
extreme front position. Measure at the front end of the rear main bearing with a feeler
gauge as shown.
72543
a
a -
Measuring Crankshaft End Play - (Force Crankshaft To Extreme Forward
Position)
Replacement
NOTE: Main bearings may be replaced with or without removing crankshaft.
72359
a
b
c
Main Bearing Inserts
a -
Lower Bearing Insert (Install In Cap)
b -
Upper Bearing Insert (Install In Block)
c -
Oil Groove
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