3A-46 - 454 C.I.D. (7.4L) / 502 C.I.D. (8.2L)
90-823224--2 796
4. Remove bearing cap. The flattened gauging
plastic will be found adhering to either the bearing
cap or journal.
5. On the edge of the gauging plastic envelope
there is a graduated scale which is correlated in
thousandths of an inch. Without removing the
gauging plastic, measure its compressed width
(at the widest point) with the graduations on the
gauging plastic envelope as shown.
72557
a - Compressed Gauging Plastic
b - Graduated Scale
b
a
NOTE:Normally main bearing journals wear evenly
and are not out of round. However, if a bearing is be-
ing fitted to an out-of-round journal (.001 in. max.),
be sure to fit to the maximum diameter of the journal:
If the bearing is fitted to the minimum diameter, and
the journal is out of round .001 in., interference be-
tween 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 irregu-
larity 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. Al-
ways 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 nec-
essary 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 accessory drive belts
so as to prevent tapered reading with plastic
gauge.
9. Measure crankshaft end play (see “Specifica-
tions”) 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 with-
out removing crankshaft.
72359
b
c
a
Main Bearing Inserts
a - Lower Bearing Insert (Install In Cap)
b - Upper Bearing Insert (Install In Block)
c - Oil Groove
