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6A 1-26
1977 PONTIAC SERVICE MANUAL
clean of oil.
1. Starting with the rear main bearing, remove bearing
cap and wipe oil from journal and bearing cap.
2. Place a piece of gaging plastic the full width of the
bearing (parallel to the crankshaft) on the journal (Fig. 6A1-
68).
CAUTION: Do not rotate the crankshaft while
the gaging plastic is between the bearing and
journal.
3. Install the bearing cap and evenly torque the retaining
bolts to 65 lbs. ft.
4. Remove bearing cap. The flattened gaging plastic will
be found adhering to either the bearing shell or journal.
5. On the edge of gaging plastic envelope there is a
graduated scale which is correleated in thousandths of an
inch. Without removing the gaging plastic, measure its
compressed width (at the widest point) with the graduations
on the gaging plastic envelope (Fig. 6A1-69).
NOTE: Normally, main bearing journals wear evenly
and are not out-of-round. However, if a bearing is being
fitted to an out-of-round journal (.001" 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", interference between the
bearing and journal will result in rapid beariqg failure.
If the flattened gaging 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
gaging plastic indicates more than .00lW 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.
NOTE: If a new bearing cap is being installed and
clearance is less than .OOln, inspect for burrs or nicks;
if none are found, then install shims as required.
7. A standard .OOln or .002" 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.
8. Proceed to the next bearing. After all bearings have
been checked, rotate the crankshaft to see that there is no
excessive drag.
9. Measure crankshaft end play (see specifications) by
forcing the crankshaft to the extreme front position. Measure
at the front end of the number 4 bearing with a feeler gage
(Fig. 6A1-71).
10. Install a new rear main bearing oil seal in the cylinder
block and main bearing cap.
REPLACEMENT
NOTE: Main bearings may be replaced with or without
removing the crankshaft.
With Crankshaft Removed
1. Remove and inspect the crankshaft.
Fig. 6A1-71 Measuring Crankshaft End Play
2. Remove the main bearings from the cylinder block
and main bearing caps.
3. Coat bearing surfaces of new, correct size, main
bearings with oil and install in the cylinder block and main
bearing caps.
4. Install the crankshaft.
Without Crankshaft Removal
1. Remove cap on main bearing requiring replacement
and remove bearing from cap.
2. All crankshaft journals have oil holes. Replace the
main bearing upper half as follows:
a. Install a main bearing removing and installing tool in
oil hole in crankshaft journal.
NOTE: If such a tool is not available, a cotter pin may
be bent as required to do the job.
b. Rotate the crankshaft clockwise as viewed from the
front of engine. This will roll upper bearing out of block.
c. Oil new selected size upper bearing and insert plain
(unnotched) end between crankshaft and indented or notched
side of block. Rotate the bearing into place and remove tool
from oil hole in crankshaft journal.
3. Oil new lower bearing and install in bearing cap.
4. Install main bearing cap with "F" pointing toward
front of engine.
5. Torque main bearing cap bolts to 65 lbs. ft.
CRANKSHAFT
The crankshaft can be removed while the engine is
disassembled for overhaul as previously outlined or without
complete disassembly as outlined below.
Removal
1. With the engine removed from the car and the
transmission and/or clutch housing removed from the
engine, mount engine in overhaul stand and clamp securely.
2. Remove spark plugs.
3. Remove the oil dip stick, starter and brace and
flywheel.
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