Pontiac firebird 1968 - Connecting Rod Bearings - Remove

6-26
1968 PONTIAC SERVICE MANUAL
size bearing and re check clearance. Bearings are
available in standard size .001" and .002" undersize.
5. Install a new rear main bearing oil seal in cyl-
inder block and main bearing cap if rear main bear-
ing was checked and/or replaced.
6. Check crankshaft end play with feeler gauge at
No. 7 main bearing (Fig. 6-52). If end play is over
.006, replace bearing.
CONNECTING ROD BEARINGS-
REMOVE AND REPLACE
Connecting rod bearing inserts are available in
standard size and undersizes of .001" and .002".
These bearings are not shimmed and when clear-
ances become excessive the next undersized bearing
insert should be used. DO NOT FILE ROD OR ROD
CAPS.
REMOVE
1. Remove oil pan. (See Oil Pan - Remove and
Replace.)
2. Rotate crankshaft as necessary to bring crank-
pin carrying bearing to be replaced straight toward
bottom of block.
3. Remove bearing cap.
4. Install connecting rod bolt guide set J 5239 on
connecting rod bolts. Push piston and rod assembly
up far enough to remove upper bearing.
5. Remove bearings from cap and rod.
6. Inspect crankpin for damage, out-of- round and
taper.
Fig. 6-48 Plastigage in Place
Fig. 6-49 Measuring Plastigage
REPLACE
1. Reassemble cap and rod with new bearings and
check clearance with Plastigage as outlined below.
2. Install oil pan using new gaskets and seals.
PLASTIGAGE METHOD OF DETERMINING
CONNECTING ROD BEARING CLEARANCE
1. Remove cap of bearing to be checked. Wipe the
bearing and the crankpin free of oil.
2. Place a piece of Plastigage, the length of bear-
ing (parallel to crankshaft), on the crankpin or bear-
ing surface (Fig. 6-48). Install the cap and tighten
cap bolts to 33 lb. ft.
NOTE: Do not turn crankshaft with Plastigage in
place.
3. Remove bearing cap and using Plastigage scale
on envelope measure width of compressed Plastigage
before removing it from the crankpin or bearing (Fig.
6-49). If bearing clearance is between .0005" and
.0028", clearance is satisfactory. If clearance is
more than .0028", replace bearing with next size
undersize bearing and re check clearance. Bearings
are available in .001", and .002" undersize.
4. Rotate the crankshaft after bearing adjustment
to be sure bearings are not tight.
5. Check connecting rod end clearance between
connecting rod cap and side of crankpin (Fig. 6-50).
Clearance should be .008" - .014". If clearance is
more than .014", replace connecting rod.