Pontiac FIREBIRD 1972 Service Manual page 548

6-36 1972 PONTIAC SERVICE MANUAL
4. Install oil pan using new gaskets and seals.
PLASTIC GAGE METHOD OF DETERMINING
M A I N BEARING CLEARANCE
Place a .002" brass shim between the crankshaft jour-
nal and the lower bearing in each bearing cap next to
the one being checked. Tighten all cap bolts to 65 lb.
ft. This causes the crankshaft to be forced against the
upper bearing and insures an accurate measurement
of the total clearance.
Remove the bearing cap of the bearing to be checked.
Wipe the bearing and the journal free of oil.
Place a piece of plastic gage, the length of the bearing
(parallel to the crankshaft), on the journal or bearing
surface (Fig. 6-56). Install the cap and tighten cap
bolts to proper torque. (Do not turn crankshaft with
plastic gage in place).
Remove bearing cap and using plastic gage scale on
envelope measure width of compressed plastic gage
before removing it from the bearing or journal (Fig.
6-57). If the bearing clearance is between .0005" and
.0025", the clearance is satisfactory. If the clearance
is more than .0025", replace the bearing with the next
undersize bearing and recheck clearance. Bearings
are available in standard size, .001" and .002" under-
size.
Install a new rear main bearing oil seal in the cylinder
block and main bearing cap if the rear main bearing
was checked and/or replaced.
Fig. 6-57 Measuring Plastic Gage
CONNECTING ROD BEARINGS
Connecting rod bearing inserts are available in standard
size and undersizes of .001" and .002". These bearings are
not shimmed and when clearances become excessive the
next undersize bearing insert should be used. DO NOT
FILE ROD OR ROD CAPS.
REMOVE
Remove oil pan.
Rotate crankshaft as necessary to bring crankpin car-
rying bearing to be replaced straight toward bottom
of block.
Remove bearing cap.
Install connecting rod bolt guide set J-5239 on con-
necting rod bolts. Push piston and rod assembly up
far enough to remove upper bearing.
Remove bearings from cap and rod.
Inspect crankpin for damage, out-of-round and taper.
REPLACE
1. Reassemble cap and rod with new bearings and check
clearance with plastic gage as outlined below.
Fig. 6-56 Plastic Gauge on Journal
2. Install oil pan using new gaskets and seals.