ENGINE AND ENGINE REBUILDING 125
Measure main bearing clearance by comparing
flattened strip to Plastigage scale as shown
move the cap and wipe all oil from the crank
journal and bearing cap.
2. Place a strip of Plastigage® the full width
of the bearing, (parallel to the crankshaft), on
the journal.
NOTE:
Plastigage® is soluble in oil; there-
fore, oil on the journal or bearing could
result in erroneous readings.
CAUTION:
Do not rotate the crankshaft while the
gaging material is between the bearing
and the journal.
3. Install the bearing cap and evenly torque
the cap bolts to specification.
4. Remove the bearing cap. The flattened
Plastigage® will be sticking to either the
bearing shell or the crank journal.
5. Use the graduated scale on the Plasti
gage® envelope to measure the material at its
widest point.
If the flattened Plastigage® ta
pers toward the middle or ends, there is a
difference in clearance indicating the bearing
or journal has a taper, low spot or other ir
regularity. If this is indicated, measure the
crank journal with a micrometer.
6. If bearing clearance is within specifica
tions, the bearing insert is in good shape. Re
place the insert if the clearance is not within
specifications.
Always replace both upper and
lower inserts as a unit.
7. Standard, .001 in. or .002 in. undersize
bearings should produce the proper clear
ance. If these sizes still produce too sloppy a
fit, the crankshaft must be reground for use
with the next undersize bearing. Recheck all
clearances after installing new bearings.
8. Replace the rest of the bearings in the
same manner. After all bearings have been
checked, rotate the crankshaft to make sure
there is no excessive drag. When checking
the No. 1 main bearing, loosen the accessory
drive belts (engine in car) to prevent a ta
pered reading with the Plastigage.®
MAIN BEARING REPLACEMENT
Engine Out of Car
1. Remove and inspect the crankshaft.
2. Remove the main bearings from the
bearing saddles in the cylinder block and main
bearing caps.
3. Coat the bearing surfaces of the new,
correct size main bearings with clean engine
oil and install them in the bearing saddles in
the block and in the main bearing caps.
4. Install the crankshaft. See "Crankshaft
Installation."
Check main bearing saddle alignment with straight-
edge
Engine in Car
1. With the oil pan, oil pump and spark
plugs removed, remove the cap from the main
bearing needing replacement and remove the
bearing from the cap.
2. Make a bearing roll-out pin, using a bent
cotter pin as shown in the illustration. Install
the end of the pin in the oil hole in the crank
shaft journal.
3. Rotate the crankshaft clockwise as viewed
from the front of the engine. This will roll the
upper bearing out of the block.
4. Lube the new upper bearing with clean
engine oil and insert the plain (unnotched)
end between the crankshaft and the indented
or notched side of the block. Roll the bearing
into place, making sure that the oil holes are
aligned. Remove the roll pin from the oil hole.
5.
Lube the new lower bearing and install
e
-t-
REMOVING
BEARING SHELL
Use a roll-out pin as illustrated to remove
bearing shells
INSTALLING
BEARING SHELL
1
