l-23
BASIC ENGINE
1-23
\
OVERHAUL (Continued)
CRANKSHAFT
Dress minor scores with an oil stone. If the
journals are severely marred or exceed the wear
limit, they should be refinished to size for the
next undersize bearing.
REFINISHING JOURNALS
Refinish the journals to give the proper clear-
ante with the next undersize bearing. If the
journal will not clean up to maximum undersize
bearing available, replace the crankshaft.
Always reproduce the same journal shoulder
radius that existed originally. Too small a radius
will result in fatigue failure of the crankshaft. Too
large a radius will result in bearing failure due to
radius ride of the bearing.
After refinishing the journals, chamfer the oil
holes; then polish the journal with a No. 320 grit
polishing cloth and engine oil. Crocus cloth may
also be used as a polishing agent.
~FIlTING MAIN OR CONNECTING ROD
BEARINGS WITH PLASTIGAGE
1. Clean crankshaft journals. Inspect journals
and thrust faces (thrust bearing) for nicks,
burrs or bearing pickup that would cause
premature bearing wear.
When replacing
standard bearings with new bearings, it
is good practice to fit the bearing to mini-
mum specified clearance.
If the desired
clearance cannot be obtained with a stan-
dard bearing, try a 0.002 inch undersize in
combination with a standard bearing to ob-
tain the proper clearance.
2. If fitting a main bearing in the chassis,
posi-
tion a jack under counterweight adjoining
bearing which is being checked. Support
crankshaft with jack so its weight will not
compress Plastigage and provide an er-
roneous reading.
3.
Place a piece of Plastigage on bearing sur-
face across full width of bearing cap and
about l/4 inch off center.
CHECK WIDTH OF
PLACE PLASTIGAGE FULL
PLASTIGAGE
WIDTH OF JOURNAL
MEASURING
PLASTIGAGE
A28680A
4. Install cap and torque bolts to specifications.
Do not turn crankshaft while Plastigage is in
place.
5. Remove cap. Using Plastigage scale, check
width of Plastigage at widest point to get
minimum clearance. Check at narrowest
point to get maximum clearance. Difference
between readings is taper of journals.
6. If clearance exceeds specified limits, on the
connecting rod bearings, try a 0.002 inch
undersize bearing in combination with the
standard bearings. Bearing clearance must
be within specified limits. If 0.002 undersize
main bearings are used on more than one
journal, be sure they are all installed in cylin-
der block side of bearing. If standard and
0.002 inch undersize bearings do not bring
clearance within desired limits, refinish
crankshaft journal, then install undersize
bearings.
7. After bearing has been fitted, remove Plas-
tigage and apply light coat of engine oil to
journal and bearings. Install bearing cap.
Torque cap bolts to specifications.
8. Repeat procedure for remaining bearings
that require replacement.
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