Advertisement
Section
7-Flywheel, Crankshaft,
Main Bearings,
and
Connecting Rod Bearings
23
Fig.
32-Bearing Failure-Lack of Oil
(2)
REPAIRS.
If
the end
play
is
not within
speci-
fications, replace
the number three
main bearing.
Replace
the crankshaft
if
it
shows
signs of
failure.
Dress minor
nicks or
scratches.
If
the
pins or
journals are
out-DC
-round beyond the
specified
limits,
the
shaft
should
be ground for
the
next
undersize
bearing. Calculate
the correct undersize
bearing
to
be used as
follows
:
EXAMPLE:
'I
the main
bearing
journal
will
"clea
n~
up"
before
it
is
ground
to
2.499-0.010
=
2.489
Fig
.
33-fat;gue
failure
of
Bearing
inch
es diam.eter,
finish
it to I.hal
dianlcter,
ancI
in·
stall 0.010
unde
rsize bearings.
CAUTION: Never grind
journals or
crankpins
in
excess
of
0.030-inch
undersize
.
Always
reproduce the
same radii
in
the corners of
the
pin or
journa
l
that
existed
originally.
Too small
a
radius
may result in
crankshaft
failure,
while
too
large
a radius will
result in bearing failure.
After
grinding, chamfer
the oil
holes, then
polish the
pin
or
journal with
No.
320
grit polishing cloth
and
engine
oil.
Crocus
cloth may
also
be
used
as a
polish-
ing agent.
c. Main
and
Connecting
Rod Bearings.
Steel-backed,
copper-lead
bearing inserts
are
used
for
both
main
and connecting
rod bearings. Check
the
bearings for
scratches,
improper
seating,
evidence of
radius ride,
and worn
overlay.
Examples
of bearing fail-
ures are
illustrated in figs. 32-37.
R
eplace
all defective
bearings.
(
1)
FITTING lI1AIN AND CONNECTING
ROD
BEARINGS-
PLASTIGAGE lI1ETHOD
.
The
following
procedure applies
to fitting main bearings with the
engine either
installed on
a
workstand or in the
vehicle.
If
the bearing fits are to be
checked
with
the
engine
in the vehicle,
it
wi
ll
be
necessary to
support
the
weight
of the crankshaft.
Support the weight of the
crankshaft
with a small
jack positioned to hold the crankshaft
up-
ward against
the block half
of
the main
bearin
g
inserts.
The jack
should
be placed to bear against the crank-
Fig. 34-Bearing
Scratch.d by Dirt
Advertisement
