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ENGINE
BEARINGS
2-33
SECTION 2-E
REPLACEMENT OF CRANKSHAn
AND CONNECTING ROD
BEARINGS, PISTONS AND RINGS
CO N TENTS
OF SECTION 2-E
Paragraph
Subject
Page
2-21
Adjustment or Replacement of
Connecting Rod Bearings
.
. .
. ..
2-33
2-22
Replacement ofCrankshaft Bear-
ings
.
.
.
.
.
.
.
.
. .
.
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.
.
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2-34
Paragraph
Subject
Page
2-23
Replacement
of P
istons,
R
ings
and
Connect ing
R
ods
. .
.
. .
.
.
.
.
2-36
SERVICE
BULLETIN REFERENCE
Bulletin No.
Page
No.
SUBJECT
2-21 ADJUSTMENT OR REPLACEMENT
OF CONNECTING ROD BEARINGS
In all
1948
engi nes and in approximately
5,000
engines
used at start of 1949
production,
the connecting
rods
have
bearings cast and
bonded
directl y to
rod and
cap,
and solid shims
are
provided
for
adjustment.
Replacement of
bearings requires
replacement of connecting
\
rods. Later 1949 engines are equipped with con-
necting rods having replaceable precision bear-
ings, and shims are not used. Bearings may be
replaced without r
emoval
of connecting
rods.
Service bearings
are furnished in standard size
and several undersizes, including undersizes for
reground
crankshafts.
a. Inspection of Connecting Rod Bearings
a
nd
Crank
pin
j
ournals.
After
removal
of lower crankcase, disconnect
two connecting rods at a time from
crankshaft
a
nd
inspect the bearings and
crankpin
j
our-
nals.
While
t
urning cranksha ft it is necessary
to
tempora rily
re-connect
the
r
ods
to crank-
shaft to a
void
possibilit
y of damaging the j
our-
nals through contact with
loose
rods.
If
connecting rod bearings are chipped,
scored, or worn nearly through the babbitt lin
-
ing they should be
replaced.
If
bearings are of
cast type it is necessary to replace the connect-
ing rods by removal of rod and piston assem-
blies
(par.
2-23). Precision type bearings may
be
replaced
without removing connecting rods
(subpar. c below).
If
crankpin journals are scored or ridged the
crankshaft must be replaced, or reground for
undersize bearings,
to insure satisfactory life of
connecting rod
bearings.
Slight roughness may
be polished out wit h fine grit polishing cloth
thoroughly
wetted
with engine oil. Burrs may
be honed off with
a
fine oil stone.
Use an
outside
micrometer to check crank-
pins for
out-of- round.
If
crankpins are more
than .001
5"
out of
round,
a proper adjustment
of connecting
r
od
bearings
or satisfactory life
of new bearings cannot
be expected.
b. Adjustment of Cast Type Connecting
Rod Bearings
In adjusting a cast
type
connecting rod bear-
ing the
only
method to be used is the removal
of
shims which are provided for this purpose.
Under no
circumstance
should
connecting
rod
bearing caps be
filed to adjust
f
or
wear
in old
bearing s.
1.
Remove one shim at a time
(alternately
from each side) reinstall
cap and tighten bolts.
T
est t
he
adj
ustme nt
by
rocking crankshaft or
by moving rod back and forth on crankpin as
allowed by end clearance. NOTE
:
A ridge is
form
ed
on
edge
of cap and a boss is formed on
web of rod
above
th
e
bearing.
These marks
must be toward
rear
of engine
when
cap is in-
stalled.
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