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8-18
pressed
into
the crankshaft and
should not be loose.
Inspect the
pilot bearing for rough-
ness,
evidence
of
overheating
or loss
of
lubricant.
Replace
it
if any of these
conditions are found.
FLYWHEEL-MANUAL-SHin
TRANSMISSIONS
INSPECTION
Inspect the
flywheel for cracks,
heat
checks, or other
defects that
would make it
unfit for further
service. Machine
the entire pres-
sure plate
mounting surface of the
flywheel
if it is scored
or worn.
If
it is
necessary
to
remove more
than
0.045
inch of stock from
the
original thickness, replace the fly-
wheel.
Inspect the ring gear for worn,
chipped or cracked teeth. If the
teeth are damaged, replace the ring
gear.
With the flywheel installed on the
crankshaft, check the flywheel
fac·
e
runout,
following the
procedure in
Section 1.
FL YWHEEL-AUTOMAnC
TRANSMISSION
INSPECI'ION
Inspect the flywheel for cracks
or other defects that would make
it unfit for further service. Inspect
the starter ring gear for worn,
chipped or cracked teeth. If the
teeth
are damaged,
replace the
ring gear and flywheel assembly.
With the flywheel installed on the
crankshaft, check the gear face run-
out
and
outside diaQleter runout of
the flywheel (refer to Section 1 for
the proper procedure).
CONNECTING RODS
CLEANING
Remove the bearings from the rod
and cap. Identify the bearings if
they are to be used again. Clean the
connecting rod in solvent, including
the rod bore and the back of the
inserts.
Do
Dot
use a caustic
cleaaJaa
solution. Blow out all passages with
compressed air.
INSPECTION
The connecting rods and related
parts should be carefully inspected
and checked for conformance
to
specifications. Various forms of en-
gine wear caused by these parts can
be readily identified.
A shiny surface on the pin boss
side of the piston usually indicates
that a connecting rod
is
bent or the
piston pin hole is
not
in proper
re-
GROUP 8-
ENGINE
lation
to
the piston skirt and ring
grooves.
Abnormal connecting rod bearing
wear can
be
caused by either a bent
connecting rod, an improperly ma-
chined crilnkpin, or a tapered con-
necting rod bore.
Twisted connecting rods will not
create an easily identifiable wear
pattern, but badly twisted rods will
disturb the action of the entire pis-
ton, rings and connecting rod as-
sembly and may be the cause of
excessive oil consumption.
Inspect the connecting rods for
signs of fractures and the bearing
bores for out-of-round and taper.
If
the bore exceeds the recommend-
ed limits and/ or if the connecting
rod is fractured, it should be re-
placed.
Check the J.D. of the connecting
rod piston pin bore. Replace the
connecting rod if the pin bore is
not within specifications.
Replace defective connecting rod
nuts and bolts.
If the connecting rod has been
removed from the piston it should
be checked for bend or twist before
assembling it to the piston. Con-
necting rods can be checked for
bend or twist while assembled to
the piston. Check the connecting
rods for bend or twist on a suitable
alignment fixture. Follow the in-
structions of the fixture manufact-
urer.
If
the bend and/ or twist ex-
ceeds specifications, the connecting
rod must be straightened or re-
placed.
PISTONS, PINS AND RINGS
CLEANING
Remove deposits from the piston
surfaces.
Clean gum or varnish from
the piston skirt, piston pins and
rings with
solvent.
Do not use a
caustic cleaning solutio& or a wire
brush to clean pistons. Clean the
r!ng grooves with a ring groove
cleaner (Fig. 30).
Make
sure the
oil
ring slots (or holes) are
clean.
INSPECTION
Carefully inspect the pistons for
fractures at the ring lands, skirts
and pin bosses, and for scuffed,
rough or scored skirts. If the lower
inner portion of the ring grooves
has a high step, replace the piston.
The step will interfere with ring
operation and cause excessive ring
side clearance.
Spongy, eroded areas near the
edge of the top of the piston are
usually
caused by detonation or
pre-ignition. A shiny surface on the
thrust surface of the piston, offset
from the centerline between the pis-
ton pin
holes,
can be caused by a
bent connecting
rod.
Replace
pis-
tons that show
signs
of excessive
wear, wavy ring lands or fractures
or damage from detonation or
pre-
ignition.
Check the piston to
cylinder
bore
clearance by measuring the piston
and bore
diameters.
Refer
to
the
specifications for the proper clear-
ance. Refer to
Cylinder
Block In-
Ring Groove Cleaner
FIG. 30 -Cleaning Ring Grooves
-Typical
spection for
the
bore
measurement
procedure.
Measure the
o:o.
of the
piston with micrometers at the cen-
terline of the piston pin bore and
at 90° to the pin bore axis.
Check the ring
side
clearance
fol-
lowing the procedure und<:r Fitting
Piston
Rings
in Section
2
page
8-14.
Replace piston pins
showing
signs
of
fra~...ure,
etching or
wear.
Check
the piston pin fit
in
the piston
and
rod.
Refer
to
Pistons
and Con-
necting Rods Assembly in the
per~
tinent engine
section.
Check the
O.D.
of the piston pin
and the
l.D.
of the pin bore
in the
piston.
Replace
any
piston pin or
piston that
is
not within specifica-
tions.
Replace all rings that are scored,
chipped or cracked. Check the end
gap and side
clearance.
It
is good
practice to always install new rings
when overhauling an
engine.
Rings
should not be transferred from one
piston
to
another regardless of
mileage.
MAIN AND CONNECTING
ROD BEARINGS
CLEANING
Clean the bearing inserts and caps
thoroughly in
solvent, and dry them
with compressed
air.
Do not scrape
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