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PART 1-1- GENERAL ENGINE
SERVICE
FIG.
21-Cleaning Ring Grooves-Typical
tion
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 journa
l,
o
r
a
tapered con
nect-
ing rod
bore.
Twisted
connecting
rods
will
not
create
an
easily
identifiable wear pal-
tern, but
badly twisted
rods will
dis-
turb the
action
of
the entire
piston,
rings,
and connec
ting rod
assem bly
and
may be
the
cause of
excessive
oil
consum
ption.
CUANING AND INSPECTION
Remove
the
bearings
from
the
rod
a
nd
cap (identify them
if
they
are to
be
used again), C lean
the connecting
rod in
solvent,
including the
rod
bore
and the
back
of thc
inserts.
Do
nOI
use a
caustic
cleaning
solulion.
Blow
out
all passages
with
compressed
ai
r.
Inspect the rods
for signs of frac-
tures
and the bearing
bores
for
out-of-
round
and taper.
If
the bore exceeds
the maxim
um
limit
and/o
r
if
the
rod
is
fractured,
it should
be
replaced.
Check
the
piston
pin
to
connecting
rod bushing
clearance.
Replace
the
connecting
rod if
the bushing
is so
worn that
it
cannot
be reamed or
honed
fo
r
an
oversize pin.
Replace
defective
connecting
rod
nuts
and
bolts.
Afte
r
the connecting
rods are as-
sembled
to the
piston,
check
the rods
for bend
or
twist on
a suitable
align-
ment
fixture. Follow
the
instructions
of
the fixture
manufact
urer.
If the
bend
and/or twist
is
excessive, the
rod
should
be
straightened
or re-
placed.
PISTONS, PINS, AND RINGS
CUANING
AND
INSPECrtON
Remove carbon
deposits
from
the
piston
surfaccs
and from
the undcr-
side
of the piston
head.
Clean gum or
varnish
from the piston
skirt,
piston
pins.
and
rings
with
solvent.
Do not
use
a caustic cleaning
solution
or
a
wire
brush to clean pistons.
C
lean
the
ring grooves with a ring groove
clean-
er (Fig.
21). Make
sure the
oil
ring
slots
(or holes) are clean.
Carefully
inspect the pistons
for
frac tures
at
the ring lands, skirt,
and
pin
bosses, and
for
scuffed,
rough,
or
seored
skirts.
If the
lower inner por-
tion of
the
ring grooves have
high
steps,
replace
the
piston.
The step
will
interfere
with
ring operation
and
cause excessive ring
side clearance.
Spongy, eroded areas ncar the edge
of
the
piston
to
p
are
usually
caused
by
detonation, or
pre. ignition.
A
shiny
surface on the
thrust surface
of
the piston, offset fro
m
t.he centerline
between
the
piston pin
holes,
can
be
caused by a bent connecti ng rod.
Replace
pistons
that
show signs
of
excessive wear, wavy ring
lands,
frac-
tu
res.
and
/
or da mage from
detona-
tio
n
or
pre-ignition.
Check the
piston
to
cylinder
bore
clearance
with
a
tension
scale
and
ribbon
and
the
ring
side
clearance
following
the
recommended
proce-
dUres.
Replace piston pins showing
signs
of frac ture
or
etching
and/or wear.
Check
the piston
pin fit in the piston
and rod bushi ng.
Replace
all
rings
that
are scored,
chipped, or cracked. Check
the
end
gap
and
side clearance.
It
is
good
1-15
practice
to always
install
new
rings
when
overhauling
the engine.
Rings
should
not
be
transrerred
from
ODe
piston to another regardless of
mile-
age.
FiniNG PISTONS
Pistons
are available
for
service
in
standard
sizes and
0.003, 0.020,
0.030,
0.040,
and
0.060-i
nch
over-
size. Standard
size
pistons are
divided
into two
sizes
and
are
identified by
a
daub
of red
or
blue paint.
Refer to
the
specifications
for
the
available
sizes.
The
piston
and
cylinder
block
should
be
at
room
temperature
(70°F)
when
the
piston fit
is
checked. Arter
any
refinishing
operation,
allow
(he
cylinder bore to cool before
the
pis-
ton fit
is
checked.
Calculate the
size piston
to
be
used
by
taking
a
bore
check
(Fig.
25).
then
select
the proper size piston
to
provide
the
desired
clearance.
Make
sure the
piston
and
cylinder
bore are clean
and
dry. Attac
h
a ten-
sion
scale
to
the
end
of
a feeler
gauge
ribbon that
is free
o
f
dents
or
burrs.
The
feeler
ribbo
n
should
be !I.z
-inch
wide
and of the recom
mended
thick-
ness listed
in
T
able 4.
Position
the
ribbon
in
the bore so
that
it extends
the
entire
lengt
h
of
the
piston
at
90°
fro
m the
piston
pin
location. Invert
the
piston
and
install
it
in
the
bore
so
that
the
end of
the
piston is
abo
ut
1!I.z inches below
the
top of the
cylinder
block
and the
pis-
ton pin
is
parallel
to
the
crankshaft
axis.
Hold
the
piston and
slowly
pull
the
scale
in a
straight
line
with
the
ribbon, noting
the
pull
required
to
remove the
feeler
ribbo
n
(Fig. 22).
The
piston
10 cylinder
bore
clear-
ance
shou ld be from
0.0008-0.0026
inch
(
MD and
HD
V-8 engines)
or
0.00
11
-0.0029
inch
(all
SO
V-8
en-
gines).
T
he
wear
limit
is 0.005
inch.
In T
able 4,
the
diagonal
lines
represent feeler
ribbons
of
various
thicknesses,
the
horizonlal
Jines
re p-
resent the pounds
pull,
and the
ver-
tical
lines
represent
clearance.
To
dete rmine the clearance. locate
Ihe
line
representing the pounds
pull
re-
qu ired 10
remove
the
feeler
ribbon
from the
cylinder
bore.
Follow the
horizontal
line
to the
right
until it
intersects
the diagonal
line
represent-
ing
the fee ler
ribbon.
Read
down
the
vert
ical
line for the clearance.
Exa mple
I.
If a 0
,0015-inch
feeler
ribbon
is used and
it
takes
approxi-
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