V-8
ENGINE
8-67
and
fitting of pistons should be closely coordinated.
If
bore has been honed, it should be washed thor-
oughly with hot soapy water and a stiff bristle
brush.
Using
a cylinder checking
gauge,
measure the
cyl-
inder
bore crosswise of the block to find the smallest
diameter. Record the smallest diameter of each
bore.
NOTE:
When measuring
cylinder
bores
and
pis-
tons
ii is very important that the
block
and pistons
be
at room temperature. If any or all of the parts
are
hotter or
colder
than normal room tempera-
ture,
improper fitting
will
result.
Measure
the piston
skirt
perpendicular to the pis-
ton pin
boss
(piston pin removed) and at sizing point
indicated
in Fig. 6-119.
Make
sure the micrometer is In
full
contact (Fig.
6-120).
As
the pistons are measured they should be
marked
for
size identification
and
the measurements recorded.
If
there is excessive clearance between a cylinder
bore and the piston which was installed In that bore,
a
new piston should be used.
New pistons are serviced in standard size and
.001",
.002",
.005", .010", .020" and .030" oversize.
NOTE:
Since
these are nominal or
basic
sizes,
ii
is
important that new pistons be measured to en-
sure
proper
fit. All new pistons are
serviced
with
selectively
fitted piston
pins.
After
all measurements have been made, match the
new pistons with cylinders where they
will
fit with
proper
clearance. Honing of cylinder bore may be
necessary to
effect
a proper fit. When properly
mated,
mark
pistons with cylinder numbers they fit
so they
will
not
become
mixed.
FITTING
PIN IN
PISTON
The piston pin fit In the piston is .0005" to .0007"
loose
with
pin and
bosses
clean and dry.
Fig.
6-120
Measuring
Piston
NOTE:
Piston
and pin must be at room tempera-
ture
when
checking
fit and pin must be
able
to
fall
from
piston
by its own
weight.
FITTING
OVERSIZE
PINS
IN
PISTONS
AND
CONNECTING
ROD
PIN
BORES
In
case the standard size piston pin
does
not fit
properly
in the piston, an oversize piston pin must
be fitted. Piston pins are available in .001" and
.003" oversize.
When
oversize pins are used, the piston pin
bosses
must be honed to
give
required fit. It
will
also be
necessary to hone the connecting rod pin bore to fit
the oversize pin, using a Sunnen hone or similar
accurate
equipment.
NOTE:
A
special
grit
hone
is
used
for
honing
the
connecting
rod pin
bore.
The
piston
pin
size
should
be
.0008"
to
.0016"
larger
than
connecting
rod pin
bore
for
proper
press
fit. The
piston
pin
should
not
show
any movement
under
1500 lb. minimum
load
after
assembly
in rod.
ASSEMBLE
CONNECTING
ROD
TO
PISTON
There
is a notch cast in the top of all piston heads
to facilitate proper installation. The piston assem-
blies should always be installed with notch toward
front
of engine. Position rod in piston so that oil
squirt
hole (Fig. 6-121) is toward camshaft.
REPLACE
PISTON
PIN
1. Place pilot plunger and spring in the support
base to be used as a pilot end stop. See Fig. 6-122
insert
for correct base support and pilot plunger for
type pistons being serviced.
2.
Place pilot plunger of tool J 6901 in piston pin
bore and place on arbor press.
3.
Coat
piston pin and rod lightly with graphite
lubricant.
4. Place tool J
6901-3
in piston pin and press pin
into piston and connecting rod (Fig. 6-122) until
piston pin
bottoms
against plunger of tool J 6901.
Piston
must
turn
freely on pin. If piston binds on
pin,
disassemble, hone piston pin
bosses
slightly and
reassemble.
PISTON
RINGS-REPLACE
1. Remove piston and rod assembly. See
CON-
NECTING
ROD AND
PISTON
ASSEMBLY-RE
MOVE
AND
REPLACE.
2.
Remove piston rings using J 7117 or J 22563.
3.
Clean
carbon,
varnish,
and gum from piston
surfaces,
including under side of piston head.
Clean
ring
grooves, and oil
holes
in oil
ring
groove, using
suitable cleaning
tools
and'solvent.
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