Chevrolet 1977 light duty truck, Service Manual

Page: 475 / 861

PRESS
PISTON PIN
REMOVER
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Fig. 6A-61--F?emoving Piston Pin
Check for twisted or bent rods and inspect for nicks
o r cracks. Replace connecting rods that are dam aged.
Pistons
Clean varnish from piston skirts and pins with a
cleaning solvent. DO N O T W IR E BRUSH A N Y P A R T
O F T H E PISTON. Clean the ring grooves with a groove
cleaner and m ake sure oil ring holes and slots are clean.
Inspect the piston for cracked ring lands, skirts or
pin bosses, wavy or w orn ring lands, scuffed or dam ag ed
skirts, eroded areas at top o f the piston. Replace pistons
th at are d a m a g e d o r show signs o f excessive wear.
Inspect the grooves for nicks or burrs that might
cause the rings to h an g up.
M easure piston skirt (across center line o f piston
pin) and check clearance as outlined u nder "Piston
Selection".
Piston Pins
T h e piston pin clearance is designed to m aintain
a d e q u a te clearance u n d e r all engine operatin g condi­
tions. Because o f this, the piston and piston p in are a
m atched set and not serviced separately.
Inspect piston pin bores and piston pins for wear.
Piston p in bores an d piston pins must be free o f varnish
o r scuffing w h en being m easured. The piston pin should
be m easured with a m icrom eter and the piston pin bore
should be m easured with a dial bore gauge or an inside
m icrom eter. If clearance is in excess o f the .001" w ear
limit, the piston an d piston pin assembly should be
replaced.
ASSEMBLY
1. Lubricate piston pin holes in piston and
connecting rod to facilitate installation o f pin.
2. Place connecting rod in piston and hold in place
with piston pin guide and piston pin. Place connecting
rod and piston assembly on fixture and support assembly
(fig. 6A-62).
N O TE: See figure 6A-63 for correct size o f piston
pin guide.
3. Using piston pin installer, J-24086-9, press the
piston pin into the piston and connecting rod (Fig. 6A-
64).
N O TE: The piston pin installer is a variable
insertion length tool designed to be applicable to
all G M piston assemblies. The insertion length is
varied by rotatin g the hub on the shaft much like
adjusting a micrometer. An alpha-num eric scale is
used to d eterm ine the desired length for a given
piston pin assembly. R efer to figure 6A-63 for
correct setting.
CAUTION. A fte r installer hub bottoms on
support assembly, do not exceed 6000 psi
I-
-PISTON PIN
4fI
PISTON
PIN GUIDE
FIXTURE &
SUPPORT
ASSEMBLY
FIXTURE &
SUPPORT
ASSEMBLY
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