Pontiac firebird 1968 - Clean and Inspect; Cylinder Bores - Inspect; Piston Pin Fit

6-28
1968 PONTIAC SERVICE MANUAL
J 9510-3
J 9510-2
J 9510-1
Fig. 6-53 Removing Piston Pin—Step A
CONNECTING ROD AND PISTON -
CLEAN AND INSPECT
1. Clean carbon, varnish, and gum from piston
surfaces, including underside of piston head. Clean
ring grooves, and oil holes in oil ring groove, using
suitable cleaning tools and solvent.
2. Clean piston pin, rod, cap, bolts and nuts in
suitable solvent. Reinstall cap on connecting rod to
assure against subsequent mixing of caps and con-
necting rods,
3. Carefully examine piston for rough or scored
bearing surfaces; cracks in skirt or head; cracked,
broken, or worn ring lands; and scored, galled, or
worn piston bosses. Damaged or faulty pistons should
be replaced.
4. Inspect piston pin for scoring, roughness, or
uneven wear and proper fit.
5. Inspect bearing shells to see that they are
serviceable. Fit of bearings should be checked when
engine is assembled.
PISTON PIN FIT
The piston pin fit in piston is .0003" to .0005" loose
with pin and bosses clean and dry.
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 (Fig. 6-55).
Piston pins are available separately in .001 and
.003 oversizes. If the pin fit becomes loose it should
be replaced with a new oversized pin.
CYLINDER BORES-INSPECT
Inspect cylinder bores for out-of- round or exces-
sive taper, with an accurate cylinder gauge J 8087
or comparable, at top, middle and bottom of bore.
(Fig. 6-56), Measure cylinder bore parallel and at
right angles to the centerline of the engine to deter-
mine out-of - round. Variation in measure from top
to bottom of cylinder indicates the taper in cylinder.
(Fig. 6-57) illustrates area in cylinder where normal
wear occurs. Cylinder bores can be measured by
setting cylinder gauge dial at zero in the cylinder at
the point of desired measurement. Lock dial indica-
tor at zero before removing from cylinder, and
measure across gauge contact points with outside
micrometer, with the gauge at same zero setting
when removed from the cylinder (Fig. 6-58).
Fig. 6-54 Removing Piston Pin—Step B Fig. 6-55 Checking Piston Pin Fit