Camshaft And Drive - Pontiac TRANS AM 1977 Service Manual

6A2-2 1977 PONTIAC SERVICE MANUAL
FIG. 6A2-1 L4 ENGINE
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CRANKSHAFT AND BEARINGS
The crankshaft is cast nodular iron and is supported by
five main bearings. Number five bearing is the thrust bearing.
Main bearings are lubricated from oil holes which
intersect the main oil gallery which runs parallel to the
crankshaft bores along the right side of the block.
CAMSHAFT AND DRIVE
The cast iron camshaft is supported by three bearings
and is gear driven. A cast iron crankshaft gear drives the
camshaft through a bakelite fabric composition gear with a
steel hub (Fig. 6A2-3).
Cam lobes are ground, hardened and tapered with the
high side toward the rear. This, coupled with a spherical face
on the lifter, causes valve lifters to rotate.
Camshaft bearings are lubricated (through oil holes
which intersect the main gallery).
PISTONS AND CONNECTING
RODS
The pistons are of a light weight cast all aluminum
slipper skirt type and cam ground so that the diameter across
the thrust faces is larger than the diameter fore and aft of the
engine. Two compression rings and one oil control ring are
used, all of which are located above the piston pin. (Fig. 6A2-
4).
Piston pins are offset toward thrust side (right-hand side)
to provide a gradual change in thrust pressure against the
cylinder wall as the piston travels its path. Pins are tempered
steel and have a floating fit in the pistons. They are retained
in the connecting rods by a press fit.
Connecting rods are made of Armasteel. Full pressure
lubrication is directed to the connecting rods by drilled oil
passages from the adjacent main bearing journal. Oil holes
at the connecting rod journals are located so that oil is
supplied to give maximum lubrication just prior to full
bearing load.