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6A6-2
1977 PONTIAC SERVICE MANUAL
GENERAL DESCRIPTION
CYLINDER BLOCK
The cylinder block is made of cast iron and has 8
cylinders arranged in a "V" shape with Ccylinders in each
bank. Five main bearings support the crankshaft which is
retained by recessed bearing caps that are machined with the
block for proper alignment and clearances. Cylinders are
completely encircled by coolant jackets.
CYLINDER HEAD
The cast iron cylinder heads provide a compression ratio
of 8.5:l. They are cast with individual intake and exhaust
ports for each cylinder. Valve guides are integral, and rocker
arms are retained on individual studs.
CRANKSHAFT A N D BEARINGS
The crankshaft is cast nodular iron and is supported by
five main bearings. Number five bearing is the end thrust
bearing.
Main bearings are lubricated from oil holes which
intersect the camshaft bearings. The camshaft bearings are
fed oil by the main oil gallery which is rifle drilled down the
center of the block, above the camshaft. Two additional oil
galleries are on either side of the main oil gallery to provide
an oil supply for the hydraulic lifters.
A harmonic balancer on the forward end of the
crankshaft dampens any engine torsional vibrations.
CAMSHAFT AND DRIVE
The cast iron camshaft is supported by five bearings and
is chain driven. A steel crankshaft gear drives the timing
chain which in turn drives the camshaft through a bakelite
fabric composition gear with a steel hub.
Cam lobes are ground, hardened and tapered with the
high side toward the rear. This, coupled with a spherical face
on the lifter, causes the valve lifters to rotate.
Camshaft bearings are lubricated through oil holes
which intersect the main oil gallery. The main oil gallery is
rifle drilled down the center of the block, above the camshaft.
PISTONS AND CONNECTING
RODS
The pistons are made of cast aluminum alloy using two
compression rings and one oil control ring.
Piston pins are offset 1/16" toward the 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 chromium 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 forged steel. 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.
VALVE TRAIN
A very simple ball pivot-type train is used. Motion is
transmitted from the camshaft through the hydraulic lifter
and push rod to the rocker arm. The rocker arm pivots on
its ball and transmits the camshaft motion to the valve. The
rocker arm ball is retained by a nut.
HYDRAULIC VALVE LIFTERS
Hydraulic valve lifters are used to keep all parts of the
valve train in constant contact.
The hydraulic lifter assembly consists of: the lifter body,
which rides in the cylinder block boss, a plunger, a push rod
seat, a metering valve, a plunger spring, a check ball and
spring, a check ball retainer and a push rod seat retainer.
When the lifter is riding on the low point of the cam,
the plunger spring keeps the plunger and push rod seat in
contact with the push rod.
When the lifter body begins to ride up the cam lobe, the
check ball cuts off the transfer of oil from the reservoir below
the plunger. The plunger and lifter body then rise as a unit,
pushing up the push rod and opening the valve.
As the lifter body rides down the other side of the cam,
the plunger follows with it until the valve closes. The lifter
body continues to follow the cam to its low point, but the
plunger spring keeps the plunger in contact with the push rod.
The ball check valve will then move off its seat and the lifter
reservoir will remain full.
INTAKE MANIFOLD
The intake manifold is of cast iron double level design
for efficient fuel distribution. The carburetor pad is centrally
located with a passage running underneath the pad (E.F.E.)
through which exhaust gases are forced to promote faster fuel
vaporization when the engine is cold. An EGR port is also
cast into the manifold for the induction of exhaust gases into
the inducted fuel.
EXHAUST MANIFOLDS
Two cast nodular iron exhaust manifolds are used to
direct exhaust gases from the combustion chambers. The
right hand side manifold receives a heat shield that is used
to route heated air to the air cleaner for better fuel
vaporization.
COMBUSTION CHAMBERS
Combustion chambers are cast to insure uniform shape
for all cylinders. Spark plugs are located between the intake
and exhaust valves.
The contoured wedge shape of the combustion chamber
minimizes the possibility of detonation, facilitates breathing
and provides swirling turbulence for smooth, complete
combustion.
ENGINE SERVICE
NOTE: The following information is important in
preventing engine damage and in contributing to reliable
engine performance.
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