Pontiac FIREBIRD 1972 Service Manual page 92

CUSTOM AIR CONDITIONING 1A-33
of the mainshaft. The outer gear, which is driven, has
internal gear teeth mating with the external teeth on the
inner (drive) gear.
OIL FLOW
The internal parts of the compressor are lubricated by the
oil pump. Oil is picked up from the sump by the oil pump
gears through the pick-up tube and into the.pump cavity.
From here oil is forced through the drilled hole, through
the center of the mainshaft and to three outlets; one at
each mainshaft thrust bearing and one at the compressor
shaft seal.
Oil from the mainshaft seal drains back into the sump via
a hole built in the discharge plate, a notche slot in the
suction reed that indexes with a cast passag
8
(slanted) in
the front face of the front head casting, around the main-
shaft and through the mainshaft front bearing, between
the mainshaft and front head casting hub, to the mainshaft
front thrust bearing and into the sump.
Oil directed through each mainshaft thrust bearing flows
through the bearing and dumps into the sump. The main-
shaft rear bearing is lubricated from oil emitting from
clearances at the oil pump gears.
Oil that travels into the compressor assembly with the
refrigerant that is forced past the piston rings returns to
the sump as the pistons travel on their suction stroke. The
design of the piston rings is such that the scraper grooves
at the side of the ring facing the inside of the compressor
force the oil through two oil return holes behind the ring
groove (and extend toward the center area of the piston)
to dump oil into the compressor pump.
MAINSHAFT
The compressor mainshaft is driven by the pulley when
the clutch coil is energized. It extends through the com-
pressor front head, to the comptessor rear head and drives
the oil pump in the rear head pump cavities. The shaft is
supported by a needle bearing located in the front half of
the cylinder and a similar needle bearing in the rear half
of the cylinder.
A 3/16" diameter oil hole in the shaft extends from the
rear oil pump cavity to the shaft seal cavity. Four .078"
(5/64") diameter holes are drilled 90" to the main oil
passage. These drilled passages direct oil under pump
pressure to the shaft seal surfaces, thrust bearings, and
shaft roller needle bearings.
THRUST BEARING AND RACES
Two flat-type thrust needle bearings are seated around the
shaft and are located near the center of the compressor.
These bearings have rollers placed radially in their separa-
tors. Each bearing is sandwiched between two steel thrust
races, and this combination of three pieces is placed be-
tween the shoulders of the swash plate and the shoulders
of the cylinder hubs on the front and rear halves of the
cylinder.
The front end combination, consisting of a needle bearing
with a thrust race on each side, is selected to provide the
proper piston head clearance below the top of the cylinder
and the underside of the suction and discharge valve
plates.
The rear end combination, consisting of a needle bearing
with a thrust race on each side, is selected to obtain .0003"
(low limit) to .0013" (high limit) running clearance be-
tween the hub surfaces of the swash plate and the front
and rear hubs of the cylinder. This allows .001" tolerance
between the high and low limits of running clearance.
CYLINDER BLOCK
The cylinder block consists of two halves, front and rear.
Three piston bores in each half are line bored as one piece
during production to assure proper alignment and paral-
lelism. After boring, the cylinder block is cut apart at the
center and the faces are ground parallel to the two outer
ends of the cylinder.
Alignment and indexing of the two halves are maintained
by two cylindrical locator (squeeze) pins. It is important
that the two halves of the cylinder be kept together to
assure correct relationship of parts.
PISTONS
The double end pistons are made of cast aluminum, with
a bridge connecting each end. Each piston has a notch cast
in this bridge. This notched end of the piston is positioned
toward the front (pulley) end of the compressor.
Both ends of the piston have a groove to receive a piston
ring. Two oil return holes are drilled behind the ring
groove and extend toward the center area of the piston to
dump oil to the compressor oil sump. The piston rings
have an oil scraper groove at one edge (toward the center
of the piston) to wipe any excess oil back into the oil sump
(reservoir) through the oil return holes.
A spherical cavity is located in the inside center on each
side of the piston to receive the hardened steel piston drive
balls.
SHOE DISCS
Shoe discs are made of bronze and one side is a flat surface
which contacts the surface of the swash plate. The oppo-
site side has a coined concave surface into which is assem-
bled the piston drive ball.
These shoes are provided in .0005" thickness variations
and ,eleven sizes are available for servicing these parts.
Included in these eleven is a basic ZERO shoe to permit
simple gauging operations.
All service shoes will be marked with the shoe size, which
will also correspond to the last three digits of the piece
part number.