GMC 1976 ZEO 6083 Maintenance Manual page 58

BALL SEATS USED TO GIVE
.0005 TO .0010
TOTAL CLEARANCE
.D10
THRUST UNIT CONTROLS
RUNNING CLEARANCE
.0005 TO .0015
THRUST UNIT CONTROLS
HEAD CLEARANCE
of the cylinder (figure 12). This allows .001 inch
tolerance between the high and low limits .
011 Pump Gears
The oil pump gears are made of sintered iron .
The inner, or driver gear has a "D" shaped hole in
the center which fits over a similar area on the rear
of the mainshaft.
Shell
The compressor shell has a mounting flange on
the front end and four threaded studs welded to the
outside of the rear end. The oil sump is formed into
the shell and a baffle plate is welded over the sump
on the inside of the shell.
Heads
Figure 12-General Running Clearances
Both front and rear heads have an irregular
shaped casting web . These webs provide the neces-
sary seals to the surfaces of the discharge plates and
prevent high pressure vapor from flowing into the
low pressure cavity .
Suction Screen
A fine mesh inlet (or suction) screen is located in
the low pressure cavity of the rear head . Its purpose
is to stop any material which could damage the com-
pressor mechanism.
Suction Cross-Over Cover
The suction cross-over cover is assembled into
Discharge Valves
AIR CONDITIONING SYSTEM 1- 4 1
the dove-tail cavity in the front and rear cylinder
castings to form a passage for the low pressure vapor
to flow the rear head of the compressor to the front
head .
Discharge Cross-Over Tube
Since the double acting pistons supply high pres-
sure vapor at both ends of the compressor the dis-
charge tube is needed to supply a path for the high
pressure vapor to pass from the front to the rear
head . Should the cylinder halves be separated during
service operations a service type discharge tube,
bushings and "O" rings must be substituted .
Suction Reed Valves
A separate three-reed suction valve disc is assem-
bled to both front and rear heads. These reeds open
when the piston is on the intake portion of the stroke
to allow the low pressure vapor to flow into the
cylinder . When the piston reverses and begins the
compression portion of its stroke the reed valves
close against their seats, thus preventing the high
pressure vapor from being forced back into the low
side of the system .
The two discharge valve plate assemblies act to
direct high pressure vapor into the head castings.
When the piston reverses into its suction stroke the
high pressure on the opposite sideof the plate causes
the reeds to close thus maintaining the differential of
pressure between high and low pressure areas . The
discharge plates include the valves and the retainers
which prevent the high pressure from distorting the
valves during the pressure stroke of the piston .
Head to Shell Seals
Two large diameter "O" rings internally seal the
front and rear heads to the shell . A chamfered edge
on the head castings creates a squeezing action be
tween the discharge valve plates, the compressor,
and the inside surface of the shell.
Compressor Connector
Compressor connectors, are attached to the com-
pressor rear head by means of a single bolt and lock
washer . All have inlet and outlet connections con-
nected by a strap to form an integral unit .
Pressure Relief Valve
The pressure relief valve, located on the compres-
sor tear head, is simply a safety valve designed to
open automatically if the system pressure should