GMC 1976 ZEO 6083 Maintenance Manual page 105

1- 88 AIR CONDITIONING SYSTEM
Figure 77-Installing Piston During Gaging Operation
8 . Rotate shaft and axial plate until high point of
axial plate is over the No. 1 Piston cylinder bore.
9. Lift shaft assembly up and hold front thrust
race and bearing assembly against axial plate hub.
10. Position piston over No. 1 cylinder bore
(notched end of piston being on bottom and piston
straddling axial plate) and lower the shaft to allow
piston to drop into its bore (figure 77).
11 . Repeat Steps 6 through 10 for Pistons No. 2
and No. 3 .
Figure 78-Assembling Cylinder Halves
12 . Install rear cylinder half on pistons, aligning
cylinder with discharge cross-over tube hole in front
cylinder . Tap into place using a plastic mallet or
piece of clean wood and hammer (figure 78).
13 . Position discharge cross-over tube opening
between a pair of Compressing Fixture bolts to per-
mit access for feeler gage .
14. Install top plate on Compressing Fixture J-
9397 . Tighten nuts to 15 lb. ft. torque using a 0-25
lb. ft. torqud wrench .
Gaging Procedure (Steps 15 thru 18)
The gaging operations which follow have been
worked out on a simple basis to establish and provide
necessary running tolerances . Two gaging proce-
dures are necessary.
The first
is made to choose the proper size shoe
discs to provide, at each piston, a .0016" to .0024"
total preload between the seats and the axial plate at
the tightest place through the 360-degree rotation of
the axial plate at the tightest plate. The bronze shoe
discs are provided in .0005" variations, including a
basic ZERO shoe .
The second,
performed at the rear shaft thrust
bearing and race pack, is designed to obtain .0025"
to .0030" preload between the hub surfaces of the
axial plate and the front and rear hubs of the cylin-
der. A total of 14 steel thrust races, including a basic
ZERO race, are provided in increments of .0005"
thickness to provide the required fit .
Feeler Gage Set J-9564 or J-9661-01 may be used
for gaging proper shoe disc size . Feeler Gage Set
J-9564-01 or Dial Indicator Set J-8001-3 may be used
to determine proper thrust race size .
PROPER SELECTION OF THRUST RACES
AND BALL SEATS IS OF EXTREME IMPOR-
TANCE.
15 . Measure clearance between rear ball of No. 1
Piston and axial plate, in following manner:
a. Select a suitable combination of well-oiled
Feeler Gage leaves to fit snugly between ball and
axial plate.
b. Attach a spring scale, reading in 1-ounce
increments, to the feeler gage . A distributor point
checking scale or Spring Scale J-544 may be used .
c. Pull on Spring Scale to slide Feeler Gage
stock out from between ball and axial plate, and note
reading on Spring Scale as Feeler Gage is removed
(figure 79).
Reading-should be between 4 and 8 ounces.