Chevrolet DB90 Series, Service Manual

Page: 24 / 242

Sec. 1-18
CAB AND BODY MOUNTINGS
VALVE STOP
UNIT BRACKET
©
\
BRASS WASHER
FITTING
PISTON O -RING CYLINDER W ASHER VALVE
Figure 10—Valve Head
Assembly Components
c. R ea ssem b le in r e v e r se order of d isa sse m ­
bly making su re a ll p a rts are clean and lubricated
with S ilicon e G rease Type G E-SS-4067 or D C -4.
Make su re valve is properly hooked in valve bracket.
4. To replace valve head assem b ly (26), move
gear rack assem b ly (24) a s near to the opening as
p o ssib le .
NOTE: U se new gasket (14) when replacing
valve head a ssem b ly .
5. R a ise valve stop unit (22) and hook under
pin on valve stop unit bracket (fig. 10), making sure
that a ir p a ssa g e in head is directly opposite air
tube in cylinder.
6. Move rack assem b ly (24) sligh tly away
fro m end to provide clearan ce and in sta ll 6 attach­
ing sc r e w s.
P isto n Packing and Valve Stop Unit
Replacem ent
1. Rem ove valve head assem b ly (26) as out­
lined p reviou sly.
2. Rem ove top cover (2) by rem oving four
attaching sc r e w s (3).
IMPORTANT: B e su re top co v ers (2) position
a r e marked so that they can be p osition ed exactly
when assem bling.
3. Rem ove two mounting plate sc r e w s (7) and
sp a c e r s (11), then rem ove shaft (8), gear (12) with
bushings (10).
4. Gear rack (24) can now be withdrawn from
cy lin d er body (13).
NOTE: If n e c e ssa r y , tapered m otor shaft (8)
can be p r e sse d from gear (12) and bushings (10)
by rem oving nut (18) and sp acer (17). Note p osition
of shaft arm and teeth of gear are both in down
p osition for co rrect installation.
5. R em ove screw (19) from both ends of gear
rack (24) to rem ove piston p ack in g(2 3 ),piston (25),
valve stop unit (22), w asher (21) and retaining ring
(
20
).
6. Clean a ll parts thoroughly, replacing dam­
aged or worn packing or other p a rts. Lubricate
packing and cylinder w alls with a sp e c ia l form ula
g r e a se designed for th is purpose (Silicone G rease
Type G E -SS-4067, or D C -4).
7. A ssem b le p arts, making su re they are
placed in their rela tiv e position a s shown in fig ­
u r e s 9 and 10.
IMPORTANT: A shim can be u sed to slip the
gear rack assem b ly into the cylin d er as follow s:
a. Wrap en tire gear rack (24) (with piston
packing, piston, w ash er, and retaining ring in sta ll­
ed) in s te e l sh im stock.
b. In sert gear rack and sh im into cylinder far
enough to p a ss opposite end of opening in cylinder
body. Hold sh im stock and push rack assem b ly
down a s far a s it w ill go. Hold rack assem b ly at
th is point with screw d riv er and withdraw sh im .
c. Lubricate end of cylinder (13) b efore r e ­
p lacin g valve head (26).
NOTE: When in stallin g gear (12) into gear
rack (24) make su re that the teeth match the rack
CHEVROLET SERIES 70-90 HEAVY DUTY TRUCK SHOP MANUAL SUPPLEMENT