Chevrolet 70 Series 1970, Service Manual

Page: 271 / 841

REAR SUSPENSION 4-58
2. To adjust a i r intake valve le v e r gap:
a. Move the o v e rtra v e l le v e r slowly from tru e
c e n te r position to point w here intake valve just
begins to open. L isten fo r escaping a ir . Note re a d ­
ing on dial at th is point which should re g is te r
0.025” to 0.027” .
b. If n e c e ssa ry , bend intake valve le v e r to
c o r re c t setting (fig. 11).
3. To ad ju st a i r exhaust valve le v e r gap:
a. In stall valve cover on the valve using anew
gask et and four attaching sc rew s.
b. Being carefu l not to d istu rb in d icato r s e t­
ting, disconnect a ir supply fro m the a i r inlet p o rt
and connect it to the bellows p o rt (fig. 8).
c. Move o v e rtra v e l le v e r slowly to open ex­
haust p o rt while observing the in d icato r dial. A ir
should s ta r t to escape fro m exhaust p o rt when in­
d icato r r e g is te r s 0.035” to 0.037”. If adjustm ent
is n e c e s s a ry , shut off a ir p r e s s u r e supply and
rem ove valve cov er. Bend exhaust valve le v e r to
c o r re c t setting, then in stall cover and rech eck
valve opening dim ension.
d. Recheck valve le v e r gaps, then p ro ceed
with "T im e Delay C heck” following:
TIME DELAY CHECK
Figure 12—Venting Air from Silicone Fluid
6. R echeck intake and exhaust valve lev er
gaps, then p ro ceed with "T im e Delay Check" ex­
plained la te r.
METHOD USING AIR PRESSURE ONLY
NOTE: This method may be p erfo rm ed when a
vacuum so u rce is not available.
1. Connect a i r supply hose (80 to 110 psi) to
a ir in let p o rt (fig. 8).
Figure 13—Silicone Fluid Level
PRELIMINARY PROCEDURES
A fter the valve le v e r gaps have been p ro p e rly
adjusted, the tim e delay check m ust be p erfo rm ed .
A 2 to 9 second delay fro m the closing of one valve
to the opening of the o th er is recom m ended.
1. P la ce new O -rin g over delay plug, then in ­
s ta ll plug into valve body. Tighten plug to torque
lis te d in "S pecifications."
2. P o u r 6.0 cc - 0.25 cc of silico ne fluid (1000
C entistokes visco sity at 25°C) into delay piston
b o re . With valve body tilted slightly a s shown in
fig u re 12 carefully o p erate o v e rtra v e l le v e r fo re
and aft to vent a i r fro m fluid. When all a i r has
been expelled fro m pisto n pin cavity, check fluid
lev el using depth gauge as shown in fig u re 13.
IMPORTANT: With valve assem bly lev el, take
m easu rem en t fro m c e n te r of b o re only. Add o r r e ­
move fluid to brin g fluid 13/64-inch from top of
valve body. An eyedropper w ill s e rv e fo r th is p u r ­
pose.
3. P la c e new delay piston cover O -rin g in
groove of valve body. In stall cover with snap ring
re ta in e r.
4. P la ce valve assem b ly v e rtic a lly in holding
v ise (fig. 14).
5. Move o v e rtra v e l le v e r up and down fo r ap­
pro x im ately one m inute.
AIR INLET TIME DELAY CHECK
1. Connect a i r p r e s s u r e supply hose to valve
a i r inlet p o rt (fig. 8).
2. Move the o v e rtra v e l le v e r upw ard (quickly)
CHEVROLET SERIES 70-90 HEAVY DUTY TRUCKSHOP MANUAL