Chevrolet 10 Series 1970 Service Manual page 367

NOTE: No float drop adjustment is
on this carbu retor.
4. If n ecessary to adjust (e ith e r o r both bow ls), loosen
inlet needle lock s cre w
clock w ise to lo w er o r cou n ter-clock w ise to ra ise
fuel le v e l, then tighten lock screw .
NOTE: 1/6 turn o f adjusting nut equals ap­
p roxim a tely 1/16" fuel le v e l change.
ROCHESTER M V
TYPICAL ROCHESTER 2GV
ROCHESTER 4 M V
F ig . 6 c —V acuum Break A djustm ent
requ ired
and turn the adjusting nut
5. A llow a minute fo r fuel le v e l to sta b ilize then r e ­
check the le v e l at sight plug.
6. Readjust, if n ecessary, until p rop er le v e l is obtained,
then install sight plug and a ir cleaner.
NOTE: To assure p ro p er secondary float le v e l
setting it is advisable to a cc elera te p rim a ry
throttles slightly and hand operate secondary
throttle. This assu res a stabilized secondary
fuel le v e l.
Vacuum Break Adjustm ent (Fig. 6c)
1. R em ove a ir clean er
veh icles with " T h erm
s en s o r's vacuum ta k e -o ff port.
2. Start engine o r in stall a vacuum source
J-23309 to vacuum diaphragm vacuum tube.
3. R em ove choke rod from
rubber band to the le v e r in such a manner as to
react on the le v e r in a direction to close the cb ''ke
blade.
4. Slowly open a c c e le ra to r until choke c lo ses (choke
w ill not fu lly close due to the vacuum break lin k 's
reaction on it) and idle is determ ined by high step of
fast idle cam. R elease a c ce lera to r.
5. With idle determ ined by fast idle cam and vacuum
break link acting on the choke le v e r , in se rt specified
gauge (hold v e r tic a l)
horn and choke blade.
6. Adjust vacuum break setting as n ecessary by bending
rod o r tang.
Throttle Return Check V a lv e Adjustment (Fig. 7c)
1. With carbu retor choke closed and fast id le sc re w on
high step of fast id le cam, loosen lock nut and adjust
va lve to just contact throttle le v e r.
2. Adjust lock nut to lock valve in position. Tighten nut
to 90-130 in. lbs.
3. With choke wide open, operate throttle le v e r and
o b s erve action o f va lve plunger-plunger should be
depressed when throttle
position.
Additional Adjustments
The follow ing adjustments may be made without re m o v ­
ing the ca rbu retor from the engine. F o r procedu re r e fe r
VALVE
F ig . 7 c—T h ro ttle Return C h e ck V a lv e
ENGINE FUEL 6M -3
assem bly from veh icle.
A C " a ir cleaner, plug the
such as
choke le v e r and in stall a
between the carbu retor a ir
le v e r returns to closed
IDLE SCREW
CHEVROLET TRUCK SERVICE MANUAL
On