Check Dwell Variation; Check And Adjust Ignition Timing; Idle Speed And Mixture Screws - Chevrolet CHEVY VAN G10 SERIES Service Manual

ENG INE 6-8
IN LIN E ENGINES
• Remove distrib u to r cap and recheck poin t setting.
If dwell is still n o t w ithin specifications check the
distributo r as ou tlined in Section
CHECK DWELL V A R IA T IO N
Slowly accelerate engine to 1750 rpm and no te dwell
reading. R eturn engine to idle and note dwell reading. If dwell
variation exceeds specifications, check for w orn distributor
shaft, w orn distributor shaft bushing or loose breaker plate.
CHECK AN D ADJUST IG N ITIO N T IM IN G (FIG . 16)
1. D isconnect the distributor spark advance hose and plug
th e vacuum source opening.
2. S tart engine and ru n at idle speed. See tune up chart in
Specification section.
3. A im tim ing light at tim ing tab.
N O T E : The markings
increments (the greatest num ber of markings on the
"B efore" side o f the " O " ). The " 0 " marking is T D C
and all B T D C settings fall on the "B efore" (advance
side o f " O " .
4. A djust the tim ing by loosening the d istribu tor clamp and
ro tating the distributor body as required, th en tighten
the clam p and recheck timing.
SINGLE-BARREL
IDLE MIXTURE SCREW
CEC SOLENOID
IDLE SPEED (SOLENOID) SCREW
6
Y.
on the tabs are in 2°
ROCHESTER CARBURETORS
TWO-BARREL
IDLE MIXTURE SCREWS
IDLE SPEED (SOLENOID) SCREW
Fig. 17—Idle Speed and M ixture Screws
Fig. 1 6 —Ig n itio n T im in g M arks
5. S top engine and remove tim ing light and reconnect the
spark advance h o se.
IDLE MIXTURE SCREWS
IDLE SPEED (SOLENOID) SCREW
FOUR-BARREL
C H E V Y V A N SH O P M A N U A L