Chevrolet 30 Series 1967 Service Manual page 287

12—
Fig. Ignition Timing Marks
.
2 Start engine and run at idle speed (see tune up chart).
3.
Aim timing light at timing tab.
NOTE: The markings on the tabs are in 2°
increments (the greatest number of markings
on the side of the " O" )- The "O " mark-
" A "
IDLE SP EE D
S C R E W
F ig . 13—Idle Speed and M ixture Screws
ing is TDC and all BTDC settings fall on the " A "
(advance) side of " O ".
4. Adjust the timing by loosening the distributor clamp
and rotating the distributor body as required, then
tighten the clamp.
5. Stop engine and remove timing light and reconnect
the spark advance hose.
Adjust Idle Speed and Mixture (Fig. 13) (Except When
Equipped With Air Injection Reactor System)
1. As a preliminary adjustment, turn idle mixture
screws lightly to seat and back out
CAUTION: Do not turn idle mixture screw
tightly against seat or damage may result.
2. With engine running at operating temperature (choke
wide open) adjust idle speed screw to bring idle speed
to specified rpm (automatic transmission in drive,
manual transmission in neutral).
3. Adjust idle mixture screw to obtain highest steady
idle speed (1/4 turn out from lean roll).
4. Repeat Steps 2 and 3 as needed for final adjustment.
5. Shut down the engine, remove gauges and install air
cleaner.
Adjust Idle Speed and Mixture (Fig. 13) (With Air
Injector Reactor System)
To produce an acceptable level of exhaust emissions
the idle speed and mixture should not be adjusted to
obtain the highest steady vacuum reading.
The recommended adjustment procedure for Air In­
jection Reactor System equipped engines is as follows:
1. As a preliminary adjustment, turn idle mixture
screws lightly to seat and then back out 3 turns.
IDLE M IXTURE
S C R E W
ENGINE 6-7
turns.
2
CHEVROLET TRUCK SERVICE MANUAL