Chevrolet Light Duty Truck 1973 Service Manual page 344

6-8 ENGINE
INSTRUMENT HOOK-UP
Connect vacuum gauge, dwell meter, tachometer and
timing light as recommended by the manufacturer of the
equipment being used.
CHECK AND ADJUST DWELL
1. Start engine then check ignition dwell.
2. If dwell is not within specifications, adjust dwell as
follows:
V8 Engine
• With engine running at idle, raise the
adjustment
screw window and insert an Allen
wrench in the
socket of the adjusting screw (fig. 14).
• Turn the adjusting screw as required until the
specified dwell
reading is obtained.
•Close access cover fully to prevent the entry of dirt
into the distributor.
In Line Engines
• Remove distributor cap and recheck
point setting.
If dwell is still not within specifications
INSTRUMENT
CHECK-OUT
Slowly accelerate engine to 1750 rpm and note dwell
reading. Return engine to idle and note dwell reading. If
dwell variation exceeds specifications, check for worn
distributor shaft, worn distributor shaft bushing or loose
breaker plate.
C R A N K C A S E V E N T IL A T IO N FILTER
Fig. 13—Crankcase Ventilation Filter
check the
distributor as outlined in Section 6Y.
CHECK DWELL VARIATION
CHECK AND ADJUST IG NITIO N
TIM ING (FIG. 1 5 )
1. Disconnect the distributor spark advance hose and
plug the vacuum source opening.
2. Start engine and run at idle speed. (See tune up
chart in Specification section.)
3. Aim timing light at timing tab.
NOTE: The markings on the tabs are in 2°
increments (the greatest number of markings
on the " Before" side of the "O " ). The "O"
marking is TDC and all BTDC settings fall
on the "Before" (advance) side of "O " .
4. Adjust the timing by loosening the distributor
clamp and rotating the distributor body as required,
then tighten the clamp and recheck timing.
5. Stop engine and remove timing light and reconnect
the spark advance hose.
LIGHT DUTY TRUCK SERVICE MANUAL