GMC 1976 ZEO 6083 Maintenance Manual page 419

these factors are not corrected, the timing
should be retarded 2 degrees from the specified
setting.
6. Remove plug from fittings and connect hoses
to carburetor. Remove tape from manifold fitting
and connect vacuum hose, install air cleaner.
DISTRIBUTOR (FIGURE 34)
DESCRIPTION
The distributor cap has a window for adjusting
point opening (dwell angle) while the cap is mounted
and the engine is running. The contact point set is
replaced as one complete assembly . The service re-
placement contact set has the BREAKER LEVER
SPRING TENSION AND POINT ALIGNMENT
pre-adjusted . Only the POINT OPENING requires
adjusting after replacement .
Under part throttle operation when the transmis-
sion is in high gear, intake manifold vacuum actuates
the vacuum control diaphragm, thus advancing the
WINDOW
CENTR I FUGAL
ADVANCE
MECHANISM
ONTACT
SET ASSEMBLY
A-1866
Figure 34-Distributor Components
ENGINE ELECTRICAL 6Y- 3 9
spark and increasing fuel economy. During fast ac-
celeration or when the engine is pulling heavily,
vacuum is not sufficient to actuate the diaphragm;
therefore, the movable breaker plate is held so that
the ignition timing is retarded .
The centrifugal advance mechanism consists of a
cam actuated by two centrifugal weights controlled
by springs. As the speed of the distributor shaft in
creases with engine speed, centrifugal
advance
weights move outward which advances the cam,
causing the contact points to open earlier, thus ad-
vancing the spark.
CONTACT POINT REMOVAL
1 . Remove distributor cap and rotor. (figure 35)
2 . Remove two piece metal shield attaching
screws and shields. Figure 36 .
Figure 35-Removing Distributor Cap