GMC 1976 ZEO 6083 Maintenance Manual page 421

Figure 39-Installing Point Shield
6. Install rotor, Figure 40 .
7. Install distributor cap.
1/8" Allen wrench into the head of the adjusting
screw as shown in Figure 41 and adjust dwell angle
to 30 degrees.
NOTE : If the dwell angle reading is erratic,
check the contact points and condenser.
The dwell angle variation should not exceed 3
degrees at engine speeds between idle and 1750 rpm.
Excessive variation indicates distributor wear .
Figure 40-Installing Rotor
MECHANICAL ADVANCE
VACUUM ADVANCE UNIT
Removal
Installation
ENGINE ELECTRICAL
6Y- 41
Figure 41-Adjusting Dwell Angle
The mechanical advance weights and springs are ac-
cessible by removing the rotor. The mechanical ad-
vance plate is assembled to the breaker cam. In order
to remove the breaker cam and advance plate, follow
the procedure for DISTRIBUTOR-DISASSEM-
BLY and ASSEMBLY .
1 . Remove the distributor cap, shield and the two
vacuum advance attaching screws . (figure 42)
2. Turn the breaker plate clockwise and push the
rod end of the vacuum advance down so that it will
disengage and clear the breaker plate. Remove
vacuum advance unit .
1 . Position the rubber sleeve over the rod end of
the vacuum advance.
2. Insert the rod end of the unit between the
housing and the breaker plate.
3. Turn the breaker plate clockwise so that the
rod end can be inserted into the hole in the breaker
plate.
4. Install the attaching screws with the ground
lead terminal under the inner mounting screw. (fig-
ure 42) Install the shield and distributor cap.