GMC 1976 ZEO 6083 Maintenance Manual page 423

5 . Remove the two retaining screws and the
vacuum advance unit.
CLEANING AND INSPECTION
1 . Wash all parts in cleaning solvent except cap,
rotor, condenser, breaker plate assembly and
vacuum control unit . Degreasing compounds may
damage insulation of these parts or saturate the lu-
bricating felt in the case of the breaker plate assem-
bly.
2. Inspect the breaker plate assembly for damage
or wear and replace if necessary.
3. Inspect the shaft for wear and check its fit in
the bushings in the distributor body . If the shaft or
bushings are worn, the parts should be replaced .
4. Mount the shaft in "V" block and check the
shaft alignment with a dial gauge. The runout should
not exceed .002" .
5. Inspect the advance weights for wear or burrs
and free fit on their pivot pins .
6. Inspect the cam for wear or roughness. Then
check its fit on the end of the shaft. It should be
absolutely free without any roughness .
7. Inspect the condition of the distributor points .
Dirty points should be cleaned and badly pitted
points should be replaced .
8. Test the condenser for series resistance, mi-
crofarad capacity (.18 to .23) and leakage or break-
down, following the instructions given by the
manufacturer of the test equipment used .
9. Inspect the distributor cap and spark plug
wires for damage and replace if necessary.
DISTRIBUTOR ASSEMBLY
1: Install the vacuum advance with the ground
lead terminal under the inner mounting screw. (fig-
ure 42)
2 . Place the felt wick on the upper bushing then
place the breaker plate over the upper bushing and
vacuum advance link .
3 . Install the retaining ring on the upper housing.
4. Slide the distributor shaft through housing
bushings .
5 . Push the driven gear onto the distributor shaft
with the holes aligned .
6. Install the roll pin.
7. Check and adjust dwell angle, vacuum advance
and the mechanical advance. Refer to SPECIFICA-
TIONS (Distributor).
ADJUSTING DISTRIBUTOR DWELL
ANGLE
1 . With distributor mounted in distributor testing
machine, connect the dwell meter to the distributor
primary lead .
2. Turn the adjusting screw to set the dwell angle
at 30 degrees.
If a distributor tester is not available, the dwell
angle may be adjusted as follows:
1 . Mount distributor in a vise .
2. Connect a test lamp between the primary lead
and ground .
3. Rotate the shaft until one of the breaker cam
lobes is under the center of the rubbing block on the
moveable point.
4. Turn the adjusting screw clockwise until the
lamp lights, then turn the screw one-half turn in the
opposite direction.
When distributor has been installed in vehicle,
point opening must be reset by connecting a dwell
meter to the primary distributor lead negative termi
nal on the coil and ground . The dwell angle must be
set at 30 degrees with the engine running at idle
speed .
ROTOR
Engine Not Disturbed
ENGINE ELECTRICAL 6Y- 43
The rotor is retained by two screws and is prov-
ided with round and square lugs which engage with
the mechanical advance plate so that the rotor may
be installed in only one position . (figure 40)
DISTRIBUTOR INSTALLATION
1 . Turn the rotor about 1/8 turn in a clockwise
direction past the mark previously placed on the
distributor housing to locate rotor.
2. Push the distributor down into position in the
block with the housing in a normal "installed," posi-
tion .
NOTE : It may be necessary to move rotor
slightly to start gear into mesh with camshaft