GMC 1976 ZEO 6083 Maintenance Manual page 424

6Y- 44 ENGINE ELECTRICAL
gear, but rotor should line up with the mark
when distributor is down in place.
3 . Tighten the distributor clamp bolt snugly and
connect vacuum line . Connect primary wire to coil
terminal and install cap. Also install spark plug and
high tension wires if removed.
NOTE : It is important that the spark plug wires
be installed in their proper location in the sup-
ports and also in the cap. (figure 32).
4. Time ignition as previously described.
Installation-Engine Disturbed
1 . Locate No . 1 piston in firing position by either
of two methods described below .
a. Remove No . 1 spark plug and, with finger
on plug hole, crank engine until compression is felt
in the No. 1 cylinder. Continue cranking until timing
mark on crankshaft pulley lines up with timing tab
attached to engine front cover.
b. Remove rocker cover (left bank) and crank
engine until No . 1 intake valve closes and continue
to crank slowly about 1/3 turn until timing mark on
pulley lines up with timing tab .
2 . Position distributor to opening in block in nor-
mal installed attitude, noting position of vacuum
control unit .
3 . Position rotor to point toward front of engine
(with distributor housing held in installed attitude),
then turn rotor counter-clockwise approximately
1/8 turn more toward left cylinder bank and push
distributor down to engine camshaft . It may be
necessary to rotate rotor slightly until camshaft en-
gagement is felt .
4. While pressing firmly down on distributor
housing, kick starter over a few times to make sure
oil pump shaft is engaged. Install hold-down clamp
and bolt and snug up bolt .
5 . Turn distributor body slightly until points just
open and tighten distributor clamp bolt .
6. Place distributor cap in position and check to
see that rotor lines up with terminal for No . 1 spark
plug .
7. Install cap, check all high tension wire connec-
tions and connect spark plug wires if they have been
removed.
8. Connect vacuum line to distributor and dis-
tributor primary wire to coil terminal .
9. Start engine and set timing .
COIL REPLACEMENT
1 . Disconnect battery ground cables .
2. Disconnect ignition switch and distributor
leads from terminals on coil .
3 . Pull high tension wire from center terminal of
coil .
4. Remove the coil support mounting bolt or
loosen friction clamp screw and remove coil .
5 . Place new coil in position and install attaching
bolt or tighten clamp screw .
6. Place high tension lead securely in center ter-
minal of coil and connect ignition switch and dis-
tributor primary leads to terminals on coil .
7 . Connect battery ground cables .
8 . Start engine and check coil operation.
SPARK PLUGS
1 . Remove foreign material from around the
spark plug holes and remove the spark plugs.
2. Clean exterior of plugs and inspect for cracked
insulators, poor sealing gaskets or excessively burned
electrodes .
3 . Clean all serviceable plugs with an abrasive
type cleaner. File center electrode flat . (figure 45) Do
not file center electrode on new plugs.
4. Adjust spark plug gap to .040" using a round
feeler gauge.
5 . Install plugs and torque to 35 ft . lbs.
NOTE : The spark plug gaskets are the captive
type and are not to be replaced each time the
plug is removed. The same gasket will usually
seat even if the plug is removed up to four times.
HIGH AND LOW TENSION WIRES
High tension wires include the wires connecting
the distributor cap to the spark plugs, and the wire
connecting the center electrode of the distributor cap