Timing; Distributor - Pontiac FIREBIRD 1972 Service Manual

ENGINE ELECTRICAL 6E-3 1
TIMING
Periodically the ignition timing should be checked. If out
of adjustment, set to specifications with distributor
vacuum hose disconnected to insure most efficient engine
performance.
NOTE: Always ascertain tk5t distributor dwell
is set to specification BEFORE setting timing,
as a change in point gap will cause a change in
ignition timing.
SPARK PLUGS
Periodically (the actual time depending on operating con-
ditions) the plugs should be removed for cleaning, inspec-
tion, and regapping.
.
DISTRIBUTOR
Three types of distributors are used: (1) A 12 volt alumi-
num internal adjustment distributor on 6 cylinder engines,
(2) A 12-volt aluminum external adjustment distributor
on 8-cylinder engines and (3) A 12-volt aluminum unit-
ized ignition distributor.
All function in much the same manner to (1) cause a high
voltage surge from coil (2) time these surges with regard
to engine requirements through use of centrifugal and
vacuum advance mechanisms (3) direct high voltage
surges through distributor rotor, cap, and high tension
wiring to spark plugs.
MAINTENANCE
CAP AND ROTOR
The cap and rotor should be checked for chips or cracks
and carbonized paths which would allow high tension
leakage to ground. The rotor spring should be checked to
insure it has good positive contact against cap button.
CONTACT SET OR BREAKER POINTS
Under most normal operating conditions, distributor con-
tact points will provide many thousands of miles of ser-
vice. Points which have undergone several thousand miles
of operation will have a rough surface or slight transfer of
material, but this should not be interpreted as meaning
that points are worn out.
Rough contacts which are greyish in color have a greater
area of contact than new contacts and will provide satis-
factory service until most of tungsten is worn off.
Pitted or transferred contacts is a normal condition and
points should not necessarily be replaced unless transfer
has exceeced .020" (Fig. 6E-39).
WHEN TRANSFER HAS
EXCEEDED .020"
Fig. 6E-39 Allowable Contact Material Transfer
CONDENSER
Under normal operating conditions, the condenser should
not require replacement. Do not change condenser when
changing points unless there is evidence of failure, such as
arcing and severe pitting of points.
If the condenser is suspected, check on a condenser tester
for the following properties:
1. Insulation resistance (or leakage) (over 2 megohms).
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VACUUM
PRIMARY
UNIT
LEAD
Fig. 6E-40 6-Cyl. Distributor