Pontiac FIREBIRD 1972 Service Manual page 796

6E-34 1972 PONTIAC SERVICE MANUAL
At time spark is adjusted, the general appearance of
breaker points should be observed. If smudge line appears
on point support and breaker plate just beneath points,
burned points (from oil or crankcase vapor between
points) are very probable. Points which have gone several
thousand miles will have a rough surface, but this does not
mean that points are worn out. The roughness between
points matches so that a large contact area is maintained
and points will continue to provide satisfactory service. If
dirt or scale is present, points should be cleaned with a few
strokes of a clean, fine-cut, contact file. Do not attempt to
remove all roughness or dress point surfaces down
smooth. Never use emery cloth or sandpaper to clean
points. If points are burned or badly pitted, they should
be replaced and cause of this condition found and cor-
rected. If this is not done new points will also burn and
pit in a short time.
IGNITION COIL AND RESISTOR
The 6 and 8-cylinder 12 volt coil (Fig. 6E-47) is an oil
filled, hermetically sealed unit designed specifically for use
with an external resistance. The number of turns in the
primary winding results in a higher inductance in this
winding, which makes it possible for the coil to provide a
higher secondary voltage output throughout the speed
range.
SEALING NIPPLE,
Fig. 6E-47 Ignition Coil
-
6
&
8 Cyl
The primary current from the ignition switch passes
through a resistance wire which lowers the voltage to 7 or
8 volts. This lower voltage provides for longer ignition
contact life.
For optimum starting performance, the resistance is by-
passed during cranking, thereby connecting the ignition
coil directly to the battery. This provides full battery volt-
age available at the coil and thus keeps ignition voltage as
high as possible during cranking. The resistance is by-
passed automatically through the ignition and starting
switch when switch is in the START position.
SECONDARY IGNITION CABLES
All ignition cables in the secondary o r high-tension system
(coil to distributor and distributor to plugs) are neoprene
jacketed. This cable is resistant to action of oil, grease,
battery acid and road salt, and offers resistance to Corona
breakdown. Ignition cables have a multiple cloth thread
core impregnated with a graphite solution to give the
correct conductivity. These cables give proper resistance
for suppression of radio and television interference.
SPARK PLUGS
DESCRIPTION
R45TS, R46TS resistor type, tapered seat plugs with long
reach are used in V-8 engines (except 307). The R44T and
R46T are used in the 307 and 250 L-6 engines respectively.
All plugs have tapered seats.
See Engine Electrical Specifications for normal usages.
Normal or average service is assumed to be a mixture of
idling, slow speed, and high speed operation with some of
each making up the daily total driving. Occasional or
intermittent high-speed driving is essential to good spark
plug performance as it provides increased and sustained
combustion heat that burns away any excess deposits of
carbon or oxide that may have accumulated from frequent
idling or continual stop-and-go or slow-speed driving.
Spark plugs are protected by an insulating nipple made of
special heat-resistant material which covers the spark plug
terminal and extends downward over a portion of the plug
insulator. These nipples prevent flash-over with resultant
missing of engine, even though a film is allowed to ac-
cumulate on exposed portion of plug porcelains.
NOTE:
Do not mistake corona discharge for
flashrover or a shorted insulator. Corona is a
steady blue light appeanng around insulator,
just above the shell crimp. It is the visible evi-
dence of a high-tension tie14 and has no effect
on ignition performance. Usually it can be de-
tected only in darkness. This discharge may
repel dust particles, leaving a clear nng on the