SPARK PLUGS
Specifications
Type ---------- Prestolite 14 L7 or Equivalent
Thread Size ----------------------- 14 MM
Shank Length ------------------- 7 /16" Inch
Gap Setting---------------------- .025 Inch
Imtallation Torque ------- 27 Foot Pounds
Socket \Vrench Size ------------- 13/16 Inch
The purpose of the spark plug is to fire or
ignite the proper fuel mixture in the combus-
tion chamber of the engine at a preset time.
This is controlled by the breaker cam and
points. A Spark plug which does not function
properly will increase fuel consumption,
cause crankcase oil dilution, excessive de-
posit in the combustion chamber and great-
ly reduce the efficiency of the engine.
A close examination of the spark plug will
give the service man an indication in general
of the engine conditions. A fouled or burnt
spark plug can be used as good visible evi-
dence to show the customer when soliciting
a valve or overhaul job.
~
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CERAMIC
Z
INSULATOR-I
!
-TERMINAL NUT
CENTER
ELECTRODE
COPPERGLASS SEALED
SEALS
Figure F-18
Removal and Inspection
Remove the wire from the spark plug and use a thin wall deep socket spark plug type wrench
of correct size 13/16" to remove the spark plug.
The wrong size or type socket wrench can cause distortion or insulator breakage.
Spark Plug Gasket
The first thing to inspect after removal of a plug is the copper gasket. This will tell you if
the spark plug was installed correctly.
A Spark plug that has been properly torqued in place to 27 foot pounds will have the copper
gasket compressed to 1/2 of its original thickness.
A Spark plug gasket that was not compressed enough when the plug was installed can cause
compression leakage. The plug will run hotter then
it
should as the heat will not be trans-
ferred from the plug to the cylinder head as fast.
A Spark plug gasket that is compressed too much when the plug is installed will cause the
plug to run colder then it should and thus will foul a lot faster.
It
is also possible that when
the plug is installed too tight,
it
will cause distortion of the electrodes. Thus the plug gap
would be increased beyond its original setting.
F-11
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