Pontiac's as a rule like a hotter plug, at least the iron heads do. Aluminum heads like a little colder plug. Now the # 75 Autolite's seem to work the best. Ok so now were saying the # 85 Autolite plung is a Radio plug, hum ? plugs that have a longer electrode is a hotter plug, the # 85 Autolite's have a shorter electrode, they may be a Radio plug, but there still a colder plug. Put the two together, an you'll see. That's the reason why one number works better then the other.
Plug heat range plays a big part in weather or not one works better then the other, so if you find one that works better it's because it's a better heat range for your motor.That's why you'll find guys saying
NGK's work better in my motor, no two motors are the same, you really have to play, and find out what wroks best with your motor. Autolites # 75's seem to work best with most Pontiac motors, it's a real good plug to start with. Champions plugs though are out right Junk!
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