Spark plugs - 6 volt, 12 volt difference

Z

Zeke5180

Member
I have searched the forum foe a possible answer but cannot seem to find one.
I have a 37 Model 78 slantback that I converted from 6-volts to 12-volts. It has the stock 221cu in engine with a two-deuce manifold. I'm using the recommended Champion spark plug, UD16.

My question is, since I changed from a 6-volt system to a 12-volt system should I consider using a different style plug? The question may be irrelevant since the car seems to rum fine on the current plugs.

Any thoughts.

Thanks, Zeke
 
Spark plugs don't care what the primary voltage is, just secondary voltage. It sounds like yours is just fine. If it weren't, the ignition system (most likely the coil) might need to be changed, not the spark plugs.
 
You either have to change the ignition coil to 12V or use a ignition resistor in series with the coil to drop the 12V to the proper voltage for the coil. It is the coil supplying high voltage to the spark plugs. A good 6V system and a good 12V ignition system may supply about the same voltage to the plugs so there is no need to change the plugs.
 
I've always thought 12v was a "dryer" (as in amperage) spark. My stock flatty seems to like a 45 thousandth plug gap. Throttle response starting etc.
I'm running a magnetic pickup, HEI brain firing a early 2000 GM E coil
 

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