hi
i just got a new set of split fires for my 66 mustang. what should the gap be? i have been told .035 and .045? the engine engie has 10.5:1 compression and i am running high octane fuel if that makes a difference. thanks for the help!
Tyler

 

Who ever told you 0.045 inch gap, give them a bar of soap to eat. The gap is 0.032 to 0.036 inchfor all engines using BF-42 plugs, 0.028 to 0.032 for engines using BF-32 plugs.
Jim

 

Jim....he has electronic ignition.The gap can be about 0.045 for optimum performance with an electronic ignition system. And the Autolite/Motorcraft BF 42 plugs is what he should be running....not 32's. You are slipping my friend.

 

I can't read minds - hi-octane and 10.5 to 1 compression ratio equals an electronic ignition. What did I miss?
Jim

 

I take it that when you say a gap of 45 and electronic ignition you also mean he's got a 40 k volt coil?

 

Aftermarket ignitions can handle quite a bit more spark gap than stock electronic (mainly the 70's/early 80's model Duraspark)or points ignitions. Stock is in the mid-30's, while you can go fairly wide with a high-power electronic. I run 0.050 with my MSD and 12.5:1 CR.