Spark plugs for 312?

C

cjc56

Senior Member
Just finished the rebuild on my stock 312 and am wondering about the proper spark plugs to use in the engine. I know what the shop manual calls for, but with the new gas should I go with something different. The engine has been rebuilt to stock and I am running a rebuilt Holley 4000 teapot in a 56 tbird.
 
I still use the Autolites from a supply house on the original specs. If you have a pertronix or something similar you may want to experiment with adjusting the gap. Also can't say enough about a high quality choice of wiring and boots and looms. I've seen plenty of rebuilds and fine engines that have sorry primary wiring and the owner complains that the engine just doesn't seem to run it's best!? Nothing in MHO looks better than a properly wired yblock. Just like the factory.
 
I do have a pertronix inside the dist. The wires are new repros from Casco a tbird parts supplier. I think they are the best repros available. When adjusting the gap, should it be greater or less than the spec?
 
I run Autolite 46 plugs in the Merc with Pertronix and an Edelbrock carb. Just switched from Champions the PO had installed. The Autolites made a huge difference. I always heard Fords don't like Champion plugs and now I'm a believer.
 
You can run a little wider gap with a Pertronix depending on the coil you're using. You'll need to experiment a little to see what works best.
 
I have no experience with Autolite. I ran Champions, and they did not satisfy me. I switched to NGK and they are wonderful. Long lasting, no fouling, inexpensive at O'Rielly's.
 
Motorcraft BSF-82C. 82's are the proper heat range . In my experience, Champions always run hotter than the required heat range.
 
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I run the Autolite 46's in my 56 Bird (312) I widened the gap about 10 points. It runs great. I also have a Pertronix II with their coil.
 
When you say that yopu are running the gap 10 point wider, do you mean instead of a 35 gap(for instance) you are a 45 gap?
 
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