Thread: Plug Gap

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What is the best gap to run plugs on a BB chevy 396 with HEI ?

i run 0.35 gap with msd i think this is good

I think the whole idea behind MSD and HEI is since you have a hotter spark you can open up the plug gap to gain more spark. .035 is almost the stock plug gap, In my chiltons book it states that a stock 454 with HEI the gap should be .050 I think this is what i will start out at and go from there......

no no no 0.35 on msd the more CR this trys to blow out the spark the more gap the harder it is on the coil 0.45 to 0.50on stock stuff that dose on have no cr and will not see more then 4600 rpm maybe so but not on hp stuff with hi cr and hi rpm s. 0.35 .i like the spark to get to the plugs and not arc off the cap i have seen this .electricedy takes the path off lest resistance and thats off the the cap if the plug are gap to big with hi cr and hi rpm .so if it stock with a stock gm hei i would still gap it on the small side try 0.40

Then how come my stock 1989 F150 calls for 060???
It is HEI,,,fuel injected,,,,nothing special,,but a 300cube six.

Pat,
My engine is street driven, 9.50 to 1 compression mild cam no big revs with this motor, I am sure its a different story with a high rev race motor. I was told to pull a plug and ground it outside the block then gap it until i get the best looking spark, then close it slightly and that would be the best way. .040 sounds like a good starting point, there is also a real good webpage on reading your sparkplugs: http://www.4secondsflat.com/Spark_plug_reading.html
This will also help you with timing and fuel delivery setup.

OK Denny, lets here your tricks