I changed the plugs yesterday and asked what plugs and gap to use on my 383 it is 30 over , edelbrock aluminum heads with roller rockers , blackjack pistons and last got 365 horsepower at wheels on dyno. It had ngk plugs in it but they were all carboned up black so I asked my dyno shop guy what plugs he recommend and he has worked on the car trying to get it to idle properly below 1000 rpm but couldn t because the lumpy cam and was told the carb is too small its a edelbrock/carter 650 (we tried 4 different springs and different metering rods etc. Said try another carb bigger maybe holley !
Anyway yesterday I get the Autolite plugs he suggested that will help keep cleaner and he said go with between .30 to . 35 gap. I ask the guy who built the car and what he ran and he said .45 , today I talk with my buddy who knows his **** Chevy guy and he said no , not with the electronic msd ignition and blaster 2 coil I am running and go with minimum .45 gap. what the funk should I do?? Is my dyno guy who does this on the side and a few guys in this little town I moved to right or go with the .45 . I need help before I go nuts with this Mopar .

 

I agree with dyno guy but what heat range did he suggest, I personally like colder

 

One change at a time, if you changed the heat range leave the gap the same at first them make small adjustments latter.

 

One change at a time so you know what worked.

 

I was reading online also about how if the spark is too small it could jump and go bigger with msd ignition

 

That's why I said leave it at.45. with the new plugs, you should be able to go with what msd recommend.

 

If you really want to find out I suggest a few sets of plugs and a day at the dyno, I'm sure msd also suggest colder