jjam

I have a 540 street motor with 9.5-1 with the dart 320 heads. I'm running the NGK 4091 (R5671A-7) plugs. What gap would be best or is there a better plug. Running a 1050cfm pro system carb.

woodsman

What type of fire power is feeding the plugs.

jjam

I have a MSD-6AL with a blaster coil, I run them now at .045 Is there a better plug / gap?

knova70

Why such a cold plug?are you using NOS? the gap seems fine,thats the same plug I use on my blown alcohol motor.

jmarksdragster

That is the hottest race plug NGK has. 7 hottest, 11 coldest. If you have clearance, run a projected nose plug. You can try a N9YC Champion or equivalent if you need hotter. Try .035 on the gap, more is harder on cap, rotor, wires and not necessary. More chance to arc. You have to read your plugs to see what the engine needs.