I need help figuring out which plug to use. Currently im using NGK R5671a-8 gapped at 32. The enigne is 30 over, 8-1 comp mild blower cam, sorry dont have the specs. BT Alum heads w/ chvy exhust ports no porting, fresh 6-71 street blower underdriven making 5-7 psi. Carbs are Holley 660's w/ no PV 74 primary(had 76's). Plug are soot fouled now. Mallory unilite and flame thrower coil, no MSD box. It pops when cold or under light load in the pipe and surges going down the freeway. Fuel milage is about 5-6(terrible). Any sugestions would greatly apreciated!
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