I have a customer that has a 514 Ford with aluminum heads and mild cam/compression. The builder originally used an Autolite AR3934 plug which looks super cold. Carb tuning issues aside, I'm not convinced that he needs a super cold plug.. I'm thinking something similar in heat to an AC 43.. how does this AR3934 compare? I've looked around the net a bit and I'm having a hard time separating it from all the cold racing plugs, but did manage to use the NGK chart and to piece together a number (BKR9EIX) and cross it back to the AR3910 I think. There are also a couple NGK racing numbers R5671A and R5672A but I don't really know their heat ranges in comparison to what I'm familiar with...
What I need is 14mm thread with a .750" reach and a 5/8" hex.
What I need is 14mm thread with a .750" reach and a 5/8" hex.