General rule for plugs, Stock range is for iron heads and no power adder - Autolite 3925, One range colder would be for either aluminum heads or a power adder, not both - Autolite 3924, and Two ranges colder for both aluminum heads and a power adder - Autolite 3923. Gapping for power adders is as said smaller than stock to help prevent spark blow out.
I think Vib is right on this, I had a brain fart I guess , the iron head plugs are the 25 - stock, 24 - iron plus power adder, gapping according to the power adder. Sorry about that...
I think Vib is right on this, I had a brain fart I guess , the iron head plugs are the 25 - stock, 24 - iron plus power adder, gapping according to the power adder..... :
Sorry guys for bringing this post alive but I need help
I just installed TW heads and I put 3923 plugs
What is difference between 3923 and 3924
And what gap is supposed to be on my TW heads N/A