GT40 head spark plugs

[Guero]

What kind of spark plugs do GT40 heads use? And what would 2 degrees colder be?

 

[legalize420]

autolite 764 is stock , 104 is 1, and 103 is 2

 

[blksn955.o]

I use NGK's

Stock plug using NGK is a TR5, one step colder is a TR6 and to go 2 steps colder you have to go to an Irrid. plug that is called a TRi7 or TR7i. This is from NGK's tech line

I run the TR6's

 

[RydeOn]

TR6s are wrong. Plug is way too short, sits too high up in the head. Use Autolite #2544.

 

[blksn955.o]

That is what I run now and that is what NGK says to run as 1 range colder over stock...stock being a TR55, sorry just checked my paper I have it on and stock is a 55 not a 5. I went to several shops, tech lines, performance shops to double check.

I probably have ran 4-5 different plugs from what people said worked. I am 100% sure tr6 plugs are 1 range colder than stock and stock is a TR55.