Auto lite 3924 doesn't fit?

[OonDeanisS]

I have gt40 iron heads, and I bought auto lite 3924s but they don't thread in... They look identical to my old plugs but these won't thread into the hole... I don't get it. Do I need to cut off the aluminum washers or something? The old ones thread in and out fine, but those are NGK platinums. Any help appreciated. Also, gap to .030?

 

[Chuckman]

i dont know what the plain gt-40's use, but the gt-40p's use a 764 plug. looking it up on the az site, the plains use them too.

 

[Rick 91GT]

Yes 764 is the correct plug, which is a tapered seat plug (NO WASHER) The 3924 are extended reach with the washer, you would use these on a alum head.

Gap to .035" if you have boost, .045"-.053" if your NA

 

[OonDeanisS]

thank you.