Hello Doug,
Thank you very much for the great info... I just opened up the GM Heritage files (pg.59) and found the AC-46 (14mm) spark plug listed to be standard for 1939 trucks... Find it interesting that the 1950's reference would be different, but I'm not surprised... On the other hand, it makes sense for trucks and cars to have different plugs, since they used different carburetors and trucks worked much harder... So, I really wonder how much of a difference a "dash 5" plug would make compared to the regular AC 46; or what is the tempersture difference...
I'm not so much asking to have a correct plug for judging, but because I can buy 30 of them at a reasonable price...In my case, I would just use them if I thought that the engine would benefit greatly...
Last edited by Philipj; 02/13/2021 3:18 PM.
