Packard Forum Index » Pre-War (1899-1942)

I have a 1941 super 8 with the real small threads on the plugs I think they are 10 millimeter. I looked at an old post and it said autolite 308 but they are to big. Also checked the parts cross reference they are not listed. My motor manual says ac 104 but that says all motors back to 1935 that dose not seem correct to me. The plug that are in the engine now are champion uy6 but I dont know if they are correct. Thanks for any help

I always use ac104

Your UY6 is the Champion equivalent to the AC M-8 which is also an acceptable plug for your application, as is the AC 104.

Hello 29 Tons,

Owen Dyneto is right and the AC M8 is what I prefer. The M stands for Marine use and has a black coating which is period correct. Others are cadium plated and not what you would see in 1941.

Available at most auto shops and I think the same price as AC 104. Why not get the correct one?

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Owen's right as usual. AC M-8s at any NAPA store seem to be the right heat range for our 356 engines, as well as all late '30s Buicks, Cadillacs, LaSalles, Chevrolets, Packards, and probably still made for all the old Chevy trucks and cars yet running in South America. Buy them at NAPA, the one major chain still bothering to help those with old cars.

I think the M-8 is more resistant to fouling. However, if you want to use Champions you can paint the base or make up an oxide staining solution.

Both companies are victims of MBAs soaking the brand name in a race to the bottom. That is a hidden form of inflation as well, but oops, the crackpot economists say there is no inflation, or that inflation is good, or that inflation is not a problem except if you are not rich.