John wrote: "RC12LYC Champion recommend plug base bottom line plug. Thus a hotter plug one heat range hotter would be a RC13LYC plug. While changing to a hotter plug is a recommended fix for fouling, it is also a band aid to cure a problem that may have some other rational for causing the fouling. While I do not use a 4.0 head on my 1975 or 1980 258 AMC I-6, the recommend plug is an RN13YC which is a resistor/copper electrode plug the car gives me no problem using RN9YC plugs. Are you also burning quite a bit of oil? John." Yes, but trying to find the "13" plug is proving to be a a challenge. It seems that many spark plug lines, Champion included, are moving towards part numbers that describe nothing about the plug itself (physical size, element material, heat range, etc). Maybe that's old news, but the point is I'm having a hell of a time trying to find a "hot" plug. I do have fouling problems, particularly on 3 and 4, perhaps partly caused by the mis-jetted weber 38/38, but that's a whole 'nother post... _______________________________________________ Amc-list mailing list Amc-list@xxxxxxxxxxxx http://www.amc-list.com/mailman/listinfo/amc-list