I know we're not talking FEs, but I will tell you my spark plug story anyway. My engine builder recommended Champion RC9YC5 Spark Plugs, which are one step colder than the plugs Edelbrock recommends for the street (RC12YC5) for my aluminum heads. The opinion of some FE geniuses was that the Autolite #3924 plugs are better with Edelbrock aluminum heads (like mine) and everyone said I should try them. They are one step “hotter” than the Champions I was using and, apparently, with a MSD box, like mine, they would have me singing and dancing. So, I replaced the Champions with the new Autolites (regular 3924, not the “AR” or “XP” plugs). Perhaps it was the placebo effect but they did seem to run a little better. So, I'm still using them to this day. The moral of the story is to go ahead and try a different manufacturer and try moving up and down a bit in the heat range. All spark plugs are not equal and the only way you'll know for sure is to try them.
