My 67 has a late HO roller motor with a mallory dual point, edelbrock performer intake, holley 600 cfm vacuum sec. carb. Autolite 25s currently. Finally bumped up the timing to 10*, (should have been there all along) and now the plugs seem too white. They were a nice tannish brown before. I have a new set of autolite 24's (next colder plug) I was going to put in, but every now and then I put a lighter secondairy spring in the holley (little more pep and I don't want it to start fouling up the 24's. Any comments on this? or is my only choice to just give it a swing and see how it goes? Thanks!