Are those Bosch Platinum spark plugs too hot for a 390? I can't seem to get a good color on the porcelain on my plugs, it always looks like it's running lean. I've turned the carb enrich. screws out enough to where I know it's overly rich (I can smell it in the exhaust) and still no brown on the porcelain.. Am I just being too compulsive?

More info: good vacuum, rebuilt Holley MotorCraft-style carb, good compression, timing is correct.

Greg
67 F100 CCS 390 cruise-o

 

I'm no expert on this, but I did hear that you should run the standard autolite 45's and that the those others were a different temp range and wouldn't read the same. The same guy suggested that those plugs were just designed for longer runs between changes.