[Crankster]

Might be worth trying them. What are you using now? I've heard that in the points & condenser days, the spark plug heat range was a little on the high side to help prevent fouling in ordinary city driving. That sort of stands to reason. They might be suited to summer highway use or something along those lines.

Can't really hurt anything with too cold of a heat range plug, the worst that will happen is fouling. Excessive heat range is different, can cause pre-ignition.