Running a Pertronix electronic system in a warm grey motor, currently using what I've always used NGK BP5S with the original points ignition. I just finished cleaning and regapping the current set (about three months old) they seem to build up from running rich when I just do stop / start around town driving (twin strombergs) I believe the carbs are tuned correctly, mixture etc and perform without flat spots and run real well on the open road, I know that fuel these days isn't what it used to be octane wise.
So I'm thinking maybe running a hotter range sparkplug to see if it helps, what are others with non standard grey motors running?
Mick