[Gunner]

High stress point in any engine; combine it with very hot MSD sparks, larger plug gaps and more high-rpm time than most engines and you'll get breakdown. I'd guess that having the center spring contact too tight is hard on wear, as well as having the spring too loose so that the spark has to jump the gap. There may be an optimum pressure setting but I'm darned if I can figure out a way to set it accurately.