Reply To: 50’s OMC spark Plugs

[frankr]

J6J has the ground electrode cut off half way across the center electrode, presenting a sharp edge for the spark to jump to. All else being equal, a spark will jump to a sharp edge (or point) easier than to a flat surface. So in theory, the J6J should work better in a motor with less than optimum ignition. Needless to say, you can file the electrode back on the -C and get the same result. Of course, the -J is supposed to resist carbon fouling better, not as big an issue with today’s better oils.