So learned something on the HEI mod yesterday. The distributor has to have a 100% good ground on it or the low rpm section of the module will blow out. I had it grounded with the dist. machine clamp, and it came just loose and stopped working. WTF right? kind of find it tighten it all up again and nothing. Hell test the module rpm is bad. OK change it new gm module and works fine. So the bottom line is you need to use a metal base gasket and the o ring to ensure it is grounded properly. That sucks was a $120 pertronix module!