Nash, the problem is not with the aftermarket ones, it's the originals that tend to like to work with only points set ups....at least in my case....

Eightime.....here's what Pertronix emailed me back with;


"First, double-check all of your connections. A poor ground can do this. Next, feel the entire length of the sense lead to make sure the wire is not broken. We’re looking at 40 year old wiring. If all of that looks good, insert a 10K ohm, ½ watt resistor between the coil negative terminal and the tach sense lead. That should correct it. "

In my case my wiring harness is new, so will have to locate a 1/4 watt 10,000 ohm resister (must have some old radios hangin around somewhere....) I think it would be a brown black orange striped.