I did have an intermittent miss/engine shutoff with an HEI one time. It turned out to be caused by the wire coming from the tach lug on the distributor.
I had the "great idea" of having a short pigtail coming off of the tach lug of the distributor cap so that I could quickly connect a tachometer to it for tuneups.
Problem is, if that particular wire makes contact with the engine (ground), the engine will shutoff. I believe that the wire doesn't actually have to make direct contact for it to cut off the engine.
