[klayfish]

This is very interesting. I had the EXACT same problem. Last summer, my mechanic had just finished installing my 351W. We had a brand new Mallory Unilite distributor. I took it to Pocono for open track running two days later. It never ran well all day, as we hadn't been able to fine tune the carb before I left. But on my third session, it sputtered badly, backfired then stopped. Turns out it had sheered the pin, just like MZHUN described. My mechanic and I were not able to figure out why. Everything else in the motor seemed fine. Still totally confused as to what happen. We put another stronger pin in it and I've had no problems since.

Steve