What kind of Idle are you running at stop signs?

I had one that idled at 500 in gear. Thoop-thoop-thoop-thoop-thoop-thoop-thoop-thoop-thoop.........the entire car shook,with every shot.
Stock rebuild 225/904 in a 69 Barracuda.IIRC; a 1bbl.
Thoop-thoop-thoop-thoop-thoop-thoop-thoop-thoop..........