OK, I finally got a few hours to investigate the 216 that backfired hard. The vacuum advance had jammed on full retard (dist rotation stuck), I cleaned it up and got it rotating freely and it runs better - no vacuum leaks. Carb is way to rich now, something must have let loose inside as even when I screw the idle mixture screw all the way in it runs too rich at idle, I can disconnect the vacuum line going to the wipers and it runs a lot better. I also noticed a metalic smacking sound coming from the pushrod cover between cylinders 1 & 2. I can feel something with my hand actually hitting on the inside at anything above about 1500 rpm - not regular, but about every 3rd or 4th firing cycle on the #1 or #2 cylinder. No change in intermittant sound when I disconnect the plug wires one at a time. Time to rebuild the carb and take that side cover off and see what is going on . . . any ideas?
