Out of the tailpipe. Happens occasionally right after releasing the throttle after a long WOT pull to high rpms.
Unfortunately I don't have an adjustable timing light, just an old school static one. I suppose the investment would be worth it in this case... ***EDIT: Just ordered a digital adjustable timing light. It will be here the day after tomorrow. Looking forward to using it to diagnose.
My dwell is currently set to 60 degrees, FWIW. I do wonder if my distributor is worn... I need to check of the lobes on the shaft are even for starters.
No, I sure don't. No way to observe mixture at the moment.
I am going to check for vacuum leaks, check valve adjustment, and change dwell to 62 given your suggestion in the meantime and report back. Thanks again!