[AZKen]

96.4% chance it has something to do with what he did recently....or some info he has not remembered yet. I do it all the time. TJ: Jolly's site says AC4 plugs for 1964 BUT you indicate in other posts your motor may be newer. Get correct plugs and re-time even though you did not touch timing. Make sure you use the specs/parts for whatever year that motor is. Things you say are still pointing to detonation or pre-ignition or timing. But they do say that happens on Acceleration or a load. Maybe cheap/old gas, plugs too hot or as BBV6 says ...carbon. Hope it's not rod slap. Don't know if you have had this motor long enough to say it was quiet before "tune up". If it was, I don't think rod knock comes on all of a sudden. Don't think it goes away and comes back. It could change a little because of thermal expansion of parts. TJ: are you 16 years old?
EDIT: Experts say that sometimes after changing old gunky oil, with new oil, it will reveal a rod knock. Check filter for flakes/glitter.