I've noticed it as the temps heating up here in Tx. Don't know if it has anything to do with it, but I was wondering if I should mess with the timing to keep it from knocking when I accelerate? When I'm on the the hwy, if I accelerate, it'll knock. I can press the pedal more or back off of it and it quits. Usually around 60 - 65. No vacuum leaks, plugs are good, wires good...all that good stuff. It is carborated so maybe I should lean it up a little? Too many options and no clue where to start. Don't want to do anything if it's not going to make a difference. Chevy 350, stock, Holley 600... Thanks for the inputs!!!