So I just got my '72 on the road for the first time in awhile. There is a knock under my hood of my 454 and I am not sure of the difference between knocks from piston slap, detonation etc. It only occurs every 5-8 seconds and sometimes not for 10 but not really at a consistent interval. It increases in both frequency and volume under load, and I can feel it in the gas pedal. It is not so much as a click more of a thud. My guess is detonation, but I don't know squat about engine noises and I will not be able to adjust the timing on it until later this week and I'd love some piece of mind while i wait. I assume that if it was from an engine component hitting another engine component it would be at a more rapid and regular interval, right? Thanks for any advice you can give me.