Dyno a 7.5:1 400? Sure, why not?

I had a 383 Chevy I installed for a fellow along with a bunch of other work on his Camaro. He came back a day later with it "rattling like crazy". I looked at it, and said give it another 2 days and drive it both days". He called three days later and said "what did you do?" I said " those two heat cyclyes gave the Stage 8 fasteners time to tighten themselves up"...lol. At least it wasn't a knock tho Jim. That's terrible...lol.