High compression blues.

Long story short, I tried to "flood" the ping outta a hi-comp engine, with cams, carbs, timings, head gskts, heads. When pulling pistons to trim the domes, I discovered only one piston with detonation damage. Sanded the "sharp" edges off my valve reliefs, and any other edges, re-assembled, without trimming pistons, that #@$%#@ ping was gone. Check alternatives imho. 1 vacuum leak could do it.. good luck. Bore scope may be of help.