Stopping the knock: Lower compression and ported heads...

My cranking #s were in the 188 range with the 509 cam and 191 average with this Lunati cam. I had what sounded like detonation in both cases using 91octane gas. When I pulled the heads to have them ported and to install thicker head gaskets, none of the pistons showed any signs of detonation. They did have carbon buildup which I cleaned off, but there were no pits, divots, markings or cracks anywhere. I am told that detonation results in marks that look like the work of an icepick. I had none of that. In fact, the pistons looked almost like new after cleaning.
This was confusing to me. Every time I went full throttle and heard what I thought was detonation, I didn't just keep my foot in it. I lifted off of the gas. My point is that IF the engine was knocking, I stopped it before any damage occured. On the other hand, if the engine was never detonating, what the heck was I hearing ???
*****************************************************************
Related or NOT related ??
In May of last year I decided to replace the K member. The replacement one was fully welded at all the seams and had additional supports for the steering box. When I had it back together, the LH header sat closer to the steering box. At idle, there was one tube that would lightly contact it. It didn't make any noise at idle from the contact. At higher rpms as the engine smoothed out, is it possible that the knocking noise was from this? Personally I doubt it because the engine lifts the left side under a load. I know this is a long shot.