I have the cylinder head completely disassembled for cleaning and inspection as well as the block. The rocker shaft and the aluminum rocker arms are the only parts that I've found thus far that show signs of premature or what I would consider abnormal wear, but the sound that I was hearing was definitely piston slap or a loose wrist pin on #2 cylinder. You have to remember that the valvetrain rotates at 1/2 crankshaft speed which makes isolating valvetrain noise much easier. I mentioned that all 3 pistons measured exactly the same, which they do, but there is one particular measurement that I made on all 3 pistons that doesn't quite add up and remains a bit of a mystery. The skirts all measure fine at 90 deg. to the wrist pin, but when I measure approx. 45 deg. to either side of center of the skirt, I get two different readings. The piston skirts have, shall I say, small wings that extend toward the wrist pin at the bottom of the skirts. When I measure diagonally across the wrist pin from wing to wing, I get a different reading when I swap sides, which doesn't make any logical sense. 8) I plan to measure all 3 cylinders tomorrow with a brand new precision bore gauge to see if anything appears out of the ordinary in that area. My local machine shop wanted $45.00 just to check the cylinders, so I decided to spend some money on a new set of precision ball gauges and and a new bore gauge to check the valve guides and the cylinders myself. I like to take my time and check everything very closely when it comes to rebuilding engines and machinery. I'm very picky in that regard, but that's just me.
I'm just about ready to upload some pics. of my work and post a link to them in a new post titled "Pics of my engine rebuild". I've been quite busy with work lately, but I should have the pics. up in the next couple of days and will hopefully have solved the mystery by then.