I don't think it is a bearing (rod or main) because it has great oil pressure.
I am not sure if it is a stuck valve, or a bad hydraulic lash adjuster.
Everything looks good, and tight. Nothing is loose in the valve train from what I can tell.
I figured if it was a bad hydraulic lash adjuster the lash pad would be loose and easy to find.
The engine only has 40,000 miles on it and the valve train all looks brand new still.
All nice and clean ( after wiping the oil off) with no heat spots,rust or pitting.

Thats why I am thinking it might be a messed up wrist pin in the piston. Allowing the piston to wobble in the cylinder, or the piston is broke a little where the wrist pin attaches. Allowing the piston to bang up and down during the swing of the connecting rod.

Or from what some people have mentioned...I might have some carbon broke off and is banging around in the cylinder between the piston and the head.
I am not sure on what carbon bouncing around like that sounds like.
They have told me to use seafoam in the motor.... I have never used it.

The noise the best I can explain it sounds like taking two aluminum blocks and hitting them togther.
Kinda like a old engine that when you shut it off..and it keeps running ( dieseling).

 

This may come down to a hydrolock creating a slightly bent rod that is hitting. Pulling the pan is looking for the bent rod. In this condition a variety of things can hit a variety of things. Piston may even contact the crankshaft in extreme bends. Compression may be lower also on that noisy cylinder. Indicating the bent rod. The pistondownward travel may excede 1/4" more. You usually see water/a very clean piston top, free of carbon, even like sand blasted. With the pan pulled you mayfind pieces to point to the culprit. The piston hitting is a not so suttle sound, a lot different than a loose tappet sound. But one step at a time. Broken timing chain guides? One guy had chevy plugs in his and smoked them and the pistons. Craters and bad things happened.