I'm with Kevin. Rod knock is at twice engine speed, and gets worse as the oil heats up. BTW, yes the timing chain gets hot and expands, but not very much, since it never gets over oil temp, but the sprockets and block and head expand, too, so the clearance stays about the same.

Rod knock does NOT get better with a warm engine, Rod knock is a fairly heavy thunky sound, like hitting the block a good lick with a heavy hammer. Main bearing knock is the same, but louder, like smacking the block with a sledge, a very heavy thunk, thunk. You can feel rod and main knock thru the chassis, usually...