Rod Knock

[mrnickleye]

I too have seen a loose crank pulley sound like a rod knock, on a couple of cars.
Rod knock develops due to the bearing(s) on the rod that attach it to the crankshaft, getting too much clearance (gap, play).

It can happen when the oil LEVEL gets too low, and you go around a corner and the pump doesn't pick up oil for a moment. Lack of oil at the bearing is the cause.

Oil quality plays a role. If the oil level NEVER got low, but has not been changed for too long, it won't lubricate very well.

Repeated high RPMs stress the bearings.

I change my oil every 2k, just to be safe. Oil is still cheap enough, and cheaper than engine work.