I think I can here ya KNOCKING!

A trick I sometimes use is to slowly rev it up a little to about 1200 and then gently back off; all in one motion or doing. On the way up to that rpm, if it's a rod the knock-volume will increase just a little bit. Then,just as the engine transitions to no load the volume will decrease. Then as it returns, the volume will increase again. As soon as you have proved this, shut it off and don't restart it. Every second it runs is damaging the crank. The rod is probably already lost.No other noise generated by the engine does this.