I got a 2002 chevy camaro 5.7 liter and when you let the car run you hear a light knock to it, I doesnt sound like a rod bearing, but it does seem like it is coming from the bottom end of the engine. It doesnt sound like valves or what not. But when you push the throttle on the car you cant hear any knocking, the car runs and drives great its got plenty of power. I also just changed the oil in it, and I didn;t see any kind of metal flakes in the oil etc. like I said this is a light knock but it sounds like its coming from bottom end, what could it be?