i just replaced the main and rod bearings because of a knock. its still there. it sounds like a moderate to hard aluminum tap. it use to occur only at 2000 rpm and above but never at idle or below 2k rpm. over time it also started to slowly progess lower to starting at 1700 rpm. it went away for a couple days but now its back and it moved, it now taps at 2500 and above. it is definately an aluminum knock. would jumped timing cause this? jumped a tooth or something? computer not adjusting correctly? i am totally at a loss. any help would be appreciated.