engine knocking problems

i have a 7m-ge and i accidentaly let it run low on oil and it started knocking really bad, i figured i would try to put more oil in it but that didnt help at all. It sounds like it coming from the cam shafts but when i took the covers off and inspected them there didnt seem to be anything wrong. Then with the covers off and the spark plugs out i turned the car over for a couple seconds and it wasnt knocking anymore. Im not really sure what I should be looking for

Sounds like it's time to examine the bottom end and replace bearings as needed (most likely rod bearings). Also, check out your cylinder walls. If they are scored, then you are looking at serious work. Don't drive it any more. May turn out to be easier and cheaper to just replace the engine.

It stopped making the knocking noise when you pulled the plugs because you weren't making the crank/rod bearings take the load of compressing the charge. Once you load them by installing the plugs and making the pistons/rods/crank do work, you hear the out-of-spec clearances caused by the bearing wear.