My car sounds similar
My engine is making the same noise, hence my post here:
http://www.shoforum.com/showthread.php?t=28178
It sounded like the cam, so we took off the valve covers today, and they looked fine... any other ideas?
Ok, when my car is at idle or high rev it is fine. But at about 1200-1500 RPM I hear a metal on metal sound. Kind of like marbles are in there. Anyone know what this knocking could be??? Need help ASAP! Thanks.