so i got this noise in my engine it sounds like a bolt loose under the cam cover or something so i pull the cover and everything looks fine but it is like a LOUD rpm sensitive clanking..... it is not rod knock, i have heard plenty of these...i'm thinkin a stuck or blown lifter but i dont think this is it for some reason...doesnt seem like the noise would be that loud...anyone know of anything similar or heard of such a thing