Recently, ive started to notice that my motor makes this really loud "grind" sound when i rev it to 3,000 rpms. But after 3k, the sound goes away. If i rev it quickly, you cant hear it, but you can hear it when the revs drop back down. At first i thought it was something with the tranny cause it does it in all gears, but today i popped the hood and did it without it in gear, and it still made the sound. If you hold it at 3,000 rpms, its loud, and sounds like something is pretty fucked up. I have no idea what it could be. It sounds like it might be coming from the head somewhere, but its hard to tell.
P.S. Its a 98 gsr motor, all stock internals.

 

 

check exhaust manifold, or the cat. make sure eerything is tight. also check the cover that goes over the cat, that might make some noise.

 

it may be a loose mount or something is loose and rubbing

 

Try to drive it under that rpm level until you get this fixed. If you can get one of those stethoscope type things for cars, then you can rev it with the hood open and pinpoint the location of the noise - that would help out tremendously.

 

See if it does away when you push the clutch in...if so it's probably a bad transmission bearing.

 

i had the same problem, it was the catalytic converter heat guard, i grinded the bolts and removed the heat guard, no more rattle.

 

When i had the hood up, i revved it with my head close to the motor to listen closely for the sound, and it sounds like its coming from the head, but its hard to tell.