Well I got a new long block for my 94 z28. It's installed now but since i've cranked it up it has a hell of a rattle like i've never heard it's rattling and not knocking. It has me scared to do anything because of voiding my warranty. It's all stock and At the same time I've replaced the opti, water pump, egr and selenoid, knock sensor, temp sensors in the head and water pump, o2 sensors, removed air pump. I'm about to go crazy over this. It seems to be running fine except for the noise. no codes with freescan. I just don't want it to be detonation ruining my engine. no misses or anything just metalic rattling

 

it could be as simple as your flywheel bolts or torque converter bolts being loose but we would need to hear it to help find it

 

alright just checked them and they seem alright. It seems to be more of a valvetrain issue. Wonder if they adjusted the valves?

 

Exhaust pipe rattling?

 

could be broken welds on your fly wheel... Does it increase as u rev the engine?

 

Yes it increases as it's revved. I might try and drive it to see what it acts likie while driven

 

All bearing noises, lifter noises and rocker noises increase in frequency when you rev it...that doesn't tell you much.

Don't drive it until you gat an idea of what's wrong. Sure,it's possible that a weld broke on the flywheel but that isn't really likely.

Tell us more about your car so we can help diagnose it.....

 

1) What kind of dampener are you using? Are you sure the bolt isn't bottoming out in the crank? A loose hub/dampener could explain the noise at high RPMs (though I've never heard a loose dampener causing noise at idle, I suppose it's possible if it's really loose).

2) Does this car have AC? Could be a bad compressor?

If it doesn't affect how the engine runs, but the noise seems to be linked to RPMs, I've say the AC compressor and Power Steering Pump would be high on my list of suspects. A mechanic's (or cardiologist's) stethascope can be useful for stuff like this.