Hi I have a 1997 Z28 with 135k on it, Its makeing what seems to be a valve train noise. Not a tick at idle just a little noise at higher rpms (2000-3500). It almost sounds like a very small exhust leak on the manifold. I know for sure its not a leak due to having the pass side replaced and haveing smoke pumped backwords through the system and no leaks were found. Im sure its the worste case situation (Tired loose motor), but i figured Id run it by you guys and see if there is some common problem that these motors are known for and i could pinpoint the problem instead of replacing the whole motor or chaseing the problem with a full rebuild....Thanks in advance

 

lifter? or loose rocker arm

 

If you could post a video of the sound, that would help us immensely with the diagnosis.

 

and/or give us a full description of the noise and when it occurs......as a recent victim of piston wrist pin knock, on a 135k miles 350, I can tell you it sounded a lot like a sticky lifter or rocker arm at first.....but it occured under different load conditions. In my experience a sticky lifter or rocker arm will be 1. Worse when the engine and oil is hot 2. Varies with RPM, usually worse at higher RPM. 3. Does not vary much with load on the engine.
My wrist pin knock on the other hand varies with engine load - it's worst when the piston is "unloaded" - decelerating in RPM. Wrist pin knock will also tend to get worse quickly each time the engine is taken to high RPM. I too was hoping for a lifer or rocker arm, but I'm not that lucky apparently.