This is just a general question, but I've had my 1984 Cavalier for quite awhile. Father bought it knew, it sat for 12 years, and I got it running again. I had the motor rebuilt about 3 years ago, but its developed another knock that has the same characteristics. It happens:

1) At idle.
2) At 1000+ RPM the knock goes away until around 2500 RPM (neutral, no load) it can be heard again, noticeably louder.

The odd part though, when the car is under load (any gear) the knock goes away, even if riding the clutch and letting it idle forward (to rule out engine noise drowning it out). Anyone know of a part that would wear and cause this? The knock is distinctively coming from the lower end. Before the last rebuild (when trying to avoid doing it), the main bearings were fine, as was the timing chain, and computer. I'm worried they may have reused or machined the culprit for the last rebuild.

Only other thing to note was that I did a head gasket on it (personally) about a year ago before I parked until it recently but the knock was there before that. Turns out the white exhaust (found out after the motor was torn down) was due to condensation build up and a bad EGR valve (condensation had backed up in the line).

1985 Chevrolet Cavalier Sedan
2.0L I4 TBI OHV

My apologies... question turned out not to be so 'general' >.<

1985 Chevrolet Cavalier Sedan
2.0L I4 TBI OHV