Whineing noise from valvetrain

[SpecM]

Over the past few weeks, I've noticed a high-pitched whine from the engine when it was cold and off idle (like 1500-3000rpm). I thought it was a loose belt or drive bearing, as this is exactly what it sounds like. The noise is all but inaudable at idle, or when the motor warms up.

To double check, I removed both (no ac) belts and cranked the enigne. Noise still there. Replaced belts, and removed valve cover and plugged PCV hose. Noise is much louder and sounds like its comming from the head. With the cover off I can hear it at idle, but the noise still goes away once the temp gets up.

Could a worn rocker shaft cause this? All valve clearances and in spec and seem to stay that way between checks. The noise sounds 100% like a loose belt or worn drive bearing, but is not. (Its not the timing pulley either, I'm quite sure)

For what it's worth, it seemed to start after I switched to Mobil One 15w50. Any help/ideas welcome... please...

[Van Westervelt]

If it seemed to start after a change you made, logic says to revert the change and see if the fault is corrected as well.

Noises are pretty hard to decipher while not in person, let a lone over the internetz. GL

[jlevie]

The first thing I'd suspect, if the noise is present with none of the v-belts on, is the timing belt tensioner.

[SpecM]

Jim, I suspected that as well, but a stethascope held to the pulley's mounting boss reveals no abnormal noise.

Van: I may change back tomorrow, but there is reason I can think of that synthetic oil would do this.

[SpecM]

Would a loose rocker clip do this? My #5 exhaust is a little sloppy. Maybe I'm hearing the rocker dance on the shaft?

[SpecM]

OK Jim, I owe you and e-poligy. It may be the timing belt tensioner.

Why would I hear it back at the 4th-5th cylinder with the valve cover removed?

[jlevie]

The only reason I can think of for you to hear it around those cylinders would be harmonic vibration of the cam shaft. Replace the TB & tensioner and see if that helps.