Hi guys,

I just got a call from my mechanic. My 940 (light pressure turbo) is still making valve noise after a complete head rebuild.

When engine is cold, car purrs like a kitten. Once it warms up after a few minutes of driving, it makes noises.

When warm before rebuilt:
1)Tapping sound on idle. Removing plug wire from each cylinder didn't eliminate noise. Symptom remains after rebuild.
2)When cruising, valvetrain clatter randomly, not related to load or particular engine RPM. This one completely gone after rebuild.


Things we have done:
1)Replace valve hushers
2)Replaced valves. I had a set of NOS lying around, so we decided to put in it. The old valve stems were slightly worn.
3)New head, intake and exhaust gaskets.
4)Cleaned out carbon - almost non existant by the way.

My trusty mechanic is at a loss with this. He is a wizard with RWD Volvos and completely rebuilt the B20 and M41 on my 144 6 years ago, with no problems until today. He plans to pull the head off again in case he "overlooked something".

What else could it be guys? Distributor gear? Camshaft? Or shall I look deeper into the block, eg wristpins, etc? I plan to keep this car for the long run, so I don't mind rebuilding the entire block. Its just that my previous 940 did not require any engine work up to when it was destroyed in a crash last year at 160k miles.

By the way, car runs excellent without missing a beat before head rebuilt, and it runs even smoother now. Does not burn oil, does not ping. If only I can get rid of that annoying tap on idle, it would be close to showroom condition.

All help appreciated. Thank you.