Fiat twin cam 2.0 turbo, exhaust valve stem appearance

[deki]

Hi Guy,

While replacing exhaust manifold on my integrale I have noticed that exhaust valve stems had something that appeared as oil film (wet area) in the upper region, just bellow guide when valve is open. This was visible through exhaust ports but no closer inspection was possible at the time. The head was recently rebuilt.
Is any oil permissible in this region? Also, the exhaust ports are covered with dark residue, but the car is running too rich at the moment - so it may be masking some other problems.
There is occasional puff of smoke I notice when driving - especially when coasting to a stop at the lights, for example.
No noticable oil consumption for now.
Is there anything I can try before I start to pull things apart - again... Thanks...

Sorry, no photos this time - I was too shocked to see the oil film (or at least what I think is the oil film) on valve stems after recent head rebuild... :-(

thank you

Dejan

[Guy Croft]

Oil in that region:

- Bores and rings not bedded-in effectively
- Worn inlet valve guides
- Worn out compressor seal (sucks oil into inlet at idle)

This does not sound good.

The ex guides are never subjected to vacuum unlike the inlet guides so it is unlikely to be ex valve guides unless they are chronically worn in which case the valves and seats are never going to perform well. The puff of smoke can be caused by any of the above. Light dry/grey carbon deposition on the ex guides is normal but wet and heavy deposits are a danger sign.

Also note that running high boost with a mismatched turbine/housing is often the cause of high exhaust manifold back pressure and then you get reverse flow of (dirty) exhaust gas on the valve overlap phase back into the cylinder and back up the inlet tract (can be made worse if you have cams with higher-than-standard lift at tdc). Sure sign of this is carbon on the inlet valve stems and heads and the injectors too. Take out an injector and have a look.

GC

[deki]

Thanks Guy.

thank you,

Dejan