redrow951

So after 13 years of turbo ownership, I have joined the ranks of those with catastrophic engine failure. Luckily this failure is not so bad. I had been running the engine lean for at least 3 track days due to over boost (~14psi peaks), before I corrected the problem. I ran two more track days and then toasted the #3 exhaust valve (see photo). This car is running stock chips and at the time of the failure stock boost controlled by the cycling valve. I did discover the small plastic vacuum line from the TB to the thermo valve was melted closed in the middle.

Before the tare down the compressions were 145 - 120 - 0 - 145. So there is also an issue on #2, but I have not removed the valves to inspect. The event also damaged the #3 valve guide cast boss that protrudes through the port liner (see 2nd photo)

The big question is can this head be saved or should I be looking for a new/used one?

Thanks for any help.

J

Spidey944

Ouch. Looks like it's time to look for another head, would take an amazing shop I would think to get in there and fix it right.

OntarioTurbo

I just went through the exact same scenerio. #3 at zero and #2 low. My exhaust valve was brurned it two seperate areas however.
It's tough to see the extent of the damage to your guide area in that photo. I ended up getting an exchage head from Markus Blaszak for mine. Perhaps a local shop in your area can do the same and then they can repair the guide area before they rebuild it for someone else. Also, I believe VOoDOoGTX had at least one, if not two used turbo heads available. Food for thought. It's not a fast or easy fix, but the engine runs great now and I am very happy with it.
I will be posting a few pics of my repair soon. Good luck!

Chris White

Not really - just replace the valve guides - and you should do that while the heads apart anyway...

PS - welcome to the melted valve club!

redrow951

So, there is no need to repair the damage to the casting in the port? If repairing this head I will replace all 8 guides, all 4 exhaust valves, seats re-cut. The head has been reworked once before (about 10 yrs ago) with a light cut. The valve free lengths are ~13.5mm measured per the workshop manual.

Not so happy to be in the club, but thanks for the company

J

OntarioTurbo

I agree with Chris. In fact, the exchange head I put on had a little chunk of aluminum missing by one of the guides in #4. The guide is still firmly in place and I'm sure wont cause any heartache. If your other exhaust valves are ok then you can re-use them. Up here one sodium filled exhaust valve goes for $192.00. So re-use them if you can. A proper three angle valve job with hand lapping should be fine.

Spidey944

I guess from that angle it looked like the head was cracked/split near the guide.... my bad

jerome951

Be sure to have the head checked for warpage before you decide what to do. When I burnt my #4 valve, the head warped too much to be machined flat (it had already been machined previously) so it became a boat anchor.