My 850 Turbo overheated and I blew a head gasket and subsequently warped the cylinder head. I had .026" milled off and now I am putting everything back together. My question is-what do I have to do with regard to the valve timing now that i have "lowered" the head closer to the pistons. I noticed the cam sprockets are slotted. Do I compensate using these slots? If so, how do I check this? Thanks in advance...

This raises some questions. but I wouldn't worry about it.

The interference occurs when the engine is grossly out of time. This forum is repleat with stories of timing belts off by one or more teeth, and no one has ever talked about interference. Total valve lift is .333, which is 13 times your 0.026 distance. In my mind, there's a lot of room to work with there.

The 0.026 IS way beyond spec however. I read the milling limit as 0.012 in some places and 0.011 in others. But manufacturers typically would set a spec like this very tightly.

I think you tensioner, as long as it is in good shape should be fine.

Write us back a year from now and let us know how everything went.

Thankfully I don't speak from experience, but I would consider the following:

1. Will there be adequate clearance between the valves and pistons with .026" metal removed from the head? Remember that this is an interference fit engine, meaning the valves are already very close to the pistons.

2. Will the increase in compression cause any problems? Remember that the turbo has a lower compression ratio than a NA engine for a reason. You might want to pull some fault codes shortly after running the engine under load and check for any codes from the knock sensors.

3. Will the TB tensioner be able to handle the 'extra' length of the TB? I would consider replacing both the TB and the TB tensioner while you are reassembling the engine, if it isn't too late.

4. If any doubt, I would think about about putting in a thicker head gasket to compensate for the material removed from the head, assuming someone makes them for the 850T.

Good luck. Keep us posted with your experiences with this. It's one of the ways we all learn from each other.

Don
95 855T
85&86 245 (donated), 95 854 GLT (t-boned/parts), 93 854 GLT spare

Should need to do nothing except assemble as if there was no milling. I had to do a head a year ago and it was also milled. Just follow the usual instructions.


dick

I would just set it up per the manual and go from there. I just took apart a non turbo engine last week and when I set up the jig for the cam it was obvious that it was off one complete tooth and the customer never complained about any driveability or lack of power issues before he overheated it. Put it together by the book, run it, and evaluate it from there.

Mark