85 3.2 - cylinder head/barrel sealing face

[rob911]

Afternoon all.
Looking over my 3.2 Carrera last night and I noticed the last time it was on the road was 2015!
I placed up the car to find the source of a misfire that eventually was traced to a broken head stud.
The motor has been sitting on an engine stand ever since with the top ends removed and stripped right back to the crankcase.
The heads need rebuild with the guides showing wear.
One concern I have is a section of the barrel sealing face (barrel to cylinder head) adjacent the broken head stud which is showing a burn pattern that when checked with a DTI -its showing this sealing face isn't true.
I have read up on machining the cylinder head sealing face but what about the barrel sealing face?
Can these be refaced or will a new set of barrels be required?
Cheers
Rob

[yelcab1]

Take that barrel down to the machine shop that will work on your heads. Tell him/her to remove exactly xx.xx mm from the surface to make it true.

The xx.xx is the thickness of the shim you can buy from Porsche. It fits at the base of the barrel to make up for the amount you remove at the top.

[rob911]

Cheers for that. It's what I was hoping to hear.
Wasn't sure if the barrel outer face was coated or just plain.

[yelcab1]

You will also need to compensate for the amount they take off the heads in the same way.

[brighton911]

And changing the assembled height will probably impact the cam box. Having one cylinder shorter than the other 2 means the cam box will be bowed. I would have all 3 cyl/head combos on that side modified to ensure the deck heights are the same. To check, with the heads and cam boxes torqued, make sure your cam turns freely (no rockers in place). If so, then you are good to go.

[proporsche]

what i would suggest to you is ...Having the machine shop cut a groove into the cylinder and use seal as it is on 911SC.I did that couple of times from some friends and it works very well , it is an extra sealing....
like this on 1985 Carrera..no need extra measurement at all ..like a deck h. and e.t.c.
engine came out very good
https://www.youtube.com/watch?v=c_7I3hDiAv8
Ivan

[trond]

I had my heads cut back 0.25mm and used thicker 0.5mm gaskets. Unfortunately the machine shop made them all different height. I managed by playing around with head/barrell combinations to get combined height variation within tolerance. In other words the new Mahle Motorsports cylinders (new set of 6, all stamped with height group5) were NOT the same height either. Both cylinders and heads are hard to measure for an amateur without all the tools. If you have parts machined you don't be a dummy as I was but 1) use a shop with good reputation for aircooled 911 work 2) Make a real effort to have heads and cylinders accurately checked by a third party.

[yelcab1]

Originally Posted by brighton911

...Having one cylinder shorter than the other 2 means the cam box will be bowed. ...

That is why you add the shim at the base of the cylinder barrel that was cut to compensate for the cut so that the cam tower fits correctly.

[trond]

shims. where and how ? I tried but did not succeed in finding 7/100mm. Or even 5/100

[yelcab1]

One google search for Cylinder Base Gaskets

[yelcab1]

I think LNE even sells them.

[85RedCarrera]

For a 3.2, I think you stuck with .25mm, .50mm, and 1.0mm shims...there is nothing in-between.

For .75mm you have to stack a .25 and a .50

If there are .75mm shims out there, I could not find them. LNE sells a lot of custom shims for the older engines

My Mahle Motorsports (Moritz single-plug) piston/cyl kits required .75mm shims with the combustion chambers that I got back from my machinist (~89.5cc) to keep the deck heights above 1.1mm

[brighton911]

Right you are 85Red. With .25 mm increments equaling 0.010", one would be very lucky to land on the right height combo.