Cylinder head issue
 

I am rebuilding a 1971 911T 2.2L engine and need some help in confirming what the machine shop did to the Cylinder Heads.
They re-surfaced the fire ring face (where the Cylinder mates to by 0.75mm or 0.030".
i heard after the fact that this may be too much as it changes the compression chamber dome Characteristics and will require a large shim at the cylinder base that in addition to line bore done to the case will require a 1.25 mm shims.
any help or comments will be appreciated.
Thank you

That is a lot to cut and it does raise the compression which isn't necessarily a bad thing. I would be concerned as to the accuracy of the cut since they have to be within a .oo1''. You may have to add a shim at the bottom of the cylinder, but begin by solder and clay checking piston to head and valve to head. A T should have ample margin. Bob

Thank you Bob..... sorry for the late reply.
need to take the heads to a machine shop to check the cut accuracy.
do you know if a 1.25 mm shim under the cylinders is acceptable or this is too much in your opinion.
I need 1.15mm total to compensate for a 1.00mm cut on the heads and a 0.15mm cut in the case as a result of align bore the case.
any help will be greatly appreciated.

Never heard of cutting that much off. Might want to source another set of heads. Any time you take machine work in, best to write down exactly what you expect and not leave it up to whoever gets your job handed to them.

Any time you have to go to a thick cylinder shim due to a cut head, you are just replacing the material that was removed from the head. By cutting the heads that much though, the head dome has now been pushed somewhat into the chamber area hence the need to shim the cylinder to get correct separation between the head and piston. I don't know this, but as you go thicker with the shim, I would think the chances of an oil leak would become greater. Get all of your measurements first, then come up with a plan. The suggestion of another set of heads may be the way. Bob

Hi Bob,Thanks for yours and John Walker's input.
yesterday i was able to find that Porsche allows 0.25mm +/- 0.001mm MAX. machining on cylinder heads rendering my heads to be obsolete as they are machined 0.75mm making them out of specs.
now i am facing the challenge of sourcing a set of heads. new ones are very expensive and used ones are very scares as most what is on E-Bay are modified heads and or damaged. any help in sourcing a set of usable 6 cylinder heads will be greatly appreciated.
part no. 911 104-036 01 for a 911T, 2.2L 1971 carburated engine.

I believe there was a set of 2.2T heads for sale cheap in the classifieds here the other day

I just found a set of 5/70 heads complete. Gotta clean them up for a better look. Need a go-through and maybe a minor flycut.

Edit: sold them.

You can make your heads work. Some massaging will be needed on the heads and pistons, but if the heads otherwise are OK, They will work. A less cobbled up set is prefferable, but can you find t hem?

Good info guys.