3.3 Turbo Mystery Part...

[MJR]

Tore down the engine and found these 0.5mm shims between the cylinder and head. Not a fire ring, and I see no benefit other than lowering compression and brinneling the aluminum (sarcasm)...

Wondering if someone's seen them before, and what the possible purpose could be if it's an actual aftermarket part and not someones back-woods engineering development program.

FWIW, the head to cylinder interface depth, and cylinder deck height check out to stock, so there's been no machining.

Thanks,
Matt

[motorracer]

Hi I have them on mine as the heads were cut that amount.

[MJR]

Originally Posted by motorracer

Hi I have them on mine as the heads were cut that amount.

Thanks for that. Do you know who makes them?

This motor is untouched (machine work wise), which is why I can't find any reason for them

[billjam]

If your turbo is a 91-ish model, they are standard head gaskets.


If you need a set, PM me. I bought a set by mistake. Got my part numbers mixed up

[motorracer]

mine came from ollies when the heads were cut hope that helps

[MJR]

Originally Posted by billjam

If your turbo is a 91-ish model, they are standard head gaskets.

If you need a set, PM me. I bought a set by mistake. Got my part numbers mixed up

Car's an '89, so there should be no gasket. The motor's been apart before, so maybe the rebuilder installed the later head gaskets...

[winders]

Originally Posted by MJR

Car's an '89, so there should be no gasket. The motor's been apart before, so maybe the rebuilder installed the later head gaskets...

If it is an '89 motor and there is a recess in the heads for the gasket in the heads, and you have gaskets, why are you wondering what the gaskets are for? There would be no recess for the gasket if the heads were untouched '89 heads...

Wait...is this for an '89 Turbo motor? I know the '89 3.6 Liter didn't have head gaskets....I don't know about an '89 Turbo 3.3 Liter.

Scott

[MJR]

'89 930 turbo motor. Book says it's not supposed to have anything in there.

My initial post is a little misleading, I think. My question should be: "Am I missing something here?"

I build high performance and race engines for Japanese and American cars, but this is the first Porsche 911 engine I've ever been inside

Also, these "gaskets" are .5mm stainless steel shims, which doesn't qualify them as a gasket. They wouldn't contribute anything to sealing, that I can see.


Cheers,
Matt


On a side note: several different hacks have been inside this motor. You wouldn't believe the things I've found... Four of six pistons with the pin offset in the wrong direction, sealed with Indian Head gasket shelack, silicone gooped all over everything, exhaust studs that were broken and drilled between the stud and aluminum for a 6mm bolt, these shims, cracked injector housings that were gooped over with epoxy, silicone and god knows what, centered rocker shafts.

Three broken dilivar studs, one of which was a 993 stud... Someone took it apart before and replaced only three broken head studs with 993 dilivar... They left the rest, and now two more original ones and one of the 993's is broken.

Pelican Parts is lovin' it!

[cgarr]

If you have a big mic you can see if the heads have been surfaced a lot thus the need for the shims. Head should be 84.5mm from the top cam surface to the sealing surface and the max cut head would be 84.25mm

[MJR]

Originally Posted by cgarr

If you have a big mic you can see if the heads have been surfaced a lot thus the need for the shims. Head should be 84.5mm from the top cam surface to the sealing surface and the max cut head would be 84.25mm

Pretty dang close.

[lucittm]

My 1991 Turbo has those sealing rings. I replaced three of them with identical parts from our host when I did a one side rebuild. Are your heads stock? What is the date casting? 1989 may have been a cut-over for the head sealing ring for the Turbo. Consider yourself upgraded, that was the state of the art in 1991-1992.

Mark

[Henry Schmidt]

The head gasket application is more a function of appropriate cylinder than the head unless the head was modified.

If your cylinders have full fills and measure 97mm they are in fact 91-92 C2 Turbo cylinders and they were designed to used with head sealing gaskets.

If you cylinders have partial fins and measure 97mm they a 78-89 turbo cylinders and were designed to function without sealing gaskets.

The gaskets in your picture are indeed 91-92 C2 Turbo sealing rings.

What we are talking about here is basically a dimensioning question.

If you install the gaskets will your engine produce the compression you a looking for? To answer that question you must perform a simple compression calculation.

Good luck

[MJR]

Originally Posted by Henry Schmidt

The head gasket application is more a function of appropriate cylinder than the head unless the head was modified.

If your cylinders have full fills and measure 97mm they are in fact 91-92 C2 Turbo cylinders and they were designed to used with head sealing gaskets.

If you cylinders have partial fins and measure 97mm they a 78-89 turbo cylinders and were designed to function without sealing gaskets.

The gaskets in your picture are indeed 91-92 C2 Turbo sealing rings.

What we are talking about here is basically a dimensioning question.

If you install the gaskets will your engine produce the compression you a looking for? To answer that question you must perform a simple compression calculation.

Good luck

I can't believe I didn't think of the compression... So flustered, I guess...

Anyway, the engine is an '89 3.3 for sure. Cylinder fins on the lower half only, no base o-rings, and the sealing surface on the deck is 113mm dia.

Quick down-and-dirty compression ratio check shows 6.75 with and 6.97 without the rings. So, toss 'em it is.

Thanks Henry and everyone else.