ste1999

Hi all great to be back here, years ago I was here when pulling the head on my UK 944 turbo, now I’ve just removed same on my 1995 968S (uk spec Club Sport variant).

At 132 k miles I’m thinking this is hopefully the first time its been off and wanted to check the dimension to confirm that before sending it to a machine shop for clean up and valve job. Need to decide on head gasket thickness after any skim. P 15-19 of the 1992 Porsche workshop manual I have indicates a dimension A on the exhaust side of 147 +/- 0.1 mm for a new head. The only machined measurement flat I can find is behind the 4


1995 968S head exhaust port 4


th exhaust port (pictured). I get 130.2 mm on this head, sense checked a few times! Overall the head measures 149.6 mm. Nothing is near 147... Im guessing the measurement flat might have moved from the 92 to my 1995 model??? Any advice or updated specs appreciated, be a shame to have to play guess the right gasket...

Steve

michaelmount123

You're using the wrong pad. Look at the diagram closely.

michaelmount123

Here's more to consider:

-968 C/R is typically LESS than the spec (yep), so removing .010" (.25mm) or so will probably bring it close to where it should be. You'll be fine with decent fuel.

-Cometic head gaskets are available in any thickness. If you use Cometic, however, torque to 65 ft.lb. in 3 steps, then back off each one in sequence and re-torque individually back to 65 ft. lb. If you don't, you'll find the center nuts will be loose.

-If you use a Cometic head gasket thicker than .045", request a 5 layer gasket. They'll tell you they don't make one, but they do if you insist. Thicker Cometic gaskets resist compressing with only 3 layers.

ste1999

Hey thanks so much for both posts! OK so I’m using the wrong pad. I just need to work out where the right one is then, not seen it yet!!. Regarding your valuable comments on compression ratio, I’m thinking that this head will need much less than 10 thou skimming from it as there is nothing visibly wrong, tho obviously will take the machine shop view as final on that. You are suggesting that the the 1.1mm gasket is likely to be fine for the rebuild assuming that’s the case, helpful info

Steve

ste1999

1995 968S head
So here is my head. Exhaust side. On the left is the originally pictured flat behind port 4 I thought might be the measurement place. On the right is another flat in front of port 1. There it’s 149mm approx. Not finding the right place as yet 😟😟

Steve

ste1999

Just trying to attach a full picture of this head again. Thee is a flat in front of no 1 but this doesn’t measure as anything meaningful. Otherwise nothing I see.

michaelmount123

The pad to reference is above and to the right of #1 exhaust port in your last photo (contrary to what the factory manual says). It's above the forward most 8mm threaded boss. Here's what you do:
1. Measure total had thickness from the deck surface to the valve cover surface.
2. Using a depth micrometer, measure from the reference pad to the valve cover surface.
3. Subtract #2 measurement from #1 measurement and compare to the spec.

Clear as mud?

ste1999

Hey thanks so much again. I’m beginning to wonder if the factory manual was written just to confuse the newcomer rather than explain how to do this measurement. Also the random machined flat behind 4, why is it even there, weird... Tomorrow I will do it the way way you suggest and see what we get. Measuring/subtracting can’t be as accurate as a single measurement as on the 944T/951 head I’m familiar with. The engineering here seems as weak as the design of the camshaft sprocket bolt but that’s another story. Thanks again. Steve

ste1999

Couple of images in case in future anyone else needs to see this done: