Cylinder base gaskets

[AES]

Some cases seem to use more effective cylinder base gaskets than others. I currently have an '86 3.2 and a 91 3.6 case disassembled. The 3.2 uses a simple flat base gasket while the 3.6 has a groove, flycut into the case wall for an o- ring gasket.

Why, the different designs, does the 3.6 pressurize the crankcase that much more, or is it an example of the factory engineers over designing something(probably not likely), does it make any real world difference, is it a track only thing?

[Jeff Curtis]

I dunno why Porsche would've done this except that maybe a Viton "O"-ring is quite a bit cheaper than a copper base gasket?? ...or they just wanted a change.

Another reason that would probably make more sense is that an "O"-ring would seal the cylinder better when compared to aluminum/copper/aluminum.

[AES]

Thanks for the reply Jeff. One mechanicaly gifted friend suggested that the bigger, higer compression engines pressurize the crankcase more necessitating a better seal. I dunno either, but it seems that a lot of effort went into a better seal.

[Bill Verburg]

The bigger cylinders leave very little meat for the flat 3.2 type seals. Here's a pic of my 102mm RSR cyliner base, as you can see not much sealing surface.

[cstreit]

Bill,

I'm not familiar with the later cylinders... What are the threaded portions in the cylinder walls for?

MAN those pistons must be as big as freekin coffee cans!

[Bill Verburg]

Knock sensors. Another reason to covet the later engines.

Chris, are you going to keep us updated on your progress? I would be very interested in a pic of your new pistons like this one, showing the wrist pin.



Nevermind I just found the ones from Nov. Which also coincidently show the meatier sealing shoulder on the 95mm cylinders.

[nick-moss]

My '74 2.7 has a Mahle 92mm P+C conversion. There are no base or head gaskets save for an aluminium shim at each base to set the deck heights



Spot the deliberate mistake in this photo

[Bill Verburg]

Is that the famous twin piston/bore engine? Though not a mistake that also looks like 993 studs?

[nick-moss]

Bill, I'm not sure of the studs, but they are genuine Porsche, but no that's not the mistake

[thesey914]

Cylinder upside down?

[Bill Verburg]

Started at the wrong end

[nick-moss]

thesey914 gets the prize. The first barrel I put on upside down, and didn't realise until I had timed both the cams. At least I got extra practice at that!

[thesey914]

YESSSsssss

Sorry to hear about the unexpected tear down -Nick

[nick-moss]

It only took 90 minutes to sort out