993 102 mm LN Cylinders with no top gasket

[Cupcar]

I just received my LN 102 mm cylinders and JE pistons for 993 build and note they have no groove for a sealing ring at the top.

Anyone done a build without a sealing ring between head and cylinder?

Seems adventurous to me or am I missing something?

[Steve@Rennsport]

Depending on how the engine is used and its configuration, I do machine these heads for the 993 sealing rings.

One example would be an RSR-spec engine with more than 11.3 CR that will see 7K+.

[Cupcar]

Thank you Steve, do you mean you machine the heads for the sealing ring or the LN cylinders.

Just checking to make sure I understand.

[Steve@Rennsport]

Originally Posted by Cupcar

Thank you Steve, do you mean you machine the heads for the sealing ring or the LN cylinders.

Just checking to make sure I understand.

The heads have grooves for sealing rings; I simply machine the LN cylinders to match in certain circumstances.

[Trophy]

Hey Bob, any pics of the pistons?

[Cupcar]

Originally Posted by Steve@Rennsport

The heads have grooves for sealing rings; I simply machine the LN cylinders to match in certain circumstances.

My 993 heads have no grooves for sealing rings, are there any Porsche engines that came with them from the factory?

Reading the LN literature, which I should have read more closely, I find they claim they don't machine for sealing rings because they feel this is a source of failure at the head joint.

When I both emailed and talked to Charles at LN he says in email they will not machine for the rings "because we don't recommend them".

However, in a phone conversation, he added that LN recommends that the cylinder head surface be freshly machined as well as, ideally, the crankcase cylinder deck to make sure the head seals correctly with a perfectly squarely fit cylinder.

Hmm...this all seems a bit of an experiment to me. If the cylinders were more expensive to make without the top rings and cylinder base O rings the argument would carry more weight with me.

I think of Porsche could make the cylinder joint without a sealing ring they would do it, after all they tried with the first 3.6 engines to go without a sealing ring, albeit with a tapered joint, but I am sure they would move from a seal, particularly if it were cheaper and better.

I remain a little skeptical here.

[Bill Verburg]

I just had the heads resurfaced


the 102x109mm Mahle cylinders have grooves

[Cupcar]

Originally Posted by Trophy

Hey Bob, any pics of the pistons?

Here you go:

Shiny piston new 102 mm, 11.5:1 J&E with 22 mm wrist pin bore and the old one a 100 mm Mahle.

The 102 mm J&E is the J&E optional "Forged Side Relief" (FSR) special order box type piston and weighs 444 grams without pins or rings.

The stock Mahle is of the same FSR or box type and in 100 mm weighs in at 422 grams. The J&E is presumably heavier because of its larger diameter as well as its 22 mm instead of 23 mm wrist pin bore.

The wrist pins weigh in at 91 grams for the J&E and 112 grams for the 1 mm larger diameter Mahle pin.

So the 102 mm J&E with wrist pin is 1 gram heavier than the 100 mm Mahle with wrist pin.

The ring set with the Mahle has a 2 mm oil control ring while the J&E (Goetze ring kit) has a 3 mm oil control ring.

Note below that the 100 mm Mahle has much less deep valve pockets than the 102 mm Mahle Bill shows above and that both Mahle's have a bowl type combustion chamber and the J&E has a pop up piston.

Note: If you don't special order the FSR piston option and specify the standard J&E piston in the J&E catalog, you will receive a barrel type piston that weighs 50 grams more at 494 grams for 102 mm & 11.5:1 and looks like this:

[Trophy]

That's great, thanks bob....

I need to get my butt into gear and place my order....