Originally Posted by Juha G

Slip-in = the cylinders "slip" into the engine case. Cylinder bottom sealing is done between the flanges. (this is as original street engines).

Bore-in = Engine case needs to be machined (borred) to fit the cylinders. Sealing by O-rings which requires further machining of the case for the O-ring grooves. Sealing between the flanges is not possible because there is just not enough surface area on the flange for proper seal after machining.

The original case has cylinder openings for the 3.6 cylinders. The 3.8 cylinders are bigger in diameter so you can either have same outer diameter (=slip in) with thinner cylinder walls or original thicker cylinder walls which require enlargening the case openings (=bore in).

All the racing engines had the thicker cylinder walls. I think any of the top end engine builders will advice to go with the thicker cylinder walls. It will cost more because of the machining work needed but it is the right way to do it.
Both slip in and bore in cylinders are available for the engines.

I went with the Mahle "bore in" / Motorsport cylinders in my "RSR" build. Here are some photos: https://m3supercar.1g.fi/kuvat/993RSR/Winter16/

Originally Posted by eddieb4

Pic of old 3.6 jug and piston- if you look closely you can see that there is no groove for gasket and you can see oil residue where is was leaking out on the face of the jug. As I understand it, only a small percentage of "ringless" actually leaked at this junction. Mine was one of the small percentage of engines that leaked at the base cylinder area.

Next pic: New Mahle 3.8 jug ... you can see the groove.

Originally Posted by onevoice

Interestingly though, the gasket was a crutch to stop the wetness, not the reason for it. The earlier 3.2 engines, and turbos, didn't have head gaskets, and weren't known to leak. I would hesitate to even call it a leak, because there is no oil there to leak, the combustion chamber side of the piston is never really wet with oil. Henry (from Supertec) says the design of the head causes it to warp somewhat from the clamping force of the head being torqued. So the wetness isn't really an oil leak, it is combustion byproducts, oily water and probably fuel from cold starts when the aluminum hasn't reached operating temp. Unless an engine has a serious problem, it is unlikely an engine will ever have enough leak there to ever cause more than wetness, not a drip.

Originally Posted by onevoice

Interestingly though, the gasket was a crutch to stop the wetness, not the reason for it. The earlier 3.2 engines, and turbos, didn't have head gaskets, and weren't known to leak. I would hesitate to even call it a leak, because there is no oil there to leak, the combustion chamber side of the piston is never really wet with oil. Henry (from Supertec) says the design of the head causes it to warp somewhat from the clamping force of the head being torqued. So the wetness isn't really an oil leak, it is combustion byproducts, oily water and probably fuel from cold starts when the aluminum hasn't reached operating temp. Unless an engine has a serious problem, it is unlikely an engine will ever have enough leak there to ever cause more than wetness, not a drip.

Originally Posted by eddieb4

It debatable ... talked to George at Midwest Eurosport and he recommends sleeved. I can have him weigh in.

Newly powered coated engine bits.

Pic of old 3.6 jug and piston- if you look closely you can see that there is no groove for gasket and you can see oil residue where is was leaking out on the face of the jug. As I understand it, only a small percentage of "ringless" actually leaked at this junction. Mine was one of the small percentage of engines that leaked at the base cylinder area.

Next pic: New Mahle 3.8 jug ... you can see the groove.

Originally Posted by Juha G

????

Your photos show the top of the cylinder. There is no oil that can leak there. The base seal is on the bottom of the cylinder.

Also, I'm really curious to hear in what way a thinner walled slip in cylinder is better than one with original cylinder wall thickness (cost put aside)?

Originally Posted by Juha G

????


Also, I'm really curious to hear in what way a thinner walled slip in cylinder is better than one with original cylinder wall thickness (cost put aside)?

Originally Posted by onevoice

Interestingly though, the gasket was a crutch to stop the wetness, not the reason for it. The earlier 3.2 engines, and turbos, didn't have head gaskets, and weren't known to leak. I would hesitate to even call it a leak, because there is no oil there to leak, the combustion chamber side of the piston is never really wet with oil. Henry (from Supertec) says the design of the head causes it to warp somewhat from the clamping force of the head being torqued. So the wetness isn't really an oil leak, it is combustion byproducts, oily water and probably fuel from cold starts when the aluminum hasn't reached operating temp. Unless an engine has a serious problem, it is unlikely an engine will ever have enough leak there to ever cause more than wetness, not a drip.

Originally Posted by ezinternet

Hi Ed

I had a similar bit of work done by George at Eurosport Racing in 2010 (time flies!) on my '91 964.

3.8 Mahle p/c, ARP bolts, ported head, 993 RS valves, Ti retainers, custom cam ... trans rebuild w a few new synchros, LWFW, RS clutch, JRZ ... I'm sure I'm forgetting some things.

I put on the Fabspeed exhaust w/heat. Great sound, and a modest drone that went away with time. I don't get enough heat from those small sized heat exchangers to drive in the winter in Chicago.

I also sourced a 964 Euro RS ECU. I recall George did some extra dyno work and replacing the pressure regulator to maximize that benefit.

The car is at Autobahn in Joliet if you'd like to see it or give it a listen/drive when next you're down there.

Can't say enough good things about George and his team, as I'm sure you know. You're in good hands.

Dyno results attached ... YhpMV ... I'm sure you'll love it

Best,
Ez

Originally Posted by Bill Verburg

Curious as to why you bought a 964RS DME?

Is that data flywheel or rear wheels?