95mm 3.0l cylinder?

[jeffery dalcour]

Can the groove for the gasket at the top of the cylinder be machined off or filled with a weld bead to make them usable cores for boring to 98mm?

[Steve@Rennsport]

JMHO, but I would simply never do either one,...........I'd get a set of good used Carrera cylinders to have them bored and plated.

[911TT33]

Doesn't that groove / sealing ring provide a MUCH better seal than just a flat cylinder <-> head junction, making it optimal for higher compression engines? I would have thought so?

Anyone care to comment?

[Walt Fricke]

Or even a not so good set of 3.2 cylinders, as long as the damage was on the piston side, since that will be machined off.

The issue with the sealing ring for overbores is that the overbore narrows the distance between the combustion area and the ring, increasing the chances of it burning through.

Porsche decided with the 3.2s that the CE ring was not necessary. I know that some guys building turbos like to install a different kind of ring, but that calls for significant extra work and expense.

I infer from his comment that Steve thinks the 3.2 approach is adequate for hopped up motors, at least ones which have had their displacement increased.

[Steve@Rennsport]

Walt,

The problem with boring the SC cylinders is that it leaves far too little material between the bore and the sealing ring grooves. Any sort of mild detonation results in failures and a chunk of cylinder wall falling into the bores.

Thats why Mahle eliminated the CE rings in the 92mm RSR, 95mm Carrera, and 98mm cylinders.

They went back to using sealing rings in 100mm and larger bores but that was due to increased stud spacing and head bending issues. Thats a totally different story for another day.

[911TT33]

Originally Posted by Steve@Rennsport

Walt,

The problem with boring the SC cylinders is that it leaves far too little material between the bore and the sealing ring grooves. Any sort of mild detonation results in failures and a chunk of cylinder wall falling into the bores.

Hey Steve, what if the SC cylinders are not bored? Is it thick enough to sustain decent boost levels with a good tune, twin plugs, and retaining the CE sealing rings? This is on a decompressed motor using a 1.0mm+ base shim.

[Steve@Rennsport]

Originally Posted by 911TT33

Hey Steve, what if the SC cylinders are not bored? Is it thick enough to sustain decent boost levels with a good tune, twin plugs, and retaining the CE sealing rings? This is on a decompressed motor using a 1.0mm+ base shim.

Stock cylinders are fine. Be very careful about how much boost and timing you run, especially on pump gas.

"Less is more".

[911TT33]

Originally Posted by Steve@Rennsport

Stock cylinders are fine. Be very careful about how much boost and timing you run, especially on pump gas.

"Less is more".

Planning to decompress the motor to ~7.5 and run 1.0bar... Possibly twin turbos.