Replacing cilinder liners

[prebordao]

Is it possible to replace just the liners instead of the complete cilinder?

[Flat6pac]

That's what is done when the cylinders are renikisiled or opened to 98mm 3.2/3.4.
Bruce

[Mark Henry]

Aircooled it's not done with a liner, it's a plated, so you can have them replated.
Iron and biral cylinders could be bored oversize, I have done this on the 914 T4 cylinders (93/94 to 96mm) but not on 911.

996 it's a liner that's used for replacement.

[prebordao]

The reason I ask is I have a scratched / scorched cilinder, as a washer found a way inside.
Engine is a standard 2.7 and i want to keep it that way.
So replace the cilinder right?

[bpu699]

I think some builders on here like Bruce and Henry can sell you a good used cylinder...

[Flat6pac]

Yes, you need to know several things to get one to replace your scratched one.
With 2.7 there is several combinations that you need to know what you're ordering.
There was 2 manufactures. Kohlbenschmidt (KS) or Mahle
KS are alucil cylinders.
Mahle, you have to read the casting number inside the pistons (such as 90L58 is nikisil,
90L61 is alucil.
On the cylinder will be two stampings one is a triangle with a number 5 or 6 inside. This is cylinder height. Next to it will be a number, 0,1, or 2. This is the piston size stamped next to the triangle
also stamped on the face of the piston. You want to match everything for your replacement.
Bruce

[Mark Henry]

If replacing one cylinder you need to know and match the group height number.
Numbers 1 to 6 in a triangle, bottom of the cylinder.

Also your cylinder could be nikasil or alusil, you can tell with a magnet nikasil has a slight pull. Replacing alusil might be a crap shoot as it needs special rings and honing. There is no plating on alusil.
In spec nikasil should work out OK with new rings.

As for re-plating, nikasil or alusil cylinders can be used for nikasil plating.

[prebordao]

Thanks guys! Replacing a cil requires more knowledge than I thought

[prebordao]

I added some pictures to help...

Markings on cil. I can understand is from Mahle, but what about the rest ?



Inside of cil: Greyish like this means Alusil, right ?



Finally, the bad one... Besides the piston, the cil has a groove on the surface.



If I replace just one P/C, I'll get different compression values from the rest... Is it acceptable ?

[prebordao]

bumping

[Flat6pac]

You need to match the casting number inside the piston and the stamped number on the face of the piston. You need to know if you're looking alucil or nikisil.
The red sealant has got to go. So much excess, chips will get into the oil and ruin the crank and cams, guaranteed
Bruce

[Tippy]

Just have the damaged cylinders replated.

[Mark Henry]

Looking at those and a educated guess, the dull even grey colour is likely alusil. Easy enough to check, with a magnet on the bore surface nikasil will have a slight pull, alusil will have none.
The height group is the 6 in the triangle.

I cringe whenever I see all that orange RTV, tells me right away a amateur hack has had a go at the engine.

[Flojo]

red sealant stuff clogs up the bores. very bad.

[prebordao]

Believe or not, the red sealant was put there during a rebuild 10 yrs ago by a "reputed" local Porsche shop...
Go figure...

[JJ 911SC]

El Motor de Meister???

[prebordao]

Sportclasse

[Mark Henry]

If it is alusil and your thinking of getting the cylinder plated I'd read this.

Using Alusil pistons in Nikasil cylinders