Mahle compatibility with KS

[r lane]

The last couple of 3.2 motors I have built, I had the cylinders re Nikasiled as they were Nikasil cylinders. A current build has KS cylinders which are Alusil and I am in a quandry as how to handle this. They actually measured out well, but practically no hatch marks to be seen. I understand that mixing these two products, as in say a KS piston and Mahle cylinders, or vice versa, can be a problem as to the expansion and contraction parity between the two. in that the Nikasil coating is I think is no more than .010'', and I know Alusil cylinders can take the Nikasil, will that work with a KS Alusil piston. Anyone have experience here. Thanks, Bob Lane

[faapgar]

The Alusil cylinders are fine to replate.I use 3.2 Alusil cylinders and bore to 98mm.

[r lane]

Originally Posted by faapgar

The Alusil cylinders are fine to replate.I use 3.2 Alusil cylinders and bore to 98mm.

I know that the Alusil cylinders can be Nikasiled. What I don't know, can you run the Alusil KS piston with it's replated Alusil cylinder now having a Nikasil finish. Bob

[Zuffenwerker]

KS pistons in a nikasil plated alusil cyl. I’ve wondered this myself. Obviously they were not designed for each other. KS pistons have the mysterious ferrocoating on the skirts. I would say mahle or aftermarket pistons would be a safer bet.

Daniel

[Trackrash]

If your KS cylinders are truly in spec they can be honed and reused. IF the correct honing procedure and the correct rings are used.

[r lane]

Originally Posted by Trackrash

If your KS cylinders are truly in spec they can be honed and reused. IF the correct honing procedure and the correct rings are used.

I think these are a good candidate for honing and I understand that specific fluid, stone and procedure are a requisite. Would you know of a service for this. Thanks, Bob

[SCadaddle]

Originally Posted by r lane

I know that the Alusil cylinders can be Nikasiled. What I don't know, can you run the Alusil KS piston with it's replated Alusil cylinder now having a Nikasil finish. Bob

Here's what you do: You call Don at EBS Racing in Reno and discuss it with him. Then send him both your pistons and cylinders so they can have the cylinders Nikasil coated then honed to match your pistons. Have EBS supply the Goetze ring set when they send them back to you. I did this exact same thing about 10 years and +/- 10,000 miles ago on my 82 SC engine. It's worked for me so far, and I think if it wasn't going to work it would have already been a problem.

[SCadaddle]

Originally Posted by Trackrash

If your KS cylinders are truly in spec they can be honed and reused. IF the correct honing procedure and the correct rings are used.

And from the discussions I participated in 10 years ago, here is the rub.

1) You'll need the special Sunnin hone.
2) You'll need the special Sunnin paste.
3) You'll need the special KS Alusil ring set. Good luck finding those, at any price. 10 years ago they were virtually unobtanium. Maybe things have changed by now.

They say "hindsight is 20-20". I was in your same situation way back then. It can be a deep rabbit hole to go down if you go down it. My dilemma was part of a tear down to replace the lower Diliavar head studs of which only one had broken. Looking back now, I'm more than certain I would have proceeded as: Before tear down, perform a compression and leak down test. If that looks good from a perspective of the rings sealing, then just leave it all alone in disassembly. I wouldn't even remove the pistons from the cylinders. Yes, it does seem counterintuitive to reuse the old rings, but when faced with the alternatives it may well be the better alternative.

One thing is certain: You won't be second guessing your decision to run a KS Alusil piston in a Nikasil coated cylinder for 10 years and counting every time you notice one of these threads pop up for discussion!

[Speedy Squirrel]

The absence of cross- hatching is not a disqualifying condition for Alusil. It does not rely on that approach for oil retention. Check surface finish Ra and Rmax. If they are not scored or otherwise damaged, and the surface finish is in spec why would they not be ultrasonically cleaned and reused?

[Rosco_NZ]

You either run Nikasil bore & Nikasil specific rings or Alusil bore & Alusil rings .. they’re not inter-changeable.

Nikasil plating Alusil cylinders works really well … more silicon makes for more thermally stable cylinder .. obviously use Nikasil rings.

[Jeff Alton]

We have thes alusil cylinders refurbished/honed here locally by a machine shop with the correct tools and vast experience. NO issues.

Cheers

[Speedy Squirrel]

This is a great video covering the process on a BMW. To do aircooled cylinders it is similar, except with a fixture to hold the cylinders.

https://youtu.be/J43RkJTHdCE

[faapgar]

There is a lot of hype on the interenet and this forum about Alusil verses Nicasil.If the car is broken in correctly the Alusil cylinders have twice the life oF a Nicasil comparision.Last month I fixed an SC with 90,000 miles I did a leakdown with 2-3% leakdown.The top ring was at 8 thousand.New is 6 for the top end gap.You do not see a crosshatch because they never had one.If it only wore 2 thousands WEAR in 90000 mies and is broken in.Tell me what is better than that.944 & 928 HAVE THE SAME COATING.

[SCadaddle]

Probably every 944, 928 and some BMW's (such as the one in the video linked above) used an Alusil liner and the piston rings are readily available. No argument that some 911 engines used KS Alusil cylinders and some used Mahle Nikasil cylinders.

Somebody show me a source, a readily available source, for a set of piston rings for a KS Alusil 911 setup, because I can't imagine that IF there was one, the idea and procedure for Nikasil plating a 911 KS Alusil cylinder would even be a consideration much less a reality.

[Henry Schmidt]

The issues with matching/mismatching Alusil and Nikasil components is just that....mismatching.
The cylinders are designed/manufactured to size and the pistons are designed with the correct tolerance for expansion.
Due to the high silicon content of the aluminum in Alusil, Alusil and Nikasil cylinders expand at different rates. You also have different expansion rated on the pistons. Most Alusil pistons are cast (low expansion) and almost all Nikasil pistons a forged.
And then you have to deal with the iron coating on the Alusil pistons. Nikasil is not happy with the iron contact.