Are Nikasil cylinders supposed to be honed?

[billncolo]

Are you supposed to "hone" Nikasil cylinders when replacing the rings? I have heard everything from "you must", to "never", to "you can't because Nikasil is too hard"?

Bill Leonard

[cstreit]

I know Alusil you can't hone... Nikasil I think you can though.. (i'm working from heresay)

[zuffenhausen]

I've heard different opinions on this as well, but I found some information from some knowledgeable people that suggests that they probably don't need it, but if they do you must do it correctly. Conventional machine honing like would be applied to an iron cylinder is a no-no, although I've been guilty of running a ball hone in them by hand (made me feel better and certainly didn't hurt anything).

Geoff Slater in a post at finishing.com:

In normal use, it should be unnecessary to hone nikasil-type engine cylinders since the wear resistance and oil retention derives almost as much from the presence of the silicon carbide particles in the nickel matrix as from the original underlying honed surface finish. In Mr.Schaal's situation, it appears that there are marks on the bore which will need to be removed to avoid damaging new components during a re-build, and so honing will almost certainly be required. It is important that this be carried out using diamond honing tools of an appropriate grade, since the original surface finish can easily be "polished" by using conventional honing stones, and that may lead to a lack of adequate lubrication during the initial running of the engine.

If you decide to have them honed, check out shops that do motorcycle work. Lots of motorcycle cylinders are Nikasil and they'll certainly be familiar with how to hone them properly.

-zuff

[J P Stein]

The advice I got from my piston vendor.
Clean used cyls well.....thas' it.
No oil on pistons, cyls, or the rings......gulp ?
Light that puppy off....sweat blood.

I used non derergent oil. The rings pretty well seated in 100 mi.
I gained about another 5psi compression in the next 2000 (or so )
miles.

[speeder]

JP, How long did you leave the ND oil in it? TIA.

[Leland Pate]

Nikasil must be rebored then replated. You can't "hone" it.

EBS will do it for about $1000 I think. Fairly reasonable compared to buying a new set of P/Cs from Mahle.


"edit" this applies only if you're talking about clyinders that have worn out of spec.

[dhoward]

As a person who has had extensive experience with Nikasil plated cyliders, You CAN hone them using a ball hone, But usually I just cleaned them up with a scotchbrite pad. You are really just trying to de-glaze the bore. If they are out of spec, or the plating has flaked off, they can either be replated(if in spec), or bored and plated. U.S. Chrome does a great job.

[Superman]

I'll tell my story again. My Alusil cylinders (apparently the coating in Alusil cylinders is thinner than the coating in Nikasil cylinders) were well within spec but the rings were not, so I decided to use new rings. JW put the cylinders in his BFPW (large parts washer), and this procedure changed their appearance very much. It took every bit of glaze out of them, made them lighter in color and left a surface that I regarded as stone-like. Not rough, but it seemed more like smooth stone than metal.

I put a TINY TINY amount of motor oil on them during assembly. Really tiny amount. And I used ND oil for the first two oil changes. With a freshly rebuilt engine, there is certainly no need for any detergent properties in the oil. Two or three oil changes is not enough time to develop any sludge problem.

The rings seated immediately, and the engine developed more power slowly over the first couple of thousand miles. Runs like a scalded cat now.

No honing.

[dhoward]

I used to reassemble the jugs with just a touch of oil 'cause "it just don't seem right". But dry assembly is fine too. Nikasil is REALLY hard stuff to hurt in normal operation. I've seized pistons with nary a scratch, and again, just cleaned up the bore with a scotchbrite pad. Running a 320 grit silicon carbide ball hone in a hand drill up and down a few times will also clean it up if you're in a hurry. Remember, you're not trying to reproduce the crosshatch pattern like you would in a cast iron Cyl, just clean the crud.

[J P Stein]

Originally posted by speeder
JP, How long did you leave the ND oil in it? TIA.

About 100 miles.
A compression check showed about 150 psi soon after running the motor. This went to 165 psi after 100 mi. Now it's 175 psi.

I went to dino, 20-50 for 500 mi, then to Mobil 1, 15-50 (AIR).
My experience was much as Super described.
Of course, I wuz tuning on it and I'm sure that was a big help

[stormcrow]

when I did the rebuild on my 78 SC Targa, I was concerned about what to do with the cylinders - didn't want to harm them.

So, installed new rings did nothing to the cylinders and put the engine in. Would not start. Checked compression - 25 to 75.

Removed engine, disassembled and removed cylinders, used fine emory paper with oil to remove the glaze off the cylinders.

Reassembled the engine, installed, and Varoom - it started on the second try.

You need to treat the cylinders to remove the glaze otherwise your rings will not seat. What you don't want to do is damage them by over doing it.

I don't think you will hurt them if you do a light hand rub with fine emory paper and oil to remove the glaze. Do it in a circular motion around the inside of the cylinder and you should be good to go.

Steve

"A Porsche does more then just go fast in a straight line"