Honing Nikasil cylinder liners?

[75Carrera]

I'm hearing conflicts amongst our experienced Pelicans about the wisdom and/or ability to hone marred nikasil liners. First question: Can they be safely honed at all? Second question: Once honed are they reliable? Anyone have any pictures? Before and after pictures?

[Gunter]

Yes, they can be safely honed IMHO but it depends on how deep the marring is.

http://forums.pelicanparts.com/search.php?searchid=2531159

I recommend that the cylinders be checked by a shop first to see if they are within specs,
An experienced shop like EBS can mike them and tell you what needs to be done re: honing.
Two sets of my Mahle cylinders needed only a light grape-hone and the rings seated nicely after.
Meaning: The original crosshatching was still visible and we used a very light grape-hone.
Why not post some pictures to show how marred your cylinders are?
Do they have the groove on top for the gaskets?
What do you mean by liners?
Where the cylinders bored and re-lined at some point?

[Rot 911]

The silica based grape "hone" really just scuffs the cylinders. The 3 arm hones are not recommended on nikasil because they cut too deep into the nikasil.

[Nine9six]

Originally Posted by Kurt V

The silica based grape "hone" really just scuffs the cylinders. The 3 arm hones are not recommended on nikasil because they cut too deep into the nikasil.

All honing removes material...Its simply a matter of how much, depending on the desired results...Cross hatching v removing material v rectifing out of round conditions. I am sure nikasil has a minimum thickness, prior to requiring replating.

[kodioneill]

i honed mine with a ball hone as mentioned in this thread. it works just fine. use some oil and give them a light crosshatch. it only takes 5 or 6 plunges with the hone.

[75Carrera]

My understanding is that the nikasil liners are all but bullet proof and should never need honing. Once cleaned up a light scuffing is all these liners need. Hard to see why Porsche would have ever used anything else. I don't know too much about re-plating but with new pistons and rings and whatever misc would be required I'm thinking 2.5K plus? Just parts...

[Steve@Rennsport]

Originally Posted by 75Carrera

My understanding is that the nikasil liners are all but bullet proof and should never need honing. Once cleaned up a light scuffing is all these liners need.

Spot on.

Nikasil cylinders should never be honed unless being fitted for custom pistons. In that situation, special diamond hones are required as is special machinery to do this correctly.

Nikasil cylinders that will be put back in service simply need to be cleaned up using a (red) Scotchbrite pad, followed by VERY thorough cleaning with hot soapy water and brushes.

If the cylinders are scratched or damaged enough to need honing, they should be replaced.

[Bobboloo]

As Steve says Nikasil can only be honed with diamond hones by a machine that can apply enough pressure. Grape hones aren't adequate to actually hone Nikasil.

In the case of Nikasil "honing" is the wrong term for prepping used cylinders. De-glazing is more correct. They can be de-glazed with a red Scotchbrite or an aluminum-oxide grape hone (de-glazer). Aluminum oxide is soft enough that it won't harm the Nikasil.

Silicon Carbide grape hones will mar the Nikasil cross hatches and possibly make the cylinder even less likely to seat the rings.

[Steve@Rennsport]

Originally Posted by Bobboloo

As Steve says Nikasil can only be honed with diamond hones by a machine that can apply enough pressure. Grape hones aren't adequate to actually hone Nikasil.

In the case of Nikasil "honing" is the wrong term for prepping used cylinders. De-glazing is more correct. They can be de-glazed with a red Scotchbrite or an aluminum-oxide grape hone (de-glazer). Aluminum oxide is soft enough that it won't harm the Nikasil.

Silicon Carbide grape hones will mar the Nikasil cross hatches and possibly make the cylinder even less likely to seat the rings.

Hi Bobby,

Great clarification,....thank you, Sir

Grape hones can and do ruin Nikasil cylinders rendering them unable to effect good ring sealing. We see that in poor leakdown figures, even after seating the rings on the engine dyno.

[Gunter]

Great stuff; good clarification.
So, Red Scotchbrite for de-glazing leaving the crosshatching intact seems to be it.
Or an aluminum-oxide grape hone (de-glazer).

On both my Mahle sets, the crosshatching was still very visible after ~160K and a very light application of ball-honing (de-glazing) seems to have done it.

[75Carrera]

Originally Posted by Steve@Rennsport

Spot on.

Nikasil cylinders should never be honed unless being fitted for custom pistons. In that situation, special diamond hones are required as is special machinery to do this correctly.

Nikasil cylinders that will be put back in service simply need to be cleaned up using a (red) Scotchbrite pad, followed by VERY thorough cleaning with hot soapy water and brushes.

If the cylinders are scratched or damaged enough to need honing, they should be replaced.

One has to wonder how many Porsche motors are out there after being incorrectly prepared. I suppose the easy answer would be to ask the "experts" over at Motor-Meister.... LOL
Thanks to all for some great information.