nikasil cyl and getting rings to seat

Pat S · 08-23-2003, 01:49 PM

I haven't started my assembly yet but have a question on the nikasil cylinders. Normally honing cylinders gives a nice clean surface and gives the new rings something to "bite" on so they can wear in properly, right.
Since honing the nikasil cylinders is not reccomended, how do you prep them for breakin? How do you clean them? Or do you just not worry about it and wipe them down with alcohol then lightly coat with oil?

I plan to use Goetz rings from Pelican if it makes any difference.

Pat

Tim Walsh · Tim Walsh's Garage

I belive you use a ball hone on them. It doesn't cut up the nikasil like a regular hone and it cleans them up nice. I'm just a novice with all his info from books so hopefully someone will confirm this.

Wayne 962 · Wayne 962's Garage

You can use a special diamond hone to prep the surface of the cylinders. Make sure that you send them to a machine shop that does this frequently, as it's easy to mess up...

-Wayne

Pat S · 08-24-2003, 07:16 AM

So should they be honed then? Or only sometimes? If they aren't honed and are just cleaned will the Goetz rings still seat in correct?
If it helps the engine had good leakdown and is being rebuilt due to pulled studs.

Doug Zielke · 08-24-2003, 07:50 AM

A very good question. Hopefully John Walker or Steve Weiner will chime in on this one.

Steve@Rennsport · 08-24-2003, 05:09 PM

If the cylinders are glazed, they should be lightly honed so that the rings will seat.

The only way you can do this is with diamond hones, and we do this using a torque plate (to simulate the heads being bolted up) and with the cylinders bolted up into a case half. The keeps the bores round when they are at operating temperatures.

Pat S · 08-24-2003, 05:56 PM

Thanks Steve.
Not sure I'd know what glaze looks like though... How does this look? It were just cleaned with brake cleaner and cloth. I still have a bit of carbon to get off at the edge there but didn't want to scrub too hard.

http://mywebpages.comcast.net/patrick.snyder/cyl.jpg
http://mywebpages.comcast.net/patrick.snyder/cyl2.jpg

Pat

Doug Zielke · 08-24-2003, 06:31 PM

I don't know if this image will help you, but the *new* Mahle Nikasil's I used in my rebuild looked like this:

snowman · 08-24-2003, 09:09 PM

The silicone grape type ball hone is the one to use. It will NOT hurt your cylinders, and will insure a good cross hatch pattern for good oiling. This type of hone does NOT remove any material ( less than 0,0001") but puts the correct cross hatch pattern in place to insure proper seating of the rings.

Wayne 962 · Wayne 962's Garage

It's typically a good idea to send the pistons & cylinders to the machine shop to have them expertly evaluated...

-Wayne

Steve@Rennsport · 08-24-2003, 10:13 PM

Hi Pat:

Good job on cleaning things up!

I was unable to see the original crosshatch honing pattern in your pics since they were not quite sharp enough,....

As long as your cylinders' original crosshatch patterns can be clearly seen within the piston's travel, you will be fine. These rarely need honing. You can observe the Mahle factory finish by observing the cylinder below the BDC position. Its obvious to see where the pistons stop,.........

toolman · toolman's Garage

What can be done with the Alusil cylinders? Can you re-ring those and get them to seat the same way?

Doug Zielke · 08-28-2003, 08:01 PM

Quote:

Originally posted by toolman
What can be done with the Alusil cylinders? Can you re-ring those and get them to seat the same way?

Superman did, and his car runs strong as any. I know....I drove it!

Steve@Rennsport · 08-28-2003, 11:52 PM

Quote:

Originally posted by toolman
What can be done with the Alusil cylinders? Can you re-ring those and get them to seat the same way?

Hi:

Alusil cylinders cannot be honed at all. If they are scored or glazed, one simply replaces them.

Wayne 962 · Wayne 962's Garage

Steve's right - As I wrote in the book, Alusil can be re-ringed with mixed and unpredictable results. Sometimes they work, sometimes they don't - it's a gamble. Any good, professional shop typically won't install re-ringed Alusils and give a warranty at all. The best way is to get a set of new or re-plated Nikasil cylinders.

Note - you cannot mix and match Nikasil and Alusil *pistons* either. The rule of thumb is that the Nikasil is a hard cylinder wall and a soft piston. The Alusil pistons are harder and are used with the softer Alusil cylinders.

One important caveat - I do believe that you can effectively take an Alusil cylinder and have it replated with Nikasil (basically using the Alusils as cores). I'm 98% sure this is possible (off the top of my head).

-Wayne

Pat S · 08-29-2003, 04:26 AM

Just to update all, I've decided to do the right thing with my Nikasils and have shipped my pistons/cylinders off to EBS Racing for a good inspection. Hopefully I can get away with reusing them.
Pat

911pcars · 08-29-2003, 01:07 PM

A slight correction. During manufacture, Alusil cylinders are etched to reveal silicon as the main wearing surface, thus this surface is very hard. Alusil pistons are aluminum, usually cast and relatively soft. To avoid excessive wear, Alusil pistons are iron-coated to provide a buffer against the silicon. As Wayne suggests, Nikasil and Alusil pistons and cylinders are not interchangeable.

Sherwood Lee
http://members.rennlist.org/911pcars

Wayne 962 · Wayne 962's Garage

Yes, both surfaces are indeed 'hard' but the Nikasil is much harder than the Alusil...

-Wayne