Pelican Parts Forums - Deglazing Nikasils

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Deglazing Nikasils - my method

Busy 911 week for sure. After searching the Forum and reading up on the best way to deglaze Nikasils, I bought a pack of red Scotchbrite pads. I wanted to ensure there was even pressure and action on all areas of the cylinder so I wasn't big on the hand method. My bright idea was cutting the pads in long strips and stapling them to my conventional 3 arm hone. Using a variable speed cordless drill, some dish soap and a bit of water I went to work. It was not super fast but boy did it ever do a nice job. Now I better get that sink cleaned up! http://forums.pelicanparts.com/uploa...1389290783.jpg
http://forums.pelicanparts.com/uploa...1389290819.jpg

Let's see finished product.

At moment, I can't get the macro function working on my camera so the clarity is not good enough. I'll post one once I sort it out.

Dave

I'm surprised nobody's tried an aluminum oxide flex hone like this with some honing oil

2014 Goodson Catalog

Reason I say i'm surprised is because the red scotchbrite pads are aluminum oxide. I know the grape hone has been debated before and given a big thumbs down. But the dreaded grape hone in aluminum oxide is going to be basically the same "roughness" as the scotchbrite and it would be well lubricated with the honing oil

Just a personal experience here, be careful what you use. I read mixed revoews on deglazing nikasil cylinder. I used red sb pads by hand and did not feel they worked well. I found a local engine builder with a good reputation and spoke with them. They said they had plenty of experience with nikasil coated cylinders, not to worry. When I got them back they looked great, except for the spots of porosity which were now showing. Only one cylinder was concerning. Ended up recoating all of them.

Quote:

Originally Posted by KTL (Post 7848275)

that grape hone looks perfect. I couldn't find anything like that when I did mine. here's what I did, but I'm running low on sandpaper.

http://forums.pelicanparts.com/911-engine-rebuilding-forum/448165-de-glazing-nicasil-cylinders-new-approach.html

The ball/Flex hones come in different grits just like sand paper... too rough and you'll do more damage by scratching through and shredding the surface.

Here inethe lieth a problem..................
Some of the real experts that have been here for years and years get tired of re writing old post.
Most of us hate to look in the search machine (never seem to work well )
But, much has been said by real experts as far as honing a niky cylinders.
In most cases you will do more harm then good.
Last i knew warm soapy water and a little scotch brite by hand was they key.On top of that the color was important too,,,- green or red, cant remember

Red with HOT soapy water is the current method I use. But i'm just doing it for a cleaning purpose. I'm not actually hoping to cut any material from a clearance perspective. Each time i've cleaned a set of cyls, i've followed that with bore gauge measurements and they check out OK, both in terms of cyl dimensions (ovality & taper) and clearance with the pistons going in them.

If I were to hone the cyls with that Goodson hone, I would make only a few passes just to clean them up. If I needed anything truly honed to size, i'd send them out to someone who really knows what they're doing with Nikasil like US Chrome, Millenium, etc.

Farking up a set of cyls gets expensive when you have to strip & replate them all. I had one done by USC a few years back (cyls had previously been bored to 98mm & one had a sizeable chip coming off at the top) and it was $167 with my business/jobber pricing. $1000 is not something I want to spend after experimenting with the Goodson hone & oil. :D

Millenium replated mine. $1200. One cylinder had more porosity showing after replate so had to buy another cylinder $150. Then had to have that cylinder bored to correct size to match the bad one and then have the cylinder replated $200. Now $1550 in for a set of cylinders that probably would have been fine if I hadnt taken them to a shop that assured me they could deglaze them. It was not a Porsche shop btw.

If the intent is to deglaze rather than recondition, red ScottBrite and hot water and soap is the technique we've used for years.
A few years ago we did some research on bottle brush hones specifically designed for Nikasil and the test results showed an RA factor far too high to ensure long ring life.
I've been told that there are some new hones available but the specifications of the"new" hones seem remarkably similar to the old hones offered for years.

The bottle brush hones we tested showed extremely high wear in race engines that were built every 50 hrs or so. As much as .040 gap increase between rebuilds.

Henry
Most the "new Guys " are not going to know What RA is .
I have discovered us older guys have to revamp our nomenclatures
PS
You new guys welcome here, but dont reinvent the wheel,
and
Henry is in the center of the mark. Well worth paying atn to!

Ill ask for everyone, what is RA?

Google "rock well hardness"
Its a way of measuring what the material is worth that you are working with

Ah. For some reason I read his post as the test had been done to the cylinders, not the hone material. RA makes sense now.

From an old thread

http://forums.pelicanparts.com/911-engine-rebuilding-forum/163663-do-i-need-hone-2.html#post1334035

Quote:

Originally Posted by Henry Schmidt (Post 1334035)

Some of the statements in this post got my interest peaked. The statements totally contradict what I’ve seen with my own eyes. Now what? I talked to a friend of mine, John Edwards, the owner of Costa Mesa R&D and the author of SUNNEN’S COMPLETE CYLINDER HEAD AND ENGINE REBUILDING HANDBOOK and we did some testing and here’s what we found.
We used a Mitutoyo SJ – 201 Profilometer to test the smoothness of our test cylinders.
We had one new Nikasil cylinder; one unmolested Nicasil cylinder w/ 104,000 miles and one used Nikasil cylinder sacrificed for this test.
The used cylinder was lightly honed with a 320-grit hone bottle bush hone specified for use with Nikasil.
Unmolested cylinder was cleaned, as was the new cylinder.
The test.
The unmolested cylinder measured 3.0 RA, the new cylinder measured 4.9 RA, and the lightly honed cylinder measured 10.5.
10.5 is way too rough!! Because the rings are soft they will ware out before the cylinder gets smooth. In other applications the crosshatch marks will smooth with ware, and the rings will seat.
Mahle says in their literature that the honed surface of their Nikasil cylinders should be 4.2 to 6.0. Our test proves that they start that smooth.
I have read in some literature that cast iron rings as used in Nicasil cylinder want an RA surface of 18-25.
I guess that works for Fords and Chevys but we’re talking about Porsches here and as much as I love Nascar I will not use Nascar specs to build my Porsche engines. It seems that short-lived engines in motor cycles might benefit from this information.
I read through this thread and one thing seems perfectly clear. People will believe what they want, as they should.
One thing that is true: “The truth is not dependent on your belief”. In other words “it’s true, weather you believe it or not”.
An ostrich can’t see the true because is head is buried in the sand, time to pull your head out. Porsches are not like other cars, and neither are their engines. Look at the pictures and see for yourself.

Here is some information about grit and RA specs.
http://www.babcox.com/editorial/ar/eb110242.htm
If you’re switching from conventional stones to diamond, you’ll generally have to use higher grit to achieve the same Ra (roughness average) when finishing a cylinder. For example, if you have been using #220 grit conventional stones to finish cylinders for chrome rings; the equivalent diamond stones might be a #325 grit. If you have been using #280 grit conventional stones to hone for moly rings; the diamond equivalent might be #550 grit stones. The actual numbers will vary somewhat depending on the brand and grade of the stones.

A cylinder bore must have a certain amount of cross hatch and valley depth to retain oil. However, it must also provide a relatively flat surface area to support the piston rings. Ring manufacturers typically specify a surface finish of at least 28 to 35 Ra for chrome rings, and 16 to 25 Ra for moly faced rings. These numbers can be easily obtained with diamond stones and brushing, say those who use this honing technique.

One rebuilder we spoke to says he uses #325 grit diamond stones to end up with an Ra finish in the 20 to 25 range, which he feels is about right for moly rings. For some applications, though, he uses a #500 grit diamond to achieve a smoother finish in the 15 to 20 Ra range.
http://forums.pelicanparts.com/uploa...1085762130.jpg http://forums.pelicanparts.com/uploa...1085762141.jpg http://forums.pelicanparts.com/uploa...1085762157.jpg http://forums.pelicanparts.com/uploa...1085762172.jpg http://forums.pelicanparts.com/uploa...1085762194.jpg http://forums.pelicanparts.com/uploa...1085762209.jpg
http://forums.pelicanparts.com/uploa...1085764857.jpg ]

So the tests ng was done to the cylinders and the Ra is not related to rockwell hardness.

The Ra reading on the gauge John is holding in those pictures is giving a measure of surface roughness. Check out John's videos on youtube username "fiatnutz" to get some insight on what he does. The guy lives and breathes automotive service and development.