Pelican Parts Forums - do I need to hone this?

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Steve,
The recommendations for the alusil from Sunnin and the manufacturers was to use the stiff felt pads with the AD-30 silica paste to get the finish you desire on the bores. I had a shop do this for me and would immagine that the nikasil would react the same way. Not 100%, though.

One hundred and fifty miles is not enough to seat in rings.
When considering that you put new rings (round) in a used (possibly out of round cylinder) I would guess that it would take 500-1000 miles for complete seating.

As the engine builder it is always your call but in this case I believe that your test model is lacking in sufficient longevity for any accurate conclusion.

I would use oil consumption measurements and visible smoke
to determine how well the rings are seating.

Remember that most honing processes will not make out of round cylinders round again.

Interesting read.......

Henry and others,

I read this whole thread and found it quite interesting. I'm getting ready to re-build a 3.0L using the factory Mahle 9:3.1 pistons Nikasil cylinders.

BRM makes Flex-Hones in 600 and 800 grit and according to their information a 800 grit hone will achieve a Ra finish range between 3-10 and the 600 the Ra is 8-12. Henry found that the 320 Grit hone ends up at a 10.5 finish because the Nikasil is so hard but still way too rough compared to the new finish of Ra 4.9. BRM lists the Ra finish for a 320 grit hone to be 18-30.

Here is my logic because the Nikasil is so hard I'm thinking a light hone with a 600 grit should get everything clean/deglazed and ready to accept the new Goetz rings.

If the 320 grit Ra was 10.5 and BRM lists the Ra of the 600 grit to be 8-12 cutting each in half due to Nikasil being so hard it should be right in the ballpark.

Here is a link to BRM's specs:

Flexhone for Cylinders - Instantly improve Ra and surface finish!

Thoughts?

Henry,

After reading all your post it seems like using scotch brite pads is the safe way to go. I dropped of my case parts to a reputable Porsche mechanic but my feeling is he is the great trouble shooter and repair mechanic but doesn't have the experience on rebuilds. I asked him about honing the cylinders and he was quick to make the fix. But when I asked him about replacing the piston squirter's he had no idea. I'm nervous to allow him to deglaze the cylinders due to lack of knowledge. I feel that I should just let him perform a bore gage readings and I should go ahead and use scotch bright till there is a dull look. I also asked him to rebuild my case and he straight out told me he wasn't to comfortable doing it. Would that be your course of action scotch bright and be done with it?

Andy

The Key to success (ring seating) and longevity is RA factor. Too smooth and the rings won't seat too rough and the rings wear out prematurely.
If a company offers a product that will produce the correct RA factor it seems reasonable to try it.
If SccotBrite will produce the correct RA factor then use that.
It really is a judgement call as to the condition of your cylinders.
Cheers

clearing the waters with grape hones with non-nikasil liners

I can speak with direct experience with grape hones and ring wear on iron liners. I just pulled apart a Ferrari engine which I rebuilt last spring with high compression pistons and Ferrari's older racing spec camshaft (P6 grind). This engine had over 3000 very hard miles as the engine was used for a good amount of rallye work. The engine is being pulled apart at the owners request for a stroker crankshaft to be installed.

Regarding the rings I used last spring: I used what came with the Wiseco pistons which were a 1.5mm coated steel top ring made by NPR which is the OEM supplier for many Asian brands followed by a tradional ductile iron second ring. I honed the liners with a torque plate (must be done with these engines) with a grape hone of the finest grit available which I believe was 320 grit and using 30 weight non-detergent oil as the cutting lubricant. I made 5 passes in a clockwise direction of rotation and two anti-clockwise. The rings were gapped to .014 for this 3.12 bore and the rings seated quickly. I used a grape hone for the simple reason that they remove less material than a Sunnen type hone and the owner already had a set of standard size pistons he requested I use. To make matters worse the piston to wall clearance prior to honing was already .003 meaning I didn't have maybe .0005 to work with in getting it right regardless as aything over .0035 clearance is just not ok in these engines. In all, the grape hone removed less than .0005 as opposed to a traditional hone which usually removes between .0005-.001 but does indeed do a better job.

Upon dismantling the motor I measured the rings for wear in the bore, and in short there was little to none. The gap in all of the rings was no more than .015 and the bottom end of the engine sealed well.

In a pinch, they work ok and I experienced zero out of the ordinary wear issues with these particular non-nikasil iron liner cylinders I work with. In a perfect world, use a traditional hone like a C10 and then follow up with a plateau finish for a moly top ring.

Another thought process on Ra levels has to do with ring tension. Lately with good brands top, second, and oil rings have very little tension which makes them somewhat more of a challenge to seat at times but also have less dependency on Ra levels. Total Seal came out with their 'Quick Seat' product for this specific reason.

Henry, I'm confused as to how you get rings to seat with an Ra below 10? With chrome top rings, it is just not possible or at least very difficult. With moly rings it's probably possible but I would be concerned with the liners abilities to hold oil with it being that smooth. Apparently it's not an issue with Porsche engines but with Cup motors and Ferrari engines the Ra absolutely must be above 10 for the rings to seat. The grape hone did not bring it up to its advertised amount which they listed to be 18, but IIRC it was less than 12.

Quote:

Originally Posted by lvporschepilot (Post 6501227)

A cast iron bore will plateau very quickly while a Nikasil will plateau very little or not at all. The Finish has to be close to opperating finish or ring and skirt damage will occur.

As a result, Chrome rings are not compatable with Nikasil cylinders. You can use ductile iron and special moly rings.

This thread changed the shape of my head.

"The mind, once expanded to the dimensions of larger ideas, never returns to its original size."
Oliver Wendell Holmes

Quote:

Originally Posted by porterdog (Post 6502776)

This thread changed the shape of my head.

"The mind, once expanded to the dimensions of larger ideas, never returns to its original size."
Oliver Wendell Holmes

Yes, given the variables mentioned, it's a miracle any combination of piston, ring set and cylinder will work for long - then there is the break in method and oil used.

Quote:

Originally Posted by BURN-BROS (Post 6501863)

Sounds like it's safe to say that Nikasil Ra should be close to a 'run-in' Ra as once Nikasil is honed it retains the hone pattern for a substantially longer period than iron. Where with iron a slightly higher Ra can be used to begin with as the material inherently 'breaks in' and smooths out for the simple reason that iron is softer than Nikasil.

You still need a little bite. If you do not prep a used nikasil cylinder you will most likely have ring seat issues.

We have pulled 100,000 + mile Nikasil cylinders and can see the hone pattern quite nicely.

Quote:

Originally Posted by BURN-BROS (Post 6504578)

I don't do too many 308 QV, 328, or TR engines so I can't really comment much on Nikasil wear patterns, but the top end work I have done always shows a very robust cylinder liner with almost no wear when checking leak. The bottom ends very rarely need to come apart. The earlier 308s and V12s with iron liners all have to be bored and all have leakage now and need to come apart. Thankfully with modern light tension rings and modern materials iron liners last substantially longer than ever before but are still nothing compared to Nikasil.

I definitely hand it to Porsche for their crank and bottom end engineering as they are remarkably robust. Those head studs that make me crazy though

Quote:

Originally Posted by lvporschepilot (Post 6504538)

Correctamundo :)

Quote:

Originally Posted by Henry Schmidt (Post 6504616)

Correctamundo :)

Good stuff Henry.

Probably not the best pic in the world, but the hone angles can be seen. Also, finish is just the brand of 'dull' I prefer with vanilla iron liners. These are from a recent project where liners were honed with a flexhone (Ra of 11-12ish).

http://forums.pelicanparts.com/uploa...1327067092.jpg

Quote:

Originally Posted by BURN-BROS (Post 6504578)

By prepping a used nikasil cylinder, are you referring to the previoiusly discussed scotchbrite + soapy water method, or something further?

here's how I did mine. homegrown but rings seated well and no issues 3 years and a lot of miles later.

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

Quote:

Originally Posted by haycait911 (Post 6509991)

The issue is not so much "ring seating" but ring seating vs ring wear.

As long as the RA factor and groove plateau is consistent with the surface being honed, all should be good.

Desired cross hatch or 30-40 degrees can be achieved by a hone speed of 500-800 rpm and a feed rate of about 120-180 inches per min. 45 seconds per/ cylinder seems to be about right.
http://forums.pelicanparts.com/uploa...1327259414.jpg

To reach this roughness, I recommend honing Nikasil cylinders.
• Conventional stones #280 -#320 grit or
• Diamond stones #550 grit

After honing with either the conventional or diamond stone, finish your honing by smoothing the surface with a fine grit conventional abrasive (#400 - #600 grit) or to sweep the bores with a flexible brush or a nylon bristle plateau honing tool. This is necessary to get rid of jagged peaks and folded or torn material.

http://forums.pelicanparts.com/uploa...1327259604.jpg

Important Note:
Be sure to confirm with your honing equipment manufacturer that the recommended stone grit will produce the following Rz and Ra roughness recommendations.

Seriously amazing wealth of information. Thank you.

Threads like these are what makes pp such a great place to be.

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 ]

Henry,

back in 2004 you were against the use of flex hones and recommended the use of red scotch brite to remove cylinder glaze. Now, fast forward 8 years and in your last post, it seems you recommend the use of flexhones. I guess you have you experienced something new in these last 8 years to make you change your mind?

I have come across this post a couple of times before and only today have I had the chance to read the whole thread.

At the outset of this thread, I was really bought into the scotch brite camp. I was relaying this to my limited experience in reciprocating compressors. In Recips, you have similar concerns on cylinder wall finish.

In recips, at least the ones I work on, the cylinders are non-lubed and use a ring and rider (similar to a ring) made of a type of teflon. The API specification for non-lubed 25" diameter iron cylinders is 16-24 microinches Ra.

So what lubricates the rings/ riders is the teflon material that wears (slightly) into the honed cross hatched surface. Once the machine runs a few hours, then the surface of the cylinder can come in at approximately 3 microinches Ra, as an example.

So how does this relate to Porsche cylinders? Just conjecture here, and maybe more of a question for anyone that knows better...

I believe that a similar process happens in the engines too.
1. you have a specified cylinder finish, 4.9 - 6.0 Ra
2. the lubricant is oil instead of being built into the ring material, but the oil goes into the cross hatching to lubricate
3. some small amount of ring material wears and gets deposited into the cross hatched surface along with hydrocarbons from fuel (spent & unspent) and oil

So #3 is what we call cylinder glaze, right?? And this is what we want to remove. A good solvent and scotch brite should be sufficient, I would think.