Pelican Parts Forums - Worn out Nikasil, Replace all?

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Worn out Nikasil, Replace all?

Doing a rebuild on a 2.7 CIS and have one cylinder that has worn through the coating in one spot at the top of the ring travel. All of the other cylinders look fine and should take a hone. The pistons all need replaced as the top ring grooves are way out of spec. The app is a stock reliable rebuild.

My first thought is to find one good serviceable Niki and replace the pistons with new JE's. My question is are the rest of the cylinders ready to cut through the plating making this a limited life rebuild? That is not my intent.

Arent there places that can re make the nikasil surface? Seems like that would be good insurance. If one went through, ate you wondering how strong and thick the others are? I really think nikies are the coolest thing since whatever, but the cost!

I would NOT hone a Nikasil cylinder unless you need piston-to-cylinder wall clearance. If the bores are worn, you can send them to US Chrome in Wisconsin for replating.

You should have your new pistons on hand before doing this as they will need one to complete the finish honing.

Yes, that's exactly my concern. I don't want to get 20k more on this car to find out that another bore has worn through. That being said I'm not fond of spending 3k for a new set either if these will be fine. The bore gauge says they are in spec, but the one that is cut through is also in spec so…. ?

You could also just send the cylinders to EBS Racing for replating and buy a set of Pistons from them to be fitted.

Do you guys have a approximate price that they charge to plate and hone to fit a set of 6 cyls? I've looked at a couple of sites that do this including US which I've seen bad reports on, and the charge I see is somewhere between $200-300 each. At the higher price, with a set of new pistons, it is approaching the price for a set of new pistons and cylinders. EBS doesn't have pricing on this that I could find on their site.

I'm not trying to go cheap on this motor, but cost IS a factor. I think I know the answer but what is the deal on the QSC sets? Is this cheap off-shore stuff or is it just fine in a summer cruiser?

Otif has a set of Ps and Cs for $300.00. A couple of busted fins but . . .

SoyRacer, thanks, I believe those are an Alusil Kolbenschmidt set. Wouldn't want to put those in this build used.

I have a good set of 2.7 Mahle Nikasil pistons and cylinders. PM me if you are interested in purchasing them.

Quote:

Originally Posted by whisperer (Post 8702612)

You can contact Troy at EBS
DIRECT LINE 775 825 7729
E-mail: troy@ebsracing.com

I was given a price of about $900 to bore and replate 6 cylinders for a 3.2 to 3.4 conversion.

Quote:

Originally Posted by whisperer (Post 8702612)

Actual costs:
In 2012 EBS replate and bore 6 cylinders 3.6 to 3.8L = $ 894
JE Pistons and Goetze rings = $940

EBS staff are very helpful = satisfied customer.
Regards,
PS: 46 hours on race engine = still going strong

http://forums.pelicanparts.com/uploa...1436497566.jpg

I am rebuilding my 2.7 cis motor right now and I asked my machinist and some other Porsche motor heads and they did not recommend JE pistons on a stock rebuild. They said the motor won't last long. I have used JE's in water cooled racing applications and they are great, but you freshen up the motor often. I purchased new nikasil p/s's for longevity. I still have my old nikasil cylinders that may be O.K. if you need one.

What do they recommend if not JE?

Quote:

Originally Posted by KTL (Post 8705806)

What do they recommend if not JE?

Mahle, naturally. :) :)

Good point. :).

I was wondering if we'd hear an endorsement for Wossner or Omega or Wiseco or CP or whatever! :D

Quote:

Originally Posted by KTL (Post 8706089)

Good point. :).

I was wondering if we'd hear an endorsement for Wossner or Omega or Wiseco or CP or whatever! :D

I've follwed the developement process of the JE piston since before they worked and can tell you in some instances they are a better choice than Malhe.
Wossner makes an exception product as well as CP. I have used them both with top results.
No experience with Omega and poor results with Wiseco. The Wiseco experience is dated so perhaps they have a usable product as well.
Back in the day, choices for air-cooled Porsche pistons was limited and Mahle was really the top choice but as the world progresses, other manufactures have improved their products and now offer top quality and sometimes better options for competitive prices.

Quote:

Originally Posted by KTL (Post 8706089)

Good point. :).

I was wondering if we'd hear an endorsement for Wossner or Omega or Wiseco or CP or whatever! :D

Wossner, Omega, et al, all (mainly) use 2618 for their pistons and designs very widely and some are better than others (nothing Wisco for me!).

IMHO, nothing lasts as long as Mahle pistons do so thats my first choice when longevity and durability are top priorities. Naturally, when one needs special compression ratios or configurations, JE, Wossner & CP are alternatives as long as one doesn't delude themselves into believing they will last as long.

We do have Mahle Motorsports make custom applications specifically for us, however those are contained to the bigger sizes; 100mm & larger.

So I wonder if we could talk a little more about the original subject of my post? How do the Niki's seem to fail? Do they progressively wear until they are worn through the plating, or do they cruise along not really wearing compared to the relatively soft rings and pistons, until they overheat, or what?

Quote:

Originally Posted by whisperer (Post 8706965)

There is no "magic" answer to your question. Nikasil is very durable. There are a couple of things to look for. Taper, surface anomalies, ovality and RA factor.
The taper on early cylinders will tell you wear. Nikasil is about .005" thick. If you measure more than .0015 to .002" taper look for a different set.
The surface anomalies is pretty self explanatory. Grooves, pits and hot spots are dealt with on a case to case basis.
Ovality is interesting. Although Malhe calls out a spec of around .004" that is really deceptive. In fact, meaningful ovality can only be measured under pressure. Use of a torque plate is the only way I know of to accurately measure ovality.
In talking directly to the techs at Mahle, they suggested that an out of round cylinder can be brought back by "pranging" them. That's right kids, strategically smacking them with a mallet.
RA factor is something I know quite a bit about. Early on, in an attempt to justify reusing cylinders, I did a study on piston/ ring and cylinder longevity and the effects of RA factor.

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

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 ]

Steve, if we just ignore the condescending nature of your "delusion" comment, what do you see as the major wear issues you've documented in your vast experience using after market pistons. As an engine builder, I need all the input that your experience can bring to the table.
How many engines have you built and tested using these ("inferior" my word not yours) pistons?

Henry, thank you for the in-depth info. That clinches it for me. My cylinders all mic out at .001 or less taper except the one that has worn through in a small spot at the top of the ring travel on the bottom (installed) of the cylinder. That one measures .0025 taper and .003(25) bore wear at the top where the wear spot is. I am measuring with a rolling bore gauge so the dial gauge measures reliably down to .0005 but I can read the span between marks to get an idea where the measurement falls between marks.

I'm assuming that this particular cylinder had a heat issue and caused the problem. There are no other anomalies with the other 5. I will replace this bad cylinder and of course a full set of pistons. The honing info is excellent info. I'm thinking I will hone lightly with 600 and then do a hand wipe with 1000 to get close to the RA with my equipment. I will be honing on my lathe.

I would caution you against relying on a 0.0005" resolution bore gauge in the cylinders to establish a size for your replacement JE pistons. I have been bitten by this and ended up with pistons that don't fit the cylinders- too much clearance. PLEASE use a 0.0001" resolution gauge and check your measurements again.

Realize on 2.7 Mahle also made Alucil cylinders and the piston casting numbers reflect alucil pistons.
Bruce

Kevin, are we on the same page here? My .0005 DI reads to 1/2 a thousand on the dial face and it is very easy to read "between" the indicated lines to judge where it is.

Bruce, Yes, Nikasil.

With JE pistons you want 0.0015" clearance and I don't believe 0.0005" resolution gives you the accuracy you need to get that clearance right. I used a 0.0005" Fowler dial to spec out set of pistons for a low mileage set of cyls. I sourced. Recently I measured the cyls again with a 0.0001" CDI dial (using the same 0.0001" micrometer) and my measured cylinder bore dimensions were drastically different. So now i have pistons that don't necessarily fit my cyls. I have too much clearance. Which is better than not enough, but still not good/acceptable.

I don't think it's advisable to read between the dial increments. That's what a higher resolution indicator is for. Plus, most 0.0005" indicators will have + or - 0.0005" accuracy- one increment. So if you're off one increment on the indicator? You're off by + or - 33% of your clearance spec. That's a lot.

Kevin, I'm with you on that, and for the most part agree, but I am checking the bore gauge with my mitutoyo 3-4" micrometer and it is matching perfectly for reading (on an even number) so I am not expecting a discrepancy in the reading. As for in between the lines, this particular DI has 1 line between the 1/2 thousands lines, so indicated is down to 1/4 thousands (visual) and I can definitely see where the needle falls between those lines. I agree, this particular gauge is a little strange like that. It is marked on the face as .0005 and has lines at 00025 in between the 0005 lines. My Starett 0005 DI does not have those lines but has a much smaller face.