atb

Hello all,

I'm gathering info on cylinder coatings for the 928 block so I can run domestic pistons in my stroker project. I've come to the conclusion that obtaining a set of 968 pistons probably isn't going to happen in my lifetime, and that something needs to be done to find alternatives to running Porsche pistons. I know some of you (John K.) have recently had coating work done. I'd like to hear from you regarding the coating used, why you chose it, co$t, and who did the coating and machine work on the block, and what kind of pistons you used.

I'm currently in contact with U.S. Chrome for the Nicom coating. They've respondend via email that they've coated "several" 928 blocks. Any of you guys out there?

My plan is to have JE (not Eifert) make a set of 60 over SBC pistons with basically a 968 crown, compression height, and skirt length. My thinking is that since it will be an SBC slug, it should reduce cost. At 60 over the small block chevy piston is 103.XXX mm, just a little shy of the 104mm 968 piston, which should give me a little extra insurance in cylinder wall thickness. Also, in using the SBC piston, I won't have to hog out the SBC rods that hang on the 928 Int'l/Scat stroker crank in order to fit the mondo Porsche wrist pin.


Yes, in a perfect world I would run the 968 pistons to 100K trouble-free stroker miles, but times are a-changin' and if the coated cylinder works out it will be better for all. If it doesn't, well I'll have just built the most elegant hand gernade in history.

Wish me luck.

John..

Adam,

Short of sleeving (read band-aid), the only viable option is to go with a Nikasil coating. I chose Millennium after looking at Millennium and US Chrome. They both do great work, but Millennium offered a lifetime warranty and was about $180.00 less. US Chrome only offered a 1 year warranty.

As for the pistons....I would have a custom set made. JE does EXCELLENT work and made the pistons in my car. We used a 911 ring set from a 95 mm bore 911 and used the wire locks, not the JE spiral locks as would be found on their production stuff.

As for costs:

$20.00 to build my crate
$100 to ship to Wisconsin
$800 to Nikasil
$150 to ship back to KY
$1200 for Pistons, wristpins, circlips and ring packs (Goetze rings made for Nikasil)
$250 to balance the assembly and polish the crankshaft
A *hitload of time...evenings and weekends
One somewhat angry Fiance

My car runs between 0.0023 and 0.0025" of wall clearance. Stock is about 0.0016". JE recommended a minimum of 0.002" and we added a tad because of Turbocharging.

I have lots of pics if you want some just e-mail me.

Check with Mark Anderson on the US Chrome block. I talked with someone up there in Wisconsin about thier work...word back was the Nikasil was beautiful but the clean-up was poor. This was on a 928 stroker motor...400 CID if I remember correctly. I can't say mine was perfect, because it wasn't but they did a very good job overall. I'd rate the job at a 8.5 to 9.0 on a scale of 1 to 10.

1200 miles thus far and it runs great. Bimmer had serious issues with Nikasil, but I have to ask myself why then is Porsche still using it on 996 TT, GT2, GT3 and Carrera GT? It is also still in wide use with motorcycles, aircraft cylinders and industrial engines. I just hope mine holds together for a long time.

BC

I still don't understand why you are always saying sleeving is a band -aid John. Its just simply not.

When someone wants more than 104mm, what the hell should they do? And even 104mm with the resultant wall thickness is not good with boosting. Go buy another car? There are more options for the person that is not directly pinned to what is purported on the internet.

You can either make sure the sleeve doesn't move with a "lip" over the original bore top (machined down), or even experiment with replacing the whole tower with a sleeve of ANY BORE, and make sure you grout the bottom of the block and secure the top.

Its not just about bore. Its about piston and rod choices, and the prices resulting from them.

And why can't someone just use the normal bore surface, make sure the correct material is used in the rings, and then "coat" the piston with a low-friction coating from places like www.swaintech.com or www.performancecoatings.com ? The only issue with "other" pistons is that they will not work with the original bore surface. Galling and scuffing occures. Well, with a coating it won't, at least until the coating wears off.

Don't like Coatings? Thats what USchrom and Millenium do. Coatings.

Fastest928

We developed a coating that works...and have coated over 6-7 engines worth of pistons....BUT, we had one piston that allegedly failed. It may have been due to fuel washdown from poor tuning on the owners part, or actual coating failure...no one knows

I have lost track of the engines, except for three...and they are running fine.

Lucky has a US chrome coated block but is hesitant to use it due to sulpher laden fuels...eventually he will build it up. Lets keep our fingers crossed for John.

We have a SC engine in the shop now that has mystery parts inside...lets see how it holds up.

Build it and they will come!!

Regards,
Marc

atb

Brendan C. wrote:

Personally, I'd rather take my chances on proven ring and piston material that works with a particular coating. Then the only "what if" is if the coating will stay adhered to the alusil surface.

I haven't heard of anyone having luck with coated pistons, other than what Marc has mentioned above.

I'd be interested in hearing if anyone has gone this route, but not likely to walk point on that one.

BC

Absolutley Adam. But what about when you want more bore? And then wish to run boost?

atb

Dang Brendan, you get your crystal ball back from the polishers already?

John..

If I was building a weekend only, warm weather race motor, then sleeving would be fine. Ask around about sleeving and you will hear the same concerns I mentioned. Also, it was about $1,000 more. Live where it gets really cold....smells like problems to me. How about the larger wall clearances you have to run? The fact that you have two different metals, neither in intimate contact with the other? So, higher wall clearances AND less heat transfer! Millennium also does sleeving....the Engineer there told me that is like going backwards in technology.

I know, based on what I did, I made the best chioce...

The Nikasil is a plating, which is very different than a coating. The bond strength on the Nikasil approches the strength of the base metal in most cases. These mystery polymer coatings are still in question. I made my chioce based on cost and the history of the Nikasil. Phil Threshie had a coating to be used with a Wiseco piston but he had no engines finished with it. Nobody had a good enough answer on coated pistons running on Alusil....other than factory pistons. I wasn't about to hang my hat on "it should work".

Yes, I paid my money and took my chances but I believe the route I took was the least risky of the others. Don't know about where you live, but I don't know of a machine shop here I would feel comfortable with doing that kind of work on a 928 block. I was ready to send my block to California to be sleeved, when the machinst there (who came highly recommended for sleeving blocks) told me he would not mess with sleeving and would go straight to Nikasil. That told me something right there.

Also, Porsche has employed this technology for 30+ years in the 911 and it is still employed in the new $400,000+ Carrera GT V-10. Those manufacturers still using cast iron sleeves cast them into the block for better heat transfer and a mechanical lock.

Why does one need 104 mm if you are going to run boost anyway? Just drop the extra money on a bigger compressor, charge air cooler and turn up the dial. That extra displacement isn't anything a few lbs of boost won't easily match.

I chose not to experiment....I simply didn't want to spend the time to re-re-build my engine after finding out something unproven failed.

Brendan,

Build a sleeved 928 engine like you mentioned above and tell us the results. Until then, don't act like you are the authority on Alusil blocks. My car is on the road and running with excellent results. I can open my big mouth because I can stand by my results.

atb

John K wrote:

Because we can?

I'm probably going to try one of the coating processes, someone's got to do it. John, you've got the Nikasil covered, and Sterling has the sleeves. I know both of you are fully confident in your choices, but I still think that in some respects you have taken some risk. By the same token, I'm willing to take a "risk" with a coating process. If it melts down, I guess I could always go to sleeves.

Fastest928

Adam,
Good luck with the piston coating....the coatings we used were developed specifically for one type of piston material...which is no longer being produced in any quantities. It matched perfectly with the Kolbenschmidt and Mahle materials used in their forged pistons. The coating was unique and worked very well...except for one bore/piston.

We have a engine in the shop built that uses a plasma/moly piston in the 390 bore.....I have sampled the oil and the result is still confidential.

For longevity, there is no technolgy that will match the low friction and longevity of the native technolgy. hopefully, some folks efforts will result in getting "close enough" so that we can all benefit from their R&D.

Good luck,
Marc

Jim bailey - 928 International

Marc..."hopefully, some folks efforts will result in getting "close enough" so that we can all benefit from their R&D. " That is an interesting point particularly in light of the prior comments you made Marc......."I have sampled the oil and the result is still confidential. " ..."The coating was unique and worked very well..." Those comments , in my opinion , do not seem to " share " much information . I also find the "..Good luck, " to be somewhat demeaning and condescending as it implies that luck rather than research , knowledge , information , skills would determine the success of such a venture .

Bernie

Ouch!

bcdavis

I just hear a lot of black magic juju when it comes to strokers, 928 engines, pistons, and superchargers. Mystery coatings, tales of destroyed engines under boost, etc...

It seems like it could, and should, be common shared knowledge about what cranks work, where to get them, what rods and pistons will fit, and it they are strong enough. Shared information on coatings should also be encouraged. There seems to be a lot more sharing of info, when it comes to superchargers, because it has been a privateer, grassroots effort. I don't see Huntley, or F.A.S.T. sharing their ideas and knowledge, because they want to sell their kits. Same thing for the Devek stroker kits and pistons. They put a lot of time and R&D into their products, and they do not want to lose business.

Fastest928

Hmm....Lets try to be objective on this front.

1 We develop products for 928. We spend money on internal and external engineering services, subject matter experts, protptypes, testing, more testing and then marketing and selling.

2

BC

John I never acted like I was an authority on the OEM block surface. I nenver acted like I was an authority on the surface you chose.

What I am acting like a person that does not understand the "inherent" issues with sleeving. The internet is like a game of telephone. The first guy could have said "boy, I sleeved my block for more bore and now the car really moves". and the last guy at the end heard:
"Tomboy was bored, so he sleeved his block and they moved"

I just wish everyone would remember that we are all sitting there on the tip of the iceberg chatting on our computers when the rest of the 928 owners in the worls are on the remaining 90% of the block of ice. We can't hear them, and they can't hear us.