mutzman951

Hello all,
I have been away from R-list for some time. Having 2 boys in diapers is much more challenging than I ever anticipated.

My 89 2.8L had a little problem with a piston ring breaking and tearing the living heck outta my #4 cyl and piston.

I see that Vertex offers a re-sleeving service for about $1000. Has anyone used this service? Can anyone offer advice?

I realize I need 4 new pistons. I got the head off, and found the mess inside last November. I haven't had the time or $$ to tackle it. Now that the weather will be cooling off in Florida, I will have a limited amount of time to work on it.

The cyl is pretty torn up.

Also, I was wondering if I can have it sleeved 1mm over, and what the displacement would be?

Any and all input would be, as always, greatly appreciated!

Thanks guys and girls.

Doug

fast951

Sorry to hear about the engine trouble. No information with the sleeves from Vertex. I would contact Chris White, he's doing the MID sleeves for the 951.

mutzman951

oops!

I meant to say that 944online offers the resleeving service.

My apologies to Vertex.

George D

Why not have the block redone. www.uschrome.com. This way you will only need new rings and one piston.

Just an option.

George

rcatherton

George,

Give us the rundown. Is this nickel silicon carbide similar to the old 911 bores? How thick did you go and what was the cost? What rings and pistons could Doug or any of us use with this plating? Is there an advantage over the Alusil when there is no bore damage?

Thank You!

George D

It's the exact same process as the factory did originally on our cylinders. US Chrome has taken this process and made it better.

This is what I did with my 3.0 block. The cylinders are so pretty now!!!

This is from their website:

The US Chrome process is trademarked as "NiCom®", (because Porsche holds the trademark on the term "Nikasil®") , but the process was brought over from the Mahle plant in Stuttgart and is identical to the quality and finish that Mahle performs for Porsche on its OEM engines. There are a few other platers in the US that have an aluminum block plating process, but they do not deposit the density of 2 micron-sized carbide particles as NiCom® does, and the end result is inferior.

George

pole position

I asume you have a crank/rods stroker. How many miles are on the block ? 100k,200 K ? How many miles are on the sleeved ones ? Is there on with 20 K ? Doubtful. I would get a used block in good shape, maybe go one over and call it the day . Reliable with no headaches.

SeaCay

PM sent.

Chris White

NiCom is the finishing system used on 911 barrels - not the same as the homogenous Alusil material in the 944 / 928 family of blocks. So US Chrome has not made the Alusil process ‘better’, they have changed it to a plating system similar to the 911 system.
Just pointing out the facts – not knocking the NiCom system, just mentioning that it is not the same as original.

gt37vgt

yeh have to back Chris up here my block is original silicone inpregnated matereal (Alusil) bored .7 over and then lapped with felt and special oil as per service manual . there are some trick groups over here that can build the coating allowing you to keep your standard pistons but the price here is statospheric. it may be cost effective there as it may allow you more freedom with piston choice .

George D

Not to beat a dead horse, but I thought that this community would find this interesting and educational:


Nikasil vs Alusil Cylinders - In 1973 Porsche introduced a new type of cylinder used on the 911 2.7 Carrera RS. Engineered by German manufacturer Mahle, Nikasil cylinders are manufactured out of a dense, aluminum alloy that is centrifugally cast in a mold. The cylinder bore is then electroplated with a very thin layer of nickel-silicon carbide. Originally designed and used on the venerable 1971 917, these cylinders provide several unique advantages over the older-style ones. The primary advantage is that the micro-thin layer is extremely durable, and allows for thinner cylinder wall thickness as a result. As a result, the piston bores can be enlarged without changing the original cylinder head stud bolt pattern. In addition, the reduced friction along the cylinder walls combined with the surface properties of the nickel-silicon coating creates a tighter seal against the cylinder. The result is a slight increase in overall horsepower, due to the increased efficiency. These Nikasil cylinders are the most durable of any of the production cylinders and are highly sought after for engine rebuilds. These cylinders can be retrofitted to the earlier cars, however, you will need to install the updated piston squirters in to your early case (1970 and earlier) if it doesn’t already have them. The piston squirters lower the piston crown temperatures so that you can run the close clearances used by Nikasil or Alusil pistons and cylinders. It’s also important to note that Mahle makes Nikasil pistons and cylinders for 2.2L and 2.4L engines.

In 1974, Porsche introduced the Alusil cylinders, manufactured by Kolbenschmidt. The Alusil cylinders were primarily used as a less-expensive alternative to the Nikasil cylinders. These cylinders are manufactured out of a special 390 eutectic aluminum silicon alloy, and are used with a special iron-plated, ferrocoat piston. Like the Nikasil cylinders, they are plated with a special coating on inside bore. This coating is electrically etched to leave a microscopic layer of silicon particles exposed on the cylinder wall. The iron-plated piston and the silicon-plated cylinder walls operated together to create a durable dual-surface. In addition, the Alusil cylinders have the same thin-wall construction of the Nikasil cylinders, meaning that they too can maintain the same head-stud spacing pattern.

So what are the main differences between all of the available pistons and cylinders? The early biral cylinders can be honed and reused just like other cast-iron cylinders on non-Porsche cars. Starting in 1974, Porsche mixed and matched the Alusil and Nikasil sets, so it’s really the luck of the draw as to which set you have in your car. For the most part, Porsche used mostly Alusil in the 2.7L and 3.0L engines because of the reduced cost of production. The Alusil cylinders, unfortunately, cannot be honed. The honing process destroys the etching layer, and renders them useless. In fact, a general rule of thumb is that the Alusil cylinders are a one-time-use product, and should not be used again if the engine is rebuilt.

Alusil cylinders cannot be reliably reringed. This indeed is a common misconception in some Porsche circles. There are no replacement rings available that are specifically designed for the Alusil cylinders. Of course, throwing out your current pistons and cylinders can lead to the large expense of new ones, so a lot of people reuse them anyway. In some cases, the new set of rings seat fine, and they indeed can be reused successfully. However, you cannot hone these cylinders, nor predict whether the rings will indeed seat properly. The correct action to take is to purchase new pistons and cylinders, otherwise you may be tearing down your engine again in less than a mere 1000 miles. These Alusil cylinders typically have a ‘KS’ Kolbenschmidt logo cast into their base, although for a time, Mahle also made Alusil cylinders. The coating on the Alusil cylinders is non magnetic, so you should be able to tell the difference with a simple refrigerator magnet.

If you are tearing apart your engine for reasons other than worn out rings or valve guides, then you might opt to reuse your Alusil cylinders. This would be the case, for example, if you were tearing down your engine to replace broken or pulled head studs. If this is the case, I would recommend that you take your pistons and cylinders off of the engine, put them high up on a shelf, and don’t touch them until you are ready to reassemble. Don’t pull the pistons out of the cylinders and don’t dislodge or disturb the rings. Of course, you are taking a risk here that you will have worn rings in the near future. However, if your engine is a 3.0L, with 100K on the odometer, then there is a good chance that you can get 100,000 additional miles or more out of your set of rings, cylinders and pistons. I don’t necessarily recommend playing the odds like this, but if you’re rebuilding a good running engine with excellent leak-down numbers for the purpose of replacing head studs or some other non-wear problem, then it might be a good bet.

The Nikasil cylinders can indeed be honed and reused. They typically have a ‘MAHLE’ stamp on the lower side of the cylinder. The nickel-carbide surface needs to be lightly honed with a special silica impregnated tool, or what is commonly known as a grape or flex hone. The surface properties are too hard for normal tool steel honing machines. The Nikasil coating will be ever so slightly magnetic when you place a magnet next to it. The honing process is performed using special tools – either a specific tool designed to hone the cylinders, or a grape hone. Either way, you should only have an expert familiar with the Nikasil cylinders perform the honing process.

-Wayne
__________________
Wayne R. Dempsey, CEO, Pelican Parts Inc., and Author of:
101 Projects for Your BMW 3-Series Available for Ordering NOW!!!
101 Projects for Your Porsche 911... Available Now!
How to Rebuild & Modify Porsche 911 Engines Now Available!!!
101 Projects for Your Porsche Boxster & Cayman - Coming 2008

gt37vgt

well that was very interesting and educational .
If the alusil set up is not to be rebored or ringed or lapped why does it tell you how to do it in the work shop manual ? and sell .5 over OEM pistons .?
Also you seem to make a lot of reference to aircooled gear was the audi truck motor in my 944 even made in the same plant ?

George D

My point here is that a good used 951 block should not just be used as the basis for a new engine build. It should be coated with Nikasil or NiCom or sleeved. I've seen through the years blocks sold as "NEW" 2.8 strokers that have not been touched because they had no visible or measurable issues within the cylinder walls.

When spending the kind of money to do a stroker motor, you should address the cylinders and make them as new. New means new Nikasil or NiCom coating or sleeves done by someone like Chris.

Don't think that you will get your money's worth by not addressing the limitations of our factory blocks. I've seen reputable shops selling stroker motors that have not addressed this issue. Their lifespan is nothing like the original from the factory.

Good luck with your block.

Regards,

George

gt37vgt

Hmmm got me worried . do many of the manufactures for the air cooled sleeves do customs or stuff as big as 104mm i've seen well priced sleeve and pistons kits occasionally but tends to be beetle .
My only option is to make sleevs send them to the US to treat then intall in the block or cast sleeves i think i just have to suck and see at this piont

evil 944t

George D,

I don't want to start any trouble here but I think that whole article is on 911 cylinders. Notice the 2.7ltr/3ltr sizes, Those are 911 bore sizes of the carrera and the SC models. ie 1974 to current aircooled engines.(from Pelican parts, a very 911 oriented site)

It is VERY possible to hone and over size a factory bore. It happens everyday! There is no need for coating cylinders when rebuilding. Thats just what your builder likes. It also allows you to use JE/Aries/whatever American pistons you want, just like a steel sleeve application.

Ski has made Mahle oversized pistons that work in a honed cylinder. I have made pistons that work in a honed Alusil bore. Its a common practice and cheaper than the coating process.