BC

Ski - you are saying that you simply coated a regular aluminum (forged) ARIAS piston with Swain's PC9 and thermal on top and put it into the original alusil bore? No problems at all? For how long?

Zero10

PC-9 is supposed to be able to go on aluminum pistons in aluminum bores without any issues. It is the coating of choice among many engine builders.

Ski

jwl, took his Tom C pistons, sent them to Swain for coating. Now, I'm not sure how much of the coating they took off before they put on the skirt coating - they have been in the 2.8L for almost 2 years and doing great.

There is some other experimenting going on but it's not for me to say. I can tell you that a test engine was just broken down after 10k miles and the results were very good.

Ski

Brendan, let me elaborate a bit more on this. When Jim did his 2.8 stroker, he was contemplating pistons and he really didn't want to spend $1700 for a set of 2.8 ones from Andial. Tom C had not done a set with the wrist pin relocated so after they (Tom and Jim) got the particulars worked out, Jim ordered a set from Tom. Jim got the pistons and we started talking about different coatings, and Tom was in on this as well. Anyway, Jim contacted Swain and the set up the coating. Duffin did the machining, tolerance was .0015" for the pistons and now that the engine is built, broken in, 2 years now it performs like a scalded A$$ ape, with new Griffiths A/C like the Artic. It was a bit of experiment, not that Jim has $$ to throw away, but he/we do have two spare engines between us(our own cars or the track car) and he wanted to try something new. We, JAB Racing, are having some RACE only pistons done with Mahle, they are lighter than stock and we may sell them, but only after we've tested them in our own car to make sure that they will be vibration free or if there is a vibration, where is it, what to do about it, etc.

All that said, pistons - there are 13, maybe less after I've posted this a few times, sets of 2.5 100.5 Mahle OEM pistons available worldwide. I believe Andial has an arrangement with Mahle for the 2.8L stroker pistons in 100 and 100.5, Heritage ??? or other, has arrangements with Mahle for 968 104.5 turbo pistons, all of these are in the $1500 to $1800 range, plus the maching of your block. Now, throw in Tom C pistons at $1100 to $1400 a set, plus maching. Now add Nicaksil coating from US Chrome at what $800 -$1000, plus the cost of new rings, 964? What if we could increase the bores to 4", run a Chevy domed out piston that had 8.5:1 compression...ah, but we would need custom rods and then have to coat the pistons as well. Now add, Chris White who probably has the best sleeving that I've seen come forth in the 944 world and his delivered product is damn good bargain at his price.

Either way you slice it, to rebuild these engines, no matter what route you go, you are going to spend at a minumum of $2000 to keep the breed going, this just gets your short block in good shape(with gaskets/bearings).

Trying to take shortcuts, to save money, ends up costing you money in the end - do it right the first time. After Hurricane Rita, my drilling rig, the Transocean Marianas, suffered great damage to the mooring system and the winches that control that system. The huge bearing caps on the winches were all elongated. These are 18", 5'' think caps, so imagine the load to do that. Well, our company chose NOT to use the manfacturers machinist suggestion because they were too high. The machinist they did choose, are now on their third, weld, bore, finish,etc. because they got all the welding procedure wrong the first times and cause cracks from the heat process. Their bill, the second time around was equal too or greater than the original bid from the machinist my company didn't want to use. I hate to sound like a cliche, but "pay me now or pay me later".

Jim and I have been fortunate in our endeavors with these engines. We both spent some serious time at Tom C's shop, we try to follow procedures and torque values and tolerances, but hell, we could have just been lucky too and disaster may be waiting around the corner, hope not but who knows. I think we owe to ourselves to do good research, talk to knowledgable people and take only the calculated risk that you can afford to take. Then we share that information, no matter good or bad, so that we can all keep em running and kicking A$$.

Buckaroo Banzi

Making the decision to re-assemble my motor to factory specs (or trying to do it right) is not as simple for 944 engine as it would be for a
American or Japanese motors. The availability of good used blocks in my recent experience at a reasonable cost is zero.

My definition of a good used block is NO SCORING, NO CYLINDER TAPER, MEETS 100mm FACTORY SPEC.

By this definition considering the age the low volume production numbers and popularity it is not surprising to find vendors
now charging $2000 dollars or more and if demand increases the prices will easily double.

So what does a prudent not very experienced 951 owner who is staring at his scored block and knows he has one chance
due to his health to put his motor back right do?? These are my current options and why.

1. Purchase the brand new 2.5 short block being listed on Great Brittan UKE/Bay site. Expensive Hell Yes!, Easy Oh Yes! No sweat re-assembling block with my recently purchased brand spanking new head it would be a piece of cake to re-assemble. Cost estimated to be $5-7K but it would be a rare privilege indeed to own one of the last brand new factory 2.5 motors left in the world.

2. Nikasil the block and re-ring re-use standard pistons?. Easy No! Would have to strip all steel from block pack crate and ship. Receive back and re-assemble block from scratch PITA. Chance of screwing up? Considerable. Cost estimated on the high side including shipping would be $1300 that includes rings from EBS racing. Also there is some questions in my mind about Nikasil there has been only one Rennlister that has come out and indorsed Nikasil

3. Machine Shop perform over size bore (100.50mm) and hone Alusi block. Order pistons from Tom Chatsworth oversized (100.50mm) quoted $990 shipped wherever I choose. Easier Yes! Costs $1400. Cons to this are finding a machine local or out of state shop that knows what they are doing. Second can I trust Tom C’s pistons? With all respect to you Ski and your endorsement there does not appear to be tidal wave of support out there for Tom’s pistons even you have hinted there is risk involved there is not enough of an installed base to draw conclusive long term reliability conclusions. So I don’t use Tom C’s pistons and I purchase stock oversize. Now the price jumps from $1400 to $2100 or higher if I can track down a set.

4. Re-sleeve the block. Call me old school but I am not a big fan of this. I think there are some very nifty new self locking deck systems that are being used on a variety of imports with success. Cost on the other hand is high $3-5k and up. I personally am still on the fence on this one. It’s a hold over from my high school chemistry and auto shop classes on the whole combining dissimilar metals results.

Ski

I fully understand. I don't endorse anything, if I use something, it's just my experience with it. Do I trust Tom C pistons - yes, having been in on 4 installs and seeing the cars and still seeing them running with no problems and great compression/leakdown - yes I trust them.

Get the Mahle oversize pistons - call Sunset Porsche, call Vision Motorsports or Andial and ask if they do their own machining or where you can get the block done locally with Alusil experience, locally I mean CA. If they say they send them out, send it to me and I'll get the guy here to do it, or call Duffin Engine in San Antonio for the block work.

This is where your own research and money come into play. Good luck

Tom M'Guinn

If you use a local machine shop for the block, PM me for some local caveat emptor info. Sending parts away to a trusted shop can be cheaper and faster in the long-run, even if it doesn't seem that way at first.

BC

So yes, they were simple Arias Pistons machined out of 26XX or 43XX AL? And then coated to whatever thickness with PC-9 and stuck back in a prepped ALUSIL bore? And now 10000 miles later under boost it all peachy? Then great. This is good news.

I can get a set of JE pistons for my V-8 for just over 1000, but it was always what coating or what changes i make to the alusil bore because I still have the common idea that AL+ AL does not mix. Its about 1500 to Nikasil our bores, or I can pay big money and have 110mm sleeves put in at over 4k.

Ski

or buy a set of Porsche OEM 100.5 pistons @ $1600, with the original Ferrostan coating and have your block done to new spec to accept the pistons. Tom got a good deal on his last pistons, not sure if the tooling was already set up or what but I think he may have them for $975. pm jwl and get his take.