Correct.
When doing a dry steel sleeve, this is a real issue.
Many dry sleeves come loose or rotate in the aluminum bores.
This is not a process a rookie machinist should be messing with.

The Alusil sleeve process is certainly the best long term option, for damaged bores.

 

I talk to Todd about 2-3 times a week. We've talked extensively about this subject and in no uncertain terms has said that any 928 / 944 engine I get involved with going forward should be Nikasil coated. To him, the advantage of being able to use superior rings / pistons outweighs any additional work required, on top of that, the fact that such coatings can save blocks that would otherwise be junk..... what's not to love?
The engine in his twin turbo actually had a very deep groove in one of the cylinders before it was coated. 25,000+ miles later making over 1,000hp spinning to 8,500rpm, no issues (and Kibort's current engine)

My first foray with Nikasil was a couple 951 race engines back in the 90's I helped prep and assemble. Since then a couple 928's.

I'm currently involved with Yamaha engines, every single one of them is coated from the factory and a common upgrade is a big bore kit (which requires redoing the coating). My local Yamaha engine builder has sent over 20 blocks in the last 6 months for Nakasil.

Maybe you should call Todd and see if you can pick up a few pointers, especially on the piston slap issue since the engines he's build with Nikasil, don't have that issue.

 

Who is doing the coating?

 

I will only add my n of 2 datapoints as the guy that got to clean up a block post-Nikasil, it's a day's worth of cleaning and scraping and chasing threads and washing and blowing out holes before a block is ready for assembly. Certainly there are applications where doing Nikasil and custom pistons is appropriate, but as Greg said, it's multiple kilobucks just for the block and pistons.

 

I'm using a different piston design, currently, which has allowed me to tighten up the piston to wall clearance, but there's still some slap.
I use Nicasil mostly on my higher end stroker engines and in order to get enough counterweight to not need 2K worth of Mallory, the skirts are fairly short, which, of course, makes them more prone to slap.

It's tough to beat that .0007" piston to wall clearance of a stock 928.

 

This -^ is one of the devils in the details of a long story, the short story for which I wrote, earlier, that IB's stupid javascript ate.

Here's what I wrote as best as I can remember...

Interesting Thread.

The answer to the question posed by the thread title is Yes but it is best done on a client-by-client basis.

The expense of any 're-manufactured' short block that comes with a warranty (either stated or implied by reputation) is going to put it out of reach for the vast majority of 928s owned by folks without the wherewithal to add low five figures to a full engine rebuild.

Since there are no pistons available and a single(?) source for bearings and rings (that work in AluSil) any 928 block that has cylinder wall damage is going to be "un-remanufacturable" with 928 parts. A "business" that depends upon that is going to discard 4 of 5 blocks. That's a guess. Greg, you can probably guess better.

What you're left with is Nikasil. And that ain't a paint-by-numbers deal. Not by a long shot.

Even then, who in their right mind would warranty a Nikasil'd (or just built with 928 parts) short block that someone else would build into a motor and install in a 928?

 

I was lucky on my last full rebuild to score oversized pistons for $3500 cdn from Porsche. Even finding a machine shop to work on the Alusi block is becoming a serious challenge, the one shop I had has closed down so now I am pretty much SOL here in Southern Ontario.

 

My favorite horror story goes back about 4-5 years ago when I bought my 90 S4 - owner bought the car from a Porsche dealership. Customer tossed them the keys when Porsche's answer to a broken timing belt was a $25k replacement engine.

The new owner thought he saw scratches on the cylinders. Took it apart, split the girdle ordered all bearings, rings, head gaskets, had the heads rebuilt - the whole enchilada.

Then he decides to abandon that when he got an estimate for the fixing the scratches. I felt the scratches. Not even worth honing.

That's when he buys a used motor off eBay. Drops it in and it won't produce any oil pressure. Spends countless hours trying figure out the problem and finally gives up.

After the car has been sitting in his shop without an engine for a couple of years he puts it on craigslist.

I buy the 90S4 for $4500 which includes service manuals and the engine in a hundred pieces. I bring it home and put humpty dumpty back together and it runs great.

A couple of years later he visits me - he says he finally figured out why the eBay engine would not build oil pressure.

Drumroll, please....

He took it apart and it turns out it only had one thrust bearing shell.

That was my first foray into assembling a 928 engine. I say assembling because I didn't pretend to be an engine builder.

I assembled it from the parts the PO bought - I did not check clearances - I just assembled. My only screw up was not getting the girdled sealed - had to do that twice. Lesson learned.

That car runs amazingly. Oil pressure is the best I've seen. Oil pressure at startup is 5+ bars - pegged. Idle is 2.5 to 3 bars at idle and 5+ bars off idle. I can watch the oil pressure and tell you exactly when the oil thermostat opens up.

Building a good short block or a long block is not rocket science. You need the right tools to make sure the core start with is good. Bore gauge, a setting ring and good micrometers in the correct ranges and you are off to the races.

And let me tell you about the AC - it blows ice cubes - it's the original AC compressor converted to 134a and still has the black o-rings not the green ones and the non-134a expansion valves. I happen to have the best AC guy in the southeast.

People on this platform will tell you need a PH.D to work on our engines. I'm here to tell you that is BS. If you passionate about what you do - you will be fine. And don't be afraid to ask questions.

I am very choosy about who's cars I touch. I tell my customers I charge half what the commercial shops charge and take twice as long. :-)

My shop motto is: "I have fun playing with other people's cars at their expense."

My daily drivers are all 928s - I bet you will not find another 928 mechanic that boast that - well maybe Speedtoy's daughter. :-)

Now I sit back and await the pitter patter of Greg's feet as he steps all over another of my latest posts. He'll say some pretty scary things. But, don't you believe him.

 

Did you read all comments? Refreshing good blocks who are rare isn‘t the challenge.
Your business plan was to collect blocks and sell them overhauled. Totally different task.

After a few years you have a little hill of worn out cores in your backyard.

Greg and the other guys here who build engines invest time and give you a good view of the challenges of the plan.
They build engines with warranty and want lucky customers.
Use their advice wisely. I don‘t think someone of the crowd will not your best.

 

I wish people would drop the negative energy and instead encourage those who want to be a resource for 928's. I am no engine builder but I am interested in this topic. I have always been impressed with guys who seem to do more research on their own than Porsche did with millions.

Some threads sharing a lot of good info on this topic, both guys boring out the cylinders, how is Todd's engine?

The MS engine build > https://rennlist.com/forums/928-foru...ct-pics-2.html
The todd engines > https://rennlist.com/forums/928-foru...he-making.html

No need to repeat conversations
block issues post #4 and #6 plus others > https://rennlist.com/forums/928-foru...-thoughts.html


As an interested bystander I think that there is a way to take the best solutions that have already been done and put them together to make it work. There is NO need to make REPLACEMENT engines produce BIG HP numbers. That seems to be one of the STRESSES that may contribute to block failure. Replacement engines keeping stock redline and producing 400hp instead of 600 seems the way to go. I need to refesh my memory on Greg Gray's engine work.

 

I have two engines picked out, I've split the blocks. An 89 and 87. Retrieved 2 sets of pistons and rods from my storage unit. That plus the set I have from the 87 brings the total to 24.

Next step is to have all of that dry ice blasted. After that all the bores will evaluated and documented. I have plenty of low mileage crankshafts (<50k) to choose from.

I even have a cross drilled S4 crankshaft that needs a home and another empty block I bought a couple of years ago.

My machine shop has the appliance I had them make for adding an additional groove in the thrust bearing to improve oiling. The improved thrust bearing will be in all my engines.

This an interesting way to slowly empty my storage unit.

Kevin

P.S. If someone is interested I also will have an 85 auto long block here at the shop soon. Bent valves.

 

on the ice blasting,
I would practice on non usable pistons to make sure the chromium coating is not damaged.

 

That's the plan. I have plenty to choose from.

I really miss Chem-dip's old formula - the current flavor is so much weaker.

 

I'm certainly in the same boat as I'm assembling my engine at home from a split girdle, but I wouldn't do it for profit for other people. You can run the same engine oil on 20,000 mile intervals and it's going to still run. For a while. You can slack on the bearing tolerances during assembly and it'll run great. For a while. I suspect people who drop 5 figures on a remanufactured block are going to expect a kind of longevity that was designed in from the factory, and that DOES only come from experts in engine assembly.

Yugos didn't usually have any problems for their first 30k miles, either. I always fall back on it because it was drilled in our heads during our mandatory 0-credit hour Engineering Ethics seminar in college, but the severely under-designed Kansas City Hyatt walkways stood in place for a year before they collapsed.

 

Hint: When assembling the girdle after you apply the sealant - I keep the girdle above the block using paint stirring sticks between the motor mount supports while I put the nuts, washers and bolts on. I have an electric ratchet that only can torque to 11-15ft lbs. I tested every one I have looking for the one with the sweetspot.
I remove the paint sticks, drop the lower girdle and use the aforementioned electric ratchet to run all the hardware down quickly.
Then I torque all 13mm hex bolts to 15ft lbs.
Then I go back to the WSM bolt tightening sequences. I actually have that laminated. OCD much?

This is not something I dreamed up - I read a lot of posts here and that one was buried in one of GB's responses over the years. (Credit where credit is due)

It makes perfect sense - where will it leak? Then torque them first.