slate blue

Alex sorry to see this, have you tried Langcourts for the Nicasil? They are in the U.K also Perfect Bore will do it also, They offer hot honing with stress plates etc.

Vilhuer

AFAIK one of the reasons for damage like that is too much fuel which will wash away oil from cylinder wall.

One option which I hope will work is to put Wössner pistons into stock block without machining it to oversize. This will at least leave one very large problem source of getting correct Alusil surface done off the table.

There is one or two Swedish companier which have done Nicasil to 928 block but their price is too high for most people. Seems like dry steel liners is only relatively cheap option.

GregBBRD

The later 944/968 blocks are completely different and way stronger than the early 944 blocks and any of the 928 blocks.

The blocks are completely solid, 2/3 of the way up the cylinders. Only the last 1/3 of the cylinder is exposed to water cooling. There's a lot of material in these blocks and wet sleeves are a "walk in the park".

Way different thing, in a 928 block.....it's going to crack. Absolute 100% money back guarantee.

GregBBRD

Yup, that's what they look like. Seen a bunch of those. 6000 miles is wonderful, most never make it a few hundred miles.

GregBBRD

Down another experimental road......I admire your patience.....and your bank account that keeps "playing" with things I tell you won't work.

Weigh your crankshaft and think about it swinging around at 7,000 rpms. Know also, in race situations, I've seen more than just a couple cracked blocks.....thus my desire to build a billet block.

Now machine a bunch of material out of the block and expect it to.....crack.

Ship the damaged block over here and have it Nicosiled and properly prepared. The shipping back and forth will be less than a gasket set and bearings.....forget the labor to keep building engines!

The bores will live forever and you can be done with this bull**** and drive your car.

Yes, the block will crack up through the mains and out into the water jackets, eventually.....but hopefully that will be many years.

And by then, you can put one of my lightweight cranks in a billet block.

drnick

Greg, have you already indicated price on a nikasiled block?

Al, what has Adrian done with his engine?

Cheburator

Porsche already did this - not starting an argument - but my GTS block is one of the mythical factory linered blocks. They did take away material to insert the liners. Are you saying they did something wrong? I am planning on getting dry sleeves fitted. Or am I missing something here - btw, most of the shops in the UK that repair the swiss cheese 997.1 and 997.2 scored bores use exactly the same liner. Genuine questions...

Adrian had his S4 block bored out to accept 968 pistons that he bought 2nd hand. Then he got a set of custom Carrilo rods to match the Moldex crank and was done and dusted. Don't want to go down that route as it would make the car ineligible for pretty much any series outside of the UK. Still not given up on the dream of driving a competitive lap on the Ring in it one day

GregBBRD

You once told me "I know you've done this, many times, but I need to do this on my own, so that I can learn what it takes to make one of these engines work."

And I just shook my head, in wonder, and let you go on "experimenting".

However, it seems like you might be getting frustrated and wishing you were not doing this, with this car.

So, at this point, I'm just trying to help, not hinder your process.

Common knowledge

Alusil is silicon and aluminum mixed.

The entire "upper" 928 block casting is made from Alusil.

The resulting material is very hard (when properly prepared) and can be used directly for cylinder bores....however, it is very brittle.

The entire "lower" 928 block "cradle" casting is made from an aluminum alloy that has no silicon....to "remove" the brittleness problem.

Porsche had early engines crack, in testing, in the main web area. They had to go back and strengthen the web area to prevent this from happening.

The cylinders are an integral part of the main web area and provide a significant amount of strength to this area.

I've seen both 100mm and 104mm blocks crack, in the web area, when subjected to high loads (racing).

It is my belief....from what I have observed:

Any significant removal of cylinder material reduces the strength of an already "marginal" block.....wet sleeves, dry sleeves, even 104mm bores....and "cracking" is inevitable.

The more material removed, the quicker the cracking will occur.

Reducing the amount of material removed will result in the most reliable result.

I've built dozens of engines using Nicosil lined cylinders. It is time consuming and expensive to do. When the block are done being Nicosil plated, the work is just beginning. There are significant steps that need to be done, from this point, to make the blocks reliable.

I've had the opportunity to take several of these Nicosiled engine back apart (for a lot of different reasons). The bores/pistons are never an issue. I consider, this part, of the "problem" to be solved.....bulletproof.

ptuomov

A-B-C: ;-)

I think everyone agrees that Nikasil/Nicom plated cylinders is the best solution out there. It's also probably the most cost effective solution in expectation because it's so reliable. But that doesn't make it true that for _every_ other solution. For example, Mike Simard's got wet sleeves that seem to work very well with long stroke, higher rpms, and high cylinder pressures.

I'd be very surprised if the lower block half has no silicon. Lower silicon that Reynolds 390, sure, but no silicon, really?

Someone with some engineering background should comment on the strength of an interference fit. I think that's the key when something is bored out and something else is inserted in its place.

GregBBRD

Obviously, you, sitting at your desk, reading what the "internet experts" on engine building have to say, are always going to trump my meager 928 experience and engineering background.....so disagreeing with you is somewhat moot.

Of course, there is going to always be trace amounts of silicon in everything.....but the alloy is not Alusil on the cradle.....that's the point. Alusil is extremely/exceedingly/very brittle....the cradle is not made of this....because it would crack, instantly.

I have no idea how long Mike Simard's engine is going to "live" before it cracks....and I have no idea how many hours Mike has, on his engine. However, I greatly respect the effort that Mike has put into this "experiment".....but Mike knows full well that I think it will crack why I think it will crack. A major part of the "strength" from the block has been removed. The "remaining" material, in the webs, above the crankshaft, is very thin and made from Alusil....which is very brittle. Mike made extraordinary effort to "support" the block, with special custom studs (art) and a special custom lower support (art), but the fact remains that the block is very thin in the web area and very brittle.....and a 62 pound crankshaft, whipping around there at 7,000 rpms, is hell on that area, regardless of what supports it, from below.

Perhaps if you would go find and review what Porsche found out about using liners in the "early" 944 blocks, as used in the 944 GTR program, you would better understand that this "method" didn't work there....with virtually the same "support" above the crankshaft (cross-sectionally, the blocks are virtually identical.) The blocks all cracked in testing.....and they were forced to recast the engines in another alloy. Note that the later, larger bore 944 engines, added a huge amount of material to the area above the crankshaft (they essentially "filled" the bottom of the cylinder area) to increase the strength of these engines.....this was the direct result of the 944 GTR block "testing" experiment.

The funny thing about debating this, is that Porsche, not me, has already done all the research, engineering, and testing......way back in 1987.

ptuomov

The 944 GTR experience and 944/968 blocks are obviously relevant to some extent. However, there are a couple of important reasons why I think the experience with 944 GTR doesn't automatically make similar efforts with the 928 doomed.

The most important reason is the following: An inline four, especially a racing one without balance shafts, is going to have a secondary dynamic imbalance. In other words, it will shake your teeth off. I don't recall anyone building as big inline fours as Porsche 944's and 968's, and the imbalance of those engines especially without the balance shaft is dramatic. (A digression: I know that Porsche Germany tried to endurance race 944's without the balance shaft, and had to put it back in. I don't know whether the US effort with the 944 GTR had a balance shaft or not. If you recall, I'd be interested in learning that.)

As you know, the situation is completely different with a dual plane 90-degree V8 that can be counterweighted to have a second order balance. The V8 also has overlapping power strokes, unlike the inline four, which is relevant when we start getting into turbocharged engines that make some power. That's why you see 13L liter V8's being raced at 8000 rpms but you don't see 6.5L inline fours doing the same -- regardless of the block material!

It's my opinion that the abuse that a 5.0L 928 block is subjected to is nothing like the abuse that a 2.5L 944 block is subjected to, at the same RPM and hp/l. Therefore, I don't think one should make definite claims about inevitable cracking of 928 blocks based on evidence from 944 blocks. Just my opinion.

SMTCapeCod

retracted faulty reference.

GregBBRD

Valid points, well thought out.

The obvious problem is that the only way to find out is to do more experimenting....and I kind of get the "taste" that Alex might be getting tired of this.

As one other data point: In all the time I spent building and working on "regular" 951 race engines....I never saw one crack, in the main webs. However, I've seen several of the 928 blocks crack, in high performance use. Consequently, my conclusion was just the opposite....I figured that the 928 blocks cracked easier.

Not knowing exactly how many miles the 928 blocks had on them, or what those used 928 engine blocks had been through (before they were transformed into a race engine) is the big variable. It is very possible that the 928 blocks were "used up", before they became race engines.

All the 944 GTR engines retained the balance shaft belt...or at least they retained it until it broke or flew off....which happened.....and not intentionally.

gb

ptuomov

I think there is demand for dry sleeve solution, because not everyone is fortunate enough to live within economical shipping distance from US Chrome or Millenium shop.

One thing that I've thought about is dry sleeves that undersize the bore. That is, if you are going with custom pistons to start with, why not make them smaller. The minimum sleeve thickness from the sleeve maker is 1.5mm, so with 97mm bore one could conceivable just cut the relief for the flange on top of the cylinder tower and install 1.5mm sleeves on the bores without reducing the original cylinder wall thickness at all. Or one could bore out the tower to 103mm and install 1.5mm sleeves with 100mm pistons. There are a lot of engines out there with Nikasil bores and about 102.5mm bores, and they seem to last.

It's still not a slam dunk because Reynolds 390 is brittle and the dry sleeve is going to have a different coefficient of thermal expansion, but I have a hunch that someone with engineering education could probably match the materials and thickness in a way that the temperature difference between the cooler, outer aluminum tower and the hotter, inner iron sleeve cancels the difference in coefficients of thermal expansion.

If the thermal expansion issue is solved/matched, then I don't see why the dry sleeve would make the block weaker if one doesn't remove any meaningful amount of material from the original cylinder tower. But maybe someone with an engineering degree could chime in.

ptuomov

Here's one more data point: John Kuhn has one of the original Callaway twin turbo blocks. It has dry cast iron sleeves. The block has survived decades of bad tune and boost. It's a survivor, it's not cracked, and it has been "ridden hard and put up wet." I think that this is a counterexample to inevitability of block cracking.

Now, please don't confuse this with me or John saying that sleeving is superior to Nikasil/Nicom plating. It's not. John was the first person to Nikasil plate a 928 block with Millenium and I believe the first person to Nikasil plate a 928 block in the US at any facility in the US. So he's a pioneer in bringing the best solution to the 928 world. The question is whether there's any other solutions that work for those who don't have access to Nikasil plating.