And the carbon-carbon clutch ... must resist ...

 

Good luck with that list....I'm not even sure what I have!

I'm a person that likes to create and improve things. Really poor at marketing and making money from those things. I make a few of everything, when something works extremely well and then sell those pieces to people that happen to be standing close by, but I'm terrible at taking the time to work on an Internet Site and sell those pieces to the greater population. Instead, I move forward to the "next" thing that I see which needs improvement and I "fix" that.

I guess I'm easily distracted and eaily bored. AADD? Not much doubt.

Regarding a billet block....yes, quite a bit of thought and effort has been devoted to this idea. The "block", in the 928 engine, is the current limitiing factor to moving forward and making more power (and bigger engines). Frankly, the Silicon Aluminum material is too brittle to really make reliable engines with big power. Porsche "saw" this very early in the 944GTR engine program and thus created a block made from "normal" aluminum with "free" standing cylinders (and dry sumped.)

This is not going to be a "cheap" thing to do. Someone is going to have to "step up" and want one or two, to make it happen. After the first couple, it gets easier and much "cheaper".

Note that "cheaper" is a very relative term.

 

Resisting the force is futile.

 

I think you should ask one of your customers to maintain your web site in exchange for some 928 work done. Your existing and potential customers, especially in far away locations, would value a simple explanation of what each product is, what it does, and what product fits together with what and what's an alternative solution. You never know what the silent majority in the world outside California and Rennlist will find useful and decide to buy.

 

Who knows, the person who wants/needs 2-3 Billet Blocks may stumble your way when he sees what all is available from PM. I assure you that pricier items have been sold via a random Google search.

Good God I just bought 22lbs of intricately machined Titanium Boeing C-17 wing root hinges & currently have nothing better to do than use them as book ends! Could not resist @ $39.00

Does the Sultan of Brunei have any 928's in his collection?

 

I had Rob Rossitto that did this, until he passed.

Rob Edwards is helping with the web site, now.

We are going to work on getting the Web Site more current, when I catch a breath. Rob is bored if he doesn't have 22 hours of work to do, every single day! I've got two stroker "cars" that need to be delivered to their owners, before Christmas. And one other "car" that I've promised by the end of January.

Building an engine is one thing....but building an entire car is quite another.

 

Have camera, will travel.

 

Put that up on a wall somewhere. I will too.

 

Potentially a cheaper and I suspect for the vast majority of applications a suitable option could be the following; bore the existing towers out much like Mike Simard and Todd Tremel have done, then have a dedicated casting made that consists of the 4 cylinder towers. I am no expert but I suspect these would just be sand cast like the engine is and have the machining done by CNC. The block would need to machined in a matching program to suit.

The towers would be conjoined which they would need to be if they were going to be in the 109 to 110 mm range. This would add to stability and be quite robust. These alloy towers could then have the option of having a relatively cheap iron sleeve inserted or be Nicasiled in the owner wanted a tighter piston clearance. If there was ever a problem with the bores these could be relatively again repaired without having to redo the whole engine.

The alloy towers would require only the slightest or zero interference fit depending on the alloy used. Using this method to create a new bigger capacity engine means less material and less machining. Maybe somebody with enough cnc experience could give some idea on machine time? I have seen this idea used in race engines, it is not a original untested idea of mine.

 

Shouldn't we be breaking some stock blocks before CNC of a new block?

For that matter aren't there some known good blocks that might be tweaked for use in a 928?

 

The problem isn't the "towers", it's the main bearing area that suffers from high output fatigue.

 

"We" already have.

 

Greg,

I long ago floated the idea of a meeting of minds on tuning one of your engines to Neel Vasavada of Apex Speed Technology but gather he likely stays equally busy to you. They are located on S. Sepulveda & have gained reputation enough to do the tuning work on the Singer Porsche recreations so I am guessing he also knows his business!

What's a mere 38 miles in LA?

 

I am far from a expert in failure analysis but for high output fatigue to be happening I would have thought that it was the lower cradle cracking and I don't know of myself any cases of this happening? Or is this the case?

If it is the block that is cracking and granted it is a brittle material I would be more suspicious of mass forces. To have ago at analsysing from a far I would say you have to look and compare high output stock stroke engines that have been converted to forced induction. That way you have a relatively good engine to make a comparison. If those engines are not cracking blocks then mass forces may well be the culprit.

As you know I have always been suspicious of the use of high mass forces and some strokers aslo have tied into the mix 6CWT cranks for additional imbalances and flexing. The other factor that may well be an issue is a stroke that is overly long.

This was the reason I had Moldex make me a few years ago a 8CWT crank that had a reduced stroke of 3.55" and used 48 mm rod journals. It came with a bob weight of approx 1600 grams versus the stock Porsche crank at 2350 grams.

Now not being one for paying attention in maths class but wondering how much quicker this new lightweight wunder assembly would spin up, I posted that very question on a technical engine building site. The answer came back, no difference! The reason I was given was that because of my increased stroke the effect of swinging these parts further from the centreline of the mains was that it basically equalled the higher stock mass much closer to the centerline.

I hadn't though achieved nothing, I hadn't increased the mass force loadings, if my stroker was the conventional stroker stroke which was used from the very early days, that being 3.75" then I would have had slightly increased loadings over stock.

So those are my thoughts on main bearing fatigue cracking, not saying it is right but it might be. The other minor supporting fact is when you view Conrods that have run in race engines you can seen the loadings are very much in a downward direction and that the power loading would be felt more by the lower cradle. If this is the cracking hot spot well that would make sense as the lower cradle seems to be made from a poorer quality material.

 

Mike Simard made some highly intelligent comments on the forces impacting the block. Perhaps not coincidentally, his engine sleeved with his own sleeves is holding together.

If a block fails, it would be nice to know the specific circumstances of the failure. First, was it an S4 or earlier crank, a GTS crank, or stroker crank? That matters for the main bearing loads in many ways. The GTS crank, for example, appears to be a design that minimizes production cost and not main bearing loads. Second, was the engine sleeved or with original cylinder towers. Mike's success aside, I am sure that it's possible to sleeve these blocks in a way that weakens them. Third, was that just a thrust bearing failure that caused it? The answer to all of these failures is not "let's make a new block." It might be "let's make a new crankshaft" (the topic of this thread) or "let's not sleeve the engines the wrong way" or "let's not let the thrust bearing fail."