Marti

Marti

Strosek Ultra

Sure, the purpose of this forum is to have fun with our cars - right? We all can share experience to help each other to successful modifications of our cars making life even more fun. We can continue this thread or shall we start a new one?
Åke

Strosek Ultra

Thank you Spencer, a lifetime of building up a business and a workshop ends up with a lot of stuff. Still there are some stuff I like to have like a flat grinding machine and a hub dyno.
Regarding the harmonic balancer I have not come so far but it probably will be 7" ATI Super Damper part no. 917020 with my own custom made hub.
Åke

Strosek Ultra

The Volvo insert cylinder block is cast iron. For the 928 I will make aluminium insert cylinder blocks having cast iron sleeves. The insert block will be made from four aluminum cylinders welded together. The advantages I can see are easy to machine and hone the cylinder bores when the insert block is out of the engine block, improved strength, same heat expansion as the engine block, no problems to heat the bulky engine block for the installation of interference fit sleeves not talking about pressing down the sleeves (post # 102).
It will be bore 4.250" and stroke 3.750", 426 CI or 7.0 liter.
Åke

Marti

ptuomov

In my opinion, the 928 block isn't particularly fragile. A thrust-bearing failure, severe high-boost detonation, wildly imbalanced rotating assembly, or poorly designed sleeves could get it to crack. However, since it's a cross-plane V8, it balances nicely naturally and the forces acting on the block are much smaller than in a four-banger 944 sister engines. A 3.5 liter inline four is an order of magnitude harder on the block than a 7.0 liter cross-plane V8. Just my opinion.

Strosek Ultra

To summarize what has been said so far. How many 7 liter strokers are out there? The answer is just a few. Will the bored out 7 liter engine block crack? The answer is nobody knows, just pure speculations. Time will tell when more 7 liter motors are finished and being used.
Åke

Catorce

Again, I think 7 liters is going in the wrong direction. Why is so much displacement needed to achieve more power? Although I own a 6.57L stroker that made 602hp with the custom manifold shown on my thread, it begs the question as to why the motor has to be so big to achieve that power level. As a counterpoint, I just placed an order for the Huracan Performante - 5.2L V10 normally aspirated, 640hp. Many people think this is underrated since the Performante smashed the Nurb lap time of the 918 Spyder, a much more powerful car by like 5 seconds.

I know, the new motor has DFI and a bunch of other doodads, but at the end of the day 640HP is being achieved by a motor that is smaller than that of the 928 GTS even. To me, that is a way more exciting challenge at this point - to build a super high horsepower 5.0 or 5.4.........

Marti

Carl Fausett

I agree with you Ake, and have had the same experience. In the early days we machined our dry liners to sit on a shelf we machined into the block at the bottom of the cylinder. On occasion, we would experience a leaky head gasket that after disassembly, we were able to confirm was cause by the cylinder liner descending. So we changed two things: 1) now we machine our blocks to accept a T-Top (Darton style) sleeve instead of resting on the bottom as before, and we heat cycle the assembled long block with MLS gaskets and heads torqued in place. Once cooled, we re-torque the heads and usually find that we get a better/tighter torque the second time after heat-cycling. Since these changes, we have had no head gasket issues on dry sleeved motors.

On wet-wall cylinders, I have less experience, having only built the 1 so far. I understand your point and it sounds valid. I would think they would almost have to be pulled in (not pressed) individually, not in a bank of 4 at a time like we do on the dry wall liners, to insure they are fully seated before further assembly.

Beautiful machine shop, Ake!

GregBBRD

My changes don't come from induction related issues but of concern over piston speeds in the larger stroke engines.

Drag racers rarely worry about piston speeds....they spent only a few tenths of seconds at rpms that would tear a road racing engine apart. Road racing is very different.

The engineers at Chevrolet found that with a 3.750 stroke engine, 7,600 rpms was the absolute limit, even with super light pistons and titanium rods ( with engines used in Trans Am racing.)

Mark Anderson's 928 race engine used an extremely "beefy" connecting rod (heavy) with relatively heavy pistons for years. He reved this engine 8,000+ for years. The only side effects were cracked blocks, pounded bearings, and rapid cylinder wear.

When we switch to a lighter rod, engine failure (rod failure) occurred very quickly. Analysis of the remaining pieces of the failed rod (not all of the pieces remained) at Carrillo found no defects or problems (with the pieces we supplied.) They said that the rod failed from excessive loading (too many rpms) and asked for any recorded data to see what rpms the rod had been subjected to. We had no such data.

Final engineering findings resulted in no changes to the design of these rods, but simply a suggestion to reduce the piston speeds (or use a lighter piston) and "gather" some recorded rpm data.

"Research" resulted in finding Chevy's information about piston speeds with a 3.750" crankshaft.
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V2Rocket

...can you make more....
"no replacement for displacement" unless you can add RPM.
that V10 does 8000rpm out of the box, and then some.
928 bottom end needs cubic dollars to survive anywhere near those RPM level. crank work, rods+pistons, dry sump oiling with windage and draining managed.
for a stock oiling system capped out at maybe 6000rpm plus a little bit, HP = CI.

Marti

Congratulations on the purchase, I am sure it will be a heck of a car to drive. I generally don't comparing different engine types as it is of little meaning as people are typically committed to one direction and happy with it. Also where does it end, should you compare to something with much less horsepower and feel better, so it's a road that is difficult to get any direction on. I did look up the Huracan engine outputs and saw some impressive figures, the torque however ranged from 398lb/ft to 443lb/ft, now the lower end of that scale is a figure than an S4 or GT could match with some simple tuning. To me that's pretty good for an 80's design with some 90's and 00's development.

Marti

So because it would be very difficult to get the 928 V8 to rev to 8000 - 9000 we add CC to compensate. If the engine can take 7.0 or 7.2 reliably then why not.