heinrich

LOL, show us ONE failure as a result of that open deck design, boosted or not.

Gretch

My complements on your restraint, h.

Jim: "Lots of things are "said" that has little to do with how accurate the statement happens to be , this Forum proves that every day !"

I will attest to that, man...................

John..

Oh man, the open deck block discussion again! I love this place. I just stripped Goldmember's block totally naked...try removing those head studs without some heat....BRUTAL. The block is now in close proximity to Lag and Murf getting the special sauce next week! Stay tuned for details!

GoRideSno

John,
Your block is going to to be close to Tim and Lag? Well it will also be very close to, less than 30 miles from, Wisconsin International Raceway where they have street legal, run what ya brung test and tune sessions tonight, and on Wed Sept 15th. hint hint
Bon Voyage to your block John.
Andy K

John..

The question is, will we get performance specs on the Murf cars?...inquiring minds want to know!!! Heck, I may even take the Goldmember to Edgewater here just for kicks...but that will have to wait, as it is in pieces in multiple states!!!! I'm not a big fan of the drags, but it is fun nonetheless.

GoRideSno

BTW there was new class of boostards having a twin-turbo discussion a few days ago. Take a look a few days back.
Andy K

Lagavulin

Jim, I guess that I did not make myself clear, my fault. It's not just the block, but the ENTIRE engine right from the factory is reliable up to 1000hp at the crank, so laugh even harder if you'd like. Forged crank, forged pistons, Manley rods, all the 'good' stuff. The reports of 1000hp is not coming from one source, but from enthusiasts and performance engine builders alike. Keep on smiling...

Now you have me smiling since I'm sure you already know the answer with respect to the new GT: weight. Keeping the weight down on their supercar GT is a much higher priority versus their everyday Cobra. The alloy block is not nearly as strong, but they evidently did not want to pay the 60lb weight penalty incurred by using their iron block. And if a same-design aluminum alloy block was stronger than an iron one, then the F1 teams would have used it instead of the iron blocks they used for their 1000+hp engines.

'Sean Hyland Motorsports' has an aftermarket alloy block available for the 4.6L 32v that so far is good up to 1500hp using a centrifugal supercharger.

I can show you hundreds of open-decked Hondas and Subaru's which have experinced problems once they started raising the boost/horsepower. The 951 guys with their open-deck have the same problems too when they crank up the boost.

How did all the camps address the problem? By closing up the pathetic open-deck block themselves.

There is no doubt the 928 block is reliable for low-horsepower applications, just like the Honda, Subaru, and 951 engines are. However, since nearly every single 928 engine ever made exist in a low-horsepower environment, that means there are hardly any high(er)-horsepower (..500+ rwhp) engines to observe, thus virtually no one are aware, nor even heard of, these types of problems. I know that living in a 'stock' world can be cruel and slow, but it's the easiest solution by far on one's wallet, that's for sure.

Here's additional food-for-thought. Why have most, if not all of the 500+rwhp 928's (..racing strokers and supercharged street) have experienced head-gasket problems? How could that be? I do not think in the least it's coincidental.

The 928 engine has only recently crossed the 500+rwhp mark, and for now there are only a handful of 928's putting out that kind of power using exclusively either centrifugal superchargers on stock blocks, or NA strokers (..soon to be a hybrid too, Big Bird). Both types have experienced the same kind of problems as the open-decked Honda, Subaru and 951 engines.

With so few 928 engines to openly observe at that hp level, it looks like the 928 block is dutifully headed in the same direction as the other high output open-decked engines too, shackled by a design decision motivated by cost and ease of manufacturing (..which more than suffices for lower horsepower applications though), apparently rendering it useless for high-horsepower use unless modified.

The higher horsepower may be causing the top of the unsupported cylinder to sway too much and chafe away at the head gasket, especially so in the case of the much thinner cylinder walls resulting from the 104mm bore of the strokers.

To illustrate what is going on, try this simple experiment. Get a tall water glass and support it only at the very bottom with your hand, and with your other hand, grab the glass anywhere and see how easy it is to shake and make the top of the glass sway (..that's the piston going up and down and pushing/thrusting on the cylinder walls). That's an open-deck block. To simulate a closed-deck block, grab and support the very top of the glass, and with your other hand, grab and shake the glass; comparitively, it is nearly impossible to move. Keep in mind the clamping force of the head is the same for both scenarios, thus it is omitted. Simplified I know, but illustrates the point nonetheless.

In closing, if the 928's open-deck block design is such a good idea, then why was the Cayenne engine designed with a closed-deck? Porsche could have chosen to cut manufacturing costs once again, but more than likely opted not to since they know an open-deck is not adequately reliable for 450hp at the crank.

heinrich

We are not talking about Hondas or Subarus or 951's. And actually I am willing to bet you have no knowledge of failures in those other cars as a result of open decks either. I know 951's very well, and have never heard of any single failure as a result of open deck design. My challenge stands, show me ONE 928 engine failure as a result of open-dec design. Here:

Just remove the words "open deck" from your post and it all makes perfect sense. You have decided that the open deck is the root of all evil, but you have done so with no data. I don't run waterglasses in my Porsches, I run Alusil cylinders. Using the waterglass model I can easily have you bend a crank out of solder, and stress it, and say "see, look, there you have it, all that strain on a crank will bend that sucker like a piece of soldering wire, therefore the crank design is a baaaad idea".

Do you want a wonderful example of the ultimate Open Deck design at over 1100bhp? Have you looked at the Porsche 935; 917 and all other air-cooled Porsche supercars? They are all OPEN DECK.

heinrich

How open does this Porsche 917 deck look to you? Can any deck be more open?

http://www.lnengineering.com/911.html

Lagavulin

A valid point for sure.

However, each one of those cylinders has it's own independent cylinder-head and head-gasket (..except the 964's which had no gasket and were crap) bolted to the top of it. When the piston pushes against the cylinder and rocks it, it's cylinder-head and head-gasket can sway along with the cylinder, maintaining the seal between the cylinder and the cylinder-head.

On the other hand, the open-deck 928 design shares a single, static cylinder-head with four cylinders. When the piston pushes on the cylinders hard enough, they will rock too; however, the cylinder-head and head-gasket remains static and do not move when the cylinder wiggles beneath it and subsequently fatigues it over time.

The 928 open-deck design sucks, big time, more so than even the Subaru's.

heinrich

I think that's reasonable ... how about we agree to disagree

Lagavulin

I'm disappointed that you didn't bite on the Subaru remark!

heinrich

Yes I had debated that option but in the end, I felt so much love from my supercharger and parts on the way, that I just had to share

heinrich

Lagavullin, you have just posted your 928th post.

SharkSkin

Maybe he'll stop for a while and savor it

(Sorry, Lag)