heinrich

That may be true (dunno) but the stroke on the 968 is the same as the 944S2 and those are longer than the GTS. We're talking about 2.1mm difference.

944 turbo 100 x 78.9mm
968 and 944S2 104 x 88.0mm
928S4 100 × 78.9mm
928GTS 100 x 85.9mm

Vilhuer

4 cylinder cars have few mm lower deck height than 928 and thats why they use same 150mm rod blanks as 928 while piston compression height is smaller than in 928 pistons while engines have same stroke even. Using 968 or 944 S2 pistons with GTS crank and any 928 rod will result piston being below deck at TDC.

heinrich

I don't recall someone saying they were going to use a stock 928 rod? And I recall someone relocating the wrist pin on 928 rods to alter this? But I thought the bone of contention here was not at the top but the bottom of the stroke.

Fastest928

If I remember correctly, Porsche used both Mahle and Ks pistons in the 968. There is a delta between the S2 piston and the 968 piston...the cutout on the skirt is different to account for the dleta in cw design between 968 and 944S2 strokes....the 968 has a deeper cut. Al the pistons are forged.

Way back when designing the original 8 CW DEVEK cranks, after multiple failures with 6 CW in high hp/rpm 928 applications (Bob D broke two), I talked to a factory engineer, he was the "crank, rods and pistons" guy, who provided background on 6 cw vs 8 cw designs and why they choose a 8 CW for the GTS and not the S4....

CP make excellent blower pistons...but does not use 4032...those CP's pics in the photos appear to be 2618....but only Jim will tell

IcemanG17

Bob D broke two cranks.........................DAMM...but he was pushing over 700hp too out of a 16V with super high compression...13.0 comes to mind from what Bud Hart said....

I can't think of a modern stroker crank failure?

Fastest928

Most, if not all, of the highest hp 928 engines are built using DEVEK 8CW cranks...Ott, Hanson, Dey, Fan, and others. plus there are now copies of them sold via moldex.


Best,

Marc

GregBBRD

I have all my Moldex cranks built using 6 counterweights...always have and always will. Moldex will build almost any crank, in any configuration, for anybody...including cranks with 8 counterweights, but Whitey thought it was "idiotic" to throw "extra" weight on a crank that wasn't spinning over 12,000 rpms. Whitey had a way of making things really simple, if you took the time to ask him.

I too have communicated with friends at Porsche about the 8 counterweights. They claim it was completely done in an attempt to make the engine smoother. The GTS models were so expensive, they felt that they needed to make the engine idle smoother to be accepted. No other mysterious reason...they just needed the thing to idle smoother for the "higher" end buyer.

It does not surprise me that some of the Devek cranks broke...if you've ever tested the "hardness" of "that" 4350 material. Not going to say much here...just that the "Chinese 4350 Steel" that these are built from, is not remotely the same as "Moldex 4350 steel".

As a point of fact:

Fan's crank was so soft that it wore out the rod journals without any damage or change to the rod bearings! The journals wore .0015-.003" undersize, but the rod bearings looked like the day they were installed! Granted, the rod bearing material I was using was pretty hard...but harder than 4350? Should not be! We thought that this crank must have "missed" being heat treated, but the guy that ground it .010" undersize said that it was the softest crank he had ever touched! It had to be replaced. We did use it to hold doors open when the wind blew....worked great for this....and the "extra" two counterweights did prove to be an asset, for this job.

Regarding the 104mm pistons in the 968 and the other 944 models....you guys are making this too tough. Porsche claims that there was only one variety of piston used in each of these models, without any overlap. If you look at "PET", you will note that they do not list a manufacturer of pistons under the list of replacement pistons, like they do, when they use both Mahle and KS in the same models (look in the 911 piston sections to see this.) One piston "style" used in each model. Porsche insists this is true...and would have a hell of a hard time providing a "Mahle" replacement piston for a 968, or a KS piston for a 944S2, since they don't even have a part number for one.

Fastest928

Greg

You *** u me wrongly - they were not DEVEK cranks!

The failures were not "just" a crank problem! It was a system design problem. When you build high hp 928 engines you learn things that others dont see.

Moldex makes nice products. I would have no problem ordering from moldex and have, although for chevy rocket block 421 ci engines and yea, 6 CW worked just fine.

That is interesting what Whitey said about 6 vs 8 cw cranks but I don't believe your story, and your factory friends claims.

Obviously, your conversations with your friends at the factory did not include data behind the decisions for an 8 CW crank. And it was not because of the desire for "smoothness", but even if smoothness was "desired", and it worked - point proven...right?

It is quite possible a crank was unhardened or "soft" as it left the Scat...possible, but most competent engine builders check hardness prior to building engines. I am sure you do also.

Who built Joe's engine?

Again, the highest HP 928 engines all have DEVEK 8 CW cranks in them.

Best,

GregBBRD

Very confusing....first sentence says they are not Devek cranks....last one says they are. Very hard to figure out. But, as I frequently say, I'm easy to confuse.

If you knew me better, you'd know what many others do...I don't lie and I don't exaggerate...lord knows that there have been enough people exaggerating about what they can do with a 928 to last everyone a fricking lifetime! So many people have been ripped off by "928 experts", it is hard to count them. Know this: I'm pretty active in this market and still in business...for over 35 years...in the same location. My phone number is listed and everyone can call and talk to me. My email address is common knowledge and I communicate with many, many people. I'm still building engines and developing pieces...every day of the week. I'm proud of what I do...and there are not many out there that have issues with me or what I've done! You can believe me about my conversations with Whitey, or not...that's your choice. However, I've got a whole pile of these engines running around every day, with 6 counterweights. If you feel better putting 8, 10, or even 12 counterweights on a crank...have at it! I've concentrated on reducing the rotating mass...not increasing it...

I do believe that you would be absolutely stunned at how many big 928 engines I build. You'd also be really surprised to see my shop and know that I have my very own Rockwell tester....but I've never ever ever felt the need to check a crank journal to see if it is harder than the bearing material....just something that never occurred to me to do. Putting a big "ding" in the middle if a crank journal from a Rockwell tester is, quite frankly, something that I'm not going to start doing/have never seen anyone do. Are you actually serious about doing this...or am I reading something into your post? Obviously, from your post, I'm not competent enough to build an engine, because I don't check to see if a crank is harder than the bearing, but I have always just assumed that this is a given. Silly me.

I build both Joseph's engines and Mark Anderson's engines...and there is and always has been an open invitation to anyone that thinks they are fast to come out to Willow/Fontana and race either one of these cars....with either one of them driving. Dyno results/horsepower claims are pure bull****....only one data point, in a pretty complex equation. Give me ET's or lap times and you begin to have credibility.

I frankly, have never had anyone come to me and ask me to build the highest horsepower 928 engine I can build. Just never has happened. I'm instead, trying to build uber reliable high output 928 engines, that can be driven every day for tens of thousands of miles....certainly a different market. The big horsepower engines that I build for "track" use seem plenty adequate for that use. More horsepower would be a complete waste, at this point in time. We are/have been tearing the crap out of gearboxes, as it is. Before the gearbox issue, we could not find a clutch that would handle the torque, but we finally solved this problem. We are addressing the weaknesses in the 928 gearboxes and will have pieces to upgrade these, in the future. Then we might go looking for more horsepower.

I find it very, very interesting that we have found the "limits" of the 928 drivetrain with relatively moderate horsepower (compared to your engines) and you never seem to have had this problem. Must be a "local" clutch/transmission/drivetrain issue, isolated to Southern California. This confuses me, greatly. Again, it is easy to confuse me.

Look, I really have no axe to grind, with you or anybody. I think that the "early" efforts to build high performance 928 engines were great, given the available knowledge. Many of the "early" efforts were obviously not perfect...there doesn't seem to be a huge quantity of these engines still running....and the "horror" stories are all out there for people to read.

However, given that I've been personally building 928 engines since 1980 and have been involved in the "stroker" efforts, from the very beginning. I'm smart enough to know that something which was "state of the art" ten years ago, is not be "the best" now....I feel lucky to be smart enough to know this. Pieces evolve and change...almost always for the better. If this was not the case, pieces would always remain the same....why change something that works perfectly? Hell, let's run Chevy offset rods in 928 engines forever!!

Look, I know I'm not perfect. I'm smart enough to know that the more I know about something, the more I don't know. I'm learning new stuff every day....and happy that I do. I'm living in the present, not languishing in the past.

There's a great saying, in racing, for people that try and live in the past: "The older I get, the faster I was."

That's not me. I'm more: "The older I get, the more I realize I don't know."

Cheers,

atb

Not my fight, but just an observation:

The highest HP 928 engines all have Louie's ITB set up.

danglerb

So what broke the cranks?

The boosted guys aren't having any crank issues are they with the stock cranks?

GregBBRD

Yes, they seem to do have this in common. I don't understand how Louie's clutch and gearbox stands up to this punishment.

BTW...Not a fight. Just observations and reality, from my eyes.

Rob Edwards

Let Mark A. drive it. He'll find the weak spot.

Hilton

I'd guess the harmonic balancer wasn't custom made to match the engine?

I don't have a clue what I'm talking about when it comes to engines, but I'd suspect that is more of an issue for strokers than for the boost guys, as the boosters run mostly stock internals/weights/dimensions.

GregBBRD

There's actually more to this whole crank story than I told. I've actually had 2 of these crankshafts in engines I've done/redone. One engine (that was built by one of the other "928 experts" ran for a total of 50 miles, before it puked (not the fault of the crank, BTW). However, the crank was so soft, that I swear, if it fell over, it would have bent in half.

I was actually going to use it, but I had already had the "experience" with Fan's crank....and was somewhat "afraid" of these cranks. I had my machinist check it. He called me up and made me come to his shop to see it.

This is no bull****. He was checking/balancing 2 engines, for me...at the same time...one with the Devek crank and the other with a Moldex crank. He had already drilled a pilot hole in each crank for a "chunk" of Mallory. He drilled a hole through a counterweight in the Devek crankshaft (where a Mallory chunk would have gone, if we used that crank) with a 3/4 inch drill. It went through that counterweight like it was made of 6061 T651 aluminum! He then drilled the Moldex crank...with the same drill. It smoked and drilled like you'd expect a piece of steel would. He stopped and stood back....and asked me if I really wanted him to continue. I called the customer and brought my machinist another Moldex crank, the next day.

Look, I know that Devek wasn't making these cranks in his shop out of a chunk of steel with a file. He didn't do it. I do know, from these two cranks, that there must be a huge variance in the quality of "Chinese Steel". I choose to use something different...and better, in my mind...in the engines I build.