Cylinder Head Stud: Choice, and Why!?

[Aircooled4evr]

I'm curious why everyone in here seems to choose e.g. Supertec Performance, ARP, and so on, instead of Porsche's own DILAVAR head studs?
If they really weren't good enough, why did Porsche use them until sometime in the 90's? They were, and are, not exactly engineering amateurs.....
There is a meaning to the fact that they expand at the same rate as the aluminum cylinders. And yes, they break over (after how many 10.000km's of use?) Today, our old 911s are lucky if they run 5000km in a season. right?

If it's a question of price, I can understand it. but otherwise, why?
I simply love the way Americans think out of the box, and down to earth approaching! so it should not just be the super rich who should be able to race, in their dream cars. But all men. who is ready to work a little for it! (ok, most cars have always been "somewhat" cheaper in the US than in many countries in Europe !!)
Thus, there is also far greater everyday experience with the Porsche 911 and race, in America than in Europe, where the former applies to a great extent .... So "You" can easily have a lot of knowledge, "We" miss.
Is there a compression problem, if one is looking for more hp than original? (in my case 280 to 300hp in a 3.0l SC block, (now 3.3))

So what would YOU choose, and perhaps more importantly, WHY?

Thanks in advance for your answer, Mads

[Aircooled4evr]

whoops, I think I left out an important detail... My dream, (until I get in touch with Henry Schmidt again) is to use 100mm 964 cylinders, and CP pistons. And thus I will have to mill the holes in the cylinders up, to make room for my SC head stud pattern... Maybe Dilevar is too wide?

[RDM]

The Dilivar studs corrode and fracture, leaving you with broken head studs. The steel ones do not corrode and fracture.

I'd say that's the main reason I changed to the Supertec studs.

[winders]

The exception here is the 993 Turbo dilivar heads studs which are used by most of the top high output engine builders. Certainly on 3.6L and larger builds.

[Ollies930]

There have been about a thousand discussions on every Porsche forum wether to use Dilavar or aftermarket head studs. The people who believe that everything Porsche has done is beyond reproach, use Dilavar. Others, who know that everyone is fallible or have had a bad experience with Dilavar, will use someone elses. There is also a question of application. On a monster turbo that makes silly cylinder pressure and you have to torque the studs to 50-52ftlbs to keep the heads from lifting, there is no way you would use Dilavar, but Henry's studs (Supertec)would more than likely hold up.

Winders
the people who build serious turbo motors, do NOT use Dilavar. Look at Evoms website for instance, he has somebody custom make studs for him. Dilavar would never hold up to 1500-2000hp kind of cylinder pressures.

[winders]

Actually, I was thinking about normally aspirated engines as I have never contemplated having a forced induction engine built so I have not researched head studs used for that application.

I know that Jae Lee and William Knight use and recommend 993 Turbo head studs for their normally aspirated high output builds. Knight uses 993 Turbo head studs on his big turbo builds too. Steve Wiener uses them as does Aaron from Burnham Performance. I am pretty sure Jeff Gamroth (Rothsport) uses them too.

I don't think this is a "Porsche does no wrong" deal. It is a "what works for them" deal.....

I think Peter Dawe uses SuperTec.

[Mark Henry]

I've used stock (all steel), ARP and I have Henry's on my 3.0 twinplug.
Stock (all steel) has it's place, I didn't like the ARP over torque spec and IMO Henry's are a nice piece of kit.

[Henry Schmidt]

Pelican Parts is the #1 seller of Supertec head studs.
There are many reasons to use Supertec studs. Clamping force is the number one reason.
The Dilavar stud was not a response to improved clamping force. Quite the contrary.It was a response to warranty issues. The factory was seeing warranty claims based on cylinder head leaking on cool down. It was simply a cost vs. performance question. The factory's attempt to phase out Dilavar in the 964 is a perfect indication of this.
They tried half Dilavar, coating the Dilavar, all Dilavar, steel and then all thread and never changed the cold clamping force of the studs.
They finally managed to phase it out completely in the 996 GT3. Mezger based engine. Strangely they stuck to the ridiculous all thread design (an attempt to improve clamping force) but not Dilavar.

The Supertec design (coarse/fine thread) is the same design used by Cosworth, Hewland, Rolls Royce, Lycoming and almost every designer that torques a stud in an aluminum part in a high performance application.
The coarse thread offers the best holding power in the aluminum case and the fine thread nut end offers improved accuracy.

There is also the issue of environmental exposure. The cylinder head studs in a 911 operate in changing environments. By that I mean, every stud has a different exposure to heat. If heat changes the expansion of the Dilavar, how can you get even clamping force across the entire bank of heads?
Answer, you can't. Control expansion by reducing the environmental effect and you improve cylinder head stability.

Supertec studs also offer an ease of assembly not available with Dilavar studs.
With Supertec studs, you can install the piston /cylinder combination before you install the stud.
This technique shaves hours off the assembly time. There is also the convenience of no need to set stud height. The fine thread, 12 point, 12.9, flange nut used by Supertec is light years ahead of the course thread Allen nut Porsche started using in the 60s.
Keep in mind, this 12 point nut also gives the builder spark plug clearance necessary for twin plug application.

I wasn't aware that Aaron was using Dilavar. Funny thing you should mention Aaron Burnham. Just last week we were spitballing ideas to improve the Supertec stud. The discussion centered around ways that we might reduce clamping pressure to eliminated excess forces. The decision was, maybe changing a 20+ year old part that has zero reported issues might be chasing unicorns.

One the most interesting engine builds on the "Engine Rebuilding Forum" involves Tommy Olsen. You might note that when he chose a head stud for his ground breaking build, Supertec was his choice.
If you want some insight as to those who criticize our stud, ask them if they have ever tried them. To my knowledge, only people trying to over-torque or install the product improperly have ever complained about these studs.

Many of the most vocal champions of Dilavar have never built a 911 engine.

[winders]

Yep, Kevin Roush uses a proprietary stud or the 993 Twin Turbo studs....another builder that doesn't think that 993 Turbo studs are terrible.

I am really tired of this crap that says because I don't build engines that I therefore can't know anything and have no right to speak.

No where have I said that Henry's studs are bad. All I have done is post what my research into the subject has revealed....which a lot of respected race engine builders like, prefer, and use the 993 Twin Turbo studs for their builds. That counters the argument that all dilivar studs are always an abomination. I am sure that most are...but based on my research, at least one part number is not.

Hell, if anything, Henry should recuse himself from such conversations as he has a massive conflict of interest. Of course his studs are the best...he would say that even if they were not.

[Ollies930]

Or maybe we will keep listening to Henry, who has been an extremely valuable source of information on most anything regarding building and tuning Porsche engines on this forum and ignore your internet based knowledge. Maybe before you make any more statements like the one above, you should meet and spend some time with Henry and check out his studs in person and have him explain the engineering and metallurgy behind their design.

[Henry Schmidt]

Just to be clear, Scott called me out by name so I will respond.
It seems in response to "Cylinder Head Stud: Choice, and Why!?" Scottie is offering: "if I was going to build an engine, I would use Dilavar because all the cool kids do it".

That's why experience matters: you can give advise based on actual results not supposition based on "research".

[detroit]

As I'm just about to undertake of a 3.0 SC motor this is a very timely topic...

Henry one thing you stated intrigues me. What design aspect of your studs allows for installation post cylinder/piston install? Or perhaps a better question is what design aspect of other studs precludes this?...

[Henry Schmidt]

Originally Posted by detroit

As I'm just about to undertake of a 3.0 SC motor this is a very timely topic...

Henry one thing you stated intrigues me. What design aspect of your studs allows for installation post cylinder/piston install? Or perhaps a better question is what design aspect of other studs precludes this?...

Most head studs designed to work on the 911 engine require a specific stud height measurement. Although it may be possible to measure head stud height after the cylinder is installed, it would be challenging. The Supertec instructions clearly state that stud height is no longer an issue (extra length and 12 point nut) and that means installing them after the cylinder is in place is now a preferable assembly technique. (See pictures in post #8.)

[detroit]

Ah!... That is due presumably to the internal drive nuts used by the factory. If the head studs are too long, one won't be able to tighten them.
Thank you, sir!

[Henry Schmidt]

Originally Posted by detroit

Ah!... That is due presumably to the internal drive nuts used by the factory. If the head studs are too long, one won't be able to tighten them.
Thank you, sir!

That is only an issue with Porsche weird head nuts.
Our 12 point nut allows us to play around with thread depth and OAL as well.
Our stud has a longer case end thread which allows for maximum thread engagement. Our longer OAL allows for custom, long rod builds that require a taller cylinder stack. All in all, far more versatile than the arcane design Porsche refused to amend.

[Coupe 77 silver]

Originally Posted by Henry Schmidt

That is only an issue with Porsche weird head nuts.
Our 12 point nut allows us to play around with thread depth and OAL as well.
Our stud has a longer case end thread which allows for maximum thread engagement. Our longer OAL allows for custom, long rod builds that require a taller cylinder stack. All in all, far more versatile than the arcane design Porsche refused to amend.

Your studs look nice Henry and I like the feature to install the studs after putting pistons and cylinders together. Discussing different stud materials became a kind of "religion", together with the methods to reinforce the according threads in the crank case. Either Magnesium-cases or Aluminum-cases. What kind of case savers do you prefer? Timesert, self made bushings,...?

Many thanks in advance.

BR
Omer

[Henry Schmidt]

Originally Posted by Coupe 77 silver

Your studs look nice Henry and I like the feature to install the studs after putting pistons and cylinders together. Discussing different stud materials became a kind of "religion", together with the methods to reinforce the according threads in the crank case. Either Magnesium-cases or Aluminum-cases. What kind of case savers do you prefer? Timesert, self made bushings,...?

Many thanks in advance.

BR
Omer

The CaseSavers we us are custom made...a left over from the old VW type I days.
It's a steel, 10 X 14(2.0)mm insert. Different builders have different preferences but we use the open bore type. It allow for better thread engagement.

[Mark Henry]

Originally Posted by Henry Schmidt

The CaseSavers we us are custom made...a left over from the old VW type I days.
It's a steel, 10 X 14(2.0)mm insert. Different builders have different preferences but we use the open bore type. It allow for better thread engagement.

I agree, they're slightly bigger and longer than a timesert. They've been used since the 60's, the 70's beetles with the AS21 mag cases for the 1600cc these casesavers were installed from the factory.
Casesavers are a standard upgrade when we machine T1 cases. They have to be done right, you want them straight, so they should be done on a mill.

[Henry Schmidt]

Originally Posted by Mark Henry

I agree, they're slightly bigger and longer than a timesert. They've been used since the 60's, the 70's beetles with the AS21 mag cases for the 1600cc these casesavers were installed from the factory.
Casesavers are a standard upgrade when we machine T1 cases. They have to be done right, you want them straight, so they should be done on a mill.

Sliding cylinders over porcupine studs....yikes. 993 all-thread Dilivar....forget about it.

Another benefit of using Supertec studs when installed after the cylinder is in place. The slight misalignment of CaseSavers in not a catastrophe.

[KNIGHTRACE]

I was asked for my opinion on studs by a few people recently. The most important thing in studs is the proper expansion rate in relationship to the motor and of course not breaking. I have used stock steel studs, 993 TT and supertech studs with good results.. I have had ARP and RACEWEAR give problems from not enough expansion. That being said it depends on what the motor is used for and what the power level is. If you building a 200 hp to 300 hp street motor even ARP or Racewear will be fine.. It also depends on the case, 993/964 have O rings and no copper base gasket to crush and cause leaks.
I use the 993 TT on my higher HP builds because I have very good results with them.. The supertech stud could be as good or better in that application I just do not have the experience with them north of 400 hp to say for sure. I have used them in 320 3.6 builds and a few 3 liter to 3.2 motors. They look like a good stud, The advantages they have like install after the piston and cylinders are on is probably helpful to a nonprofessional engine builder. I put them in before P&C so little to know difference. I have used the 993 TT on a 3.5 liter turbo motor I ran at 2 bar of boost with no issues.
if your building a mag motor I suspect the supertech stud may be the better choice due to Henry putting in much more time and effort than even Porsche did. If it doesn't expand enough on a magnesium motor you pull the stud from the case not break it. Henry has had 44 years to improve the stud on those motors when Porsche stopped, I have a similar advantage on camshaft design, I have had about 25 years of development and testing since Porsche quit.. These advantages or advancements made by small shops like Mine and Henrys and other shops help the enthusiast today. It give you good choices.
Summary, there is a time and place for everything and you have to factor cost vs benefit.