Too much emphasis is placed on breakage alone.
We have seen a total of 3 broken Late Dilavar studs. Keep in mind that we work primarily on early, 89 and earlier engines by choice.

What we do see more often than not (that means most) is seeping at the head and evidence of cylinder to head movement. I assume that this movement is caused by an insufficient clamping pressure offered by properly torqued Dilavar.
Simply put, the head studs allow the head to lift off the cylinders.
This is not the case with our studs.

henry, pm sent. johnny in alpine.

If we accept for argument sake that dilavar has similar expansion rates as the cylinders and steel less so then in theory the steel studs will have a higher clamping force when at operating temp than dilavar. Instead of trying to prove or disprove it with math why not look at the cylinders from each after being run for a long period of time. I would imagine a large bore 100mm cylinder would show uneven wear patterns if it were being over torqued from the differences in expansion rates on the steel studs. It would also show in the leakdown test.

I am just offering another way to look at things.

WE do and we have. The results are that the Dilavar studs show signs of extensive head movement where the Supertec studs do not.

We see the same movement with Racewear and we see ARP head nuts coming loose so those heads are definitely moving.

Of course we see most of this phenomenon with race / high performance engines.

I am sure the Supertech studs are very well made and good. However, the issue of studs breaking is something rare.

I am sure if you asked ARP or racewaer thay may say the same about the Supertech studs.

Most often, heads moving and leaking is the result of some other issue. Pistons hitting, Heads softening from use and the washer load bearing surface collasping, the case threads pulling or stretched in the case. ARP and racewear studs stretching under load I find hard to believe as the tensile ability of the materials used is well above the tensile values exerted upon use.

Seems to me studs are sold and promoted for the sake od making sales and not finding the real cause and solution.

JMHO.

If you're going to post a veiled accusation that I'm lying about my observations just to make a sale, the least you can do is use your name.
JMHO

I spend a great deal of time here assisting DIY engine builders in their pursuit of excellence. I'm not going to be called a lyre by some Gysmo who lacks the stones to use his own name.

http://forums.pelicanparts.com/uploa...1265584521.jpg

I am sorry, I did not hear anyone accuse you of lying here. The underlying problem is that the obvious self promotion and quiet sales has no place in a forum like this. In my last post I stated the same thing, I have nothing against you or your products but I am not fond of your self promotion or the fact that you obviously get angry when someone calls you on it.

Ouch!!!

I suppose that puts me in my place.

There are many company's who build engines with some very talented experienced personnel that do not behave the way you do we questioned about their products or ways.

They are either knowledgeable from experience or have an engineering background where they can answer questions with emperical data, unlike yours.

Gizmo is kind of cuddly but do feed him after midnight or he'll gum up the works.

No, I didn't put you in your place. I just asked your name so that we could put an appropriate weight behind your words.
If we knew who you were, we could understand the experience and engineering behind your claims.

I put my name behind my posts and yes I make a nice product that I'm proud of.
Americans used to be proud of what we made and weren't afraid to say so. I guess I'm a throw back.

And you've done what to contribute here?

No one has attacked you sir, or your product.

If you feel your answers have in some way contributed here, I stand in humble silence.

However, I read posts by Rennsport, Burns Bros and others and learn something.

Head Studs
 

I hve been trying to follow all of these posts with a detached and objective attitude as some of the questions raised seem quite important and valid but some of the staments being made concern fundamental engineering and don't seem to make sense.

Dilavar seems to be condemed out of hand for all sorts of reaons but lets look at the basic case for using this material.

The basic alloy is a realtively high Nickel content steel with a controlled expanison of 20 x 10^-6m/m/degK - very similar to an Aluminium Alloy barrel but higher than a Biral or cast iron Barrel and maybe its not a good idea to use this type of stud on an early engine as they may lose clamping force with expansion.

There doen't seem much other information about Dilavar other than its tensile strength which is quoted at 170000psi.

We also know it is non-magnetic and this would indicate that it is an Austenitic Stainless Steel which, I believe, has been precipitation hardened to produce the high level of strength.

It would also be good to know the Young's Modulus for this material but as it is around 80% iron a figure of around 195GPa would be a reasonable guess.

I have asked the manufacturer for data on several ocassions but without success.

If a Dilavar stud is correctly tightened I can see no reason why clamping force would be reduced when the engine was running unless it had Biral/cast iron barrels (see above)

I would agree that the clamping force would not increase as much as a conventional steel stud as the engine warmed but there would be no other differences.

Even if we consider ignition forces on a Turbo engine there should be little effect.

Assuming a BMEP of around 15MPa the force on a single head would be about 165 lbs. This would increase the stress in each stud by about 500psi.

Assuming a Supertec stud has a similar Young's Modulus to Dilavar there would be little or no difference.

As we don't have any information about Supertec studs again the Modulus Value is an estimate but all alloy steels tend to be between 193 and 202 GPa so errors would be very small an well within the normal scatter caused by manufacturing tolerance and torque wrench uncertainty.

The only real problem I can see with Dilavar is that if it is an Austenitic Stainless Steel it will be prone to Stress Corrosion Cracking particulalry in the presence of Chlorides and this must be the cause of failures.

The phenolic coating on the new studs would help this problem.

I was interested by the example of the Dilavar studs which seem to break after a few years of being tightened in a engine which has never run nor been outside.

I am not really able to find a failure mechanism that can account for sudden brittle facture in these circumstances. The only mecanism tht could cause this type of failure is Hydrogen embrittlement but I don't think Dilavar studs are electroplated and I can't see another source of hydrogen and Austenitic Stainless Steels are are commonly used in Hydrogen environments as being safer than more conventional engineering steels.

I would be confident that using Dilavar would be a good idea on early mag case fitted with Nikasil barrels.

The relatively low Young's Modulus of magnesuim alloys would allow the thermally induced stresses to concentrate around the studs and any reduction in strength of the Elektron caused my overaging would account for failure.

This is much less of a problem with a Biral or cast iron cylinder and with an Aluminium engine case.

Looking at the ARP studs, there is reasonable information about all of the alloys the supply and with the exception of mag cases/Nikasil barrels I can't see any problems.

If the nuts used on these studs are coming loose then they were either not tightened correctly or they haven't been machined correctly so the thread from is wrong. It is fairly easy to measure the thread form. I can't see any meatllurgical issue with ARP studs.

My conlusion is that in terms of stud selection there isn't really a one size fits all.

I would certainly use the latest spec Dilavar without too much concern, especially on ealry mag enines with Aluminium cylinders but not with Biral or cast iron (as previously stated)

I would be quite happy with the majority of ARP fasteners on Aluminium engines as there is sound data available.

With regard to Supertec Studs, I am sure that they do just what is promised but I would be nervous about the lack of technical data and probably not use them for this reason.

Wow, I've posted 3,300+ times and you haven't learned anything from them? Here's something to learn.

Please note that I did not participate in these threads: Of course this is a very small sampling.

http://forums.pelicanparts.com/911-930-turbo-super-charging-forum/520405-head-studs.html

http://forums.pelicanparts.com/porsche-911-technical-forum/151881-ultimate-head-stud-poll.html

The technical data / material spec sheet has been posted more than a couple of times. I will post it again when I return to the shop.

Oo-oo-oo-ooh boy, that sucking sound you just heard is Henry running to the Supertec Technical Reference Library.

ix0ifan, nice writeup, btw.

For me, I'm outta here. Two active threads on the same subject is just a bit much, don't you think?(The other Dilivar thread)

I used the 993tt head studs because....

Strong endorsement by Steve Warner.
Previous 993tt never leaked at 600tq x 600hp
2 other builders (not going to name drop because they are not part of this discussion and I don't want to be quoting them) of BIG 3.8 turbo motors uses them. Both of these guys have done tons of these builds without head leaking issues.

As a previous poster said there is no one right answer. It all comes down to making a choice based on what you know and who's opinions you trust the most. While I truly respect and value Henry's opinion the other side of the table has a longer list of people who I also respect and trust.

this is an interesting read... I read thru most of it just to understand why my Dilivar studs broke in my SC. I just recently had to pull my engine to address the issue. of the 12 Dilivars, I had 3 missing and a 4th simply break off in my hand. All of them seemed to be broken at or near the same place and all of the non-broken studs had corrosion at the same spot on the stud. For me, the problem was simply corrosion and time. So.... do the new 993 Dilivars have a new metalurgy or is it simply the same ole Dilivar with a better coating? If the metalurgy hasnt changed, only time will tell if the special coating will last. Considering all of this, I cant make an argument for Dilivar. So to answer the original question, "I would not use the 993 studs unless money is an issue." its all a calculated risk.

FWIW, I went with OEM steel studs, top and bottom when I put my SC back together, simply because of costs and the fact that its just a stocker. I replaced all of the exhaust studs and re-used the allen hex bolts and washers when I could.

At what point does an engine builder start to be concerned about the strength of the case? I know for a fact that I had several head studs that I was not able to "bottom out" into the case because of the limitations of the allen head stud nut threads(wayne's book). So basically, im not using all of the available threads on the bottom so I can use all the threads on the top. This might not make much difference on a stock motor. On a much higher HP motor or a Turbo, I would want as much thread in the case as possible. Supertec studs seem to address this issue due to the open end nut.

As controvertial as head studs apparently are, Henry made a very good stud. He did his homework and did not compromise. The material specs have been posted numerous times and IIRC they are similar to steel. The studs do not loosen up nor have I seen issues at the sealing surface.

The last 993 dilivar studded engine that I was around had to have one head welded and resurfaced due to excessive head movement. 4 out of the six had movement. This was a 3.0 liter turbo.

Hundreds of engnes have Henry's studs in them with zero problems reported. That's pretty good claim to be able to make.

[QUOTE=Kemo;5173207]
On a much higher HP motor or a Turbo, I would want as much thread in the case as possible. QUOTE]


I don't think that the horsepower has much influence on the studs. If we consider the barrel/head as a closed hydraulic cylinder the ignition forces involved are relatively small compared to the preload.

The forces involved due to thermal expansion are much more significant.

I think high horsepower turbo engines must have higher case temperatures and would almost cceratainly have higher head temperatures and this is the most damaging effect. The very high power Turbo engines seem to have water cooled heads to help with this problem and the engines with EB welded head/barrels eliminate the problem of the thermally induced stresses by removing the expansion/seal problem completely.

I would think that when using Nikasil cylinders the hotter the engine the more Dilavar is the best solution.

The length of thread engaged is also probably a bit of a 'red herring' and I think that the improvements offered are not too significant.

With a simple nut and bolt the stress distribuiton within the nut is very poor.

The first engaged thread carries a disproportionate amount of load.

The other threads only carry the amount of load transmitted to them by the deformation of the threads. About 35% of the load is carried by the first thread.

The last thread carries zero load and making nuts longer does little to increase their strength.

A similar situation exists with studs and the first few threads carry the majority of the load so I don't think adding a couple more threads would do much for the overall load bearing capacity.

Just searched for the Supertec Stud spec and found the following:

17-4PH 38-42 HCR 4hrs @1025

I think this translates as: (I hope I interpreted this correctly)

17-4 PH is a precipitation hardening maternsitic stainless steel

38-42 Rockwell C is the hardness condition and equates to values between 175000 and 195000 psi.

H1025 is the aging condition and relates to 4 hours at 552degC with a typical hardness of 38HRC (175000 psi). This is also known as an overaged condition.

It's Young's Modulus is typically 196 GPa and Coefficient of expansion
11 x 10^-6 m/m/degK

It is rated as having excellent corrosion resistance.

As with all of this type of alloy heat treatment is very significant to ist performance.

In a solution treated condition this material will have a tensile strength of around 160000psi but its corrosion resistance and resistance to SCC will be poor.

After precipitation hardening the corrosion resistance increases significantly but is resistance to SCC isn't great. At a strength of 195000psi it would be rated as 'poor' in this respect.

Following a heat treatment complying with H1025 resistance to SCC is said to be excellent and this still relates to s strength of 170000psi (38HRC)

As ageing temperature increases resistance to SCC continues to improve and H1150 is the optimum heat treatment if this is an overiding factor. (33HRC, 150000psi)

In fact in sensitive application areas such as oil fields or petrochemical plants a maximum harndness os 33HRC is specified as in the presence of sulphides and chlorides some failures have still occured, but these are very 'ugly' environments.

I have used 17-4PH for transducer applications in the past (force measurement in helicopter engine dynos) and I am sure it is a very good choice, the only problem that could occur would be due to incorrect heat treatment.

I would agree with your thread theory if the threads were not loaded in the first place. Supertec studs allow you to install the stud to the bottom of the hole and tighten them some, which loads all the threads making the entire tapped hole part of the load bearing structure. Without pre-load in the threaded hole, like most other studs, the first few threads indeed carry most of the load.

Lindy

The stud material Henry chose WAS directly from the 935 program.
They dumped the dilivar studs due to the heads lifting at higher boost levels.

So Porsche eliminated studs completely from their prototype turbo programs... and eliminated Dilivars fro the 935 program. To go back to a Dilivar after they eliminated it does not seem prudent.....


You will have to clarify, this seems more appropriate in sheer/or bending loads(at the nut)....not tension. Truthfully there is too much mental masterbation over this, no offence.

Just because Porsche continued the Dilivars into the 993 turbos does not mean they are right....They thought running 9mm rod bolts was an appropriate choice as well.

ixOifan,

Pretty sure you have gone over the top of most heads here.

I think all of the studs offered to the aftermarket are good and very similar in quality,including the Supertech ones. These would include ARP, Raceware, A1 Technologies and the Porsche OEM. The missing brand is the Performance Development studs.

They used to make studs for many years before ARP and Supertech were around. Raceware were making studs back then. PD stopped making them as the newer Porsche OEM types are a good stud. Prior to these newer OEM studs, the Porsche Divilar types were prone to fail, so PD made a stud as an alternative. Cannot tell you what material they were made from as I do not have this info, but I do know it was special. There were never any issues with these studs.

I have been told that the reason heads come loose is never because any of these aftermarket studs fail. I am sure there are many engines out there that have Raceware, ARP, Supertech, etc and never had any failures. In most cases I'm told failures occur due to other reasons. Poor quality threads in the case often caused by studs been installed all the way to the bottom then tightened. All this does is stretch the threads in the case and weaken them. Or the heads collapse around the stud due to a softening of the head material from use, or from overtightening of the nut. Always user caused. Most of the time the builder will always blame the stud, never what they failed to address.

It was found that when all of these factors were addressed, the new OEM stud worked very well. I asked Neil once why they stopped and his reply was " if I wanted to make something just to put my name on it to sell, I'd go into the T shirt business".

If there is no engineering advantage, why do it? I suppose one could argue that Raceware and ARP are in the fastener business, so it make some business sense to make an alternative. But an engine builder doing this just to do it, make sense only if you want to sell something. It's apparent then that PD stopped making the aircooled studs because the OEM stud did it's job and well.

I think you are correct about staying with the OEM stud. As it has been suggested in other posts, some really well respected engine builders use the new OEM stud without any issues.

If you have any doubts about what stud to use, I'd stick to the OEM stud and look at the other factors. Case threads, Washer platforms in the head etc., before spending any money on any stud. After you have these all sorted, make up your mind based upon good engineering judgement, nothing else.

Call Steve @ Rennsport, Neil @ PD, ARP and get their opinions. At least you can speak to people who understand engineering and who are engineers.

Good luck, but reading your posts gives me reason to think you have this all figured out already.

This statement seems to talk down to the potential reader. Seems a touch condescending. I guess I'm not the only one guilty of such transgressions.
Call your experts and ask if any of this is false.



The potential benefits of fine threads are:

1. Size for size a fine thread is stronger than a coarse thread . This is both in tension (because of the larger stress area) and shear (because of their larger minor diameter).

2. Fine threads have less tendency to loosen since the thread incline is smaller and hence so is the off torque.

3. Because of the smaller pitch they allow finer adjustments in applications that need such a feature.

4. Fine threads can be more easily tapped into hard materials and thin walled tubes.

5. Fine threads require less torque to develop equivalent bolt preloads.

On the negative side:

1. Fine threads are more susceptible to galling than coarse threads.

2. They need longer thread engagements and are more prone to damage and thread fouling.

3. They are also less suitable for high speed assembly since they are more likely to seize when being tightened.

It seems all the negatives deal with assembly error. Our design addresses thread galling issues with dissimilar materials and anti seize.

Potential benefits of the 12 point nuts.

1) Quality of material 12.9 fine thread

2) Ease of assembly, standard 12 point socket

3) no need to measure stud install height

4) spark plug clearance for twin plug application

5) will never seize on stud from corrosion

On the negative side

1) can't use your cool allen wrench

2) Need to make new cylinder holders for assembly.

Forgot one more thing, the nuts are manufactured for Porsche and carry a Porsche part number.

BTW: m42racer Thank you for allowing me to list the engineering advantages of Supertec studs. It's not advertising if you're just answering a question. Any more questions.

To summarize this WHOLE thread:

Old Dilavar studs suck
Stock steel studs suck for anything bigger than 2.4L
Fully threaded 993TT studs work awesome, but can still corrode
ARP studs seem fine, but...
Supertec studs have taken the lessons above and applied learnings from them all with diligence and care.

I've said it before: I took every detail in this thread, many even before the were written, and chose the Supertec studs. 993TT were a VERY, VERY close second - price was the tie breaker.
If you've ever held a set, you'd understand.

I may sound like a "honk", but b#!!$hit walks...I work with guys I trust. Cross me once and I am done. Every penny I have spent with Henry has been unregretably spent. Same goes for Steve Weiner.

I rebuilt my 88 Carrera due to two broken Dilivar studs with 88,000 miles. These studs were the coated studs to prevent corrosion which didn't stop the studs from breaking. Dilivar studs will break. Carrera's are getting to be old enough to repeat the same thing with studs that SC have been happening for some time. This will continue as dilivar ages.

Using an after market product make a lot of sense as well as being less expensive to buy than replacing the stud with Porsche replacements as that would cost $740 for using 12 dilivar and 12 steel with washers/nuts and over $1000 for all dilivar. I have read the threads over the last 7 years and have seen many threads about broken studs. DILIVAR FAILS! Just a matter of time.

The engine builders that post here are a great resource for all of us here. Of course each of them have their way of doing things and what they have found to work. How many of us here have rebuilt hundreds of engine to know what works? As Aaron stated that heads move when using dilivar. Pretty hard to argue with this as more than one engine builder is seeing this happening. And I have read threads about the ARP nuts coming off. Might be an installation problem but the ones that I saw were sure they were torqued properly.

When I did my engine I used steel all the way around. Had this been for racing or higher compression I would have used the Supertec studs as IMHO are superior to the other available options. As Aaron said, Porsche thought going to a smaller rod bolt was fine too. Not so much. There have been many examples of failures from the rod bolt stretching. Mine has ARP. There are products that are better than what Porsche designed, head studs and rod bolts are just a couple of them. As far as promoting products here I have no problem with it as Wayne doesn't seem to have a problem as they sell the product.

m42racer
I would like to know more about heads softening. I have not seen any reference to
this before.

+1 on what Aaron said that this subject There is too much "mental masterbation" over this subject. Use what you are comfortable with. There is more than enough info to make a decision...

For those of you with sensitivity towards passionate retort please skip this post.
V
V
V
V
V
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More than once on this and other threads I have been accused of touting my products for profit.
Just to be clear, I make 10 sets of studs every quarter (making me the smallest player in the market) most of which we use . I could and do make more money playing poker than I do selling studs. I make them because I don't feel that any other stud on the market is good enough for my motors.

Some people put their name on tee shirts. I put my name on every motor Supertec builds and behind every post I make. Our motors may not be the best product on the market but they are the best we can build. I use our studs because I believe they help us to build the best engine we can. I'm on this board to help you DIYers do the same.

If bragging about my products seems somewhat crass, oh well. I've been called worse.
There is an ignore button that allows you to skip my posts, if you are truly offended please use this option.
Cheers

You make the studs or do you have them made? I don't care either way but if you have a thread rolling machine why not make rod bolts and other fasteners? I still want to know if the original poster was helped throughout this bloated thread?

Time to go
 

Having followed this and many other threads which try to deal with what seem to be serious issues I think its time to go.

We have the studs made to our specifications by a company that makes studs for other Porsche stud suppliers. They actually market their own stud and find my design and material superior to theirs but too expensive to make a profit manufacturing.
They also feel that Porsche owners are finicky about new designs so they thought a conventional looking stud was easier to market. Their words not mine.
We don't make rod bolts because we believe that ARP got it right with their rod bolts.

When Steve @ Rennsport talks....I listen. That is all I needed to hear on this subject.

Einstein wrote, "Blind respect for authority is the greatest enemy of truth."

Henry, I have worked with Steve on several Porsche projects from my 993 to my current 3.2ss. I dont have blind respect. He has fully earned the respect that I have given him and his company. After spending several hours in several different instances talking to him (as well as spending thousands and thousands of hard earned dollars) and analyzing his advice, I choose to take his opinions and advice with authority. I have never heard him say derogatory things about his competition or talk down to me or others. This does not mean your advice etc isn't appreciated because it is. I just dont appreciate your superiority complex over others in your field. You may be the best in the business and quite frankly I haven't heard anything negative about you or Supertec. I am sure that you didnt get to where you are by not being very good. In fact it is probably to the contrary. It just seems that you like to get people worked up. That is all well and good sometimes. In fact, I do the same from time to time. You would probably be fun to go have a beer with but it just seems a bit childish here. Just my opinion. Im out.

I've used both Supertec and the late 993 Dilavar studs and I like both.

Personally, if there is no corrosion on those Dilavar studs I would use 'em.

Carrerax let's evaluate your last post.
You don't want to hold hands, walk on the beach and you're not going to vote for me as prom king. You can't believe how sad that makes me.
I'm not here to be popular. If you don't like my style don't read my posts.
First, I have never said anything bad about Steve or anyone else who didn't attack me first.

Let's evaluate Steve's statements.

Originally Posted by Flieger View

I will admit there are better studs, though.

Steve's response
Not really,....
This is in fact him (Steve) saying, no stud is better.

Next we see this

"To be fair, we've not used the Supertech head studs as of yet simply due to our successes with the late 993TT studs (same as RSR/GT-2)."

I wonder if we would have a 4 valve head if Cosworth would have taken that same stance. "two valve heads have been so successful why would we try 4 valves".

Next we see :
"R&D and new product evaluations are normally done on our own personal equipment or when a customer consents to being the "guinea pig" in such rare circumstances."

None of this is wrong, it just shows a mindset. We were willing to identify a problem, step out of the box and try something new. Strangely enough not one person who has actually used our studs has ever reported to me that they had a problem. All of the critiques comes from people with ZERO experience with my product, stating someone else's experience. That is blind ....edit....respect for authority. "Porsche did it so it must be good", "we never used those but these are better because we have used them successfully". The logic escapes me.

I get it. Some of you don't like my style. I don't care. Just try your best to set personalities aside and reason through the information.

Steve @ Rennsport has my full support and I suggest any of you out there who have received his unselfish support for years, do so in thread as well.

"Blind authority"? Enough is enough.

Don't be an idiot.
I didn't mean to say "Blind authority". I meant "blind respect for authority".'
All that means is you should open your eyes and see what is right in front of you.
Steve is a great asset to this board and an honest agent. He stated what he honestly believes and then added a caveat.
All I did was ask you to read what he said and don't ignore his caveat.

Opps I just reread my post and I was wrong. I meant to say "blind repect for authority".

Such a passionate topic.

We all know porsche used dilavar, had problems and switched to steel. They then started reusing dilavar again. One has to ask why? Economics? Doubt it. Why switch back to something that caused so many problem after finding a solution for it? What do the smarty pants engineers at porsche know that we don't?

Porsche only has to design something to make it through warranty. Of course we know that dilavar has lasted much longer than that but they have continued to try and make different versions of these studs to get it to work. The newest threaded version has not been out enough to know if they solved the issue. From some reports they have broken before the engine was ever started. There is enough information to know that dilivar breaks and is not just SC's that have broken dilavar studs.

After reading just about the entire engine rebuild section before I decided on what I was going to do on my rebuild, factoring the budget, that I was not going to use Dilavar. This subject has come up numerous times and every one can use what ever they want. If you think Porsche had the best product use it, you or someone else gets to fix it again as the odds of failure are good, historically speaking. Others will use a superior product or even Porsches own steel studs of which there have been no failures that I have seen or John Walker has stated that he has not seen them fail.

I have taken advice from the posts of Henry. Steve, Aaron and John W as they are of great value to this forum and all contributed to my engine rebuild. Someone here tell me which of you that have more hands on engine rebuilding experience to judge what studs work and what doesn't. I do not blindly following Porsche as having the best engineering with everything, they don't and has been proved many times as each series of cars has their own issues. There are after market solutions that are better than the original for these issues and maybe Porsche's last try at dilivar will last.:rolleyes:

I didn't see any post as an attack on anyone. If Steve feels slighted by this (doubt that he was) I do believe that he can fend for himself. Henry is who he is Like it or not. I have done business with Henry and received great information on what I advice I was asking for. Everyone makes a decision of what head stud to use and what mechanic to put their faith in for advice. Your choice your money!:cool:

When was the last time Porsche did any engineering on air cooled head studs? Is it not possible that with today's technology and historical data that Porsche would have used a different design if they had to make these again? It seems like Henry is just modernizing an old design, not really competing with Porsche engineers because they were done with these a long time ago. Makes sense to me.

No question about better resources today. Look at the CAD modeling available to the laymen. I think windows 3.1 was the standard PC OS when the latest 911 (993) was designed.

No doubt Henry's approach of threading the stud deeper and using fine threads on the nuts is better than stock. Its the mystery of material choice that has me wondering what Porsche engineers know that we don't. To start with dilavar then go to steel to solve the breakage problem then switch back to dilavar.

Porsche has made some mistakes in the past. Most were based on sound engineering principals. The problems were mostly related to poor materials. 9mm rods bolts and dilavar stubs are one such example in my opinion.

I would guess that economics played a large part in it. The air cooled motors were on the way out, they had experience with Dilavar and steel and there were advantages/disadvantages to both. Starting over with an entirely new metallurgy would have meant lots of time and money whereas just updating an existing design would be less expensive.

We all agree that the Porsche body of work is impressive but there will always been room for improvement for those willing to spend the time and money to find it.