ARP vs Stock studs

[Geronimo '74]

I have bought things from Chris and Henry.
Both sell good stuff.
I cannot attest to the quality of the studs Chris sells but I would have no problem buying them if I was not already using Henry's Supertec headstuds. Like he said, zero issues, zero complaints!

[chris_seven]

Max,

EB Welding the heads to the cylinder isn't too difficult and will eliminate cylinder head joint issues.

I don't think it will help with pulling studs out.

[Flieger]

Originally Posted by chris_seven

Max,

EB Welding the heads to the cylinder isn't too difficult and will eliminate cylinder head joint issues.

I don't think it will help with pulling studs out.

I was thinking of the aircraft style cylinders, not welding the heads. The stud gets shorter but the thickness of the clamped aluminum reduces by the same amount. I guess that would cancel out?

[DSPTurtle]

Yeah Damn It... I have to keep a set in stock cause he is always selling out. But to his credit, Henry has always made sure I was never held up on a build. Good product and great attention to detail. I sure do like the idea of an allen key to install the studs. Maybe even a depth notch to know you've gotten them to a sufficient thread depth without using a measuring device? What do you say Henry? Maybe a serration or something to ensure proper penetration. Kinda like ribbed for her pleasure.

Originally Posted by Henry Schmidt

We have sold over 1200 sets of Supertec head stud kits to over the last 12 years and to date have had ZERO complaints.
It is the number one selling head stud kit on the Pelican Parts website.
They are used by professional engine builders and DIY enthusiasts for both street and racing application.
They are selling so well that we are struggling to keep up with demand.
I notice the Chris has copied some of our unique design features to make his titanium studs which is indeed quite flattering.


Supertec Head Stud Kit

[Ronnie's.930]

Originally Posted by DSPTurtle

Maybe a serration or something to ensure proper penetration. Kinda like ribbed for her pleasure.

Now this is my kinda' thread!!!

[Bob Kontak]

Originally Posted by Henry Schmidt

We have sold over 1200 sets of Supertec head stud kits to over the last 12 years and to date have had ZERO complaints.

Based on your hype, Henry, I figured you had sold a million sets by now.

[Henry Schmidt]

Originally Posted by Bob Kontak

Based on your hype, Henry, I figured you had sold a million sets by now.

If by "hype" you mean pride, you are entirely correct.
I am proud that so many builders in the Porsche community have the confidence to choose our product to enhance their labor of love.
Porsches are more than a car, they have character as do the owners and if they found fault in our product, they would shout it from the roof tops.
To those who have made our product such a success (all be it only 1200 sets), I say "thank you".

[Alan L]

1200 looks like a solid number to build a reputation on. Statistically robust a statistician would say.
Well done Henry.
Alan

[chris_seven]

Originally Posted by Alan L

Statistically robust a statistician would say

Interesting comment but I don't think it is correct.

I am not trying to make a comment about the quality of a specific product just how we should make an assessment from a design perspective.

Whilst 28800 studs is a good number statistically there is no published data so no real conclusions can be made other than as Henry states he has received no complaints but it would be impossible to sell critical fasteners for many applications on this basis but we can draw some conclusions.

The first point to make is that the standard steel stud used by Porsche rarely suffers failure. (Clearly discounting Dilavar)

If we took a rough guess at the number of steel studs produced during this time then I don't believe that 5 Million parts would be excessive so we can be confident that the 'base' design is sound.

As there is no real test data showing a traditional Weibull Distribution/operating conditions or test results then all we can draw from this observation is that the basic stud has an extremely low stress ratio and that it operates well within its fatigue crack initiation threshold. It is clearly 'fit for purpose'

It shouldn't, therefore, be difficult to make a suitable replacement.

If we then 'design' and manufacture a stud using a different material and some other detailed changes we need to consider the impact on the life of the part.

If we chose a material with either enhanced mechanical properties in terms of yield strength, tensile strength, ductility and possibly fracture toughness then we can be fairly confident that failures won't occur.

If we also increase the cross-sectional area we reduce the stress due to preload but increase the stress due to expansion so they tend to balance out depending on the precise duty.

The load on the threads increases but the stud is relatively unaffected.

Once we have looked at basic stresses it is also important to consider the operating environment and ensure that corrosion and other issues don't dominate the behaviour of the part. - Something Porsche clearly didn't manage well enough with Dilavar.

If all these aspects of a new design look favourable then as a Metallurgist with a speciality in Engineering Materials Behaviour I would be comfortable to use the part and to recommend it to my colleagues.

I do believe that Henry's Studs clearly fall into this category and have no doubt's about their reliability.

However, having been involved in Probabilistic Failure Design early in my research career, I don't believe that I could offer any statistics to back up this statement and it is at best apocryphal.

The cost of doing the work to make either an Insurer or Safety Agency happy would be eye watering and in the case of a head stud a waste of time unless it were an Aero engine part

The real problem with 'our' industry is that a huge number of parts are being sold using baseless claims, many of which are completely untrue and used to hide either a complete lack of engineering knowledge or just a simple lie.

Clearly Henry does a much better job then many of his competitors but in general caveat emptor does apply.

When we design a new or replacement product we always produce a 'Technical Construction File', we carry out a basic stress analysis, we look at the impact of changes of material and the risks associated with failure and we consider all environmental aspects of our choices. We take either a conservative or pessimistic approach and if we are not 100% confident in our choices we don't proceed.

We would always be prepared to explain an justify the conclusions we have reached and why we believe them to be appropriate.

[Henry Schmidt]

Chris, your point is?
You spend a great deal of time bloviating and we spend our time testing by actually running the product in it's intended application.
The statement "Zero complaints" is a reference to more than just breakage. It applies to failures of any kind reported to us about the product in the environment it operates.
That means no breakage, no pull outs and no reports of loosening nuts, no reports of leakage at the cylinder/head joint.
I appreciate your attempt to critique the products you encounter and your expertise is well documented but really aren't we as engine builders interested in success rather than sudo scientific head scratching?

[chris_seven]

My point is that there is simply no data and hence 'statistically' there is no correlation that can be made.

To simply state 'we have no problems' is, of course, useful but it does not fully substantiate a design. I do accept this statement as the complete truth but was just trying to point out that an Aero Engine designer would need much more as he would have to show real stress levels, real pull out forces and a great deal of fatigue analysis.

I would be happy to elaborate but I don't really believe that you are interested.

The definition of pseudo is as follows: not genuine; sham

If you are making this as a point then you are being quite insulting as the comments that I endeavour to make are based on a lifetime's work studying Engineering Materials Behaviour and are to the best of my ability and knowledge fairly accurate although I do accept that I don't always provide all of the math.

Suffice to say that I am sure that the studs you sell are more than adequate for the job they do, which is a comment, I believe that I have made many times.

This brings me to a the second point I was trying to make which is that without data it is impossible to support a real argument hence my comment on another thread about a 'religious' belief.

Without real data we either believe or don't believe, we can make subjective judgements which we can either accept or dispute but there is nothing we can show to prove a point.

Karl Popper makes this point far more elegantly in his book 'Objective Knowledge'.

For years now you have described my comments as 'theory' and not based on practical experience but in fact you have little or no idea of my working life and the projects I have been involved with in the last 40+ years.

I find it amusing that you take this view and do accept that the argument between Science and Practice has been going on for a few hundred years and sadly it seems to me that 'practical engineers' find it hard to accept that both approaches are needed to provide complete solutions and a real understanding.

Whilst I don't agree with all of your comments I hope that I don't make any insulting remarks and I hope you realise that disagreeing with someone's opinion is not an insult.

I could just accept that it is impossible to make any comment about head studs on this forum without offending you but where's the fun in that

[Henry Schmidt]

Chris
I guess my point is we can talk a load of crap and continue to use products we know to fail or we can get out and try to improve the process.
Progress belongs to those willing to try something new, observe the results and offer sound, honest opinions based on those observations.
Do I have a scientific understanding of metallurgy or engineering principles? No
What I do have is a love for the process of rebuilding and improving the air-cooled Porsche engine.
Would I lie about my observations to sell some hardware? Hell no
When you suggest that observations based on years of experience have no validity you insult the person offering those observation.
If discounting my experience is your intent, where's the fun in that?

[chris_seven]

Originally Posted by chris_seven

I do accept this statement as the complete truth

Suffice to say that I am sure that the studs you sell are more than adequate for the job they do, which is a comment, I believe that I have made many times.

Whilst I don't agree with all of your comments I hope that I don't make any insulting remarks and I hope you realise that disagreeing with someone's opinion is not an insult.

Henry,

I have spent the majority of my working like in a Research environment and have had a significant input into the design and development of test systems that measure and provide the data required to be able to make progress for many years.

My point was to suggest that without data we must either believe or disbelieve and I am surprised that you are trying to twist my meaning to suggest that I am trying to say that you are not being truthful or that the observations you make are not worthwhile. I am merely saying that in my view real data would be useful and I believe that in general the Engineering community would agree.

Without data and design any product development surely becomes 'poke and hope'.

This approach really does slow down the pace of engineering development because of the timescales involved in obtaining a result.

I found your comment in regards to the Ti Head studs we manufacture to be interesting.

Your comments were roughly as follows:

'When you have 2-300 hundreds of sets in hundreds of engines with 100 000+ miles of success we will re-visit the question'

I assume that this means that Supertec didn't sell any studs until you met the same criteria or did your experience of engine building help you to produce a stud that my Engineering and Metallurgical knowledge couldn't emulate?

To carry out such extensive testing is clearly unaffordable and we need some way of shortening this process.

Where we should agree is to accept that by using 'prior art' and 'experience' we are starting down the path of good practice which is completed when we produce good data to back up our observations with scientific explanation which enables us make much better decisions.

I co-edited a book in 1996 entitled 'Computational Methods and Testing for Engineering Integrity' which sheds some light on the methods that I believe we should try to use whenever possible.

I am happy to accept your studs do a great job but as you know I question some aspects of their design in terms of Magnesium cases, hence the stud we produce.

I have never questioned your experience but this does not mean I believe that you are infallible.

We don't have to agree in all areas and it is unlikely any of us has a 'perfect' solution.

As you well know the 'fun' in debating the best solution is to have our ideas and propositions challenged and questioned. It makes us focus on our assumptions, justify our decisions and think through our efforts in a hopefully constructive manner.

From time to time it also helps to make us aware of our mistakes.

We have a small team of only 3 people involved in our product development and we constantly question and challenge our decisions and I hope this helps us to make better products. My two colleagues are both Mechanical Engineers and I tend to focus on materials.

If you feel, however, that a scientific and engineering explanation of a product is crap then we are really wasting our time in debating this subject.

[Henry Schmidt]

You are correct. When we started making head studs we did not use them in customer engines. We spent 3+ years testing them under racing condition before ever selling a set. In the early stages we tried four different designs in an attempt to get it "right. I never wanted to be in the stud business, I just wanted a better stud for the engines I built. All told we went through seven different iterations before landing on the present configuration.

I enjoy the discussion as well it just seems that some of the discussion questions my integrity and I will not take that lightly. I may be overly sensitive (rarely accused of that) and if that is the case I apologize.
I consider you a friend so challenging your comments is not done lightly either.
I welcome your comments but I lack the patience for condescension

[manbridge 74]

In other news, Stuttgart translates as "stud farm." (Old German)

[boosted79]

Pass me the pop corn..

[Mark Henry]

I've used steel, one set of ARP and 2 sets of Supertec.

Steel was fine for stock.

IIRC the ARP had a coarse thread on the head end and all the treads felt rough. The rounded end of the stud seemed nice at the time. The rough threads were a surprize to me as comparatively the ARP rod bolt threads were fine.

Henry's studs were super nice quality, smooth as silk treads and nice thick washers. No problem putting nuts on (negating the ARP rounded end) and perfect for using a full size 14mm twin plug.

No real issues except some head weep on the ARP, but it is on a high boost 930.
Also a bit of weep on steel, high milage stock engine built late 90's.
Not enough time on 2sets of Supertec to report.

YMMV

[Lapkritis]

Ever get stuck on an elevator ride with someone who farts loudly? It's not enough to just have heard it once. No, no way. Then you smell it...inescapable agony. If they lack decorum they next describe to their captives what they had for dinner the night before to produce such a noxious cloud. Not taco night for sure... maybe broccoli or brussel sprouts you guess to yourself. This is every headstud conversation on Pelican. Whoever smelt it dealt it, whoever denied it supplied it... but we all heard and know the first offending tooter polluter. Please toot your horn once per thread/elevator ride if you must... please also refrain from wafting it about.

[gtc]

That's odd... my ARP head studs were smooth as butter, and could have just about passed for jewelry.
I put mine in to the case with red loctite, but so I'm curious to see if the nuts loosen at some point like some people have reported.

Originally Posted by Mark Henry

IIRC the ARP had a coarse thread on the head end and all the treads felt rough. The rounded end of the stud seemed nice at the time. The rough threads were a surprize to me as comparatively the ARP rod bolt threads were fine.

[manbridge 74]

Other ARP studs were likely counterfeit. Becoming more and more common in today's world.