Re: Specific Question - ARP Head Studs on 2.7 Magnesium case - Insane?
 

Do you have any respect for a time cert magnesium case with dilavar and 22yrs before a failure of the fastener? Think about bit for a minute. Let it sink in.

Now.

Thoughts?

If you want this thread to be a defense of Henry then you're in the wrong place. I'm sure his messiah studs will work just as well with steel cylinders. You don't need to defend him because he is not being challenged. This is not about him. Get over it.

Re: Specific Question - ARP Head Studs on 2.7 Magnesium case - Insane?
 

You're not adding anything constructive to the thread other than bait for a fight. Please accept my invitation to leave while you still have your dignity good sir.

-Andrew

Question....in these cases...do the stud holes extend into the sump area...or are they blind holes?
My thinking...if they extend into the sump....it might be possible to install a "T" shaped insert from the inside.
This would spread the load to a larger area....and prevent any pull through of the stud or the insert unless the whole area cracked and broke.
Once again...brain working overtime.
Bob

Re: Specific Question - ARP Head Studs on 2.7 Magnesium case - Insane?
 

Hi Bob,

These are blind holes. I like there thought of a wide anchor behind capturing similar to the head end of the stud provided there is no interference concern within the case. I believe you may need a left hand thread so tension would not be lost and an o-ring similar to the through-bolts.

-Andrew

I want to thank Lapkritis for this thread, and for sticking to the high road. There is a lot more than meets the eye to this problem. I got your 6 sir.

I'm just curious on why you picked the 2.7 engine, there are better ones out there, 3.2/3.6 come to mind. Is it period correct? money restrictions? race application? daily driver? seems to me a proven track record is worth a lot more than re engineering a product.

oh yes, even aircraft engines fail sometimes, IO470 head popped off, there screwed into the cylinder.
http://forums.pelicanparts.com/uploa...1363638686.jpg

When we started on the stud project, we didn't whine about challenges.
The material we started with was found in a 935 engine I acquired many years ago.
We studied the issue (years of engine building, discussion with colleges and assessment of what worked and what didn't) then gave what we learned to an engineering firm that specialized in fasteners, along with the 935 stud.
Then we produced the first sets of studs and tested them in our own race engines.
As we discovered deficiencies we adjusted the design.
This went on through seven difference iterations. This lasted three+ racing seasons.
Then before offering it to the general public, we started installing them in customer engine with a life time warranty.
It was only after 60+ engines and zero failures, that we started offering it to the general public.
Now Pelican Parts is our largest single customer. Most of the direct sales we do are to well noted/ respected Porsche engine builders.

When you're ready to develop your theories to the degree that we are, perhaps you"ll gain some respect.

Re: Specific Question - ARP Head Studs on 2.7 Magnesium case - Insane?
 

This is not a thread about your studs. It does sound like you did your homework though which is not in question. Thanks for posting and not sharing words of discouragement.

Re: Specific Question - ARP Head Studs on 2.7 Magnesium case - Insane?
 

I could have purchased a 3L or larger aluminum case engine by now. My reason for staying 2.7 is because I don't really care how fast the car goes. My Jetta was my foray into serious power and I don't need the complications with the 911. The 2.7 is original to my car, numbers matching and is well maintained. I would prefer numbers matching and confidence beyond a fastener that works with a case saver. Doing my own homework here isn't my first rodeo. I will gladly work the numbers for the supertec stud to take the whimsy out of these silly posts from the retailer. The fact of the matter, and which is the issue at hand, is the plausible deniability of the forces exerted on the case by aluminum cylinders in the condition that includes the use of non-dilavar studs. The math shows you're yanking on the case and testing the limits. It is my thesis in this thread that a magnesium case will be under far less stress with steel or iron cylinders. The math is simple and agrees. The world was once flat gentlemen. There was also a time where we didn't consider the cylinder in the solution set for keeping the magnesium case together. I for one can't believe this hasn't been discussed before. Perhaps the naysayers prior to this prevented testing? Won't happen here so the words of discouragement by a few are wasted.

-Andrew

Ok...this is hard to explain...but here goes.
I once took a motorcycle engine apart (single cylinder 500cc) and found that the studs screwed into the block (aluminum) with a steel plate inserted at a 90deg plane to the cylinder about 1/2" down from the top of the block/cylinder hole.
Whew...
Apparently...the slot containing the steel plate was cut from the bore into the block...and a steel plate was pressed in...then the hole for the stud was drilled and threaded resulting in a steel reinforced stud hole.
One of the plates was a little loose...and when I removed it to see what it was...I noticed it was basically a woodruff shaped plate with the threaded hole in roughly the middle.
It occurs to me...the this also might be a permanent answer to pulling studs.
All it would take is a cutting tool...like a milling cutter...to cut a slot in the side of the bore...and press in the steel plate...then re-tap the stud hole.
How about it?
Bob

If you were paying attention, you would have noticed that temperature control is one of the necessities when it comes to 2.7 longevity.
Porsche did away with cast iron cylinders because they (cast iron cylinders) are detrimental to cooling.
Even as early as the 356, Porsche realized that cooling the cast iron cylinder was difficult.
The reason no one has played with 90mm cast iron cylinders was because they don't work well.
QSC built them because they had a cast 356 cylinder in the works and found making the 90mm cast iron cylinder was cost effective (read cheap). As one of the contributes to the QSC design and testing team early on, I saw that they produced products with little or no understanding of the synergy of a complete air cooled 911 engine. They actually sell some of my products without understanding what they do or how they work.

They even produced an 86mm Nikasil cylinder that was molded from a 2.2 (84mm) cat iron pattern. The product failed almost immediately. The failed cylinder was sent to an engineering firm that performs critical analysis on aircraft parts. They suggested an anomaly (suggesting that the cylinder in question was dropped) and that the cylinder design was sound. It wasn't until my staff analyzed the cylinder was the errant design discovered. Sometime an understanding of the practical use is most valuable than engineering principles.

[Subtle Hijack]

http://upload.wikimedia.org/wikipedi...nce-people.jpg

[/Subtle Hijack]

Re: Specific Question - ARP Head Studs on 2.7 Magnesium case - Insane?
 

The cast cylinders from QSC and the JB sleeves are not the only options I'm considering Henry. I believe it can be done for far less than $3g with USA materials which might help bring JB down to a more palatable level for folks. I could be wrong and discover costs are too high after a prototype set. Perhaps you would finally agree this can only serve to benefit the magnesium case crowd.

Re: Specific Question - ARP Head Studs on 2.7 Magnesium case - Insane?
 

Paying attention? Pardon me. Temperature and thermal expansion is the topic of this thread and perhaps you did not understand? The stack under your fastener is expanding at a different rate than your fastener. I had no idea this was hidden from the general public or simply not disclosed. This difference in expansion rate is the same force that has been pulling threads for decades. This is the conversation. We want to reduce these forces. Temperature relating to ring gap/piston wear/oil temperatures are assumed as solved or known. Those are also old challenges. You can run a large aftermarket oil cooler. You can run an appropriate ring gap for the slower expansion of the iron/steel sleeve. Your continued objections are like the crew of Columbus' ships saying they can't sail back to Spain because it's too far.

-Andrew

We played with 90mm Biral barrels years ago with no positive effects on head stud clamping. We cured the head stud issue and moved on.
We do use an 86 mm Biral on our 205 hp 2.45 but not as a budgetary concern. We use it the preserve the small spigot size on matching numbers early cases.
In fact, to create a reliable part, we Nikasil the cast iron liner.

An increase in clamping pressure is desirable. This is the point. Start with a predictable clamping pressure when cold and achieving the desired clamping pressure when hot. We have achieved that goal and stud pulling is no longer an issue as long as the hp limits (learned through experience) are maintained.

BTW: you're no Columbus and the new world you seek has already been discovered. You're beating a dead horse.

Re: Specific Question - ARP Head Studs on 2.7 Magnesium case - Insane?
 

Obviously not possible to win friends with naysayers. You prove them wrong and they eat crow or they come around. Henry and his posse aren't going to change physics and I won't drink the punch ignoring what I now know. I'd like to share my discoveries with other magnesium case owners for their benefit.

The contents of this thread just shows how much debate this subject continues to create and the same old arguments just keep going around.

Every debate starts with the same statement about studs and this is where I start to disagree.

I believe that the only studs that have ever caused concern are early Dilavar which are reported to fail due to either Hydrogen Embrittlement (HE) or Stress Corrosion Cracking (SCC).

This is a completely seperate issue to studs pulling which is concerned with the strength of the case and has little to do with the stud.

I would like to understand why the stud needs more clamping than the design requirement speified by Porsche and just what level of preload is needed.

To provide this additional clamping force using the expansion of the cylinder would be an unusual design concept, it would also not be reliable whilst the engine was warming up.

I have a problem with the idea that the stud has been 'designed' to provide the ideal level of clamping when the engine is hot as the expanisons are controlled by materials and not by stud design.

It is also interesting that Porsche were using 17-4PH in 1975.

17-4PH is an interesting choice for a stud material. There is nothing unique about the properties of 17-4PH in terms of coefficient of expansion, strength or corrosion resistance but it does have a good balance of these propeties at a very modest cost.

The most appealling aspect of 17-4PH is its ease of fabrication and has led to its inceasing use since its commercial introduction in 1969.

In detail I would prefer to use 15-5PH which would provide the same level of strength and eliminate any chance of sensitivity to SCC as can occur with 17-4PH when used in a very high strength condition.

I do accept that case savers and steel studs can solve many of the problems of mag cases and this is a practical solution but I agree with Andrew that this is a result of trial and error and not a process of design in the accepted sense.

This is not a pissing contest or a launching pad for the Friends Network.

It's called the 911 Engine Rebuilding Forum.

I come here and offer my experience to assist people trying their best to get through a rather difficult generally first time experience.
I come here to make that experience a success for the most people possible.

When people with little or no experience at successful Porsche engine rebuilding challenge well established practices with wild ass assumption and theories based in conjecture, the results quite often distribute inaccurate information and perpetuate false urban legend.