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

[Lapkritis]

This does not meet the definition of conjecture. We are using basic math and physics which is the exact opposite. We're bringing data to a topic cloaked in "just trust me" speak. I do not feel it necessary to tout my automotive hobby resume in order to have facts accepted as fact as I present them. The expansion rate of steel is less than aluminum. You don't need to "build" 10,000 Porsche engines to learn that. Your argument and moaning will not change that fact.

-Andrew

[chris_seven]

Originally Posted by Henry Schmidt

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.

I am not sure to describe the expansion of metals as a 'wild ass' theory or conjecture is sensible.

As far as I know there has been no challenge to established practice just a request for a better explantion of the solution.

The situation is quite clear:

If we ask Porsche what to use they say Dilavar.

If we ask ARP they tell us that the more we pay the better the stud and the better the solution.

If we ask Raceware they tell us they make the best studs as do Casper Labs and so does Supertec.

I am sure every individual organisation selling studs has a firm belief in their product but there has never been a qualified answer as to the engineering behind the 'best solution'.

When we try to use basic engineering principles to see if a reason can be found or sense made of the agruments it just ends up with a bit of a rant which doesn't help anyone.

Henry, I wish you well selling your studs but I do refuse to accept some of the engineering statements you make.

I am sure you have built many 911 engines and I have, in the past purchased several of them and recommended you to many UK based customers but some of the rest of us have a lifetimes experience in both Materials Behaviour and Real World Engineering at the very highest level and it would be helpful if you could ocassioanlly recognise this fact or you will merely stifle all debate.

[Henry Schmidt]

Chris, please name the engineering statement I've made that you don't accept.
Please remember to use an exact quote.

[chris_seven]

Originally Posted by Henry Schmidt

Dilivar studs offer too little clamping force

I would need to see the numbers before I could agree with this statement.

Originally Posted by Henry Schmidt

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.

I don't really accept that an increase in clamping force is desirable as increasing load will cause more damage to the case material.

I don't really believe that you can obtain the 'desired' clamping force as you have no control of the relative expansion of the stud.

As Karl Popper famously said “Our aim as scientists is objective truth; more truth, more interesting truth, and more intelligible truth"

I just can't escape from tyring to understand more about some of these issues and the reasons for the solution and am happy with any sensible objective debate.

[Lapkritis]

We are designing the sleeve/billet cylinder now. I am also going to test out the QSC 92mm set in the interim to determine if they are worth their weight in scrap or not. For all I know, they could all be tied together and used as a boat anchor or perhaps they spec out. I will share honest feedback here.

[aws]

As a professional mechanic all my life I have always adhered to the tenant that you should always be smarter than the car (or engine) that you are working on. And for the most part I have always tried to be smarter...but as a professional who specialized in computer diagnosis and emission repair I was paid to fix the car...even if the repair or parts required didn't make sense diagnostically. In the real world the customer wants the car fixed---as soon and as cheaply as possible.
As a result I can sympathize with Henry's attitude. I am interested in the engineers cause and effect--but I have seen enough engineering solutions over the years to be skeptical . I have used steel studs since 1971--my experience with dilivar has been (like Henry's) that they do not provide enough clamping force ---and break. I have used ARP's--but did not use the 36 lbs torque value..(they must be crazy---no Porsche guys on that engineering staff) and was more than a little irritated when one of the studs gaulded on installation and I played hell getting it out of a very valuable early aluminum race motor case--then had to insert it.
I have used Jim's JB birel cylinders and they are very nice pieces--but heavy--and I feel that the LN cylinders are just as good --and considerably lighter.
I have an adequate inventory of early steel studs--but when I run out I will be calling Henry.
aws

[Lapkritis]

Still digging into information on the materials. Here's some basic information on heat transfer of materials in engines:

http://www.engr.colostate.edu/~allan/heat_trans/page4/page4f.html

This shows the values of convection for various materials that are most common. Cast iron has a lower rate of transfer than aluminum which many with experience will have already known. The challenge of a cast iron cylinder and cast iron heat sink will depend upon the oil cooler as well as the effectiveness of the fan and sink design. The best test set would be to monitor not only the cylinder temperature but the head/cam tower temperature and compare/contrast to aluminum vs. cast iron cylinder. If there is an overheat problem present with the cast iron heat sink then it will show up during monitoring/testing.

[Lapkritis]

Qsc look fine and measure dimensionally as a very near match externally within .006mm on my caliper for critical dimensions. The jugs are going to have the bore confirmed as true at my machine shop. The pistons appear to be a replica cis which means aftermarket cams with additional lift will be a problem unless you want to machine the valve reliefs. I have new webcam GE40 so I plan to opt for confirmation of combined maximum dimension before custom ordering JE and honing the smallest 5 cylinders to match the largest if necessary.

Stock lift cams would probably be fine with the provided pistons. Rings are Grant brand. Pistons were inspected and found to be crack free. Should make for 6 wobbly ash trays.







Mahle RS and qsc side by side:


Qsc 92mm 9.5:1 911 piston:




I couldn't find any pictures of these parts when I searched the web so hopefully future travelers will learn from this thread.

That's all the update for now and until I have the cylinders from the machine shop and the custom je pistons in hand.

[Walt Fricke]

Your pictures bring this to mind: Looking at J&Es website, it would appear that you can order pistons with circlips for wrist pin retention, or several other means of retention. Considering the trouble dealing with other wrist pin clip types, why would not circlips be the favored part for this task?

I did once have a problem with a circlip in this function. In some manner entirely mysterious, one tip of one of them, out at the hole, broke off. The clip continued to do its job. Alas, the hardened steel tip did a job also - of etching the cylinder, first on one side, and then after traveling through the wrist pin, on the other, and so on. Had this been a more open slipper skirt design piston, the piece would have fallen into the case immediately, and most likely done no harm at all. But the wrist pin ended in a slot, not open space, so it couldn't escape.

I can't imagine what would have created a force on the tip of the clip, but something did. In time honored manner, on hearing this tale a shop owner said he never reused circlips. But nowhere have I ever seen that advice, before or since.

[HawgRyder]

Walt...personnaly I like Spiral-locks for wrist pin retention.
They a total pain in the behind to install...and even worse to extract...but...they work...and never seem to fail...even in a fuel engine that has blown the heads right off!
Bob

[chris_seven]

We used to build a number of Coventry Climax based engines that rev to 10 000rpm and produce around 110 BHP/litre.

Theu have always used pistons with conventional circlips and these do commonly cause problems.

We routinely fit Teflon Buttons into these engines and they slove all of the issues in a cost effective manner.

[Walt Fricke]

Until recently I hadn't realized that spiral locks were a pain. Just the opposite of what I want, as I waste way way too much time in both directions dealing with the J&E regular locks, even with the tool for installation.

Chris - were the problems you saw with circlips retention failures? Obviously, that trumps ease of assembly.

But the pistons on my three race motors can't use Teflon buttons, either as primary or secondary retention devices, as the wrist pin hole does not extend all the way out to the cylinder wall.

[Lapkritis]

Haven't had any issues with normal pin locks such as these:



Removal takes a steady hand and some care but once you've done a few they're fairly easy to work with. I haven't used spiral-locks before but they look like a nightmare to work with.

[Henry Schmidt]

For those of you reading this thread and hoping for success in your build, here's what we do.
Assess the case condition. Like everything else in the high performance world, parts have a finite life. A mag case that has been super heated or experience the stress of prolonged racing is not an appropriate candidate for a successful rebuild. That means clean ,clean, clean and inspect.
Check line bore to insure proper bearing crush and oil pressure retention.
Dry film moly on factory bearings.
Improve oil flow to promote cooling and engine life. By-pass mod and pump flow mod.
Cross drill crank and boring feed hole to #4 main to promote increased oil flow to # 2and #5 rod bearings.
In this engine we removed the ill advised Timecerts and replaced them with the appropriately size CaseSaver. They come in at least 4 different sizes.
Professional installation is advised to prevent "porcupine head studs".
Deck the spigots and machine the bore to clean up any anomaly in the bore from installing the CaseSaver.
Timecerts have proven a reasonable repair for the 8mm perimeter studs.
We insert the 4 stud around the #8 main bearing and the long 8mm that clamps the case around the intermediate shaft.
Use only Viton case through bolt o-rings (green).
Install Supertec head studs using the system recommended with the studs.
Use the gluing technique that comes with our case sealing kit. This gluing technique is available on this forum free of charge.
Replace oil pressure valves with update spring and pistons.
Install Nikasil cylinders to promote proper head and cylinder cooling.
Trim cooling tin to promote cooling.
Add a set of wide tensioner arms (we make a set that we believe functions better than the factory version) to extend tensioner life.
Using these techniques we build an engine that carries a 2 year-unlimited mile warranty.
Does it work every-time. Of course not, but it's the best we've found so far.

[Lapkritis]

That's great. Be prepared to see an alternative implementing the same tips Bruce Anderson detailed as well as taking it a step further in matching a jug to stud without using Dilavar. Anomaly in the spigot from installing the case saver? That doesn't sound good. Could you share some pictures of such an anomaly as you mention?

[Lapkritis]

Viton in-hand from the host. The Victor reinz gasket kit comes with the blue seals.

[Henry Schmidt]

Originally Posted by Lapkritis

....edit.... Anomaly in the spigot from installing the case saver? That doesn't sound good. Could you share some pictures of such an anomaly as you mention?

Every qualified Porsche machine shop understands this process. One of the reasons the 2.7 stud pulls from the case is their proximity to the spigot.
Installing an expanding (self locking) insert that close to the spigot tends to move the material in the thinnest area. In a perfect world (hardly a magnesium case) we would want additional material but in the real world, we deal with facts.
A none issue that has 25+ years of empirical evidence to substantiate the claim.

You can see the machine marks in the picture below. The machine mark adjacent to the CaseSaver.

[Henry Schmidt]

BTW: For any of you thinking about using the lower priced/quality Victor Reinz gasket sets, the quality of many of the gaskets fall under the category of marginal and some are even nearly unusable. Pay special attention to the CE rings.

[Lapkritis]

Now that you point out the machining I do see it in your original images you posted as well as the cert visible in the spigot area. The reason this would concern me is the benefit of a larger saver is partially the increased thread area of the larger diameter into the base material. If 20% of the larger threads are machined off because they poke into the spigot area then you're losing some of the paperwork benefit of the larger saver over smaller. Essentially the area where the saver protrudes into the spigot without case material to bind to it is free-balling.

Agreed with the Victor Reinz gasket statement - the case seals and green fiber valve cover gaskets are toss away parts in my opinion. I haven't bothered to inspect the CE rings yet ever since my plans changed not to use the RS Nikasil parts.

Let me ask you this Henry, as less experienced folks such as myself would like to know - have you tried steel cylinders on the 2.7L magnesium case with your fastener? If so, did you monitor oil temperature differences or cylinder head temperature difference relative to the aluminum cylinders? I understand all engines have a finite life cycle... however when engineered properly those life cycles can exceed our expectations. When there aren't ridiculous forces yanking the engines apart they can last almost forever even when driven hard. Plenty of cars exceed 1 million miles... Porsche should be able to do the same if we consider what is yanking them apart and address it.

Fun article:

Million-Mile Club: The World's Longest-Lived Cars - Popular Mechanics

[Walt Fricke]

Andrew - the threads of case savers or timeserts or even helicoils aren't cut off when the spigot is trued. The process of drilling, tapping, and especially, with the time certs and their roll tap, or whatever holds the case savers in, bulges the case metal between the insert and the spigot inward a little.

Sometimes this is so little that you can still get the cylinder in, it is just tighter and harder to work with. And I think the upward pulling of the head studs can cause the inserts to do the same thing - move a little spigot metal inward. You can see the spots, and sometimes you can see marks (superficial) on the spigot part of the cylinder. I don't think this causes the cylinder to get out of round.

Doubtless other times this is a real hindrance. Makes great sense if a guy has the tools to true the spigot. You can see how little is removed in Henry's picture.

Also, I suppose it hasn't escaped your attention that the T motors from 1970 through 1972 (maybe 73 also) were steel, with factory steel studs. You never hear of any of this being a problem. Aside, perhaps, from guys who may have hot rodded these motors a lot and perhaps didn't get the cylinder cooling they would have liked. Porsche dealt with this with the steel and cast aluminum fin Biral setup for their S (E also?) motors from that era. Also problem free. And all of these were mag cases - the earlier ones weaker than the 7R.