95' Junker Drag Truck

I think 30% is incredibly optimistic. You can say all you want about torsional loading and fastener material deformation, but i'm SURE ARP knows those things too....lets not forget ARP is a business that produces performance products. If the material could be torqued to 200 ft/lbs and never have an issue don't you think they would say that? Not a whole lot of companies are going to underrate their product, that's just bad marketing.

From an Engineering/QC perspective, i'd almost guarantee calculations and testing went into determining at what torque that particular fastener started to fail at a rate higher than ARP finds to be acceptable.

What this ultimately comes down to IMO, is people who are too cheap to go to either a 625 or a larger stud, have backwoods style convinced them self that pushing components to failure point is the norm. They've thought up these entirely speculative ideas and spread them as fact. IMHO, its your engine, do whatever you please, but don't tell the average guy that makes very mild power that he should be torquing to 150 ft/lbs.

30% is an arbitrary number. I was just throwing something out there. 30% is a pretty common target for safety critical components though.

As far as Engineering, I specifically referenced R99.99/C90 Weibull which is what every major engine and automotive company uses (or R99.99/C99 on very safety critical stuff). Do some reading on it if you'd like to educate yourself. It's a statistical analysis based on a torque to failure. It takes into consideration failure mode, torque mean, and spread. If parts are very consistent, you can safely specify a torque closer to failure, if there's a large spread, you need to drastically reduce the specified torque to limit failures.

I'm sure ARP would prefer to keep a good reputation rather than cut corners.

I think we're saying the same thing, but you likely have it in your head that a company makes 1,000 units and test to failure. It's more likely they do 8-16 from three separate batches, and do some statistical analysis. Then, just like stock head bolts, you're left with a specified torque that gets you to an extremely high likelihood you'll never see a failure.
 
I've gotten like 141.5 on stock bolts with long brakes between increments. I've used the Allen bolts 3 times now and went to about 150, or 149 anyway pretty easy being careful. Advise for the cheap phuckers.
 
30% is an arbitrary number. I was just throwing something out there. 30% is a pretty common target for safety critical components though.

As far as Engineering, I specifically referenced R99.99/C90 Weibull which is what every major engine and automotive company uses (or R99.99/C99 on very safety critical stuff). Do some reading on it if you'd like to educate yourself. It's a statistical analysis based on a torque to failure. It takes into consideration failure mode, torque mean, and spread. If parts are very consistent, you can safely specify a torque closer to failure, if there's a large spread, you need to drastically reduce the specified torque to limit failures.

I'm sure ARP would prefer to keep a good reputation rather than cut corners.

I think we're saying the same thing, but you likely have it in your head that a company makes 1,000 units and test to failure. It's more likely they do 8-16 from three separate batches, and do some statistical analysis. Then, just like stock head bolts, you're left with a specified torque that gets you to an extremely high likelihood you'll never see a failure.

Nobody said anything about having a monkey test 1000 units to failure.

So basically were on the same page, by torquing to 150 you increase the likelihood for failure significantly. So you're playing games with reliability of your headgasket....which if i'm not mistaken is the whole point of installing a set of headstuds.
 
Not a whole lot of companies are going to underrate their product, that's just bad marketing.

This is common practice in most industries due to liability.

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This is common practice in most industries due to liability.

That's not called under rating, and precisely proves my point, that by torquing above the torque spec you significantly increase the chance of failure.

To clarify, when I stated companies don't underrate, I mean it as in they found statistically a number they were comfortable and then cut it by a percentage just for ****s and giggles. For example, testing shows a sedan to get 30 mpg, company is not going to rate the car at 20mpg. Example 2, ARP finds that at 125ft/lbs they have a failure rate of XX.X%, which they are comfortable with, they aren't going to have you torque to 100ft/lbs just "cuz".
 
That's not called under rating, and precisely proves my point, that by torquing above the torque spec you significantly increase the chance of failure.

To clarify, when I stated companies don't underrate, I mean it as in they found statistically a number they were comfortable and then cut it by a percentage just for ****s and giggles. For example, testing shows a sedan to get 30 mpg, company is not going to rate the car at 20mpg. Example 2, ARP finds that at 125ft/lbs they have a failure rate of XX.X%, which they are comfortable with, they aren't going to have you torque to 100ft/lbs just "cuz".

If you run o-rings 125lbs isn't really enough to crush the ring into the headgaskets fire ring.
 
If you run o-rings 125lbs isn't really enough to crush the ring into the headgaskets fire ring.

A good friend of mine had brought that to my attention. He hot torques his p24 with o-rings to 135. I can't say I have input on that. I don't know enough to argue for or against in that particular scenario.
 
That's not called under rating, and precisely proves my point, that by torquing above the torque spec you significantly increase the chance of failure.

To clarify, when I stated companies don't underrate, I mean it as in they found statistically a number they were comfortable and then cut it by a percentage just for ****s and giggles. For example, testing shows a sedan to get 30 mpg, company is not going to rate the car at 20mpg. Example 2, ARP finds that at 125ft/lbs they have a failure rate of XX.X%, which they are comfortable with, they aren't going to have you torque to 100ft/lbs just "cuz".
Riiiiiiight.

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It's true, ARP 2000 instructions clearly state torque to 125 ft lbs with ARP ultra-lube and no retorques are necessary or recommended.

As a business owner that spends countless hours each day giving out free tech advice to diesel enthusiast callers with all levels of experience, 12v Cummins head gasket failures are extremely common, followed next by subsequent failures by guys following the ARP instructions. My first bit of advice for a frequent head gasket problem child is warm retorques. Despite the fact that ARP states retorques are not necessary, I coach the caller to try it and don't be surprised when the nuts move another 45 to 90 degrees at the same 125 ft lbs torque setting. Then for the hard causes that think the stud is simply stretching on the retorque, I coach them to check warm valve lash before and after the retorque. Magically, after doing a retorque the lash tightens up 002" to 004", despite the engine cooling off some which should loosen up the lash a bit....

Anyway, say what you want, I went through about 5 head gaskets in one race season before I finally went back to the cheaper ARP's and torqued them dangerously high. I went as far as pulling the engine, getting it decked flat, raising oring protrusion, installing the stiffer Hamilton Head, trying numerous torque and retorque sequences on the extreme studs, factory head bolts, and one time with the ARP 2000's at 125 ft lbs before I received a tip about these magical ARP 2000's holding up to 160 ft lbs of torque on a common rail. So I tried it on the Junker, took them to 150 ft lbs cold, retorqued at 150 ft lbs on a warm engine, scared to death they were going to break when I got 90* or better on a couple. Took it easy for another heat cycle and hit them again at 150 ft lbs and this time one 3 or 4 broke free. We then hit it hard on the dyno and the head gasket held!!! After a week or so, I decided it was holding pretty well so we bumped the timing higher to see if I could make it blow, because it's never held even one pull at 30* timing.

Fast forward a year or so and it's on the same head gasket, it's been warm reqtorqued 4 or 5 times now to check and they are rock solid tight, timing is now at 34* total advance at full rack travel. And it's going rounds at the drag strip, on the dyno, burnouts in the parking lot, joy rides with customers, etc. In hindsight, if I could take back all the blown head gaskets, wasted labor time, wasted coolant, wasted oil, lost race opportunities, the $1,200 ARP 625's would have been a better purchase than the $450 ARP 2000's. But knowing what I know now, ARP 2000's are a viable option for 1000 HP 12v with simple orings if torqued well beyond the manufacturer's instructions.

One thing I have noticed though, when we use real ARP 625's and torque them to ARP spec of 150 ft lbs, they move much less, maybe 45* max on the first warm retorque. If we bump them up into the mid 160 ft lbs range, they almost don't need a retorque as most don't budge when checked. So for the average high HP non-DIY customer that has to pay a shop to do retorques, there's a much higher chance for success using 625's with no retorques.
 
. One thing I have noticed though, when we use real ARP 625's and torque them to ARP spec of 150 ft lbs, they move much less, maybe 45* max on the first warm retorque. If we bump them up into the mid 160 ft lbs range, they almost don't need a retorque as most don't budge when checked.

So have you hot torqued a 625 and a 2000 to 150ft/lbs back to back and measured stretch? That seems like a clear sign to me.
 
Solid advice Will. Thank you for sharing this knowledge, despite those questioning your success.
 
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Will, thanks for keeping the posts going.


As for everyone else that keeps slamming them, your all a bunch of dick bag douche rockets!
 
As for everyone else that keeps slamming them, your all a bunch of dick bag douche rockets!

I've always found it interesting that every time an opposition is provided to something a social media famous person or company does, there always seems to be a few fanboys that come in and provide nothing factual or constructive other than just jabs at the opposition being "haterz" or whatever other name can be conjured up. just sayin...
 
Ive always found it interesting the internet expert never races in real life.


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Bolt Expert At ExcelWraps - YouTube

I don't even know what the debate is actually about. Lol

Those videos touch on the considerations for clamping loads.

Stretched Beyond Plasticity is one of my favorite phrases. The rest are all strings of expletives.

We've been through this over and over again. I will try to find it, but the was a user a while back that offered a good deal of insight toward maintaining plasticity of the fastener, and maintaining the proper tension and temperature to achieve the desired clamp load. It was either Ahall or Ahale I think.

At any rate, when you torque (or retorque) a fastener, you need to know the state of the metallurgy at that temperature (crystalline structure) and keep in mind that if you are trying to "retorque", you are trying to overcome the standing friction of the fastening surfaces. (why molybdemum paste is used) It's possible to overshoot your intended clamp load by using a torque increment that is too close to the last torque value. This also is where the emphasis on a nice clean pull on the wrench comes from, rather than short forceful motion with the torque wrench.




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I know we are discussing studs and not bolts. That provides another set of tensile loads to consider, but break time is over.

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At any rate, when you torque (or retorque) a fastener, you need to know the state of the metallurgy at that temperature (crystalline structure) and keep in mind that if you are trying to "retorque", you are trying to overcome the standing friction of the fastening surfaces. (why molybdemum paste is used) It's possible to overshoot your intended clamp load by using a torque increment that is too close to the last torque value. This also is where the emphasis on a nice clean pull on the wrench comes from, rather than short forceful motion with the torque wrench.

Don't bring facts into this, just set the torque wrench to 150 and crank that bish till it clicks. Boom no HG issues ever again.
 
I made a mistake earlier, but it's minor.
Elastic deformation is when the fastener is placed under tension, but will return to its original (as manufactured) state.

(Beyond the point of) Plastic deformation is when tensile force exceeds the ability of the fastener to return to its as-manufactured state.

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I made a mistake earlier, but it's minor.
Elastic deformation is when the fastener is placed under tension, but will return to its original (as manufactured) state.

(Beyond the point of) Plastic deformation is when tensile force exceeds the ability of the fastener to return to its as-manufactured state.

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Even while in the elastic stage of a stretch/strain curve, the material still stretches and doesnt necessarily return to its as manufatured state, it will enlongate. Torque a head stud or bolt half a dozen times to spec, youll find its just a hair longer. The deformation stage is where things get wonky and you throw the fastener in the scrap bin.
 
Even while in the elastic stage of a stretch/strain curve, the material still stretches and doesnt necessarily return to its as manufatured state, it will enlongate. Torque a head stud or bolt half a dozen times to spec, youll find its just a hair longer. The deformation stage is where things get wonky and you throw the fastener in the scrap bin.

Are you Wentzler 5.9 on instagram?
 
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