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Old 03-16-2019, 01:23 AM   #1
jl-wrx
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Default 14mm head stud arp 625 vs rcm

What would be the best of the 2 arp 625 vs rcm 14mm head stud? Any know the tensile strength of each can't seem to find it on the site.
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Old 03-16-2019, 12:03 PM   #2
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Originally Posted by jl-wrx View Post
What would be the best of the 2 arp 625 vs rcm 14mm head stud? Any know the tensile strength of each can't seem to find it on the site.
14mm IAG head studs are the strongest money can buy

I've been running 38psi through them for 30k miles without headlift if that says something about them
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Old 03-16-2019, 01:09 PM   #3
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14mm will be stronger than the 625's. But head stud choice should be based on how much hp/boost you aiming for.

In my opinion this is the strongest to weakest head stud.

14mm > 1/2 inch > 625 > arp2000 > oem.

My STi is going in May to be built. My end result hp goal being between 500/600whp. Technically I could get away with the arp 625's. But we jumped up to half inch head studs to be safe and also give a little head room if I ever wanted to make more power.
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Old 03-16-2019, 05:35 PM   #4
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The thing with headstuds is that they are all steel, and despite being different alloys and "stronger" the modulus of elasticity is still essentially the same. So, you take an 11mm stock bolt, and an 11mm ca625 stud, and apply the same force, and they will stretch the same amount. The benefit of the stronger material is that you can torque them down farther to provide more clamping force without them breaking or deforming plastically, but they will still stretch at the same rate.

The larger studs take more force to deflect the same amount, so that's always going to be a benefit, regardless of the specific alloy.
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Old 10-17-2021, 03:39 AM   #5
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Originally Posted by jamal View Post
The thing with headstuds is that they are all steel, and despite being different alloys and "stronger" the modulus of elasticity is still essentially the same. So, you take an 11mm stock bolt, and an 11mm ca625 stud, and apply the same force, and they will stretch the same amount. The benefit of the stronger material is that you can torque them down farther to provide more clamping force without them breaking or deforming plastically, but they will still stretch at the same rate.

The larger studs take more force to deflect the same amount, so that's always going to be a benefit, regardless of the specific alloy.
Well from the only shop that does closed deck conversions in Western Canada. They told me that CA625 head studs won't be the issue. The 11mm threads in your block will shear around 800bhp~680whp.

I'm still considering the 14mm conversion but the Gen II GTX3076 should be ok with 11mm CA625s.
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Old 10-18-2021, 12:39 AM   #6
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Originally Posted by rickjames7 View Post
Well from the only shop that does closed deck conversions in Western Canada. They told me that CA625 head studs won't be the issue. The 11mm threads in your block will shear around 800bhp~680whp.

I'm still considering the 14mm conversion but the Gen II GTX3076 should be ok with 11mm CA625s.
Is that number mustang or Dyno jet?
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Old 10-18-2021, 06:27 AM   #7
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These conversations are always difficulty because it can vary by conditions. Not to mention they all vary in material; physical properties.

Just comparing clamping forces, the RCM 14mm would be the winner, since the larger stud uses a higher torque spec.
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Old 10-18-2021, 11:09 AM   #8
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Paging Micah. Micah - your input is needed here.

Folks - Micah and I have been working on a little something and we have data that we can share soon.
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Old 01-20-2022, 09:55 AM   #9
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Quote:
Folks - Micah and I have been working on a little something and we have data that we can share soon.
So any updates on this data you guys have? I have picked 1/2 studs. I think Micah prefers to use 14mm.

Last edited by BlackFighter; 01-20-2022 at 10:50 AM.
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Old 01-20-2022, 12:10 PM   #10
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to put a plug here from my own research...oem and arp2000 have similar strength, the 2000s have a higher heat tolerance...am planning on running the 625s as my upgrade otherwise i know several people who use the stock bolts and do fine...dont think they are ridiculous power but they are doing decently!
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Old 01-20-2022, 12:58 PM   #11
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And then Clint and Micah never responded.

Look up Mechanical Advantage they did a study on head studs. Might be in Blog form.
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Old 01-24-2022, 01:31 PM   #12
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Quote:
Originally Posted by BlackFighter View Post
So any updates on this data you guys have? I have picked 1/2 studs. I think Micah prefers to use 14mm.
Quote:
Originally Posted by BlueSTI4Me View Post
And then Clint and Micah never responded.

Look up Mechanical Advantage they did a study on head studs. Might be in Blog form.
Still gathering data.

Right now I have clamp load data for ARP2000 (new), ARP2000 (used) and ARP625 (new) using three different thread lubes (one of which is the ARP lube).

I still need to finish testing clamp loads for the following:

ARP625 (used)
Special #1
Special #2
IAG 1/2"
IAG 14mm
RCM 14mm superstud

Since I'm doing this in my spare time I'm doing it when.... I have spare time. I'm hoping to get back on it really soon, but I have some heads that are being a PITA, and I have to figure out why the same valve on an FA motor keeps popping the rocker when using anti-lag.
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Old 01-24-2022, 06:23 PM   #13
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Originally Posted by cboggess View Post
Still gathering data.

Right now I have clamp load data for ARP2000 (new), ARP2000 (used) and ARP625 (new) using three different thread lubes (one of which is the ARP lube).

I still need to finish testing clamp loads for the following:

ARP625 (used)
Special #1
Special #2
IAG 1/2"
IAG 14mm
RCM 14mm superstud

Since I'm doing this in my spare time I'm doing it when.... I have spare time. I'm hoping to get back on it really soon, but I have some heads that are being a PITA, and I have to figure out why the same valve on an FA motor keeps popping the rocker when using anti-lag.
Clint, NP please don't feel as if I called you out. (I did)
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Old 01-24-2022, 06:25 PM   #14
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Mechanical Advantage Racing Blog on Choosing the Right Head Stud (C-2018)

https://www.maracing.net/choosing-the-right-head-stud
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Old 01-24-2022, 09:24 PM   #15
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That was a interesting read. Ty
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Old 02-07-2022, 12:02 PM   #16
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For those of you following along I can add a small tidbit.

As part of the project Micah and I are playing around with three different thread lubes; ARP, mystery lube A and mystery lube B.

ARP lube is just the same stuff you get in the packaging of the head studs.

I have a load cell here and made a fixture to measure clamp load. Clamp load is going to be the common factor across all the testing, and the ARP studs with ARP lube clamp load are the control.

So in this example we're going to talk about ARP2000. Following the ARP instructions and using the ARP lube we got a clamp load of X (not sharing numbers just yet until we have complete data).

Then taking that same stud, completely cleaned we used mystery lube A. To achieve the same clamp load took 30% less torque.

Just for fun I took an old ARP2000 stud, and applied the lube mentioned and torqued to full torque according to ARP's instructions which is 90lbs.

It was a struggle to reach 90lbs of torque. I could feel the stud stretching as I applied force, and this was confirmed by the readout from the load cell peaking and then falling off rapidly. When I did finally reach 90lbs the clamp load dropped over the course of time to finally at a point that was much higher than the control, BUT this is not a good thing. Feeling how it stretched, and watching the clamp load fluctuate so much tells me that it went well into plastic deformation, and is now a useless stud so it went straight into the trash.

When we are all done with data gathering one of the papers we're going to put our there is the effect of lube on clamp load. Yes, anyone with an inkling of understanding of fasteners will say "well duh Clint," but it's not too often you get to see real world relatable numbers.
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Old 02-07-2022, 01:33 PM   #17
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Quote:
Originally Posted by cboggess View Post
For those of you following along I can add a small tidbit.

As part of the project Micah and I are playing around with three different thread lubes; ARP, mystery lube A and mystery lube B.

ARP lube is just the same stuff you get in the packaging of the head studs.

I have a load cell here and made a fixture to measure clamp load. Clamp load is going to be the common factor across all the testing, and the ARP studs with ARP lube clamp load are the control.

So in this example we're going to talk about ARP2000. Following the ARP instructions and using the ARP lube we got a clamp load of X (not sharing numbers just yet until we have complete data).

Then taking that same stud, completely cleaned we used mystery lube A. To achieve the same clamp load took 30% less torque.

Just for fun I took an old ARP2000 stud, and applied the lube mentioned and torqued to full torque according to ARP's instructions which is 90lbs.

It was a struggle to reach 90lbs of torque. I could feel the stud stretching as I applied force, and this was confirmed by the readout from the load cell peaking and then falling off rapidly. When I did finally reach 90lbs the clamp load dropped over the course of time to finally at a point that was much higher than the control, BUT this is not a good thing. Feeling how it stretched, and watching the clamp load fluctuate so much tells me that it went well into plastic deformation, and is now a useless stud so it went straight into the trash.

When we are all done with data gathering one of the papers we're going to put our there is the effect of lube on clamp load. Yes, anyone with an inkling of understanding of fasteners will say "well duh Clint," but it's not too often you get to see real world relatable numbers.
Nice, looking forward to the results!
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Old 02-15-2022, 06:51 PM   #18
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Quote:
Originally Posted by cboggess View Post
For those of you following along I can add a small tidbit.

As part of the project Micah and I are playing around with three different thread lubes; ARP, mystery lube A and mystery lube B.

ARP lube is just the same stuff you get in the packaging of the head studs.

I have a load cell here and made a fixture to measure clamp load. Clamp load is going to be the common factor across all the testing, and the ARP studs with ARP lube clamp load are the control.

So in this example we're going to talk about ARP2000. Following the ARP instructions and using the ARP lube we got a clamp load of X (not sharing numbers just yet until we have complete data).

Then taking that same stud, completely cleaned we used mystery lube A. To achieve the same clamp load took 30% less torque.

Just for fun I took an old ARP2000 stud, and applied the lube mentioned and torqued to full torque according to ARP's instructions which is 90lbs.

It was a struggle to reach 90lbs of torque. I could feel the stud stretching as I applied force, and this was confirmed by the readout from the load cell peaking and then falling off rapidly. When I did finally reach 90lbs the clamp load dropped over the course of time to finally at a point that was much higher than the control, BUT this is not a good thing. Feeling how it stretched, and watching the clamp load fluctuate so much tells me that it went well into plastic deformation, and is now a useless stud so it went straight into the trash.

When we are all done with data gathering one of the papers we're going to put our there is the effect of lube on clamp load. Yes, anyone with an inkling of understanding of fasteners will say "well duh Clint," but it's not too often you get to see real world relatable numbers.
This is neat and I will be interested in seeing the results. As a mechanical engineer who has designed a few bolted joints...I will chime in with some thoughts.
  • First, I am skeptical of some of the numbers in that mechanical advantage webpage. I called ARP and asked them for the clamp load for the 11 mm, ARP 2000 head studs. They told me it is 15060 lb at 90 ft*lb and 15730 lb at 92 ft*lb (using their lube). This is quite a bit lower than mechanical advantage reported. I will be interested to see what you report.
  • Mechanical advantage did not pull the "clamp load" off of the ARP website, as ARP does not have that information on the website. They grabbed the yield stress...there is a difference.
  • The OEM bolts are not disposable and I do not think they are torque to yield. Reading the factory service manual supports this. As an aside, just because a fastener is designed to yield, that does not mean it is garbage after one load (there are fasteners that are designed for multiple uses in this fashion). Also you get a nice constant-force spring when you use fasteners in this way. In fact, this why torque to yield fasteners are used, you eliminate the rather piss-poor torque-tension relationship.
  • This whole torque-tension ambiguity is what that for things that "truly matter" (not subaru engines), other methods are used to determine clamping such as: tension indicating washers, tension indicating fasteners, ultrasonic length measurement, direct length measurement (like rod bolts), or torque to yield. That said, I do not think we are that sensitive in the EJ (+- 15% tension is probably fine?).
  • Can you post pictures of your test rig?
  • It would be good to measure the before and after length of the hardware, particularly that stud you tossed (probably need a decent height gage, .0005" sensitivity would be good). It is possible that yielding/relaxation is not due to stud yielding, but the internal thread. Measuring the before/after stud length will show what was going on.
  • For a given clamping load, it is better to have a less-stiff fastener providing that load. This make the whole assembly less sensitive to small dimensional changes (higher stiffness equals more load change for a given displacement change). When designing bolted joints a simple mantra is more smaller (or longer) fasteners vs. fewer large (or shorter) fasteners. Obviously we can't change the number of fasteners but we do have control over the size. The 1/2" (or 14 mm) are stiffer and can supply more load. I think for normalish engine builds the benefits of the higher clamping force far outweigh the drawbacks of a stiffer fastener. I have wondered if it would be useful to have a slightly longer stud (with thicker "washer") when increasing the diameter.
  • Given there is decent access to the top of the stud, you could fairly easily measure the height of the top of the stud. It is reasonable to infer this is the stretch, though you need a decent depth micrometer or height gage. .001" sensitivity should be fine. This will (along with the clamp load measurement) shed a lot of light on lube affect and would be worth comparing clamp load to calculated clamp load using known material properties and stretch.
  • There is a significant change in torque level to achieve load when a fastener is reused. So your used vs. unused fastener is interesting. That said, I think most people building an engine end up in the end, with "used" fasteners. The fasteners might get used during block machining and measureing. Somewhere I have some papers on the torque-tension relationship and will dig up.
  • Here is a great quick bolting reference (has some nice joint stiffness curves which illustrate what I mention above): http://www-eng.lbl.gov/~shuman/NEXT/...renceGuide.pdf
  • The ultimate bolting reference is Bickford: https://www.amazon.com/Introduction-.../dp/0824792971

looking forward to your findings...meanwhile I will just try not to blow up my engine, which at this point is parts on my bench (because I gone done blow up the last one)
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Old 02-16-2022, 12:53 PM   #19
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Quote:
Originally Posted by cpreissner View Post
This is neat and I will be interested in seeing the results. As a mechanical engineer who has designed a few bolted joints...I will chime in with some thoughts.
  • First, I am skeptical of some of the numbers in that mechanical advantage webpage. I called ARP and asked them for the clamp load for the 11 mm, ARP 2000 head studs. They told me it is 15060 lb at 90 ft*lb and 15730 lb at 92 ft*lb (using their lube). This is quite a bit lower than mechanical advantage reported. I will be interested to see what you report.
  • Mechanical advantage did not pull the "clamp load" off of the ARP website, as ARP does not have that information on the website. They grabbed the yield stress...there is a difference.
  • The OEM bolts are not disposable and I do not think they are torque to yield. Reading the factory service manual supports this. As an aside, just because a fastener is designed to yield, that does not mean it is garbage after one load (there are fasteners that are designed for multiple uses in this fashion). Also you get a nice constant-force spring when you use fasteners in this way. In fact, this why torque to yield fasteners are used, you eliminate the rather piss-poor torque-tension relationship.
  • This whole torque-tension ambiguity is what that for things that "truly matter" (not subaru engines), other methods are used to determine clamping such as: tension indicating washers, tension indicating fasteners, ultrasonic length measurement, direct length measurement (like rod bolts), or torque to yield. That said, I do not think we are that sensitive in the EJ (+- 15% tension is probably fine?).
  • Can you post pictures of your test rig?
  • It would be good to measure the before and after length of the hardware, particularly that stud you tossed (probably need a decent height gage, .0005" sensitivity would be good). It is possible that yielding/relaxation is not due to stud yielding, but the internal thread. Measuring the before/after stud length will show what was going on.
  • For a given clamping load, it is better to have a less-stiff fastener providing that load. This make the whole assembly less sensitive to small dimensional changes (higher stiffness equals more load change for a given displacement change). When designing bolted joints a simple mantra is more smaller (or longer) fasteners vs. fewer large (or shorter) fasteners. Obviously we can't change the number of fasteners but we do have control over the size. The 1/2" (or 14 mm) are stiffer and can supply more load. I think for normalish engine builds the benefits of the higher clamping force far outweigh the drawbacks of a stiffer fastener. I have wondered if it would be useful to have a slightly longer stud (with thicker "washer") when increasing the diameter.
  • Given there is decent access to the top of the stud, you could fairly easily measure the height of the top of the stud. It is reasonable to infer this is the stretch, though you need a decent depth micrometer or height gage. .001" sensitivity should be fine. This will (along with the clamp load measurement) shed a lot of light on lube affect and would be worth comparing clamp load to calculated clamp load using known material properties and stretch.
  • There is a significant change in torque level to achieve load when a fastener is reused. So your used vs. unused fastener is interesting. That said, I think most people building an engine end up in the end, with "used" fasteners. The fasteners might get used during block machining and measureing. Somewhere I have some papers on the torque-tension relationship and will dig up.
  • Here is a great quick bolting reference (has some nice joint stiffness curves which illustrate what I mention above): http://www-eng.lbl.gov/~shuman/NEXT/...renceGuide.pdf
  • The ultimate bolting reference is Bickford: https://www.amazon.com/Introduction-.../dp/0824792971

looking forward to your findings...meanwhile I will just try not to blow up my engine, which at this point is parts on my bench (because I gone done blow up the last one)
Oh man! This will be great. I love having another ME check over what I'm doing and make sure I didn't miss anything. I'm being genuine here/no sarcasm.

Let me see what I can address:

1) For my initial testing I took 3 brand new ARP2000 studs, and using their lube, and their instructions I do not hit a clamp load of 15060 at 90lbs.

2) Wholeheartedly agree with you.

3) OEM bolts are actually on my list to test, but alas time has not favored an opportunity to keep working on the project. I need to get on that.

4) In all of my testing I have been consistent with what studs are what, and measured min cross section of each. So now I have cross section of each stud, I have clamp force for each stud using 3 lubes, and the next step will be to measure stretch at each indicated clamp load. Then with some mathery I SHOULD have every variable filled to answer any and all questions.

5) I'm not even sure what photo loading software nasioc is using these days. If you want to see a pic head on over to the Turn In Concepts facebook page as I posed a pic about a month ago. I CAN describe what I have though. I have a block of aluminum milled as flat as my head surfacer will do. In that is a threaded bore for receiving the stud. On top of that I have a steel hat washer, then I have a 20T load cell, then I have another steel hat washer. The stack-up height of everything matches what you would get out of a case and head combo accurate to within .010". One thing that I did do that is different is I formed the threads in the aluminum block which is 6061. I figured that given the repeated cycling I wanted that bit strong, and it should be non-affective on the outcome since it will be used across all studs I'm testing.

6) I too was a little concerned that I ripped the threads out of the aluminum block, but see note above. I also cross checked it after against a virgin stud, and threading it in did not cause any issues so I don't believe I damaged those threads in any way. I know it's not the best method to test, but that's all I could come up with. I do wish that I had measured before and after, yet sadly I did not. Honestly I just wanted to torque the crap out of something because the process of torque, write a number, torque, write a number was getting pretty boring. Not to worry I'm sure I'll get bored again and feel like breaking something so I'll have more opportunities.

7) We're still limited on length due to where the threads need to fall, and I don't believe (correct me if I'm wrong) that any additional length above the nut would have any benefit. In all of this Micah and I have been approaching this with the philosophy that studs are springs. Sure they can clamp just fine, but what happens in a big knock event? Hence a good part of this exercise. We need it to take the load of a bang, and return to normal clamping. At the same time we can't go TOO big or by the time we've reached proof we'll end up deforming the head (I know from talking with JJ that this is a real concern because if you get carried away with their 14mm you can crack the head).

8) You absolutely nailed it with how I'm going to measure the stretch. I have a gauge that does .0001" that I'm going to use for getting that, and that process is my next big push in data gathering. I'll also throw this in there - people will bring up temperature affecting things. All the studs and my test rig have been living on our engine build room (sometimes in Ethan's way). That room is kept at a constant 68F and is closed off from the rest of the shop.

9) For years I have wondered about the relationship of clamp on fasteners that are reused. Now, here we have two cases. Case 1 is where we're just using them for something like measuring during assembly or even fastening torque plates. Case 2 is truly used hardware where someone had a stud in an engine, blew it up, and then reused the studs for the next engine. Over the years I have adopted the philosophy that heat cycling is the key to this. Bolt things down and measure means no heat so good to go. Reused studs from a broken engine means heat so reconsider their use. NOW I finally have the ability to refine what honestly has been a wild ass guess. As of right now I have clamp data for all new studs. I need to get clamp data for used studs.... and I have PLENTY of those here to test with. That exercise will truly be eye opening.

10) Just popped open that pdf in another tab. I believe I have read this one years ago, but I'll give it a quick read today to see if anything stands out.

11) Thank you for the link on the book. Just ordered a copy.

No worries on blown up engine. Mine is in pieces, and has been for a couple of years. I have a real problem working on my own stuff because if I'm at the shop I always feel I should be working on customer stuff. Even when I come in on the weekend. As my wife will tell you I have a VERY poor work/life balance.
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Old 02-17-2022, 01:29 AM   #20
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Quote:
Originally Posted by cboggess View Post
Oh man! This will be great. I love having another ME check over what I'm doing and make sure I didn't miss anything. I'm being genuine here/no sarcasm.

Let me see what I can address:

1) For my initial testing I took 3 brand new ARP2000 studs, and using their lube, and their instructions I do not hit a clamp load of 15060 at 90lbs.

2) Wholeheartedly agree with you.

3) OEM bolts are actually on my list to test, but alas time has not favored an opportunity to keep working on the project. I need to get on that.

4) In all of my testing I have been consistent with what studs are what, and measured min cross section of each. So now I have cross section of each stud, I have clamp force for each stud using 3 lubes, and the next step will be to measure stretch at each indicated clamp load. Then with some mathery I SHOULD have every variable filled to answer any and all questions.

5) I'm not even sure what photo loading software nasioc is using these days. If you want to see a pic head on over to the Turn In Concepts facebook page as I posed a pic about a month ago. I CAN describe what I have though. I have a block of aluminum milled as flat as my head surfacer will do. In that is a threaded bore for receiving the stud. On top of that I have a steel hat washer, then I have a 20T load cell, then I have another steel hat washer. The stack-up height of everything matches what you would get out of a case and head combo accurate to within .010". One thing that I did do that is different is I formed the threads in the aluminum block which is 6061. I figured that given the repeated cycling I wanted that bit strong, and it should be non-affective on the outcome since it will be used across all studs I'm testing.

6) I too was a little concerned that I ripped the threads out of the aluminum block, but see note above. I also cross checked it after against a virgin stud, and threading it in did not cause any issues so I don't believe I damaged those threads in any way. I know it's not the best method to test, but that's all I could come up with. I do wish that I had measured before and after, yet sadly I did not. Honestly I just wanted to torque the crap out of something because the process of torque, write a number, torque, write a number was getting pretty boring. Not to worry I'm sure I'll get bored again and feel like breaking something so I'll have more opportunities.

7) We're still limited on length due to where the threads need to fall, and I don't believe (correct me if I'm wrong) that any additional length above the nut would have any benefit. In all of this Micah and I have been approaching this with the philosophy that studs are springs. Sure they can clamp just fine, but what happens in a big knock event? Hence a good part of this exercise. We need it to take the load of a bang, and return to normal clamping. At the same time we can't go TOO big or by the time we've reached proof we'll end up deforming the head (I know from talking with JJ that this is a real concern because if you get carried away with their 14mm you can crack the head).

8) You absolutely nailed it with how I'm going to measure the stretch. I have a gauge that does .0001" that I'm going to use for getting that, and that process is my next big push in data gathering. I'll also throw this in there - people will bring up temperature affecting things. All the studs and my test rig have been living on our engine build room (sometimes in Ethan's way). That room is kept at a constant 68F and is closed off from the rest of the shop.

9) For years I have wondered about the relationship of clamp on fasteners that are reused. Now, here we have two cases. Case 1 is where we're just using them for something like measuring during assembly or even fastening torque plates. Case 2 is truly used hardware where someone had a stud in an engine, blew it up, and then reused the studs for the next engine. Over the years I have adopted the philosophy that heat cycling is the key to this. Bolt things down and measure means no heat so good to go. Reused studs from a broken engine means heat so reconsider their use. NOW I finally have the ability to refine what honestly has been a wild ass guess. As of right now I have clamp data for all new studs. I need to get clamp data for used studs.... and I have PLENTY of those here to test with. That exercise will truly be eye opening.

10) Just popped open that pdf in another tab. I believe I have read this one years ago, but I'll give it a quick read today to see if anything stands out.

11) Thank you for the link on the book. Just ordered a copy.

No worries on blown up engine. Mine is in pieces, and has been for a couple of years. I have a real problem working on my own stuff because if I'm at the shop I always feel I should be working on customer stuff. Even when I come in on the weekend. As my wife will tell you I have a VERY poor work/life balance.
Ha. fantastic...I haven't been frequenting NASIOC that much recently...but have been wondering about EJ crank/block geometry and main bearing locations so have been searching for things on that and happened to see this thread. It is nice to have some decent discussion because the stuff on FB, while it has the benefit of easy access without using the web 1.0 interface, the level of discourse makes my brain bleed.

That is disappointing about the M11 ARP 2000 stud and not seeing the clamp load that they say they achieve. That said, I will be interested to see what you did achieve. I think there is a lot of variation with this stuff...and part of me when on the phone with them wanted to ask "and what was the sample size and standard deviation?"

I saw the test setup on your FB page and I think that looks good. I have done similar for some testing in my real life.

I think you are doing a good job with covering the bases for a meaningful set of data once you are all done. This stuff takes time and it is cool you are fitting this in.

In regard to my comment about a larger diameter bolt being stiffer if the same length as the smaller diameter, I was talking the length from nut bottom surface to top of threaded hole. I think my comment about trying to keep stiffness the same may be a bit silly. The stiffness of a fastener in the axial direction can be approximated as k=AE/L, where k is stiffness, A is cross sectional area of root (or smallest) diameter, E is Young's modulus, and L is the grip length. If you want the same stiffness and say an M11 is fastener 1 and M14 fastener 2 you can say k1=k2 or L1/A1 = L2/A2. The M14 fastener that would be the same stiffness as an M11 can be found by L2=L1*A2/A1. Using a M11 stud on my bench I measure L1 = 170 mm. The M11 root diameter is ~9.25 mm and the M14 root diameter is ~11.9 mm. This works out that for an M14 stud to have about the same stiffness as a M11 stud it would need to have a grip length of 281 mm, which obviously can't happen. I do wonder what the implications are for a fastener that is 66% stiffer. while clamping force is for sure higher, it is also more sensitive to changes across the joint. Interesting to think about in off/normal situations of knock. (I just cracked a liner and this caused me to call ARP and was also looking at journal papers for normal and knock cylinder pressures and was shocked at how high they can get)

from the temperature standpoint I don't think there isn't an issue for testing purposes. Your tests are relatively short and the temperature change small. Even if you have a 5 degree C change that results in I think a small change in clamping load. Aluminum has a coefficient of thermal expansion of ~22 um/m/C and steel is ~13 um/m/C. The difference is 9, so with the 5 degree C change you have an ~8 micron effective change in stud length. This works out using the AE/L for stiffness and the 8 micron length change to be 1047 N (234 lb) change in load. That is at the 1.5% level for one of those ARP 2000 M11 fasteners and quite a bit less for a M14. This is basically in the noise. You are also likely not having a 5 degree C swing during the test.

it might be interesting to check the increase in clamping load that happens in operation and maybe over heating conditions.

I will try to dig up where I have seen stuff about clamp load and torque as a function of number of times tightened.

That fastenal ref is my go to place for quick clamp load estimates for various fasteners...not too onerous to find. Bickford on the other hand...that is massive and will make for a good door stop even if you don't read. I am always amazed at how complex threaded fasteners are if you start to look closely.

anyhow...enough blathering...this is interesting stuff. I am going to assemble my new engine with ARP/IAG 1/2 studs and will be interested to see what you found with those.
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Old 02-17-2022, 10:57 AM   #21
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Ha. fantastic...I haven't been frequenting NASIOC that much recently...but have been wondering about EJ crank/block geometry and main bearing locations so have been searching for things on that and happened to see this thread. It is nice to have some decent discussion because the stuff on FB, while it has the benefit of easy access without using the web 1.0 interface, the level of discourse makes my brain bleed.

That is disappointing about the M11 ARP 2000 stud and not seeing the clamp load that they say they achieve. That said, I will be interested to see what you did achieve. I think there is a lot of variation with this stuff...and part of me when on the phone with them wanted to ask "and what was the sample size and standard deviation?"

I saw the test setup on your FB page and I think that looks good. I have done similar for some testing in my real life.

I think you are doing a good job with covering the bases for a meaningful set of data once you are all done. This stuff takes time and it is cool you are fitting this in.

In regard to my comment about a larger diameter bolt being stiffer if the same length as the smaller diameter, I was talking the length from nut bottom surface to top of threaded hole. I think my comment about trying to keep stiffness the same may be a bit silly. The stiffness of a fastener in the axial direction can be approximated as k=AE/L, where k is stiffness, A is cross sectional area of root (or smallest) diameter, E is Young's modulus, and L is the grip length. If you want the same stiffness and say an M11 is fastener 1 and M14 fastener 2 you can say k1=k2 or L1/A1 = L2/A2. The M14 fastener that would be the same stiffness as an M11 can be found by L2=L1*A2/A1. Using a M11 stud on my bench I measure L1 = 170 mm. The M11 root diameter is ~9.25 mm and the M14 root diameter is ~11.9 mm. This works out that for an M14 stud to have about the same stiffness as a M11 stud it would need to have a grip length of 281 mm, which obviously can't happen. I do wonder what the implications are for a fastener that is 66% stiffer. while clamping force is for sure higher, it is also more sensitive to changes across the joint. Interesting to think about in off/normal situations of knock. (I just cracked a liner and this caused me to call ARP and was also looking at journal papers for normal and knock cylinder pressures and was shocked at how high they can get)

from the temperature standpoint I don't think there isn't an issue for testing purposes. Your tests are relatively short and the temperature change small. Even if you have a 5 degree C change that results in I think a small change in clamping load. Aluminum has a coefficient of thermal expansion of ~22 um/m/C and steel is ~13 um/m/C. The difference is 9, so with the 5 degree C change you have an ~8 micron effective change in stud length. This works out using the AE/L for stiffness and the 8 micron length change to be 1047 N (234 lb) change in load. That is at the 1.5% level for one of those ARP 2000 M11 fasteners and quite a bit less for a M14. This is basically in the noise. You are also likely not having a 5 degree C swing during the test.

it might be interesting to check the increase in clamping load that happens in operation and maybe over heating conditions.

I will try to dig up where I have seen stuff about clamp load and torque as a function of number of times tightened.

That fastenal ref is my go to place for quick clamp load estimates for various fasteners...not too onerous to find. Bickford on the other hand...that is massive and will make for a good door stop even if you don't read. I am always amazed at how complex threaded fasteners are if you start to look closely.

anyhow...enough blathering...this is interesting stuff. I am going to assemble my new engine with ARP/IAG 1/2 studs and will be interested to see what you found with those.
My beef with the 1/2" studs isn't the studs but the install. Those are 1/2-13 and your block is M11x1.25. When they install them they just recut new threads over the old. Now, I haven't done the math or the modeling, but I suspect you lose anywhere from 20-30% of your thread mating doing that. I don't like it at all. If you're going to do that please do threaded inserts.
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Old 02-17-2022, 10:59 AM   #22
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My beef with the 1/2" studs isn't the studs but the install. Those are 1/2-13 and your block is M11x1.25. When they install them they just recut new threads over the old. Now, I haven't done the math or the modeling, but I suspect you lose anywhere from 20-30% of your thread mating doing that. I don't like it at all. If you're going to do that please do threaded inserts.
Crap. I had not thought about that. I agree. darn it...wish I had just gone M14, but I was trying to reduce time at the machine shop for the head modifications. (half inch use the same dowels)
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Old 02-17-2022, 01:38 PM   #23
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Kendall Samuel, where are you? LoL
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Old 02-17-2022, 03:25 PM   #24
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I too went with 1/2 studs. I thought when they machine the heads and block for 1/2 studs, they cut out the old threads and tap new ones.

Your telling me that they just cut the thread "tips" and thread in the 1/2 studs?
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Old 02-17-2022, 04:49 PM   #25
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My beef with the 1/2" studs isn't the studs but the install.
Don't get me started on this!!!

It's such a bad idea; lets put a stress riser on a stress riser

If Carroll Smith knew he be turning in his grave! The reality of it is there aren't known issues because of this poor practice. At least not that I am aware of.
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