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Old 03-18-2010, 04:56 PM   #1
AMR
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News 14mm Head Studs was last year....with bigger power comes a BIGGER STUD!!!

AMR is proud to announce the largest head stud ever designed for the Subaru applications! The AMR 9/16" "BIG BOY" head studs for the Subaru community. Unlike any stud currently on the market, 11mm or most 14mm. Our 9/16" studs have NO TAPER and have been designed with american thread making taping the block easier and thread strength stronger!

The AMR 9/16" BIG BOY head studs are made out of 8740 chromoly. They have a 220,000 psi clamp load rating and a hardness of RC39-43. The threads on the AMR studs are rolled rather than the typically cut design. The studs are also heat treated.

AMR 9/16" BIG BOY Stud Kit:
- 12 AMR BIG BOY Studs
- 12 8740 chromoly washers
- 12 8740 chromoly nuts











-Rob
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Last edited by AMR; 03-19-2010 at 08:54 AM. Reason: specs added
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Old 03-18-2010, 04:58 PM   #2
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but my weight savings....
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Old 03-18-2010, 07:12 PM   #3
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What are they made out of? What psi rating? What makes these better then a h11 11mm stud?
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Old 03-18-2010, 07:31 PM   #4
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how are these better than arp. and whats the cost
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Old 03-18-2010, 07:47 PM   #5
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Just saw these today at AMR's place along with there nasty T70R turbo (wish list ). 1 word.....HUGE
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Old 03-18-2010, 08:01 PM   #6
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bigger doesn't mean better. You have to tell us the material, tensile strength and yield strength.
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Old 03-18-2010, 08:46 PM   #7
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So 14.2 wow what a difference.... What is the american thread all about and how different is it from the rest of the threads apr and cosworth use?
Won't this distort the aluminum block putting in something SO BIG?
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Old 03-18-2010, 09:37 PM   #8
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It's not about the size of the boat but the motion... oh wait, never mind...
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Old 03-18-2010, 10:29 PM   #9
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dont you want finner threads to you have more grip from the nut, and can tighten down better
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Old 03-18-2010, 10:50 PM   #10
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Old 03-19-2010, 08:42 AM   #11
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Quote:
Originally Posted by ChrisKwan View Post
bigger doesn't mean better. You have to tell us the material, tensile strength and yield strength.
^^^ +1.
Horrible pic, but where's the taper.
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Old 03-19-2010, 08:54 AM   #12
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Quote:
Originally Posted by SubieFiesta View Post
Just saw these today at AMR's place along with there nasty T70R turbo (wish list ). 1 word.....HUGE
It was great to see you again.


Quote:
Originally Posted by fobiawrx View Post
What are they made out of? What psi rating? What makes these better then a h11 11mm stud?
Quote:
Originally Posted by moorebl View Post
how are these better than arp. and whats the cost
Quote:
Originally Posted by ChrisKwan View Post
bigger doesn't mean better. You have to tell us the material, tensile strength and yield strength.
Quote:
Originally Posted by waynoSTI View Post
So 14.2 wow what a difference.... What is the american thread all about and how different is it from the rest of the threads apr and cosworth use?
Won't this distort the aluminum block putting in something SO BIG?
Quote:
Originally Posted by soobaviator View Post
It's not about the size of the boat but the motion... oh wait, never mind...
Quote:
Originally Posted by seanathanq83 View Post
dont you want finner threads to you have more grip from the nut, and can tighten down better
Updated post 1!

Quote:
Originally Posted by bertune View Post
^^^ +1.
Horrible pic, but where's the taper.

You can clearly see the taper on the smaller stud as well as the center of the shaft. Again, this is on most. We just took what we know from building Subaru engines and push to make components better.




-Rob
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Old 03-19-2010, 10:58 AM   #13
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Ok let me ask this. What is your definition of big power that you would need these over your competition's product?
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Old 03-19-2010, 11:27 AM   #14
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Quote:
Originally Posted by hybrid gti 2 View Post
Ok let me ask this. What is your definition of big power that you would need these over your competition's product?
Keeping the head on the vehicle and preventing head gasket failure is a problem when producing a lot of power out of an EJ series engine. These larger head studs are used to hold the head from moving around and stretching which in turn causes head gasket failure. This is very common with the EJ motors. By using a larger style stud, you are able to use a higher clamping load and torque specifications. This, along with the studs larger diameter, keeps the stud from warping, stretching and moving with the head under extreme pressure (boost) and high hp. This is the largest stud you can put in an EJ series block without removing to much material and hurting the blocks strength. We recommend using these studs for 500hp+ engines.
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Old 03-19-2010, 11:46 AM   #15
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so the cosworths h11 or arps l19 have a 260,000 psi tensile strength and they are a direct fit. no drilling out the head or drilling and taping out the block with them. and from all the big drag racers i have talked to about this say at the pressures your motor makes when pushing high boost you want as much strength holding that stud into the block along with a strong stud. you don't want to take away material from the block because it weakens it. you need the stud to be as strong as it can be.
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Old 03-19-2010, 01:48 PM   #16
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Interesting
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Old 03-19-2010, 07:29 PM   #17
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Quote:
Originally Posted by AMR View Post
You can clearly see the taper on the smaller stud as well as the center of the shaft. Again, this is on most. We just took what we know from building Subaru engines and push to make components better.
-Rob
Sorry, i mean't the taper on the 14mm, so how much is this going to set the consumer back?
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Old 03-19-2010, 10:56 PM   #18
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Quote:
Originally Posted by fobiawrx View Post
you don't want to take away material from the block because it weakens it.
I'm curious how they determined how much to remove, or that they haven't removed too much.
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Old 03-20-2010, 12:32 PM   #19
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I'm curious how they determined how much to remove, or that they haven't removed too much.
well go look at a block. all blocks are the same. you have a wall thickness from the taped hole to the water jacket. you remove material to allow a bigger stud and you shrink the wall thickness making it weaker. some of the big power honda guys like kenny tran have told me they ran in to problems with motors cracking from taping bigger holes to allow a larger stud. they went back to the stock size stud and used a h11 or L19 (what ever you choose to call it) and have not had problems.
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Old 03-20-2010, 01:22 PM   #20
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Right, I'm wondering if they did any tests to failure with a load cell, or at least tried to do some FEA on it. Without either, using those threads and a larger stud would be pure gimmick that turns your motor into a guinea pig.

The 220kpsi 14/14.2 studs do have a significant increase in clamp force over the 260kpsi 11mm studs. If the block can hold it reliably it's probably the way to go, depending on the price of h11/L19 and peak cyl pressures.

Last edited by Merp; 03-20-2010 at 01:28 PM.
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Old 03-20-2010, 02:01 PM   #21
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Every engine builder has there own theories. For those who want to use them, we have them available.

All we know is, we have been building Subaru's for a VERY long time. As we continue to push the products and power limits we hit walls along with finding failure points. As we find the "failure points" we then figure out how to fix and/or make the product better and move ahead. We have pushed the 11mm stud to its limits and have had them stretch, crack, warp and even snap. Companies who manufacture the 11mm studs know this so they decided to upgrade the material to L19. While making the material stronger, we found we were able to go a tad further but still ran into the same issues. So we took it upon ourselves to design a stud we feel will "get the drop done" and have been running these studs in our high power engines trapping 140+mph along with those trapping 150+mph consistant without any issues.

The main reason people do not go with the larger studs is the effort of maching the block and heads to suite the larger stud. As far as taking material out, you will notice the holes on the block in which your stud stands in are already 14mm in diameter. The hole only shrinks to suite the 11mm wear the thread lies. So you are in turn filling that "stud hole" by inserting our stud and maching the threads larger to suite it. The factory head gasket as well, has large enough wholes which suite our stud. Here are some pictures to explain what I mean:
























-Rob
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Old 03-20-2010, 03:03 PM   #22
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great explaination there Rob!

can you please post pics of the heads too if it needs machining or not with your head studs?

subaru head gasket is one of the problems by high hp engines.

I wish your head studs were around 2 years ago when my engine was being rebuilt.

Now i'm getting tempted to put your head studs to my engine, or build another engine with your headstuds in it. devil is tempting me when I see good products from you
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Old 03-20-2010, 04:50 PM   #23
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I am not advocating either the 11mm or "big boy studs" however some critiques leveled have been based on pure speculation so I will do the same;-).
We all seem to agree that more clamp load is a good thing when it comes to retaining head gaskets. Many have found success in using studs made of exotic steel that has a much greater tensile strength than the factory head bolts, allowing more fastener torque resulting in higher clamp loads. Stop to consider for a moment that all 11mm fastener upgrades do not address upgrading the strength of the threads in the block; through either dimensional or material change.
While I understand that taking material from the block to accommodate larger threads has the potential to weaken the block, perhaps it is necessary and even beneficial?
With an 11mm fastener into the stock cast aluminum block you are exerting X clamp load. All of this load is bore via tension in the studs and threads (both on the studs AND in the block) and compression of the crankcase and head castings. Even though the material AMR uses with their 9/16" studs has a lower tensile strength than 11mm "h11/L19" studs their cross section more than makes up for the material properties difference, and results in a higher achievable clamp load; perhaps higher than the stock block threads could take.
I believe some are getting fixated on tensile strength and not taking into account other aspects such as thread profiles, engagement, cross sections etc.

Also, worth note is the bore size of a EJ257 Vs. many other import motors. For an equivalent cylinder pressure the Subaru will generally see more force applied to the head studs due to it's unusually large bore size.
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Old 03-20-2010, 10:06 PM   #24
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Can you show pics of your stud against some heads? While you tested these at a drag strip, how have they done at a road course?
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Old 03-20-2010, 10:12 PM   #25
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As long as the stud material is of good tensile strength the benefit to larger studs is a larger contact area in the threaded area. So its not just the stud thats part of the equation but rather the thread contact area. Basics for mech engineers...
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