Gauging interest: H11 head studs for FI applications
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From: Cottage Grove, MN
Gauging interest: H11 head studs for FI applications Would anyone be interested in an H11 head stud alternative? Pricing would be in the $530 range which is about $250 cheaper than ARP 625+, let me know!
Last edited by maperformance; Oct 15, 2013 at 09:49 AM.
Looked long and hard for some, but none were available when I bought studs. I'd be interested in a set. The custom 625 came out after I bought mine. That's a good price point also.
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Are you claiming that the H11 studs are as strong as the ARP studs?
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Standard ARP head studs use 8740 chromoly which has a tensile strength of 190,000psi. Our H11 studs would have a tensile strength of 260,000psi which is equivalent to what i have been seeing in regards to ratings for the ARP Custom Age 625+ (although some claim 280,000psi) but at a much lower price point 
This leads me to another question, do most people stay with the 11mm studs or do they modify their block to accept 1/2" studs?
This leads me to another question, do most people stay with the 11mm studs or do they modify their block to accept 1/2" studs?
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Make a set for the Dart Ls next gen block and I will buy a set. Got to remember guys who are buying studs like this are probably using a 6bolt heads too. I would make sure to do 6bolt kit is what I am getting after.
Last edited by transam69230; Oct 15, 2013 at 08:22 PM.
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Standard ARP head studs use 8740 chromoly which has a tensile strength of 190,000psi. Our H11 studs would have a tensile strength of 260,000psi which is equivalent to what i have been seeing in regards to ratings for the ARP Custom Age 625+ (although some claim 280,000psi) but at a much lower price point
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From: Cottage Grove, MN
It's mostly the material and manufacturing processes but depending on the application there may be design features like a dog point that can be of value also.
Please note that the pricing I outlined in the original post was for 4 bolt applications, I will have to look into pricing for 6 bolt applications and report back.
Please note that the pricing I outlined in the original post was for 4 bolt applications, I will have to look into pricing for 6 bolt applications and report back.
I had a set of 625 on my bbc aluminum heads, torqued them down to 120lbs and after the first rebuild you could plainly see the indention of the washer in the head from the pressure the nut was putting on the head.
at what point does the extra strength of the stud not benefit as the head starts to collapse
at what point does the extra strength of the stud not benefit as the head starts to collapse
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I can't say that I've ever encountered that, although 120ft/lbs does seem quite high. Here is an interesting blurb from a conversation I had with A1 technologies recently regarding different moly lube and torque values, it seems that extra torque doesn't necessarily equal additional capacity:
...you can achieve the same stretch of the fastener, stretch = clamp-load, with a lower torque. Lower torque means less torsion is applied to the fastener to achieve proper stretch. Tension, the stretch of the stud is one load, which applies the clamp force holding the head down properly. Torsion is the twisting that occurs due to friction when torque is applied to a fastener. This is a secondary load simultaneously applied while stretching the fastener, biaxial loading, is the technical term. Torsion serves no beneficial purpose to the proper loading, (stretch), of a fastener and is actually detrimental to the UTS (Ultimate Tensile Strength) of a fastener. Because torsion is a secondary load occurring while stretching a fastener is can reduce the UTS (maximum capability of a fastener) by up to 20% or more.
In a perfect world stretching a fastener then spinning the nut freely down to the head surface then releasing the fastener (stud) would achieve the proper stretch & clamp-load (preload) without any torsion load to the fastener. As this is not feasible the next best option is to achieve the desired stretch, clamp-load (preload) with the least amount of torsion load, which is caused by friction. This is why we prefer an assembly lube with a lower friction coefficient and utilizing less torque to achieve the stretch, clamp-load, desired.
...you can achieve the same stretch of the fastener, stretch = clamp-load, with a lower torque. Lower torque means less torsion is applied to the fastener to achieve proper stretch. Tension, the stretch of the stud is one load, which applies the clamp force holding the head down properly. Torsion is the twisting that occurs due to friction when torque is applied to a fastener. This is a secondary load simultaneously applied while stretching the fastener, biaxial loading, is the technical term. Torsion serves no beneficial purpose to the proper loading, (stretch), of a fastener and is actually detrimental to the UTS (Ultimate Tensile Strength) of a fastener. Because torsion is a secondary load occurring while stretching a fastener is can reduce the UTS (maximum capability of a fastener) by up to 20% or more.
In a perfect world stretching a fastener then spinning the nut freely down to the head surface then releasing the fastener (stud) would achieve the proper stretch & clamp-load (preload) without any torsion load to the fastener. As this is not feasible the next best option is to achieve the desired stretch, clamp-load (preload) with the least amount of torsion load, which is caused by friction. This is why we prefer an assembly lube with a lower friction coefficient and utilizing less torque to achieve the stretch, clamp-load, desired.
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I had a set of 625 on my bbc aluminum heads, torqued them down to 120lbs and after the first rebuild you could plainly see the indention of the washer in the head from the pressure the nut was putting on the head.
at what point does the extra strength of the stud not benefit as the head starts to collapse
at what point does the extra strength of the stud not benefit as the head starts to collapse
I guess that will vary with head designs and materials used. Something we dont have much control over.
Nut base diameter, washer diameter and thickness....I guess we do have control over that to a certain degree.
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Isnt H11 the tool grade steel that got banned from aircraft because its brittle? Did the properties change that made it better recently? Cheap I get. What I don't get is why anyone would still manufacture with tool grade steel when there is much better material to be had. Or is the good stuff cost prohibitive?
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Isnt H11 the tool grade steel that got banned from aircraft because its brittle? Did the properties change that made it better recently? Cheap I get. What I don't get is why anyone would still manufacture with tool grade steel when there is much better material to be had. Or is the good stuff cost prohibitive?