01ssreda4

iTrader: (96)

When you find that out, let us know would ya please. In the meantime Im going to use the closest example i know works. I know you may have a hard time grasping my reasoning.

OBeer-WAN-Kenobi

I don't know,
Is he intelligent, handsome and super popular? If so, he could be my brotha' from anotha' motha'.

01ssreda4

iTrader: (96)

Nope, nope, and nope.

OBeer-WAN-Kenobi

If the physical material properties are close to the same, you can probably get away with it. For example, both 8740 and 190K ultimate tensile. The larger point is just to be cognizant of how this works and to be careful.

I wasn't trying to target anyone in particular with my post. It just seemed there was a lot of speculation and misinformation in the thread. I also happened to be working on torque calculations for something else, so decided to plug the numbers in for this while I was at it.

01ssreda4

iTrader: (96)

My last set I believe I went 25/50/75. They are holding well.

OBeer-WAN-Kenobi

They definitely should, if they are the material they are advertised to be. At 75 ft lbs, each of your studs is holding approximately 10,454 lbs of tension.

Just to illustrate differences in material, If your fasteners were Grade 8.2 instead of 8740 Chrome-Moly for instance, the data would show they were beyond yield if using engine oil to torque them in:

Not lubricated:
80 ft lbs at 85% of yield
94 ft lbs at yield
Oil Lubricated:
60 ft lbs at 85% of yield
70 ft lbs at yield

The BallSS

iTrader: (9)

While we're on the topic of head studs, I've got ARP studs in my 02 LS1 and am currently building an 05 LM7, will I be able to reuse my studs from my LS1?

truckdoug

iTrader: (25)

probably not, or at least not the long bolts

Dian

obeer, i wonder where your data comes from. what im seeing for shcs is somewhat different (not by much).

pantera_efi

iTrader: (1)

Hi ******, some may try to put your B'sToW's.
MY METHOD IS DIFFERENT, I like to help LS-1 tech members.

YES, reuse your studs, you will need some "singles" to convert to a GEN-IV block.
You can buy/I can buy them from ARP "tech" side for $12.00 each.
They all need to be the same size, the most common present.

The ARP studs are top quality, ALL here (the posters) HAVE NOT BOUGHT THEM.
The Quality ARP "LS" stud IS UNDERCUT for the CORRECT "stretch".
Thus correct fitment with AL head expansion.

Lance

01ssreda4

iTrader: (96)

Just did another set, 5.3, LS9 headgasket, china studs, 25/50/75 with motor oil. No issues. There is no doubt the ARPs look higher quality, Ive owned/run them also.

OBeer-WAN-Kenobi

My data comes from my own calculations (tensile area/shear area/torque etc.) that I built into an excel spreadsheet several years ago. I didn't trust the tables out there so I calculated everything from scratch. Most likely my data will show a little less torque in a given bolt/material combination than some of the charts out there as I did all my calculations at least material condition of the hole and fastener.

So, depending on where you found the SHCS data and what material they are made from I'm sure the data will be a bit different. When I did my initial testing of the spreadsheet though, I was always really close to published data for SHCS's. Also, the "K" factor used is the biggest single variable.

Dian

nice. usually the values are determined experimentally. so you assumed the same coefficient of friction for the threads and the head? which gets interesting into an aluminum block.

ls13ater

iTrader: (3)

I did not read every page just skeemmed, I have Never had a problem with arp, you can tq them at 120 and they won't stretch, I have made 734on 22lbs and stock unbolted heads on a iron block, I had a head lift on a l33 and parts house bolts at 715whp, I personally think iron/aluminum expands less then aluminum/aluminum , I have a 4.8, ls9 and China studs in my motor now 822whp@23lbs and it's holding strong, I had a friend snap a China stud at 85lbs

OBeer-WAN-Kenobi

With a stud, I think you would use whichever has the least friction since that is where it would rotate. That would probably be the nut/stud junction assuming you're using a washer. So it seems to me that it really is steel on steel, even considering an aluminum block. You would only be concerned with the shear area of threads in the block for a possible weak point, I would guess.

With a bolt, it should be the same as above if you are using a washer in an iron block however; if you are not using a washer or you have an aluminum block, then yes, it would need a different "K" factor, and that would probably need to be determined experimentally. Likely, someone has already done it and it's out there somewhere.

Yes, in real-world application, ideally calculated data doesn't usually match empirically derived data. In the case of torque, that's what he "K" factor or "nut" factor is supposed to correct. I've had to do some interesting experiments with "nut dilation" at work which goes even deeper down the rabbit hole and can cause an enormous effect on thin-walled applications. I often have to use calculations to get the proper torque for a certain resultant tension that is enough to make two mating flat surfaces seal. In that case it's necessary to go well into elastic and sometimes into plastic deformation of the two surfaces but not over the yield of the thread mate. Lot's of fun, that.

In the end, engineering is really just scientifically controlled, mathematically derived guesswork. SWAG. It's to get you close enough that you spend less money when you have to do the empirical testing that either proves your calculations were right in the first place, or determines that you need to go back to the drawing board and change your calculations. Wash, rinse, repeat until they are close enough for your given application. Luckily, a lot of past experimenters and engineers have already done a lot of the testing and trial and error for us which is why we have cool equations in the first place.

OBeer-WAN-Kenobi

They had better stretch. Be useless otherwise.

I'm guessing you meant yield but I couldn't help myself.

Dian

i wonder if you have any insights into this: we are talking about 150k/180k psi screws/studs in A356 T6 (30k/40k psi). how come they dont rip out the aluminum? if you look up torque values into aluminum, they usually are very low. the same situation with other screws into the block, e.g. water pump, m8 and 22 lbs/ft.

also, fact is that a nut deforms when tightened (that why they are softer) and the torque to get the same strech insreases with every subsequent tightening. i believe it roughly doubles after 20 times. you can use new nuts on studs but you cant use a new block with bolts and the threads deform like they would on a nut, right? so, how do we account for this?

OBeer-WAN-Kenobi

Just warning you.....I typed this on my phone...

The threads don't strip out of the block because of the depth of the threads. As long as the combined shear area of the threads does not go into yield, they won't deform permanently or strip.

A thread is really an inclined plane, wrapped in a circle so think about a wedge like you'd use to split wood. Now think about it being much smaller and being a 60 degree triangle. Take the area of the side of that wedge with it wrapped that around your thread diameter once. That would be the shear area for 1 thread. As tou wrap it around more, the shear area gets larger and the joint gets stronger up to the point that the tensile area of the bolt will fail before the shear area of the threads. That's what you want, plus some safety factor. I usually want the bolt to fail ultimate tensile before the threads yield if possible.

As for the nut, it should act like a hole unless the hoop stress is enough to overcome its wall strength. In the case of the block, it has thick enough walls that this shouldn't come up. Anyway, the reason hoop stress becomes relevant here is because the thread really is a wedge, or inclined plane. As it's wedging against the mating thread, they want to push each other away. This results in hoop stress in the nut and hole and causes........nut dialation. This is what I eluded to in my last post. We are getting into some dynamics here.

​​​​
As a nut dialates larger, the thread shear area becomes less which makes it easier to strip both on the stud and on the nut. Depending on the stud material the nut may need to be a different material or hardness to keep it from gauling. If its softer, it will be the weak point which may be "as designed" so the nut, being easily replaced, will fail before anything else.

Although it could grow each time if the hoop stress overcomes yield and eventually strip when the shear area is overcome , I'm thinking that a nut shouldn't take more and more torque to get the proper tension as it's reused though, unless it's gauling. Gauling would cause that to happen because the friction to overcome it would increase the torque needed to get to a resultant tension. Different hardnesses of the mating parts or different materials all together help guard against gauling.

Dian

well, if you believe "conventional wisdom", the first thread takes 35% of the load, the second 20% etc. they yield and deform. after the have deformed they dont take much of a load, next time the following threads deform, at least thats my understanding. some people even propose to drill out the first threads* for this reason. so after a few times you have deformed all threads in the block and the situation must be different, how exactly i dont know.

* not in an engine block

Ja Ja

So if you had to choose between a high quality head (BOLT) OR low quality head (STUDS) what would you choose. Obviously studs are the better clamping method. It seems like you could get a really high-quality bolt for not much more than low quality studs would cost, so just curious if that was your only choice which one would you choose.