[Elarson]

Yup, all material stretches or deforms under load. The measure of it is modulus of elasticity.
You'll also find that all steels, regardless of alloy, have nearly the same modulus. The stronger alloys can tolerate more load (and the corresponding higher stretch) before yielding or breaking.

Eric

[GTOGEORGE]

Originally Posted by Dragncar

Yes they do. All bolts stretch with tq. ARP 2000 7/16 rod bolts have a stretch number from Molnar.
A 1/2" ARP main stud also stretches . Its called clamp force. Engineers have calculations for such things.
https://www.securitylocknut.com/how-...ly-calculated/

Measure a main stud. Take a main cap by itself and put a ARP 2000 main stud in a inner hole. Nut on both ends and torque it. Then measure.
There is your bolt stretch.

My ARP2000 head studs are far better then my OLD 8740 ARP head studs I used previously ! I’m just trying to share my results on using both head studs, do you you want with the info.

[mgarblik]

Originally Posted by GTOGEORGE

My ARP2000 head studs are far better then my OLD 8740 ARP head studs I used previously ! I’m just trying to share my results on using both head studs, do you you want with the info.

I think possibly there is just a little terminology difference here. To get the desired clamp load, non-torque to yield fasteners, like we are talking about, need to be put into their "elastic range". They are being stretched, but not into their "deformation range". Meaning they are stretched into a range for use and when taken back out, return to their original length. They can be reused more than once. That's the way the majority of ARP fasteners are designed. If you take any fastener into it's deformation range, it reaches it's maximum clamp load, and won't go any higher. The fastener continues to stretch a little more, applying no additional clamp load, then it yields. (breaks). Possibly, George's 8740 studs were in the deformation zone for some reason, not applying additional clamp load. The better ARP 2000 material may apply slightly more clamp load before going into deformation. That's all I can think of. On the Boss Bird engine, the small outer 7/16" fasteners were only available in 8740 material. I would measure the overall length when new and they would deform big time in operation. Some were .100+ longer when I measured them at every rebuild. This was permanent deformation. Those studs were replaced of course. Of course a 1/2" stud at a given torque value will stretch less than a 7/16" stud. Have to find that balance.

[GTOGEORGE]

Just gave some information!



GTO George

[Tom Vaught]

Originally Posted by Elarson

Yup, all material stretches or deforms under load. The measure of it is modulus of elasticity.
You'll also find that all steels, regardless of alloy, have nearly the same modulus. The stronger alloys can tolerate more load (and the corresponding higher stretch) before yielding or breaking.

Eric

Thank You Eric for that comment.
Tom V.

[GTOGEORGE]

Metals stretch Pontiac heads lift…..not good, that’s why better head bolts/studs are needed or go to larger diameter bolts/stud.



GTO George