Used head studs

Twinboys

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Any scientific reasoning out there as to why or why not install used ARP head studs?

Does anyone know if they will permanently stretch before they snap?
 

Mdub707

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You can measure the length and check it against spec to see if they've been permanently deformed or not. Pretty sure I was told they've re-used the standard ARP's in king kong like 8 times or something.

Scientific reason... yeah, if they're permanently deformed, they're weaker, ie, someone cranked on them beyond spec and yielded the material.
 

Twinboys

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That is exactly the answer I was looking for. I wasn't sure if they would snap before yielding, making checking them unnecessary. I don't know what spec is, but I should be able to check them all for variance.
 
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You need a bolt stretch gauge.
You need to torque it to check stretch.
Checking stretch is only accurate if you checked each one new for baseline of that particular bolt/stud.
 

lenzhotrod

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I would be surprised if ARP says 3 times only! During racing there where many times we pulled heads off more than 3 times!
 

Mdub707

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You need a bolt stretch gauge.
You need to torque it to check stretch.
Checking stretch is only accurate if you checked each one new for baseline of that particular bolt/stud.

How accurate is that method with torque scatter?

At work here we hydraulically stretch studs, which is a much more accurate method. Wish there was an easy way to do it on these really small studs, everything we work with is in the 3"+ area in OD.
 

Twinboys

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If a stud has been permanently stretched, but hasn't yet necked, wouldn't it actually be harder to stretch further than an un-stretched one because of work hardening? And yes, I know it will be more brittle.
 

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