stock head studs reusable?

[christdeyoung]

My ARP studs were recommended to be torqued to 125 ft-lbs, so I did. No problems.

[NismoS-tune]

ARPs studs are pretty cheap and it's an upgrade, if the engine is out, rebuild it, fix the known bad actors and get new studs. End of story.

[RSTuning]

You can reuse arp studs but you should measure them prior to initial installation, if being re used the original measurement should have not been affected. if it has then replace them with new units.

[caliber676]

Your supposed to replace any torque angle/torque to yield bolt if your a decent engine builder.

[M13]

89ft/lb as per OEM FSM.

I dunno, ARP studs are like 250 bux (not 100, I dunno where you are coming up w/ these prices LOL) and I would think it's a good insurance for building up an engine with a budget in the thousands...


I guess I'm just crazy.

[nelsonmxmarc]

80 ft/lbs is what arp recommends. The general consensus is to go +5/10 above. I went to 85 to be safe. OEM
is 90 if I'm not mistaken..

[nelsonmxmarc]

You can reuse arp studs, because they DO NOT stretch (or if they do it's not detrimental to the characteristics of the metallurgy). Marus summed it up.. Stock bolts stretch, it's the nature of that particular metal. And this is the reason the the head torque sequence in the fsm states to return to 0.. One torque sequence stresses the metal, whereas the following one seats it. Arp doesn't require this, as structurally they remain integral, and arent supposed to stretch.

Different story for conrod bolts..

[MarusGTR]

yeah Marus, Ive read something similar to what youve described, angle torqued studs are usually torqued beyond the point of elastic stretch to what they call plastic stretch. I also contacted a nissan/infiniti dealer and the guys told me as long as the studs has no visible damage to them, then they should be reusable....but i have a feeling the dont really know what they are talking about

On a side note, arp head studs from what ive read dont need to be angle torqued, the spec was 86ftlbs instead
can anyone correct me if im wrong?

It wouldn't be torqued to plastic deformation for a few reasons. Main reason is that plastic deformation weakens the atomic structure and it's integrity; inter-atomic fissures cause the metal to decrease it's ultimate yield. The structure deforms in the plastic domain to diffuse energy from the strain of elasticity, becoming soft and microfissure prone.

Basically take for example people who torch springs; you get one saggy POS spring that makes the car lower because the atomic structure slowly cooled to a softer state, reducing the spring rate.

[gezed]

Really? i thought you can reuse arp studs for sure as long as theres no signs of damage cause although they do stretch, they arent pushed to the point at which they are deformed. so when you loosen them again they wont remain stretched assuming that they arent torqued way over the specifications

[M13]

and you have to use ARP moly-lube.


I wouldn't re-use ARP studs either. They are meant to be used once and replaced. EVERYTHING stretches and loses tensile strength. To say that they won't is just outright ignorant.

[gezed]

yeah Marus, Ive read something similar to what youve described, angle torqued studs are usually torqued beyond the point of elastic stretch to what they call plastic stretch. I also contacted a nissan/infiniti dealer and the guys told me as long as the studs has no visible damage to them, then they should be reusable....but i have a feeling the dont really know what they are talking about

On a side note, arp head studs from what ive read dont need to be angle torqued, the spec was 86ftlbs instead
can anyone correct me if im wrong?

[MarusGTR]

As an engineer, and purely theoretically since I haven't physically dealth with them, I wouldn't.

There's tensile stretch on any studs by their nature, but I'm pretty sure head studs are torqued so that they strain harden in their elastic point of deformation. They are stretched to a point where they the metal's atomic layering becomes permanently affected and if you take the load off, the next time you torque them to spec they can go past their ultimate tensile strength under engine load (aka they can snap.)

http://en.wikipedia.org/wiki/Strain_hardening

[GTRADDICT]

Personally I would wait until you had the funds to replace them. that way you have the re assurance that it was done propper the first time. reusing the stock head studs may be ok or it may cause larger problems in the future.

IMO do it right or do it twice.

+1...

[S13Jordie]

Personally I would wait until you had the funds to replace them. that way you have the re assurance that it was done propper the first time. reusing the stock head studs may be ok or it may cause larger problems in the future.

IMO do it right or do it twice.

[Terrh]

stock bolts aren't studs.

You can't find ARP head studs for an RB26 for $100 anywhere.

If a bolt survives being torqued without breaking it's still good. If it doesn't, you'll know.

The manual says to replace them every time, but they say the same thing about the main bolts and a lot of people have reused those 2-3 times without an issue.

Personally? I'd probably reuse them if you can't afford the $250+ that a set of studs costs. And if you can afford studs, they're better.