How many times can you reuse ARP Head Studs?
03-21-2019, 10:30 AM
#2
TECH Senior Member
I would bet ARP might have an answer for you. ALWAYS go to the source....
03-21-2019, 11:25 AM
#4
TECH Senior Member
03-21-2019, 12:06 PM
#5
Their tightening specs do not seem to indicate torque-to-yield, leading one to think permanent deformation not to occur.
From their website: https://arp-bolts.com/p/FAQ.php
From their website: https://arp-bolts.com/p/FAQ.php
Are ARP bolts and studs re-usable? Yes. As long as the fasteners have been installed and torqued correctly, and show no visible signs of damage, they can be re-used. If they show any signs of thread galling or corrosion, they should be replaced. In the case of rod bolts, if any of them have taken a permanent set and have stretched by .001” or longer, you should replace them immediately. See page 29 in the catalog for more detailed information on this critical measurement.
03-21-2019, 02:16 PM
#7
The correct answer is:
Until they yield
They are not TTY bolts, and by design, should never yield in regular use. However, stuff happens. You should accurately measure the free-length of your studs before installation. Upon rebuild, re-measure their free-length again. If they've lengthened more than .001 or .002 from their starting point, they should be replaced. This is standard operating procedure for rod bolts, but not often applied to main/head studs. Probably because you can almost always just keep reusing head/main studs and they just keep working.
On a side note: About 15 years ago, I was assembling the bottom end of a 5.4L dohc Ford. During mock up assembly, as I tried to put the 75-80lbft (don't remember exactly) onto one of the main studs, I couldn't get my wrench to click - instead it felt like I was stretching the bolt. I back it all off, inspected, then tried again. This time after I felt it "stretch", I put another 45-60º rotation into it. Still didn't increase torque. Disassembled again and inspected, to find an obvious "neck" in the coarsely-threaded end of the stud that went into the block. Necking is where the diameter gets smaller so that the whole fastener can get longer. Called ARP, and they took this very, very seriously. They sent me a UPS Red call tag for the fasteners and redded out another set. They were extremely attentive to the heat treat lot# associated with the bad fastener. I loves me some ARP...
Until they yield
They are not TTY bolts, and by design, should never yield in regular use. However, stuff happens. You should accurately measure the free-length of your studs before installation. Upon rebuild, re-measure their free-length again. If they've lengthened more than .001 or .002 from their starting point, they should be replaced. This is standard operating procedure for rod bolts, but not often applied to main/head studs. Probably because you can almost always just keep reusing head/main studs and they just keep working.
On a side note: About 15 years ago, I was assembling the bottom end of a 5.4L dohc Ford. During mock up assembly, as I tried to put the 75-80lbft (don't remember exactly) onto one of the main studs, I couldn't get my wrench to click - instead it felt like I was stretching the bolt. I back it all off, inspected, then tried again. This time after I felt it "stretch", I put another 45-60º rotation into it. Still didn't increase torque. Disassembled again and inspected, to find an obvious "neck" in the coarsely-threaded end of the stud that went into the block. Necking is where the diameter gets smaller so that the whole fastener can get longer. Called ARP, and they took this very, very seriously. They sent me a UPS Red call tag for the fasteners and redded out another set. They were extremely attentive to the heat treat lot# associated with the bad fastener. I loves me some ARP...
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03-23-2019, 07:02 PM
#8
9 Second Club
Depends how accurately they are torqued in the first place....and whether they have stretched, threads deformed, etc etc.
They might last forever...or one time lol
They might last forever...or one time lol