TTY bolts vs studs
01-07-2008, 05:22 PM
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TTY bolts vs studs I started another thread about tty bolts in the engine section but I need some input fron some fi guys.
Has anyone rebuilt a engine using tty bolts instead of studs? Or has anyone lifted a head with tty bolts?
I know arp studs have a higher tensile rate, but tty bolt have more clamping force and a more even torque across the head..
Has anyone rebuilt a engine using tty bolts instead of studs? Or has anyone lifted a head with tty bolts?
I know arp studs have a higher tensile rate, but tty bolt have more clamping force and a more even torque across the head..
01-08-2008, 06:22 PM
#3
I have seen lots of threads of guys running the arp head bolts with good results as well as the studs. Not sure why you would want to try running torque to yield stock bolts on a FI engine especially one running higher boost. They work fine on low boost applications..5 to 8 maybe even 10psi. Beyond 10 psi would go for arp bolts or studs.
01-08-2008, 10:13 PM
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I have seen lots of threads of guys running the arp head bolts with good results as well as the studs. Not sure why you would want to try running torque to yield stock bolts on a FI engine especially one running higher boost. They work fine on low boost applications..5 to 8 maybe even 10psi. Beyond 10 psi would go for arp bolts or studs.
I understand that ARP has a High tinsel strength, but if a TTY bolt is stretched to near fracture, will it be less likely to stretch and allow gasket failure over a stronger less stretch bolt/stud?
I really just want to know if anyone has gave the TTY bolts a fair chance. I'm willing to bet that most FI engine's crack a piston and then gets rebuilt with studs. but has anyone tryed TTY bolts?
A few quote for more reasons why I'm so curios..
Torque-to-Yield Bolts
One-time-use, or torque-to-yield (TTY), fasteners take advantage of the torque yield principle. Most torque specifications build in a 25 percent safety margin--they can be overtorqued by 25 percent before damage occurs. TTY bolts do not have this safety zone. They are designed to be tightened just into the yield point but not to the extent that the metal is distorted. The advantage is they deliver 100 percent of their intended strength, versus the 75 percent strength provided by regular bolts. The drawback is that they can only be used one time. Once they are removed from an application, they can no longer support the load they previously did, and they must be replaced with TTY bolts. Installing a conventional fastener in their place will result in a 25 percent weaker clamping force. Because TTY fasteners are used in a variety of applications, such as subframe mountings, it's important to identify these during the estimating process--not just for the additional cost involved but also to alert the technician.
One-time-use, or torque-to-yield (TTY), fasteners take advantage of the torque yield principle. Most torque specifications build in a 25 percent safety margin--they can be overtorqued by 25 percent before damage occurs. TTY bolts do not have this safety zone. They are designed to be tightened just into the yield point but not to the extent that the metal is distorted. The advantage is they deliver 100 percent of their intended strength, versus the 75 percent strength provided by regular bolts. The drawback is that they can only be used one time. Once they are removed from an application, they can no longer support the load they previously did, and they must be replaced with TTY bolts. Installing a conventional fastener in their place will result in a 25 percent weaker clamping force. Because TTY fasteners are used in a variety of applications, such as subframe mountings, it's important to identify these during the estimating process--not just for the additional cost involved but also to alert the technician.
Torque-To-Yield
Torque-To-Yield (TTY) is a term that you should be familiar with because it describes a type of head bolt that is used on many late model engines. Unlike ordinary head bolts, TTY head bolts are designed to deform - but do it in a controlled way. Like a standard head bolt, a TTY bolt will stretch and spring back up to its yield point. But once the yield point is passed, the bolt becomes permanently stretched and does not return to its original length. Because of this, TTY bolts should not be reused.
Why intentionally stretch the head bolts? Engineers discovered they can get much more even clamping on the head gasket if all the bolts are evenly loaded. Since variations in friction between bolts always causes some uneven loading, stretching the bolts guarantees all the bolts will exert the same clamping force regardless of the torque reading on the wrench. The result is improved cylinder sealing, longer head gasket durability and less cylinder bore distortion (for reduced blowby and more power).
Torque-To-Yield (TTY) is a term that you should be familiar with because it describes a type of head bolt that is used on many late model engines. Unlike ordinary head bolts, TTY head bolts are designed to deform - but do it in a controlled way. Like a standard head bolt, a TTY bolt will stretch and spring back up to its yield point. But once the yield point is passed, the bolt becomes permanently stretched and does not return to its original length. Because of this, TTY bolts should not be reused.
Why intentionally stretch the head bolts? Engineers discovered they can get much more even clamping on the head gasket if all the bolts are evenly loaded. Since variations in friction between bolts always causes some uneven loading, stretching the bolts guarantees all the bolts will exert the same clamping force regardless of the torque reading on the wrench. The result is improved cylinder sealing, longer head gasket durability and less cylinder bore distortion (for reduced blowby and more power).
01-10-2008, 03:02 AM
#5
you gotta compare the yeild strenght of the stock material to the yeild of the arp for a first comparison
yeild is not the point before fracture it is the point before permanent deformation u still got a long way to go before a fracture
sure the tty are holding down with more intial pressure but they will deform under the high boost anytime the highest previous pressure above yield strenght is reached on the bolts.
the arps yield strenght is probably much higher then the stock matarial (i don't know what the arp's are made of)
also the arps are much more tensile meaning the deflect far less for a given amount of pressure and hence why you can run them at a far less intail pressure ie the 65ft lbs u torque them to, this is so much so that you keep the heads down even better then stock and you can reuse them.
there seems limit to this however becuase of the blocks aluminum threads i wonder what kind of a advantage one would get using steels theads in the block . you'd have to compare bolt yield strenght to the thread shear streght equation (which is pretty simple Ssy=force/(pi)(diameter bolt)(.75)(thread height))
yeild is not the point before fracture it is the point before permanent deformation u still got a long way to go before a fracture
sure the tty are holding down with more intial pressure but they will deform under the high boost anytime the highest previous pressure above yield strenght is reached on the bolts.
the arps yield strenght is probably much higher then the stock matarial (i don't know what the arp's are made of)
also the arps are much more tensile meaning the deflect far less for a given amount of pressure and hence why you can run them at a far less intail pressure ie the 65ft lbs u torque them to, this is so much so that you keep the heads down even better then stock and you can reuse them.
there seems limit to this however becuase of the blocks aluminum threads i wonder what kind of a advantage one would get using steels theads in the block . you'd have to compare bolt yield strenght to the thread shear streght equation (which is pretty simple Ssy=force/(pi)(diameter bolt)(.75)(thread height))
01-10-2008, 09:05 AM
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you gotta compare the yeild strenght of the stock material to the yeild of the arp for a first comparison
yeild is not the point before fracture it is the point before permanent deformation u still got a long way to go before a fracture
sure the tty are holding down with more intial pressure but they will deform under the high boost anytime the highest previous pressure above yield strenght is reached on the bolts.
the arps yield strenght is probably much higher then the stock matarial (i don't know what the arp's are made of)
also the arps are much more tensile meaning the deflect far less for a given amount of pressure and hence why you can run them at a far less intail pressure ie the 65ft lbs u torque them to, this is so much so that you keep the heads down even better then stock and you can reuse them.
there seems limit to this however becuase of the blocks aluminum threads i wonder what kind of a advantage one would get using steels theads in the block . you'd have to compare bolt yield strenght to the thread shear streght equation (which is pretty simple Ssy=force/(pi)(diameter bolt)(.75)(thread height))
yeild is not the point before fracture it is the point before permanent deformation u still got a long way to go before a fracture
sure the tty are holding down with more intial pressure but they will deform under the high boost anytime the highest previous pressure above yield strenght is reached on the bolts.
the arps yield strenght is probably much higher then the stock matarial (i don't know what the arp's are made of)
also the arps are much more tensile meaning the deflect far less for a given amount of pressure and hence why you can run them at a far less intail pressure ie the 65ft lbs u torque them to, this is so much so that you keep the heads down even better then stock and you can reuse them.
there seems limit to this however becuase of the blocks aluminum threads i wonder what kind of a advantage one would get using steels theads in the block . you'd have to compare bolt yield strenght to the thread shear streght equation (which is pretty simple Ssy=force/(pi)(diameter bolt)(.75)(thread height))
hellbents10, Did they fail after 900 fwhp? or is the engine still running? Also is it turboed, supercharged, nitrous, other? I guess it shouldn't matter, cylinder pressure is cylinder pressure....
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01-10-2008, 09:10 AM
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Keith
01-10-2008, 09:29 AM
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That is not true. A stud will always have more clamping force and even torque than a bolt. With a bolt, the torque force is drawn through the entire bolt up to the head and produces and pulling type of clamp force. A stud, the torque force is only on top and produces and pushing type of clamping force.
Keith
Keith
I understand a stud has more clamping force and a more even torque across the head compaied to a standered bolt, but I thought that was one of the biggest benifits to a TTY bolt. TTY are not torqued down usinge a torque wrench....
01-10-2008, 10:34 AM
#10
No problems at 900hp with a properly sized turbo w/o super high pressure ratios. After that the heads will lift and start moving coolant. Studs will not get you much further w/o lifting the heads. After you make 1000-1200+ you will move coolant with the 4 bolt setup no matter what.
01-10-2008, 11:14 AM
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I have 850-900hp at the flywheel in my DD pick-up with stock GM bolts. I do not drive it with the high boost all the time, but it gets a fair amount of beating time and some trailer towing. After 60,000 miles we pulled the heads to try a different set. We did find some carbon tracking showing some head gasket leakage had happened, but I have rattled the engine a few times testing methanol kits which may have caused the leak. Overall the factory gasket/bolt combo has been very good at the lower power levels, like Hellbents10 I would say 900hp is a good limit for the fastener. The other consideration for guys pushing them hard and working on them alot is the threads as mentioned. I have damaged a few blocks on dyno mules just changing the heads to often, a stud would protect the block threads while typically having more engagement of the factory threads. One of the reasons we use 1/2 studs is to increase the thread contact on the higher torque fasteners.
My .02
Kurt
My .02
Kurt
01-10-2008, 09:13 PM
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I have 850-900hp at the flywheel in my DD pick-up with stock GM bolts. I do not drive it with the high boost all the time, but it gets a fair amount of beating time and some trailer towing. After 60,000 miles we pulled the heads to try a different set. We did find some carbon tracking showing some head gasket leakage had happened, but I have rattled the engine a few times testing methanol kits which may have caused the leak. Overall the factory gasket/bolt combo has been very good at the lower power levels, like Hellbents10 I would say 900hp is a good limit for the fastener. The other consideration for guys pushing them hard and working on them alot is the threads as mentioned. I have damaged a few blocks on dyno mules just changing the heads to often, a stud would protect the block threads while typically having more engagement of the factory threads. One of the reasons we use 1/2 studs is to increase the thread contact on the higher torque fasteners.
My .02
Kurt
My .02
Kurt
Thank you for the info, but I think it is worth more than a few cents....
hellbents10,
That is the range I'll be shoting for I need/want a 10 sec pass, so I need about 950fwhp, I doubt I'll beable to do it without sparaying on top of the boost...
01-10-2008, 09:26 PM
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Well I'm hoping the heads will be staying on for a while.....
Thank you very much for the reply, whistler. You by chance aren’t a Jethro tull fan are ya?
Thank you very much for the reply, whistler. You by chance aren’t a Jethro tull fan are ya?
01-10-2008, 09:53 PM
#16
Kurt,
Can you discuss 1/2" studs a little more? What is the preferred block? Is 1/2" viable on an aluminum block? Newer blocks have shorter head bolts...older are longer which anchor a bit into the main webbing. Do the deeper bolts create more main web distortion, which would lend to girdle support, versus shallow causing more deck distortion? What is the lesser of the 2 evils so to speak?
Bill
Can you discuss 1/2" studs a little more? What is the preferred block? Is 1/2" viable on an aluminum block? Newer blocks have shorter head bolts...older are longer which anchor a bit into the main webbing. Do the deeper bolts create more main web distortion, which would lend to girdle support, versus shallow causing more deck distortion? What is the lesser of the 2 evils so to speak?
Bill
01-27-2008, 10:34 AM
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Maybe through a more accurate torque but from everything I have found or heard of, tty bolts are superior as far as even torque/clamp force is concerned.
