Q on re-torquing head studs
#1
Q on re-torquing head studs
quick question, I just got done installing my new heads and have heat cycled the engine a couple times
I would like to re-torque the headstuds once now
I know to go one at a time in order, but how far do I back the nut off until i torque it back down??
do i release all the tension from the fastener? or instead loosen it like 90* and then torque it again?
this is on 12pt ARP studs and LS9 HG's
Thanks
Zac
I would like to re-torque the headstuds once now
I know to go one at a time in order, but how far do I back the nut off until i torque it back down??
do i release all the tension from the fastener? or instead loosen it like 90* and then torque it again?
this is on 12pt ARP studs and LS9 HG's
Thanks
Zac
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#9
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I just put mine in and arp says in the instructions that they dont need to be retorqued as long you use thier lube during the install. They say it will produce acurate torque consistently.
#11
i retorque to 95lbs, i originally torque to 90, checked after a few passes, they were only at 76-78lbs, torque to 95, seems good to 25psi now. no water pushed during a pass.
#13
with orings you have to retorque, the oring will cut deeper into the gasket and head after some run time and need to be retorqued.
everyone in this thread that posted they dont retorque has oring setups?
without the orings, one torque will work
with orings, you have to retorque.
everyone in this thread that posted they dont retorque has oring setups?
without the orings, one torque will work
with orings, you have to retorque.
#14
Makes sense with what you say about the rings
although i did do a retorque, and i think it was for the best
what i did was go in order one at a time and back the nut off 90* and then torque it back to spec. Then move to the next stud in the torque sequence
loosening 90* took just about all tension off
Most took a little more than 90* to get up to spec again, but a couple where up in the 130-180* area
I dont think it pays to just go in and check the torque with out loosening them some because overcoming the static friction to start moving the nut ***** with you
although i did do a retorque, and i think it was for the best
what i did was go in order one at a time and back the nut off 90* and then torque it back to spec. Then move to the next stud in the torque sequence
loosening 90* took just about all tension off
Most took a little more than 90* to get up to spec again, but a couple where up in the 130-180* area
I dont think it pays to just go in and check the torque with out loosening them some because overcoming the static friction to start moving the nut ***** with you
#15
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Makes sense with what you say about the rings
although i did do a retorque, and i think it was for the best
what i did was go in order one at a time and back the nut off 90* and then torque it back to spec. Then move to the next stud in the torque sequence
loosening 90* took just about all tension off
Most took a little more than 90* to get up to spec again, but a couple where up in the 130-180* area
I dont think it pays to just go in and check the torque with out loosening them some because overcoming the static friction to start moving the nut ***** with you
although i did do a retorque, and i think it was for the best
what i did was go in order one at a time and back the nut off 90* and then torque it back to spec. Then move to the next stud in the torque sequence
loosening 90* took just about all tension off
Most took a little more than 90* to get up to spec again, but a couple where up in the 130-180* area
I dont think it pays to just go in and check the torque with out loosening them some because overcoming the static friction to start moving the nut ***** with you
Since you loosened them all just about 90 degrees from where they were previously torqued, and some of them turned 130 while others turned 180 to arrive at the same torque value, I'd be very nervous about whats going on at this point, as it sounds like you may have done more harm than good. It sounds to me like some of the fasteners yielded, or possibly the surface between the head and the nut on the head studs that took lower torque galled (increasing friction and resulting in torque going through the roof without achieving the correct pre-load. If that were my engine, at this point, I'd yank all the studs out, and throw them all away, inspect the heads, then put in all new fasteners.
#16
In theory you're right...but thats the entire purpose of using the correct lubrication when you install a fastener, so that friction (between the nut and the head, and to some extend between the threads in the nut and those on the stud) is not only significantly lower, it's significantly more predictable so that you arrive at the correct pre-load on the fastener. Thats why ARP recommends using their lube, especially in more critical applications like rod bolts, main studs and head studs. The pre-load of the fastener is what actually matters, not the torque required to get it there. Thats also why so many torque specs on critical fasteners are a very low torque spec, followed by a degrees of rotation spec. The low torque number is easy to achieve without friction (due to surface prep or lubrication) being a significant factor...it's high enough torque to make sure the 2 parts are actually seated together and that the fastener is ready for pre-load...the rotation spec is then based on math taking into account things like the pitch and diameter of the thread, and the material the fastener is made from among other things.
Since you loosened them all just about 90 degrees from where they were previously torqued, and some of them turned 130 while others turned 180 to arrive at the same torque value, I'd be very nervous about whats going on at this point, as it sounds like you may have done more harm than good. It sounds to me like some of the fasteners yielded, or possibly the surface between the head and the nut on the head studs that took lower torque galled (increasing friction and resulting in torque going through the roof without achieving the correct pre-load. If that were my engine, at this point, I'd yank all the studs out, and throw them all away, inspect the heads, then put in all new fasteners.
I agree with what you say, but explain this as I should have explained a bit more
and this is why i still feel good about it
heads are new, I originally torqued these to 80 ftlbs with ARP's lube (I over do it with the stuff too, so there was no lacking lube)
heat cycled the engine 3 times
The "normal" studs acted in this way..... when backed off 90* they just about had no tension but there was just a hair still there..... then took just over 90* to come back to 82 ftlbs
The couple of "un-normal" studs that took the extra distance acted this way....... when backed off 90* there was no tension, they actually lost all tension around that 45* mark..... (which i noticed and thought was weird)
then they took the that 130-180* to come back up to 82 ftlbs
why this is, I do not know, but they all came up very even and progressive
not a biggie either way, i can do gaskets in my setup in no time
Last edited by rotary1307cc; 02-15-2011 at 10:07 AM.
#17
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Very good post by Mike.
I agree completely about the fact that some of the OP's fasteners could have issues.
For MLS apps, I have had good luck letting the fasteners "settle" overnight and then make another pass to double check the installation before moving forward.
You really shouldn't see much change, if you do, something is wrong.
My concerns about backing them off before a retorque is that that you may introduce another variable in to the process. I'm not an engineer, but I would have to think that a simpler installation process would yield (pardon the pun) more consistent results.
The torque angle fasteners used by the OEM's are a good example of eliminating any variables to ensure equal "stretch" of the fastenters.
The best fastener in the world is useless if not properly loaded or 'stretched" at installation.
For an o-ring setup, a retorque is mandatory after the engine is brought to operating temps.
I agree completely about the fact that some of the OP's fasteners could have issues.
For MLS apps, I have had good luck letting the fasteners "settle" overnight and then make another pass to double check the installation before moving forward.
You really shouldn't see much change, if you do, something is wrong.
My concerns about backing them off before a retorque is that that you may introduce another variable in to the process. I'm not an engineer, but I would have to think that a simpler installation process would yield (pardon the pun) more consistent results.
The torque angle fasteners used by the OEM's are a good example of eliminating any variables to ensure equal "stretch" of the fastenters.
The best fastener in the world is useless if not properly loaded or 'stretched" at installation.
For an o-ring setup, a retorque is mandatory after the engine is brought to operating temps.