studs getting stretch out and re torque

H

high line

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i heard to re torque 4 times before you run engine with studs to get stretch out. and then a hot re torque.
 
The reason to torque the studs three times is not to “stretch out the studs”.
Studs do not stretch as long as you do not torque them to the point where they yield.

The reason to torque the stud three times, in its lifetime, is to burnish, and mate the surface of the threads, you only have to do this on new studs, and from then on, it’s a onetime torque process. You achieve a percentage better clamping load by doing this.

If you do torque a stud to above what the engineers recommend and possibly take the fastener above the yield point, you have ruined the stud. It does not matter who tells you to torque the fastener above the recommended value, you are messing up, and this is the reasons the studs are failing.

In addition, do not torque a engine hot, , that is just plain against every engineering principal in the books engine blocks and heads expand when they heat up, if you torque the stud at that point , when the engine cools the clamping load is less.


So one more times
If some ones tells you to torque a ARP fastener over the recommended value, 125 ft lbs for 12mm ARP 2000 material, and 150 ft lbs for ARP Custom New age 625 material, or they tell you to torque a engine hot . They are wrong. No matter who,
 
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anyone have tensile test graphs from lets say stock bolts vs studs? I have access to a tesile tester and would like to see the differences. Not sure what I would get out of it but still be cool to see...
 
Forrest Nearing said:
Why would you do a hot retorque? To reduce the clamp load?
Click to expand...

I was told by a well known shop to do that every time.. I chose not to..

Although I was told by everyone to torque it once, let it get to temp, shut it off and torque it again while warm. Then the 2 re-torques were when cold...
 
just wanting to understand this better .... i hear guys say cold retq's and i hear hot retq's .... what i don 't understand is when you cold retq a head to 125 threes times you get no more turning of the nut ,but when you take that same head and retq it to 125 the thing turns sometimes over 1/4 turn ... if the head is smaller when its cold and the head expainds when its hot why would it turn ??????
 
My theory behind hot retorque is that you get more gasket crush. Although the fastener is not designed to be torqued when hot, it seems to result in a better sealed gasket due to more "squish." If you're worried about cold clamp load, retorque the fasteners again when the motor is cold.
 
With the instructions I got from Haisley it said to do the first retorque hot. The following two were cold.$.02
 
The way I did it and was told to do it is not to do any final value torquing hot. Do all the torquing while cold. Then run the motor up to operating temp and torque them again to the same ft-lbs you did cold. DO NOT BREAK THE STUD LOOSE TO TORQUE THEM HOT. After you do this then drive easy for a bit then repeat torquing the same value hot. When I did this I lost lash both times; therefore, the o-ring seated deeper in the fire ring of the head gasket. After having this result this is the way I will continue to proceed in the future if I have to tackle this issue again.

Again, do not break the stud loose before applying the torque to them while the motor is hot. As stated before this may result in looser then cold torque. By taking them past where you set them cold you are assuring yourself (so long as the stud isn't stretching) that you are not loosening anything and only gaining squish/crush on the head gasket fire rings. I went with the recommended 125ft-lbs and feel the manufacturer should know their own product.
 
NickTF said:
The way I did it and was told to do it is not to do any final value torquing hot. Do all the torquing while cold. Then run the motor up to operating temp and torque them again to the same ft-lbs you did cold. DO NOT BREAK THE STUD LOOSE TO TORQUE THEM HOT. After you do this then drive easy for a bit then repeat torquing the same value hot. When I did this I lost lash both times; therefore, the o-ring seated deeper in the fire ring of the head gasket. After having this result this is the way I will continue to proceed in the future if I have to tackle this issue again.

Again, do not break the stud loose before applying the torque to them while the motor is hot. As stated before this may result in looser then cold torque. By taking them past where you set them cold you are assuring yourself (so long as the stud isn't stretching) that you are not loosening anything and only gaining squish/crush on the head gasket fire rings. I went with the recommended 125ft-lbs and feel the manufacturer should know their own product.
Click to expand...



I'm with you on this one..I think at least a warm tq. is a good idea for those of us with o-ring'd heads...

I did my first two cold (loosening and then retighten one by one)....Then I did a third at warm temp. ( not loosening, just pulling them to 150-152 ft. lbs. and then double checking them again)....then reset lash.

So far so good!! Then even worked at 800 with my stock bolts too....I bought the arp 625's for extra future insurance..
 
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