Why loosen then tighten?
#1
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Why loosen then tighten?
Just doing some retorques on my headstuds after installing them, and according to arp's instructions it says to loosen then tighten the nuts. Why not just retorque the stud withouth loosening it?
#2
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Part of the (may not be the whole) answer is break away torque. Once they start to set the break away torque may be higher then the target torque so you may not actually get the correct re torque. So to over come this issue you release the break away torque by loosening the studs and starting over.
#3
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Its to seat the gasket, and to also stretch the studs.
I wouldnt do the retorques like ARP says.
This is the way I was told by a big diesel engine builder.
1.Do your initial torque #125.
2.Warm engine to operating temp, let cool overnight. Do a retorque, loosen each nut one by one apply more moly and retorque.
3. Drive the truck with NO BOOST for one full tank (400-500 miles)
4. Let truck cool and do another retorque, Loosen nut one by one apply more moly and put back together.
5. Drive the truck and give her some boost, but no 1/4 mile runs for 1000 miles.
Do final retorque, and that should hold for a long time.
I was told the less hard you are on it between retorques the longer it will last.
I wouldnt do the retorques like ARP says.
This is the way I was told by a big diesel engine builder.
1.Do your initial torque #125.
2.Warm engine to operating temp, let cool overnight. Do a retorque, loosen each nut one by one apply more moly and retorque.
3. Drive the truck with NO BOOST for one full tank (400-500 miles)
4. Let truck cool and do another retorque, Loosen nut one by one apply more moly and put back together.
5. Drive the truck and give her some boost, but no 1/4 mile runs for 1000 miles.
Do final retorque, and that should hold for a long time.
I was told the less hard you are on it between retorques the longer it will last.
#4
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I basically did 3 retoques already but i will do it again after a tank of fuel. I have the fuel turned all the way down, witch nets about 20 lbs of boost. Also, on the last retorque, i went to 145. Shouldnt be anyproblem with that right?
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#11
This is the purpose also of using the correct lubricant on the nut. The idea is to purely stretch (apply tension to) the stud. Of course, this done by twisting the nut. If the nut has some resistance to turning then the tension force on the stud will not be correct.
Jim
Jim
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