View Full Version : ARP head stud torque

01-09-2010, 04:53 AM
Ok well I was looking around trying to find out if I installed my mains correct but I ran into this. Thought this info would be good to have for anyone building a engine with ARP studs. This is a reply to the qustion about the 5 time method of torqing and retorque after running the engine for sometime.

Good question. Each time you torque any bolt or nut, up to about 5
times, the threads of the bolt or nut are seating in to the threads they
are going into. In a sense "polishing" each other. As this "polishing"
takes place the friction between the two pieces is reduced giving you
more torque applied to clamping load vs overcoming friction. After 4~5
times the effects are minimal. Once you do this it does not have to be
done again during assembly. If you disassemble the engine make sure to
keep the nuts with the studs, matched sets. Five times is a great way
to go but most don't want to spend the time. The reality is that it is
working for you. Don't change what you are doing!!!

Typically we recommend a head retorque after a period of time. This is
not due to stud stretch but normally to head gasket compression and
everything moving around a bit after running. That varies with the type
of gasket. Many times the head gasket manufacturer will tell you what
is needed in the instructions. Also torque wrenches and people make
mistakes so it is a good double check. What I recommend is that you
back the nuts off, one at a time, about 1/4~1/2 turn and then pull right
back to full torque. If you do one at a time that prevents the head or
gasket from shifting.

If you have any additional questions please contact me.


Alan Nichols

Where I was reading this some say to do this about 500 miles or after a few heat and cooling cycles before you push the engine hard. Also talk about doing a retorque annually.

I would like to here what guys do on here?

01-09-2010, 12:58 PM
I was always under the impression that with ARP bolts, re-torque is not necessary (as they don't stretch).

01-09-2010, 01:46 PM
I was always under the impression that with ARP bolts, re-torque is not necessary (as they don't stretch).

You should always retorque

01-09-2010, 02:55 PM
as a general rule i retorque once. i have arp studs on my 5sfe and i retorqued them after 1000 miles. they were still at spec when i put the wrench on them. pulling cams to retorque head bolts is the only thing that sucks about the 5s.

01-09-2010, 05:51 PM
Once the bolts/studs are to the right preload and stretch, they are done, you don't retorque them. The threads should already be chased and burnished by the builder.

If someone does retorque, and it's helps, then they weren't stretched properly to begin with or the threads weren't done correctly.

edit: Usually the error margin is from using torque as a spec and not measuring stretch, which is the ONLY real way to do it.

01-09-2010, 07:17 PM
Sorry forgot to say that reply was from ARP.

That is the thing Hookecho if you just put the torque wrench on them with the same torque setting they will not move. If you torque a nut to say 60 then you stop. If you needed to torque it to 65 then you would need to lossen the nut and then retorque it to 65. The reason is they are to close together and would take more torque to get it moving again and overcome the friction again.

So MrWOT you just use the stretch method and never had any problems with a head gasket? I know that it is more accurate then torque.

01-09-2010, 09:58 PM
It is not a matter of more accurate, it is the only way to measure. Torque values are just a number they think will get you to your needed stretch value. I have seen bolts require more than 15ft/lbs over spec'd torque to get the needed stretch. Depends lots on the thread finish, and the lubricant you use too.

01-23-2010, 02:32 AM
Ok well if it not accuracy then what is it about. What you are looking for a is clampig force. So if the torque is just a guess then the stud or bolt streech would also since it came from ARP. Do you think they just throw a number out that sounds good. No They come up from engineering design and testing. So yes your stud/bolt strech is the most accurate beacuse of less varables. The torque method is not as accurate beacuse of more variables. Like friction which is the big one on torque. Then you have to add in the accuracy of the wrench. One thing that ARP addresses is the friction part of this is using their moly lube and the polishing effect of toqueing the bolts five times beacuse it knocks down the imperfections of the metal making the smoother. Which I bet helps makes this variable much more constant. Were as bolt/stud strech has only the varable of the gadge that is used.

Hey this is my ideas about it and if it is totaly wrong let me know. Hey I am not no rocket scientist but it makes since to me.