I agree.If you use a gasket that says retorque then do so,that is the reason I don't use them.A real pita to retorque them in the car.
I can get to any head bolt with my set up,and the stretch method eliminates all the pre stretch,thread burnishing and all the other steps.Just crank down until you reach the required stretch.Lube and friction have nothing to do with it,it doesn't matter if they are at 75 or 200 foot lbs,it comes down to pull it until it stretches the required amount.I do use moly lube because it makes it easier to pull.I am not saying its better or worse than any other method.For me it has worked when other methods didn't.Ford head studs are the worst to try to get gasket's to live with NO,especially if a mistake is made and you rattle the motor.With Fel Pro 1011-1 or 2 I have had good luck using this method with NO and not "O" ringing everything and no copper.Most of my costomer's want to drive on the street so that pretty much leaves copper out of the picture.If you were to torque the Ford studs they would probably be in the 90 to 100lb range on the long ones and 70-80lb on the short ones with ARP lube.

 

What are you looking for, stud stretch wise, in a SBC head stud? What about different bolt lengths? I'm real curious.

WRT eliminating the cycling process...

The reason for torque cycling is not just to burnish in the threads for torque purposes, ie reducing friction. Have to keep in mind that we're talking about a sandwich joint... iron on one side, aluminum on the other and a gasket in between (or some such combination). Those materials have very different properties from one another.
George Lorimer, retired GM powertrain engineer, wrote an article in Bolt Science where he stated that one of the problems with clamp load is, "the moment you take your wrench off a tightened bolt, it starts to decrease".
He went on to say that torque cycling can reduce this relaxation effect by 50% or more! That had me doing a triple take on the subject of torque cycling. More clamping force for your dollar.

-Mindgame

 

MG,
If you torque a head stud to the recommended 65 foot lbs with lube,that stud is not tight,passable but not tight.I have proved this on Ford's when you "lift the head" with NO and blow the head gasket.If that 65 ftlb was tight then when I use the streach method it should come out to 65ftlb torque,right.It don't it comes out to somewere in the 90-100ftlb range for the long studs and 70-80 on the short studs.The stretch spects will tell you the different between the short,medium and long studs and the values are different.The stud torque is all the same number whatever the length and that goes for bolts too.How can that be and have the studs or bolts with all having the same clamping force.I can take a Ford and set it up to blow the gasket and use the torque values on the studs and sure enough it will blow.Change nothing except use the stretch method(and the gaskets) and they will hold,to me that is proof that the studs weren't tight with torque values.So either they need to up their torque values a bunch or use the stretch method.
I worked with engineers at Fel Pro on this for a couple of years and they now know what it takes to hold gaskets and the procedure to tighten the intake.

 

So you torque to 65, the head lifts and you assume you need more clamping so you use stretch (what spec?) and then go back and check torque to find 90-100 lbs-ft (long) and 70-80 on the shorties. Yet the catalog spec shows 65 lbs-ft under proper torquing procedure.

Well I can see why. That's not the procedure ARP recommends for their bolts. They recommend going 50-75% of final load 5 times (ARP lube) before final loading.

The torque wrench is, for the most part, measuring resistance... friction. If you don't cycle the bolts as recommended then it stands to reason that you'll see more friction (higher torque reading) when you check the bolts at their proper clamping loads.

I'm not making a case for or against stretch... the proper stretch/clamping is what we're after. If I were trying to make comparisons I would however, be very scientific in my procedures. Using the same exact procudures as recommended by the manufacturer. Otherwise the "why" is just a guessing game.

I don't know. On a BBC you have two different torque values. Some recommend 65-68 lbs-ft for the short bolts and 75 for the long ones. Another reason I don't like the ARP "general" reference chart.... doesn't account for different bolt lengths.


Try it as recommended (5 cycles @ 50-75%) and see what you get next time.

And let's not discount what Mr Lorimer said about relaxation.. "50% or more".

-Mindgame

 

LR:
Ok, I get the concept of a longer bolt requiring a larger stretch value to produce the same clamping force (or % shalf increase)... so you're saying the torque valve (i.e. the total resistance force) isn't proportional to % enlongation... but total elongation? Longer studs should have higher torque values for the same uniform stretch?

So I guess the question is... how do you know what stretch value to shoot for in a SBC/LT1 vs. an LS1 say? Would the LS1's aluminum block "give" a bit more as the stud's threads pulled upwards and show some elongation at the dial indicator that actually didn't exist? Nothing's perfectly ridgid... that's the while point of this exercise right?

Any stretch values in that book of yours for SBC's?


------------------------


MG: I understand the accuracy improvements of a torque-angle assmebly, and the benefits of 5 pre-cycles as ARP reccomends... however I'm wondering what torque values you use for the "retorque" when going over an engine after some heat cycles.

Do you use TTA to assemble, and then the final "torque wrench only" values for the "retorque" (just setting the final torque value and checking each stud/bolt)? Or is this a complete remove/install cycle using TTA again?


Are you considering "retorquing" another rod/bolt cycle or is this more of a "double check" on the final torque values?

 

I am not trying to discount anything.What I have been trying to tell you is that when using stretch method,friction does not enter into the picture.It makes no difference what the torque value is(and torque relies on friction) as long as the stretch value is correct.The torque value may be 100ftlb on a .005 stretch value and the recommended torque for that stud is 65ftlb's.At 65ftlb the stud has not reached is stretch value and you have to keep pulling until it does,and when it reaches it's stretch value the torque may be 100ftlb.
These are not correct number's,just an example.

 

Steve,
the threads in a cast block move too.If the recommended stretch is .005 then you have to keep pulling until the stretch is reached.The stud will not stretch to its value until the "slack" is all taken up.It will stretch some but not to full value until the gasket is crushed, the threads in the block are tight,and the threads on the nut end of the stud are tight,and the torque washer is seated.Only then will the stud reach full value.

 

wtf???? i have never in my life seen a stretch method performed on a stud. Imo the act would be worthless. now if the engine is apart and you use the method on the stud when you placing it in to the block(no heads on) there might be some benefit.

 

Stud stretch is used all the time.Wake up

 

i met head stud. maybe i should have clarified that. but for real never ever seen it done.

 

Thats because most people do not have the set up to do it and it is time consuming.Torque is good enough for most builder's and I was discussing that torque values are low as put out by ARP v stretch method.
The last big stretch job I was on was a 1000 ton American crane.It's Rol-Tek brg that it swings on is 36' in dia and has 208-3"x21"studs and the stretch was a given measurement from the nut to the end of the stud.The torque value was well in excess of 5,000ftlb.They don't make a hyd torque wrench that big so it had a fixture with a 500 ton ram that screwed on the stud and stretched it and you tightened the nut and released the stud.You kept going around the circle until the studs reached their spect measurement.Took a week to complete.I do all the head studs on a power adder motor with stretch,blown or NO.

 

Larry,
How do you know the specs are low when, by your own admission, you didn't follow the proper tightening sequence per ARP?

The reason I mentioned creep/relaxation is because it does matter when there is a sandwich joint. There is a degree of relaxation. Let's change it up a bit. We'll imagine the engine block as a big slab of steel. Now we're going to put a piece of rubber on top of the block and we're going to clamp (just like a head bolt) a big piece of oak on top of that. We have a sandwich joint... steel, rubber and wood. We're now going to stretch the bolt to .003. No cycling, just gonna go to .003. So we do, and we get our .003 stretch and our bolt is properly loaded. What happens to our clamping loads as the rubber and wood relaxes... takes it's set? Remember, everything is "elastic" to some degree.

That was my point and the point Lorimer was trying to get across in his effort to educate people on sandwich joints. To reduce the effect, you run the bolt through cycles. The relaxation of the other components in the joint don't care if you used stretch or torque or whatever. They just want to relax and take set under the load.

Steve,
TTA is used for conformability. We want the same stress on each and every both with as little variance as possible. That's next to impossible when you consider friction. Very difficult element to model. I know, I've worked on programming projects where this was a factor.

I use TTA to assemble and TTA to check the bolts. Going back to "torque" would defeat the whole process. No removal is necessary. I simply go back through all bolts and check them against previously recorded measurements.

On rod bolts, no need. You are just looking for the proper stretch.

edit: Good article on TTA, relaxation etc...

http://www.boltscience.com/pages/glo...quearticle.htm

-Mindgame

 

MG,
Get friction out of your head.There is NO friction involved in stretch ie.A bolts stretch value is .004 and I make a fixture(like the one related to above) to attach a porta power to the end of the stud with the nut already on and I pump up on the ram to a measured .004 and screw the nut down with my fingers and release the ram,where is the friction involved and the stud is stretched .004 if everything didn't compact.If it did compact and the stretch spect wasn't reached you would pump up again and tighten the nut by hand until it will hold it's stretch value.At this point you have had no friction involved you have just stretched the bolt to spect.Head studs are the same way,you reach a point where everything compacts enough to streatch the stud to it's spect and the rotational friction of the nut does not matter(like torque values)

 

Can't seperate friction and fasteners.. my comments were relevent in their context.... load variations from bolt to bolt that only increase with greater clamping loads. I don't think anyone who knows fasteners would argue that.

Now I did try reading your first two sentences LR and I'm having a hard time here cyphering your meaning. Must be Alabamie talk.

So, correct me if I'm wrong but what you're saying is that bringing a fastener directly to it's "stretch value" is the right way to do it. AND the joint materials just don't matter?
Creep and relaxation of materials along with a loss of clamping torque just doesn't matter??

Now before we go off on some other examples... let's get these things squared away shall we.

After that... let's consider this real carefully.....

There's that relaxation and creep thing again, along with the clamping losses associated with it.



Oooh, I like that... "joint conditioning". No, he aint talking about arthritis or cannibus guys. Nuts and bolts.

Now, how do you go about conditioning a joint, as Mr Lorimer suggests, without cycling?
What happens to the joint if you don't??

(50%+ reduction in relaxation)

Are we getting anywhere yet.....

-Mindgame

 

To start with you can't mix the two, stretch and torque are two different methods to reach the same end,proper bolt tension.
You can not mix the two.When you stretch a stud there is ample compaction to stretch the stud and keep it preloaded.There is no friction value involved in stretch(as in torque).If it takes 10,000,000 pounds of torque to stretch a stud to its stretch spect it don't matter the rotational friction is not the value here.When you bring the stud to stretch value the head gasket does just the same thing as torque value,it compresses.If it is torqued or streached the head gasket will do the same thing,compress.I don't know were you are going with this but what I am saying the stretch values for a ARP stud do not equal there torque values.
You can not say it takes x torque to equal x stretch.On stretch you can figure a math torque value and assign it to x stretch,but there is not a usable torque value to equal x stretch,unless you trial and error it.
If you pull the studs to stretch spect it don't relax as much because it started with more preload,The head ain't moving in other words and that is a fact and there is no need to re- torque because it never got out of spect.
Are you saying that if I used a steel(no layer's).018 Chevy head gasket that I am going to loose stud tension after a few heat cycles. No way and if a pack gasket is pulled down enough it ain't gonna move either,proved that to Fel Pro already with the tests done for them on the 1011-1 & 2's for 2 years.So I feel that bolt stretch is a superior measurement over bolt torque because you can control the bolt preload better and not have to fight the rotational friction that can not be controlled to give you a true reading.