Retorquing Cylinder Heads?

How common of a practice is this in performance buildups? How much clamping force is lost (if any) after heat cycling? I assume it would make a difference if you had iron or aluminum heads as well too. Can anybody shed some light on this?

Good Question. ARP reccomends cycling your studs/bolts 5 times in an effort to burish the treads sufficiently (and maybe "pre-set" the bolts?).

Regardless of the method you use for torquing bolts (torque wrench or torque-angle) you will have different torque numbers to shoot for depending on the lubricant used (i.e. dry > oil > sealant torque numbers... all for the same amount of bolt stretch, which is where the clamping force is actually coming from).

If the bolts were properly cycled, and at the time torqued to spec, I'm not sure what torque spec you'd use after a few heat cycles. Would the oil or other lubricant be cooked dry? would the sealant be set up and more diffucult to turn? I imagine you'd have to re-torque to a higher number at that point, but I've never heard of anyone doing so.

Just re-torquing to the final torque spec shouldn't hurt anything (probably won't even move the thing as any lube you had the first time will probably be less effective now)... but if it does move (i.e. it loosened up sufficiently) I might be worried how that happened at all.

Hopefully some of the pros here will help out on this one.

Should we just use the orginal torque spec as we did during assembly? or should the torque values/pattern change at all when checking say 500 to 1000 miles down the road?

I'm curious about this as well, especially since I am using head studs on my motor and have heard conflicting reports on whether retorquing is necessary or not.

If you are using studs you need to set up a dial indicator and do the bolt stretch method.

How common of a practice is this in performance buildups? How much clamping force is lost (if any) after heat cycling? I assume it would make a difference if you had iron or aluminum heads as well too. Can anybody shed some light on this?

My understanding is that alot of it depends on the type of head gasket you use. FelPro's Permatorque MLS gaskets for instance, don't "require" a retorque. Not my words... FelPro's. I've seen the same recommendations from other MLS gasket manufacturers. May also vary with different types of engines too.

Out of safety sake, I've always retorqued. Just make sure you do it with a fully cooled engine.... especially if it has an aluminum block and/or head. As for torquing, lubricants, etc.. check with the manufacturer.

-Mindgame

If you are using studs you need to set up a dial indicator and do the bolt stretch method.
I'm honestly curious here... how can I rig up a dial indicator to do this on a head stud?
Mindgame- you hit it on the head with the gasket. You've reminded me of a lesson I learned YEARS back in the Coast Guard... I helped with a cylinder head R&R on a V-16 diesel and after we fired the engine back up I asked the Engineering Chief about a retorque after the engine cooled. His reply was to laugh at me since this engine used no head gasket therefore no retorque was required.
Steve...

You make you a metal plate that attatches to the valve cover bolts,this does the top bolts and another plate that attatches to the plug wire holder bolts in the block and this does the bottom row, and proceed.In the case of center bolt cover's you attatch the plate to the end of the heads.If you use the bolt streach method there is no need to retorque,the bolts are way tighter than the torque spect method by 20-25 foot lbs. and the bolt is at max clamping force and stretch.

LR,
Where are you finding specs for head stud stretch? What are we aiming for here and where are the sources. Obviously it's going to change with different diameter studs...ie, different engines.

Thanks.

-Mindgame

Mindgame,
ARP has a book of spects that also include bolt stretch.

MG,
As I stated earlier when using studs that if you use the stretch method I have found no need to retorque,especially when using Fel Pro gaskets.
I have a Starret electronic dial indicator that was a lab instrument. It can measure .00005 if set to do so.I mounted the sending unit on a magnetic holder and that is what I use for bolt or stud stretch.
Take a set of ARP rod bolts and pull them to spect stretch,you will find that the torque is at least 15 foot lbs more than ARP's torque spect for the same bolt.
This is why I use this method,because the bolt and nut or stud is to it's max yield point and clamping force.When I questioned ARP about this and them not putting the torque values as high as the stretch values,they said it was due to the different compaction values that a bolt has v a stud,ie what the head is made of how many threads the block has, the gasket material,etc.

Larry,
I've been all through ARP's catalog and have never seen stretch information for anything other than rod bolts. Sure, there are "general" torque specs for different types of bolts with either ARP lube or 30W oil, but nothing on stretch of the head stud itself. Nor anything for stretch of other critical fasteners like main studs. Throw me a bone here... what are you typically seeing for stretch on a SBC head bolt? I'd like to work backwards and see what it equates to in clamping load.
ARP also mentions that rod bolts are unique in their clamping loads, for obvious reasons, where as other bolts are not and thus do not require such precision tightening methods.

Back to head stud stretch... how are you going about it? I can't find specs.. so I'd assume that you are checking the stud prior to torquing, then torquing the nut to required spec and remeasuring? Are you using TTA or just a torque wrench? Are you cycling the threads?

Checking torque with an already stretched-to-spec bolt (your ARP rod bolt stretch example) isn't really telling you much. There's an old rule of thumb that suggest a 90/10 relationship for fasteners, where 90% of the force applied is countering friction and 10% is used to stretch the bolt. So it's obvious that the type of lubricant used plays a big part on torque specs as measured with a torque wrench. Cycling the threads applies in the same way. So, unless you duplicate the original procedure to the letter... your results are going to differ. Not that it matters too much cause you're after the end result (the proper stretch).

On the head gasket and retorque... I think it still depends on the gasket. Some don't require it and others do. Has really nothing to do with the method of torquing or how much load you place on the fastener. Some gaskets just loose a little compressed height after a heat cycle or two.

-Mindgame

The spects are not in their catalog.You have to get the book from ARP you can also get the spects from Bowman in their spect book.
As stated above I use an electronic dial indictor.You zero the machine on a hand tight stug,then stretch to spect,mains, heads and rods.I can give you values for different grades and sizes if you like.
I wire brush the threads with a bench grinder and check to see if the nut will screw on by hand.If not I run a tap through it with the correct % of thread.Then I pull all bolts to 75% of torque value and back them off.Then pull to streach value.At stretch value I have not found any head gasket that shrinks to loosen the bolt after heat cycling,so I don't worry with retorqueing.That goes for "O" ringed engines and copper gaskets too.
It has been a bunch of years since I got the spect book,so I can't tell you who to talk to at ARP.This method has worked for me a number of year's,and I learned a lot from brand X with 1 less head bolt per cyl and how to keep head gaskets on,with a couple hundred horse of NO added.

MG,
I called ARP to see if I could get you a book of spects.I talked to AL and he said they don't offer those spects anymore.They just use torque values and he agreed that the torque spects are generic but usable.He said they were getting to many questions about stretch and how to do it.He said if you needed stretch spects for an individual bolt kit he could provide them,but not a book that listed all bolt products.I had better put my spect book in a safe place or I won't have one.

On the head gasket and retorque... I think it still depends on the gasket. Some don't require it and others do. Has really nothing to do with the method of torquing or how much load you place on the fastener. Some gaskets just loose a little compressed height after a heat cycle or two.

-Mindgame

Typically which type gaskets need a retorque?

Good info so far guys. Keep up the good work. :)

Brian

Some of the composition gaskets require a retorque. At least that's what GM recommends with some, like this BBC head gasket (10126768 Composition Head Gasket 1965-90)...

http://www.gmgoodwrench.com/gmgoodwrenchjsp/perfparts/partlist.jsp?cat=9339&section=ep

This is from a Victor Reinz engineer on head gaskets... last paragraph is the one dealing with retorque..

The other issue is the ability to seal combustion, which can be done in numerous ways. One of the methods mentioned briefly was the wire ring approach, a typical low carbon steel wire wrapped with a stainless steel flange balanced to the body gauge. The balance issue implies there will be enough load distributed over the entire gasket to seal all fluids while maintaining a combustion seal. The wire ring technology comes from the heavy-duty industry that seal pressures for diesel engines from 2000 psi on the low side to 4000 psi on the present limit. To accomplish these goals, the components are large and are designed to incorporate the bolt load needed for these high pressures. This is not always the case in performance engines; many components are of stock configuration and many more made of aluminum. The cylinder heads, as I mentioned earlier, are bent over the head gasket, so why use gaskets with wire rings? The use of wire rings can be justified when the firing pressure exceeds 1200 psi. Notice I did not give a compression ratio, because there are many factors that determine the actual firing pressure. The compression ratio, the volume of air, and the moment of ignition are all vital to the formula. A good example of this would be the new use of bottled horsepower; the compression ratio doesn’t change to increase horsepower yet the output when you hit the button is dramatically altered.

When the decision has been made to use the wire ring concept for head gasket, the issue of bending will be helped with the use of a retorque. Whether or not the wire ring has been preflattened the exercise of setting the gasket to the conditions of the particular application help assure a positive seal of combustion and fluids. The operation of a race engine by its nature is designed to push gaskets to the extreme limits, some push harder than others but the effort to make the gasket as a foundation to the system should not be taken lightly

Good article. If you're interested in reading the whole thing (rather long), here's the link...

http://engineparts.com/products/gstory.htm

Rol and a few other companies also recommended a retorque with some of their older gasket designs but Rol and others have gone to new types that don't necessarily "require" it. Fel pro has their Permatorque gasket... doesn't require retorque. Many of the MLS gaskets also don't require retorque. They supposedly don't take a "set" after heat cycling. But they also have very specific head/block finishing requirements to seal properly. Copper gaskets don't require retorque either.
Best thing to do is talk to the gasket maker and see what they have to say. They know what's best for their gaskets as they all have their own labs testing them.

Either way, I don't think there is any harm in running back through all the head bolts. I'm not totally sold on the validity of measuring stretch on head studs but I'm not discounting it either. Considering the use of cylinder heads with bolts running through the intake ports like the sb2.2 and how next-to-impossible it would be to get a stretch reading on those studs. I'm under the impression that there are just more important factors like...
·proper # of cycles
·good clean threads (bolt and block)
·adequate hole chamfer
·proper lube-type and application per manufacturer's recommendation
·calibrated torque wrench
·TTA for final setting

-Mindgame

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.

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.

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.

Then I pull all bolts to 75% of torque value and back them off.Then pull to streach value.

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.

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 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.


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.

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". :eek:

-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/glorimertorquearticle.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.....


Through experience we have found that headbolt clamp load can vary +/- 40% when torque control is used. Let's examine a joint and see what results we can expect. We start with a clamp load of 12,000 lbf +/- 40%, so we can have 7,200 lbf - 16,800 lbf. Initially, now we have some relaxation to account for about 30 - 35% for headbolts (gasket creep - heat, etc.). So now we have the possibility of having a clamp load range from 5,040 lbf to 11,760 lbf and the real problem is that we don't know.

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

The actual clamp load used in the example is not the important point. Rather that the needed clamp load should be determined early in the design game so that an adequate tightening strategy can be implemented. The end result is a joint that is together and has a satisfactory working clamp load during service. Some factors that influence relaxation of clamp load are:

1) Surface finish

2) Temperature (high and low)

3) Type of joint

Gasketed (soft)
Material of joint (hard or soft)
Combination of metals (steel and/or iron verses aluminum.)
4) Initial preload

5) Joint strength (spring rate)

6) Bearing area under head of bolt

7) Vibration

8) External loads to the joint, add infinitum


We can decrease the variation of clamp load by using a tightening strategy that allows closer control of the initial clamp load but the important issue is knowing what to expect out of a joint in terms of relaxation, in order to have adequate working joints for service.

I found that by conditioning a joint during the tightening process, the relaxation could be reduced by up to 50 % or more. One combination joint that this worked with was a cast iron/gasket/aluminum. The solution was to tighten to a preload torque and rotate for 90-110 degrees then wait for 2-3 seconds then loosen and immediately retighten to the preload torque and then a rotation of 90-110 degrees. The variation in the amount of degrees of rotation is due to the placement of the bolts and their working grip length.

If you consider a 4 cylinder engine with the intake on one side and the exhaust on the other. The heating forces vary widely from side to side and even from the area of coolant entry to the area of coolant return. A very difficult joint to control completely, however if you take all things into consideration success can be achieved in making a quality joint through fastening. And as a final note-all the bolts in the assembly did not require the same clamp load nor did they get them through tightening strategies. They did, however, keep the same relative clamploads by relaxing the same percentage via joint conditioning.

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.

So basically what you're saying LR... is that Mr Lorimer, former GM fastener engineer, is wrong?

The joint doesn't matter... no clamping forces are lost to creep and relaxation?

Wow... I'm speechless...

-Mindgame

This is why ARP doesn't offer stretch values any more.They told me today when I called that most people don't understand the difference and they were getting to many call's about it.
I am not disputing anything from GM,but he is using frictional torque values not stretch values.The engineer's at ARP and Fel Pro can figure the bolt stretch values but I can't,I have to have a book.
I'll bet if you ask your GM engineer what about stretch values,he would tell you there is a difference.You are using two different methods and trying to intertwine them and you can't.
I am just telling you what I have seen and done and trying to tell you how it works.I don't have any reference materal from the net to show,I just know it works,and that is good enough for me. Personally a torque reanch is the simpleist way if you have trial and errored it (both methods)to know how much to overtorque it to make a gasket hold.
Why don't you call Fel Pro and talk to an engineer named Jerry Rosenquist and ask him what they recommend for torque on a 1/2" stud on their 1011-1 and I bet it is at least 25-30ftlb's more than what ARP recommends.They do this to overcome rotational friction to achieve the clamping force (stretch)needed and people understand a torque wrench.They will also tell you they don't recommend any of their gaskets for NO.Will I happen to be holding a few gaskets with stretch,Soooo I don't know.

I am not disputing anything from GM,but he is using frictional torque values not stretch values.

No sir, he's using torque to angle and joint conditioning to ensure more equal clamping loads. Did you read the information I posted? All of that revolves around TTA procedures... TTA doesn't rely on "friction". The bolt cycling involves friction, can't seperate the two, but it is a means to an end and that end is conditioning.

Not getting any direct answers, so on to other things...

LR,
Do you do your own boring and honing? Dave said something about you being retired but didn't say from what. :)

-Mindgame

But is it neccessary to retorque the heads???
The factory doesn't do it for millions of their vehicles, even high performance models. So I wouldn't loose any sleep over the issue.

But is it neccessary to retorque the heads???
The factory doesn't do it for millions of their vehicles, even high performance models. So I wouldn't loose any sleep over the issue.

Are you using exactly the same gaskets the manufacturer used for your rebuild? If not, then why compare the two.

Other than that... your answer was covered on page 1 of this thread.

-Mindgame