1/2" head studs - block & cylinder deformation

[BoostedBeaver]

viperlp01
I have a few junk heads at the shop.. No real expense to me ..

If it is at all possible, please make a video.

Robert

 

[99gst_racer]

Also remember that a 6 bolt head isn't very stiff and flexes a lot when you apply a lot of clamping force to it.

This is my only concern at this point. I've recently sourced out some 1/2" L19's. I'd love to try them, but I'm affraid of heavily distorting and potentially cracking the head. Torque spec on them is about 120 ft/lbs. I also don't want to buy them and then not have a use for them either because they aren't cheap.

I wish I had a race team budget...

 

[97eclipseNT]

Also that FEA analysis might be too simple. The block isn't solid (water jackets). The deformation will be more than what that model says.

 

[viperlp01]

Success!!! 120 ft/lbs in 3 steps going from 40-80-120 with no issues. Pictures will be up soon.

 

[BogusSVO]

Sweeeet!

So at this time it looks like it will work!

 

[ed1380]

Is that no issues with cracking or cyl wall deformation?

 

[phunny]

Success!!! 120 ft/lbs in 3 steps going from 40-80-120 with no issues. Pictures will be up soon.

Are you using an old block/head? If so, are you going to keep going until she breaks for testing purposes?

 

[99gst_racer]

No issues with cracking. We didn't have the means to measure bore deflection, and the block wasn't bored or honed with a torque plate anyway. It is a junk block/head, but we didn't see the need to torque any farther than 120 ft/lbs. No sense in ruining the studs.

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[99gst_racer]

Well, we did a cylinder bore deflection test on Saturday. We measured the bores before and after, then torqed on a torque plate on a block with 11mm head bolts and then another block with 1/2" studs. The recorded differences are the bore changes after torquing, measuring from the top, middle, and bottom of the bore (number is average from all bores). The greatest single point of change was roughly -.0008".

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Aside from the bottom of the bores, there's not much of a deflection issue between the two sizes. So, if people can swap in 11mm ARP studs without a bore and hone with a torque plate, then adding 1/2" studs doesn't seem like it would be an issue either.

 

[viperlp01]

Go figure I have a customer that wants to run this setup. He has an Evo 9 and we are building his a pretty wicked 2.4L set up and we wanted to try it out. Some updates I guess when we get it done.

 

[danl]

Do you know how much you are stretching the new bolt after your 120 ft-lbs torque? If you know this and the material of the bolt you can figure out your clamping force per bolt. Then you can compare that to the 10mm bolts for a net increase in clamping force. It would also be worthwhile to get some pressure paper. It changes color when load is placed on it. Use it to mock up a headgasket and clamp the head down. This way you can see if the clamping is evenly distributed at the higher clamping forces due to the head flexing.

 

[99gst_racer]

ARP actually specifies clamping pressure figures for all of their materials and diameters in their catalog.

 

[LordDigi]

Any progress or updates on this mod? I see everything was able to handle the 120ft/lbs while in a non running platform. Has this been tested further to know that it may not crack under load?

Very nice thread and research here, I may add!

 

[bastarddsm]

You know you don't have to torque these to 110, or the L19's to 135... You probably really only need the same clamping force as stock. The real benifit to all of these, is the increase of the slope of the stress/strain curve. Meaning it will take higher cylinder pressures to reduce the clamp load on the gasket enough for it to fail. .

 

[JacksonAuto]

Call ARP and ask a tech what happens to the clamping load when you exceed the recommended torque by 30% and exceed the fasteners yield strength.

These heads lift between the fastener points. It's not the studs stretching. Even a fastener with 1,000,000 psi tensile strength wont help 'ya here.

 

[99gst_racer]

You know you don't have to torque these to 110,

That is their recommended torque value though. What would be the purpose of torquing a stud to only half of it's recommended value? Torque specs are derived from a given material and diameter, so it would be pointless to use torque specs from an OE 11mm bolt, for torquing down a 1/2" 8740 stud.

Call ARP and ask a tech what happens to the clamping load when you exceed the recommended torque by 30% and exceed the fasteners yield strength.

I agree that exceeding a fasteners yield strength is a bad idea. I hope that's not what you thought we did with our experiment.

These heads lift between the fastener points. It's not the studs stretching. Even a fastener with 1,000,000 psi tensile strength wont help 'ya here.

If this were true, then we wouldn't have a need for exotic materials like H11/L19. If a greater clamping force doesn't help keep the head tight, then guys like Brent Rau could just run regular 8740 ARP studs and have no issues running 90 PSI boost and making 1500 HP. Right?

 

[JacksonAuto]

Do you know that Brent Rau isn't lifting the head?

 

[99gst_racer]

Do you know that Brent Rau isn't lifting the head?

I've watched him lift the head in person. Even have pics of him swapping out the head, studs, and gasket afterward.

Nevertheless, he also isn't running regular 8740 studs torqued to 80 ft/lbs like the average DSMer. And for good reason.

 

[donniekak]

Call ARP and ask a tech what happens to the clamping load when you exceed the recommended torque by 30% and exceed the fasteners yield strength.

These heads lift between the fastener points. It's not the studs stretching. Even a fastener with 1,000,000 psi tensile strength wont help 'ya here.

I know in other platforms the area under the sealing ring of a gasket is removed, and either filled with weld, or a stanchion is added. This fixes the false "head lift" issue, which is actually the head flexing.

 

[JacksonAuto]

I've watched him lift the head in person. Even have pics of him swapping out the head, studs, and gasket afterward.

Nevertheless, he also isn't running regular 8740 studs torqued to 80 ft/lbs like the average DSMer. And for good reason.

That statement doesn't support your argument- it supports my position that the studs arent stretching. Rather, the head is lifting/flexing between the fastener points.

 

[99gst_racer]

That statement doesn't support your argument- it supports my position that the studs arent stretching. Rather, the head is lifting/flexing between the fastener points.

I highly doubt you know for sure that Brent didn't stretch his studs in the race that I was at. Unless you were hiding under his valve cover with a stretch gauge, and I didn't see you... His exact words were, "I left the line with too much boost and lifted the head". Not that his statement is any more conclusive that your guesses of what exactly happened.

I don't disagree that the head flexes to some extent. But I also don't agree with your assertion that a stronger/larger fastener cannot help keep the head sealed. Your blanket statement seem to suggest that we should all ignore head fasteners entirely and we should all chalk up cylinder head sealing issues as "head flex".

It is entirely possible to stretch a head stud. It happens all the time. I'm not saying it's the cause if every failed head gasket, but neither is cylinder head flex. Running a fastener material that has a higher yield/tensile strength will help prevent permenetly elongating the fastener with extremely high cylinder pressures and/or detonation. It IS something that some of us need to address regardless of cylinder head flex. This is why some high HP cars have sealing issues with 8740 studs, but they do not have those issues with tool steel studs. Furthermore, a larger diameter stud and washer will help displace the clamping force to a wider area to help prevent flexing of the cylinder head between the studs.

Do you disagree that different sizes and type of head studs perform differently?

 

[JacksonAuto]

Perhaps I misunderstood, my apologies. My post was in response to this portion of your reply-

f this were true, then we wouldn't have a need for exotic materials like H11/L19. If a greater clamping force doesn't help keep the head tight, then guys like Brent Rau could just run regular 8740 ARP studs and have no issues running 90 PSI boost and making 1500 HP. Right?

I surmised that your stance was that H11/L19 studs' extra strength would correct the issue of heads lifting.

And then you posted this-

I've watched him lift the head in person. Even have pics of him swapping out the head, studs, and gasket afterward.

Which contradicts your first post saying that the exotic materials will stop the heads from lifting.


Brent has a race car. If is lifts the head an pushes water who cares? THe problem arises when people read threads like this and think they can and need to apply the same things to their street car. I've got customers calling me asking to torque their 8740 head studs to 120 ft/lbs.

 

[99gst_racer]

I surmised that your stance was that H11/L19 studs' extra strength would correct the issue of heads lifting.

I am claiming that a tool steel stud can help if the issue is that the 8740 stud is stretching. I'm not necessarily claiming that a tool steel stud fixes cylinder head flex issues.

Which contradicts your first post saying that the exotic materials will stop the heads from lifting.

I've never claimed that tool steel studs will prevent a head from lifting. They're simply stronger than 8740 studs and so I've made claims that they "can help". But I'm well aware that they too have a known yield strength and aren't unbreakable by any means. I'm only claiming them to be a stronger upgrade, not an end-all fix.

The problem arises when people read threads like this and think they can and need to apply the same things to their street car. I've got customers calling me asking to torque their 8740 head studs to 120 ft/lbs.

I've made no claims or implications that anyone needs to do what we've done in this thread. This thread is nothing more than documenting an experiment. If you read any of my posts on this site regarding head studs, I'd be willing to bet you'd agree with any and all of what I've said. I'm the minority here that encourages the torque spec that ARP recommends, and not 100+ ft/lbs like many others recommend because I completely understand what 'yield strength' is.

I believe you've misinterpreted some of the stuff that I've said in this thread. I think we're on the same page here for the most part. And I generally agree with most of everything that you post on this site (hence half of your rep points coming from me).


But, while we're on the subject of cylinder head flex, hopefully you don't mind discussing it a bit. Is the flex issue typically heat related or pressure related? How much flex are we talking about? Have you guys ever implemented anything to combat it? Do you agree that a larger diameter stud could help?

 

[RWD4G63]

I'll be doing this soon, as my block is almost ready for machining. I'm still debating on which headgasket to run and if I should run o-rings.

 

[Cdc1221]

Just to add a little flavor to this thread from the turbo diesel side, while i was working as a ford dealer tech we had several f-250s come in with blown hg's and if i remember correctly, the attributing factor to this was head bolt material being too weak and stretching too much so we were required by ford to replace them with better quality bolts and retorque them to factory specs