1/2" head studs - block & cylinder deformation

[99gst_racer]

I've been kicking around the idea of switching to a 1/2" head stud on my 7-bolt. The only reason would be for greater strength (more preload and clamping force) and the fact that it would be cheaper than any exotic material. Surprisingly, a 1/2" 8740 chrome moly stud is still stronger than an 11mm L19 stud.

So, this past weekend, I took and trip over to Strictly Import Motorsports and John and I did some testing with this idea. We fit a 1/2" stud on a 7-bolt block with no issues. We didn't have to remove enough material from the hole to even raise concern whether or not there would be enough left for strength. And we were able to get the nut to tighten down past the valve spring and seat without any major modifications. All in all, this seems like a sweet upgrade for either block.

My only question is regarding deformation. I'm wondering if a larger fastener will deform the deck and/or cylinders much differently than the OE size fastener. In other words, would a hone be absolutely nessacery after switching to 1/2" studs? I'd hate to put a bunch of time and money into a junk block just for testing purposes just to answer this question, so I'm just curious is anyone has any solid opinions or experiences with doing something like this on another platform.

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[phunny]

My 7-bolt has 12mm studs that don't seat all the way down in the block and so far she's holding strong. The only pain for me was getting the washers around the valve springs, but I even found a nice easy way for that.

 

[BogusSVO]

Personally, I would to the stud mod, then torque plate bore/hone

Now is it an absolute that it is needed? No.

But with changing the stud dia, you are changing the way the stud pulls on the block, and the block on the cylinders.

How much is it going to deform? as a guess I would say overall in cylinder wall deflection, .0003 or less

You are moving from a 11mm to 13mm ( for basic math) or 7/16 to 1/2 or appox .080 larger stud dia.

1mm = .03937

But what is common in the machine shop indstry now, is a cold hone of the block (room temps) so I would expect to see about the same variance between a cold hone and a Hot hone.

So what I am saying, be as anal as you want to be on your build.

 

[99gst_racer]

Just the man I was hoping would chime in.

If I were starting a fresh shortblock build, I would definitely do this mod first and then bore/hone using the larger studs. But in my case, my block is already built and there's nothing wrong with it, so I really want to avoid tearing it down unless it's absolutely nessacery.

As long as I don't run into any deformation-related issues, then I'll give it and try and I won't be too picky about it. What would be the downfall with a cylinder wall deflection of .0003 or less? I assume not much of anything?

 

[kthackst]

Here is a quick ANSYS model of our block with 1/2 head studs torqued to 100 ft/lbs. Generic Materials. Some simple assumptions are made but yep this is as good as a 15 minute run will get ya. About .004-.006mm of deflection in the block.

 

[BogusSVO]

.004mm x .03937 = .0001547

.006mm x .03937 = .0002362

If kthackst, model is close, the cylinder deform is 1/2 to 2/3 of what I said.
Now that is rocket science tolerance!!

Keep in mind that crank journals, and rod and main bearing housings bores are kept within .0007
The thickness of a sheet of notebook paper is appox .003

Looks like you will need to invest into a gasket punch set to you can enlarge the head gasket bolt holes!!

 

[99gst_racer]

Looks like you will need to invest into a gasket punch set to you can enlarge the head gasket bolt holes!!

We actually already tested it with a FelPro composite gasket. The holes in the Felpro are already a wee bit larger that .500", so it fit perfectly.

 

[BogusSVO]

Swwwwweeeeeeeet!!!!

 

[rlacasse1]

Will the bolt holes in the head have to be enlarged at all to use these studs?

 

[99gst_racer]

Will the bolt holes in the head have to be enlarged at all to use these studs?

Yup. We drilled them out to accept the larger stud. Not much material removed there either.

 

[rlacasse1]

Cool. Guess you wouldn't really need these unless you were really pushing the engine pretty far though, huh?

 

[black_gst]

Nice work!

 

[ed1380]

Yup. We drilled them out to accept the larger stud. Not much material removed there either.

Does the block need to be re-tapped?

 

[BogusSVO]

Does the block need to be re-tapped?

It would be safe to say it did, 1/2 stud, is a bit larger than the 11mm hole, also the thread pitch is diffrent.

 

[99gst_racer]

Cool. Guess you wouldn't really need these unless you were really pushing the engine pretty far though, huh?

Yes and no. It's cheap and easy to do. It gives a stronger stud than an 11mm L19 and it's less money to boot. But, I probably wouldn't mess with it unless you wanted that extra clamping force.

I'd love to get a 1/2" L19 stud, but they don't exist as far as I can tell.

Does the block need to be re-tapped?

Yup, drilled and tapped.

 

[ed1380]

It would be safe to say it did, 1/2 stud, is a bit larger than the 11mm hole, also the thread pitch is diffrent.

I know, but it wasn't mentioned anywhere, so I had to push my luck because I just took my head off.

 

[babyviper]

Do you happen to have a link for where I could pick these up?

 

[romeen]

Personally, I would to the stud mod, then torque plate bore/hone

If I were starting a fresh shortblock build, I would definitely do this mod first and then bore/hone using the larger studs.

Probably a very good idea.

Paul, although your question relates to block/cylinder deformation relative to head bolt size my experience with over torquing head studs might have some relevance to this thread.

In May 2007 I swapped out my stock 6 bolt head bolts for standard ARP's. I did this without removing the head (one stud at a time). I was naive and listened to someone's "advice" and torqued them to 100 lb/ft instead of ARP's recommended 86 lb/ft. Compression test results taken immediately before the swap with 9.0:1 pistons was about 200 (+/- 6) across the board. Repeated compression test after approximately 2K miles. Don't have exact results in front of me but ranged from 160ish to 180ish.

I can't claim for certain that this is a result of the over torquing but nothing else was done to the motor during that time and I maintain the motor well so it seems reasonable to think that the compression loss might be from cylinder deformation.

 

[rlacasse1]

I saw you mention what the studs were in the first post but might as well ask. Where did you get them, and what's all the specifics?

 

[99gst_racer]

Do you happen to have a link for where I could pick these up?

Send a PM to John (viperlp01), you can order them through him.

I saw you mention what the studs were in the first post but might as well ask. Where did you get them, and what's all the specifics?

I got mine straight from ARP. They're pretty much just like a 1/2" version of the regular ARP's for our engines.

 

[TSIfreek]

I wouldnt loose sleep over it as long as you stick with a max torque of 90 FT lbs with moly. A MLS gasket will also help it keeping things straight as it puts more of an equal clamping force over the whole block surface.

 

[99gst_racer]

I wouldnt loose sleep over it as long as you stick with a max torque of 90 FT lbs with moly. A MLS gasket will also help it keeping things straight as it puts more of an equal clamping force over the whole block surface.

I run a composite gasket with an o-ring, and I won't be changing that anytime soon.

Also, the recommended torque spec for these studs is 110 ft/lbs. (per ARP).

 

[viperlp01]

I am already working on my parts list for my new engine and I am going to be drilling my block out soon. The head studs are crazy compared to stock. Paul and I are working on what it would cost to get a better material. If we could get anything better than the standard 8740 the gains would be incredible.

 

[assault187]

You guys aren't concerned about 110 lb/ft torque spec of the new setup? I remember a little while back reading through a discussion of people cracking the webing in the corners of the cylinder head when torquing 110-115 lb/ft. I myself ran into an issue with my previous block cracking after setting torque on a new HG @ 110. The crack looks like it may have split from the head stud hole itself. I can post pics if you like.


Excuse the quality of the pics....its the best thing I have at the moment.

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[99gst_racer]

Sure, I'd like to see some pics. Which studs were you using at 110-115 ft/lbs? That's a little high for anything 12mm.