Anyone Tried 1/2" Head Bolts??

[Dusty Bradford]

Same diameter on the o-rings.

It does look more like a surface flex issue, rather than a fastner stretch issue.

Are the heads being re-heat treated after being welded up? If they ever get soft, they'll never stop flexing. Especially in the thin area between the cylinders.

 

[BlownV6]

I understand that Dusty, but are the o-rings on a same diameter or are they on slightly different diameters so that they end up side by side, but one above and one below the gasket?

For what you're trying to do Mike, I think your move to larger fasteners is a good one, but I'd also work on those billet heads and throw those on too. Even with the studs you're using now, the gasket isn't showing much evidence of lifting right around the studs, only between them. That tells me head deck bowing between the studs is more of the problem than anything else.

In total agreement with that!!! Mike

 

[BlownV6]

I completely agree with this. There’s probably some slight increase to be had; but at a cost.

Don’t forget that as the stud gets bigger; the amount of material between the cylinder bore and the threads holding the stud are reduced. This area already cracks in stock N/A blocks that have not been bored and are using the stock head bolts.

Raising the clamping force on the head will also raise the distortion pressures working against the deck surfaces of the block and the surface of the head.

But as the studs get bigger the threads will actually start to touch the water side of the the sleeve barrells. This should actually strengthen the deck load as now it wont be pulling up in the center or the deck area as much (slight difference) Also the bigger diameter threads will distribute more load to more area of the deck so Im thinking this will actually make it much stronger with less flex. Also the increased diameter of the stud requires a bigger OD washer on the head and this will provide greater clamping area which will distribute the load over more surface area and consequently make the head more rigid. Example might be a 1/8 thick plate 3" in diameter trying to seal a 100 psi pressure. Would 6 -1/4" bolts work as well as 6 -3/8 bolts with the appropriate washer??? Thats my good ole boy mentality!! Mike

 

[BlownV6]

Same diameter on the o-rings.

It does look more like a surface flex issue, rather than a fastner stretch issue.

Are the heads being re-heat treated after being welded up? If they ever get soft, they'll never stop flexing. Especially in the thin area between the cylinders.

That same head was fixed in the same spot earlier this year. We discussed having it heat treated but I had a race I wanted to go to, You know how that goes!!! Anyway this head will get repaired and heat treated or replaced. Mike

 

[joe_schindler]

But as the studs get bigger the threads will actually start to touch the water side of the the sleeve barrells. This should actually strengthen the deck load as now it wont be pulling up in the center or the deck area as much (slight difference) Also the bigger diameter threads will distribute more load to more area of the deck so Im thinking this will actually make it much stronger with less flex. Also the increased diameter of the stud requires a bigger OD washer on the head and this will provide greater clamping area which will distribute the load over more surface area and consequently make the head more rigid. Example might be a 1/8 thick plate 3" in diameter trying to seal a 100 psi pressure. Would 6 -1/4" bolts work as well as 6 -3/8 bolts with the appropriate washer??? Thats my good ole boy mentality!! Mike

Any material removed from the deck will reduce it’s strength and resistance to fatigue.

The distortion of the deck surface is related to the pull; not really the spread of the load. As related above; removing material from the deck will allow distortion at a reduced load. The likely increase in torque applied to the studs will increase the distortion to the block deck.

The biggest problem is there just isn’t much material to work with on the cylinder block.

In your example; the ¼” bolts would work fine. Even at 500 PSI; the 1/4” bolts would be fine. At 500 PSI; I’d want a little more than the standard ¼” flat washer spreading the load; but I believe that the cylinder head itself is doing that job better than a slightly bigger washer would do.

The head bolts/studs aren’t the problem.

Look at a 12 and 10 bolt GM rear gear set; and see which one uses the larger bolts.

 

[BlownV6]

Any material removed from the deck will reduce it’s strength and resistance to fatigue.

The distortion of the deck surface is related to the pull; not really the spread of the load. As related above; removing material from the deck will allow distortion at a reduced load. The likely increase in torque applied to the studs will increase the distortion to the block deck.

The biggest problem is there just isn’t much material to work with on the cylinder block.

In your example; the ¼” bolts would work fine. Even at 500 PSI; the 1/4” bolts would be fine. At 500 PSI; I’d want a little more than the standard ¼” flat washer spreading the load; but I believe that the cylinder head itself is doing that job better than a slightly bigger washer would do.

The head bolts/studs aren’t the problem.

Look at a 12 and 10 bolt GM rear gear set; and see which one uses the larger bolts.

I respect your opinion , but disagree. Over the years the other brands of v8 engines have already been through this same problem. Better bolts ,then studs , then better studs , and studs of exotic materials have been utilized to maintain head gasket seal. Now most if not all the aftermarket blocks come with the option of larger and larger head bolt threads. You can disagree all you like and I may prove you to be correct , but thats what I believe needs to be done. What can it hurt!!
More power means you need to make more cylinder pressure!! More cylinder pressure pushes on the head and piston equally. When you begin making more cylinder pressure than you have available clamping force for the heads then something is going to give. If its the head bolts stretching slightly then you have a leak , a leak leads to a burn through of something-somewhere!! Thats my take on whats going on right now. Putting larger studs may not prove to be worth anything if the cylinder head is going to flex anyway. If larger studs prevents the leak from happening in the first place then it may be able to make more cylinder pressure before it leaks. Even if it makes no difference with the stage 2 heads it would defenetly be a step forward towards the billet heads. Mike

 

[joe_schindler]

I don’t doubt that 1/2” bolts can provide more holding potential. I just don’t think that the stud/bolt is the weak link here.

A 7/16 stud can pull the coarse threads out of a block if you torque the fine thread nut too tight. The weak link in all of this is the block; and if you drill it out to put a bigger stud in; you’re only making it weaker.

 

[BlownV6]

I don’t doubt that 1/2” bolts can provide more holding potential. I just don’t think that the stud/bolt is the weak link here.

A 7/16 stud can pull the coarse threads out of a block if you torque the fine thread nut too tight. The weak link in all of this is the block; and if you drill it out to put a bigger stud in; you’re only making it weaker.

I see it deferently. 1/2" threads in the block will surely provide a much higher pullout yeild than the original 7/16 threads. And if it doesnt work then why do the Big engines use 1/2" , 9/16" and up to 5/8" studs?? I cant wait to get hold of someone at ARP on this!!! Mike

 

[49-blues]

Does ARP make the 1/2" headstuds?

 

[BlownV6]

Does ARP make the 1/2" headstuds?

Yes they will make custom studs for about anything!! Question is do they think is worth the effort or stick with sometype of a custom space age 7/16"?? Hopefully I will know something soon. Mike

 

[Dusty Bradford]

Yes they will make custom studs for about anything!! Question is do they think is worth the effort or stick with sometype of a custom space age 7/16"?? Hopefully I will know something soon. Mike

I'm definatley no expert on this but this is my opinion.

If your issue is stud stretch, the 1/2" stud could solve the issue. I'd lean more towards the higher grade 7/16" so you could avoid the machine work and possible issues you may run into when drilling the heads out larger. Possible weaking of the water jacket and other problems.

I feel it's most likely a head flex problem, rather than the fastner stretching. I had the same issue with my SB2's. Once I reached a certain power level, you couldn't keep the heads flat. I'd pull them off after 15 passes and the head would be dipped out between the middle cylinders. I'd have to take 5-7 thou off of each head to get it back flat.

 

[joe_schindler]

I see it deferently. 1/2" threads in the block will surely provide a much higher pullout yeild than the original 7/16 threads. And if it doesnt work then why do the Big engines use 1/2" , 9/16" and up to 5/8" studs?? I cant wait to get hold of someone at ARP on this!!! Mike

Because Big Engines are BIG. Look at your 3.8 bolt holes at the upper right and left of the cylinder (these holes are the same as the production blocks) not the top one on a Stage block. You’ve got a little room to work with on a virgin block; but bore it a few times; or start with a 4.1; and there’s not much left there.

Now; you want to drill the bolt hole out and tap it oversize. This leaves even less between the stud and piston.

Imagine putting a 1” stud in the hole. From there; drop down till you are happy with the balance of mass left in the deck surface and head stud size. If you like 5/8”; give it a try. At least you’d rule out clamping force as the weak link.

 

[BlownV6]

Update!! Just got off the phone and had a Very intresting conversation with ARP rep. They are looking into custom 1/2" and using either the L19 or custom age 625 material for this project. His opinion was that I could go with the exotic 7/16 as an upgrade , or if I was willing to do the machine work required go with the 1/2" as permanent fix. He will be getting back with me on a price (wont be cheap) and I will make my decesion from there. I promise I will keep you updated on this project as it moves forward or backward!!! Mike

 

[BlownV6]

Because Big Engines are BIG. Look at your 3.8 bolt holes at the upper right and left of the cylinder (these holes are the same as the production blocks) not the top one on a Stage block. You’ve got a little room to work with on a virgin block; but bore it a few times; or start with a 4.1; and there’s not much left there.

Now; you want to drill the bolt hole out and tap it oversize. This leaves even less between the stud and piston.

Imagine putting a 1” stud in the hole. From there; drop down till you are happy with the balance of mass left in the deck surface and head stud size. If you like 5/8”; give it a try. At least you’d rule out clamping force as the weak link.

OK , I just screwed a stud in the head bolt holes to the left and right of bores (same location as the production bolts). There is approx. .400 from the inside edge of the 7/16' stud to the bore which is 4.030". With a 1/2" stud this will be approx. .36875" Thats nearly 3/8 of an inch!! A SBC block with a 4.125 bore would be way closer than that (WAY CLOSER). Sorry I dont see the problem here. Please explain further?? Mike

 

[BlownV6]

it will be an exercise in futility-------most of the time the problem is not the head bolts (assuming they are torqued correctly)------the problem is that the deck surface and mating head surface seperate by flexing apart BETWEEN the bolt spaces-------they don't remain flat under excessive pressure-------bigger/stronger bolts can't do a thing to help with this problem.........RC

I have a lot of experience with exercises in futility!! I have also conquered most things that get in my way!! On a stock engine one of the first issues that hot roders run into, I believe is keeping the head gaskets in place. Now I know how important the tune is to this problem , but its more about the tune being within the tolerance of the head clamping ability. A stock engine will perform flawlessly , however once you start bolting on performance items things start pushing the limits of the head gaskets-right?? Now is it the gaskets , the heads flexing ,or the head bolts?? I venture to say that most people starting to make enough power to go in the 10"s have switched to aftermarket head bolts or studs. Right or wrong?? I see basically the exact issue!! Bigger Badder head bolts will provide more sealing at higher cylinder pressures. Even if the head is flexing a bit, the bigger studs will help keep it from flexing!! Mike

 

[joe_schindler]

OK , I just screwed a stud in the head bolt holes to the left and right of bores (same location as the production bolts). There is approx. .400 from the inside edge of the 7/16' stud to the bore which is 4.030". With a 1/2" stud this will be approx. .36875" Thats nearly 3/8 of an inch!! A SBC block with a 4.125 bore would be way closer than that (WAY CLOSER). Sorry I dont see the problem here. Please explain further?? Mike

(WAY CLOSER) You've measured? I haven’t. SBC does have one bolt that is pretty close to the bore; but the deck is a lot thicker in that area; and a lot more mass behind it; and I believe the holes go a little further down. There are also a lot of aftermarket blocks available for the SBC that go far beyond what the production blocks did as far as retaining fasteners. I don’t see that comparing SBC to Buick V6 is a good way to make decisions.

You’ll probably have a good 0.300 from the cylinder to the edge of the threads in the hole. At least you’ll know that the studs won’t be the problem.

 

[BlownV6]

(WAY CLOSER) You've measured? I haven’t. SBC does have one bolt that is pretty close to the bore; but the deck is a lot thicker in that area; and a lot more mass behind it; and I believe the holes go a little further down. There are also a lot of aftermarket blocks available for the SBC that go far beyond what the production blocks did as far as retaining fasteners. I don’t see that comparing SBC to Buick V6 is a good way to make decisions.

You’ll probably have a good 0.300 from the cylinder to the edge of the threads in the hole. At least you’ll know that the studs won’t be the problem.

No I havent measured the SBC , but back in the early 70's , my buddy ran a 400 block , that bolt would kill the roundness of the cylinders(this is before any one that I know, ever heard of honing plates). I used to tell him that I couldnt believe that GM would build a junk block like that with the head bolts that close to the bore!!! Thats where the WAY CLOSER came from. BTW at that time I raced an AMC and was considerably faster than him , thus the GM junk coment!!
Right or wrong looks like this project is going to happen!! Mike

 

[dr_frankenstein]

BTW at that time I raced an AMC and was considerably faster than him , thus the GM junk coment!!
Mike

explains everything....

:biggrin: A.j.

 

[BlownV6]

explains everything....

:biggrin: A.j.

No offense taken!! Here this will help explain my illness!!! Yes thats my car on the cover. Went to the AMC nationals and won everthing there was to win. And was supposed to match race the Maskin & Manarno factory backed prostock car but they were having oil pressure issues (that sucked). Turned out to be a pin hole in the line from the drysump tank to the pump
Anyway , no doubt I like to do things that others wouldnt!!! Good or bad!!
Mike

 

[Adam Connell]

You may want to look into cryo treating the heads before you do anything else.

I have personally witnessed parts that used to break on a weekly basis on a VERY well known monster truck that have not broken since cryo treating... Same parts, only difference was the cryo treatment.

It's worth a shot, and it really isnt that pricey and it certainly will not hurt anything.

It is reported to make heads MUCH more stable, and also improve heat dispersion. This should also theoretically reduce hot spots that lead to detonation.

I am currently in the process of figuring out what all Im going to do to my engine, but my goal is to make the best/smoothest running most efficient stock build ever... and that's a BIG task. The only "performance" modification I am doing will be a good 3 angle valve job with the transitions smoothed out. Got a few more other treatments I am going to experiment with besides cryo treating as well... Check out Micro Blue racing if you're interested in any of the other treatments im thinking about.