Studs discussion

[B585Ford]

Well here's how it is, it takes xxxx pressure (torque) on a 16mm stud (6.4 size) to achieve xxxx clamping force for the given stretch of the psi (tensile strength) of said stud material.

Let's say it takes xxxxx psi of clamping force over the 3.87 bore (6.4 standard bore size) and three different stud brands do it at three different torques. It doesn't matter what the spec is. The fact that the same size studs apply the same clamping force over the same area = same stress in the block.

Right, that is what I was trying to say, but wouldn't the stronger stud allow you apply clamping force (not torque value) without blowing the HG because it would be less prone to stretching?

 

[RescueF250]

Well this turned out to be a good discussion everyone having different variation. Also with clearing up the issue with cracking the block.

 

[Morgan@Midwest Diesel & Auto]

Right, that is what I was trying to say, but wouldn't the stronger stud allow you apply clamping force (not torque value) without blowing the HG because it would be less prone to stretching?

Technically the higher the tensile strength the less stretch per given load. To my experiences I have yet to have a oem gasket with a properly torqued arp fail, so I really haven't seen a need for anything more.

Correct me if I am wrong but last I knew Craig's truck running 100psi + and 500hp worth of nitrous was using arp's.

 

[bigrpowr]

but wasnt all the block cracking done with ARP's ? i think i heard of one with elite A-1's, but that was it. which would lend itself to say the higher tq was causing the cracks. i'd rather use a better material than 1722 anyway.

 

[smokinstroker]

but wasnt all the block cracking done with ARP's ? i think i heard of one with elite A-1's, but that was it. which would lend itself to say the higher tq was causing the cracks. i'd rather use a better material than 1722 anyway.

This is what I was under the impression of.

Nothing against arp, as many people have success with them. But the high torque is what I feel is the common factor in cracked blocks.

 

[Morgan@Midwest Diesel & Auto]

I think that the biggest thing is that arp's are being used at a much higher volume than the a-1 are. So by theory if 10 arp's are installed for every 1 set of a-1's you would see more cracked blocks by default. And there were a lot of people over torquing arp's an not following directions.

The torque doesn't matter. The stud still produces xx amount of pull on the block to put xx amount of force on the head.

The only thing you gain by going to a higher tensile strength is having less chance of further stretching the stud under super high stress aka; lifting a head. But since we use 16mm head stands on the 6.4 factory I have yet to see a properly installed 190,000 psi arp 2000 stretch. Doesn't mean it can't happen. I just have never seen it or ever heard of it from anyone else.

 

[Morgan@Midwest Diesel & Auto]

This is what I was under the impression of.

Nothing against arp, as many people have success with them. But the high torque is what I feel is the common factor in cracked blocks.

Once again not true. The torque required does not reflect the actual streets put on the block.

I know it's hard to understand but different psi of tensile strength with different lubes takes different torques to achieve the same clamping force.

It doesn't matter, 30,000 psi of clamping force is 30,000 psi of clamping force. Regardless if it takes 190 or 275 FTlbs to apply that force it still only puts 30,000 psi worth of pull on the block. One stud just has different stretch, lube pitch that dictates what it takes to archive 30,000 psi worth of cylinder holding clamping force over a 3.87" bore area.

In no way can you achieve more clamping force over a given square area with the same amount/size of studs while putting less force on the block to hold the cylinder head. It is physically impossible to do by just changing stud material.

The only way to add more clamping force is to add more studs per cylinder or torque them to a higher yield per given psi stud.

I hope that explains it better.

 

[smokinstroker]

Much better, always overlooking that when thinking of it. Went through this on my 6.0 with arp vs A1 from Tadd


Thanks for the explanation as usual Morgan!

 

[gman1]

but wasnt all the block cracking done with ARP's ? i think i heard of one with elite A-1's, but that was it. which would lend itself to say the higher tq was causing the cracks. i'd rather use a better material than 1722 anyway.

This is what I was under the impression of.

Nothing against arp, as many people have success with them. But the high torque is what I feel is the common factor in cracked blocks.

Tadd and I both used CA 625,s and both of us have cracked blocks. I think it has nothing to do with what stud you use.

 

[Fordtrucks]

Sooooo, Does anyone feel a lesser TQ number, say 250 instead of 275 with ARPs would help anything here? Should a guy TQ to say 180 then go up to 275 in 10lb increments vers what the ARP directionals say? Would that help the amount of stress on the blocks at all?

Im about to do my studs AGAIN! I chose to order another set of studs instead of re using mine. Looking for ideas here cause im nervous about cracking something more expensive than my heads...

 

[dsberman94]

Sooooo, Does anyone feel a lesser TQ number, say 250 instead of 275 with ARPs would help anything here? Should a guy TQ to say 180 then go up to 275 in 10lb increments vers what the ARP directionals say? Would that help the amount of stress on the blocks at all?

Im about to do my studs AGAIN! I chose to order another set of studs instead of re using mine. Looking for ideas here cause im nervous about cracking something more expensive than my heads...

Read back. Ideas and the should-dos and ideas have been posted.

 

[renegade]

I think most everyone missed the point that Drunk On Diesel made. The crack is caused when the entire stud turns deeper into the block when torquing the studs, depending on the friction between the stud and nut if the stud is finger tight or tighter to being bottomed in the block if the stud turns at all it MAY exert too much tension on the threads in the block causing the crack. I was able to crack a 6.4 block that was magnefluxed to make sure that there where no cracks, one hole cracked with less than 1/16 of a turn additional rotation at 250 lbs ft of torque, the second hole on the same side we broke the stud without cracking the block after very precisely monitoring that the stud did not turn further when torqued, we where at well over 500 lbs ft of torque (the highest reading on my torque recording torque wrench) In my limited number of these I have worked on, all that cracked, the studs where more than finger tight by about 1/4 to 1/2 a turn. 2 of these I known had only been lightly finger tightened. At least 1 of the others had the old ARP lube, 3 others I worked on for other reasons used the new lube and the studs unscrewed with finger pressure and had no cracks.

 

[sootie]

I think most everyone missed the point that Drunk On Diesel made. The crack is caused when the entire stud turns deeper into the block when torquing the studs, depending on the friction between the stud and nut if the stud is finger tight or tighter to being bottomed in the block if the stud turns at all it MAY exert too much tension on the threads in the block causing the crack. I was able to crack a 6.4 block that was magnefluxed to make sure that there where no cracks, one hole cracked with less than 1/16 of a turn additional rotation at 250 lbs ft of torque, the second hole on the same side we broke the stud without cracking the block after very precisely monitoring that the stud did not turn further when torqued, we where at well over 500 lbs ft of torque (the highest reading on my torque recording torque wrench) In my limited number of these I have worked on, all that cracked, the studs where more than finger tight by about 1/4 to 1/2 a turn. 2 of these I known had only been lightly finger tightened. At least 1 of the others had the old ARP lube, 3 others I worked on for other reasons used the new lube and the studs unscrewed with finger pressure and had no cracks.

i think not, sir...



where was your crack again?

 

[dsberman94]

i still fell as though sledpull has the best reason for why the block cracks. although you have some good evidence to back up your theory by looking at his picture and his explanation of where the crack occurs and on what hole just seems more convincing to me.

 

[Morgan@Midwest Diesel & Auto]

I think most everyone missed the point that Drunk On Diesel made. The crack is caused when the entire stud turns deeper into the block when torquing the studs, depending on the friction between the stud and nut if the stud is finger tight or tighter to being bottomed in the block if the stud turns at all it MAY exert too much tension on the threads in the block causing the crack. I was able to crack a 6.4 block that was magnefluxed to make sure that there where no cracks, one hole cracked with less than 1/16 of a turn additional rotation at 250 lbs ft of torque, the second hole on the same side we broke the stud without cracking the block after very precisely monitoring that the stud did not turn further when torqued, we where at well over 500 lbs ft of torque (the highest reading on my torque recording torque wrench) In my limited number of these I have worked on, all that cracked, the studs where more than finger tight by about 1/4 to 1/2 a turn. 2 of these I known had only been lightly finger tightened. At least 1 of the others had the old ARP lube, 3 others I worked on for other reasons used the new lube and the studs unscrewed with finger pressure and had no cracks.

The problem is not that the stud pushes the bottom out the hole. They split on a casting line about 1.5" up. They only do it in two holes on each side of the block next to the lifter galley. It is thinner there and susceptible to cracking. The rest are good. I've got a few cracked blocks here to prove it.

Fwiw our pulling truck is torqued to 250 on all the holes except the four weak ones that are torqued to 225. All with arp's and the newest lube. Never used a drop of coolant. We have since been doing all of them that way and have not had one single issue to date.

Yeah. The ones next to the lifter valley second from the ends. If you have the heads off and look you see the physically less material around those two studs on each side.

Give it a try, can't hurt. We run less # than that and haven't blown any.

You can see the two stud holes in this picture have noticeably less material.

Ill repost this.

Once again not splitting the bottom of the hole.

They crack because of too much torque. I guarantee to I can take an arp with new line torque it too high and split a block every time. But only in those holes. 100% of the cracked blocks I see are cracked in the same spot. Only way to stop is is lower torque. I agree with not torquing the stud in the block, but it is not the cause.

You can torque the end studs till they snap and it won't give a F***. That's NOT the problem, they crack in the weak area by the lifters. They don't do it at the bottom of the whole. They crack up higher by a casting line. I've got three different blocks studded by three different companies all cracked all the same.

I've also seen them split the outside of the block when a unknowing mechanic torqued then to 345 to be "safe" with new lube.

Sooo, once again, I can count at least 6 that I know personably that were cracked some in my possession and some in others, all due to over torquing 100% of the time. But hell maybe they're cracking somewhere else and just no one else has seen it yet.....

 

[footlong70]

I would suggest some common sense/simple physics would help answer the debate as well. The stud bottoming out and/or hydro locking fluid in the closed hole (causing pressure within the hole or adding extra strain on the block threads) with such force to tear the block over the tension of stock head bolts is a myth. For starters, (ARPs) the top of the stud (head side) is a fine thread and the block side is coarse. The shallow angle of fine threads will always turn before coarse threads once there is significant tension. The resistance of a fine thread is much less than coarse. Secondly, the fine thread top side uses a highly engineered/refined torquing lubricant meant for high pressure and the lowest coefficient of friction possible. While the course end doesn't use anything special (engine oil, thread sealer, ect). Although a thread sealer is most common now to combat the crack. No matter how tight the fastener nut is torqued, the stud is not going to spin and torque itself into the block adding significant pressure in the hole or block threads. If that were the case you would need a pipe wrench to remove the stud from the hole next time the heads come off. The most that could happen is the stud would touch bottom before enough finger tight tension is on the stud but stop there. The fine threads would have to be severely deformed to torque the stud in the block.

The crack is clearly product of the lesser amount of material around those holes. Also a possible but unlikely contributor is the expansion/contraction rate of the studs within the block. The studs maybe pushing harder on the walls than a stock bolt at operating temp.
Something else to consider like mentioned above is the studs use a fine thread and specific torquing lube, therefore for the same amount of stock head bolt torque applied to an ARP stud would yield a much, much higher clamping force (i.e. tension on the block threads). So when were torquing these studs to 100ft/lb? more than stock, were putting absolutely massive tension on the block.

 

[bigrpowr]

I think that the biggest thing is that arp's are being used at a much higher volume than the a-1 are. So by theory if 10 arp's are installed for every 1 set of a-1's you would see more cracked blocks by default. And there were a lot of people over torquing arp's an not following directions.

The torque doesn't matter. The stud still produces xx amount of pull on the block to put xx amount of force on the head.

The only thing you gain by going to a higher tensile strength is having less chance of further stretching the stud under super high stress aka; lifting a head. But since we use 16mm head stands on the 6.4 factory I have yet to see a properly installed 190,000 psi arp 2000 stretch. Doesn't mean it can't happen. I just have never seen it or ever heard of it from anyone else.

while i agree with just about everything, the A-1's were out long before the ARP, and the cracks did not start happening until the ARP's became popular due to price and demand.

 

[renegade]

everyone that I have looked at or had experience with was cracked apprx. 1.5 inches from the bottom of the hole, NOT at the bottom. Also while I have no lab generated proof that this is the reason, I have seen way too many cases to think that it is at least a contributing factor.

 

[Morgan@Midwest Diesel & Auto]

while i agree with just about everything, the A-1's were out long before the ARP, and the cracks did not start happening until the ARP's became popular due to price and demand.

Understood, but also as the arp's came out 6.4's were becoming cheaper and more popular with more number of trucks being studded than in 08 and 09. Think about it, there were very few studded 6.4's in the first year or two, even three.
Then it exploded and everyone and their brother was studding a 6.4 and an expert torquing 325 old torques with new lube, cab on with a 1/2 drive wrench in their moms driveway.

I still 100% say incorrect torquing is at fault.

30,000 psi of clamping force takes 30,000psi worth of pull on the block to make it happen. Doesn't matter what fastener used.

 

[Morgan@Midwest Diesel & Auto]

everyone that I have looked at or had experience with was cracked apprx. 1.5 inches from the bottom of the hole, NOT at the bottom. Also while I have no lab generated proof that this is the reason, I have seen way too many cases to think that it is at least a contributing factor.

It really has nothing to do with bottoming out. Yes you could hurt it by bottom torquing but, they are cracking in the thin spots near the casting line which is a direct correlation to too much psi of pull being put in that area.

Maybe arp had their stretch a little off and put the original 325 to it. Some guys lucked out others didn't. Regardless it's a non-issue now. No reason to crack blocks with what we know about the torques and where they break the block and why. Not over torquing and being careful with the weak holes is a solution that has been proven to work. Idk why else we are worried about it.