Engine Rebuild Issue
Cargo Master
Joined: Nov 2015
Posts: 3,366
Likes: 915
From: Fort Worth, TX
When you pull heads off an active motor coolant and oil go everywhere. It's all about the cleanup afterward. You do as much as you can beforehand.
Before I put my studs in, I'll be talking to ARP.
The term scattering typically means inconsistent tension between all the fasteners. I've never heard it used for the release of a fastener twist. Unless they meant the release of the twist was causing scattering.
The release of the twisting does reduce tension, it's backing off the threads and it's well known. Ideally, you want to minimize twisting of the fastener, which is what I thought this ARP lube was supposed to do, better than any other. I think in Mac's thread I asked or stated the studs should be marked as well as the nuts so you can see if there is any twisting of either afterward. That's actually common practice on critically tensioned components. In my first professional job, I used to work with guys that built the hatches on the Space Shuttles - that's critical fastening.
One thing I was planning on talking to ARP about which relates to this is to not lube the threads in the block for higher frictional loading within the threads, and the possibility of using low or medium grade Locktite in the block threads to "plant" the studs. You don't know if the release of the twist is occurring at the block or at the nut.
Some engineers state 40% of the torque is used by the thread friction, and 50% used in the nut to washer friction. This is why I've always been amazed that ARP uses a torque value, not even putting into the equation of torque wrench inaccuracy. This is why angular tensioning was put into practice; you know the thread pitch, so with an angular rotation it's easy to determine the degree of stretch (clamping force) you have achieved by rotating 360º or whatever. It's doesn't matter the frictional forces or the accuracy of the torque wrench.
Can you provide links to where this discussion has come up before in your research?
Before I put my studs in, I'll be talking to ARP.
The term scattering typically means inconsistent tension between all the fasteners. I've never heard it used for the release of a fastener twist. Unless they meant the release of the twist was causing scattering.
The release of the twisting does reduce tension, it's backing off the threads and it's well known. Ideally, you want to minimize twisting of the fastener, which is what I thought this ARP lube was supposed to do, better than any other. I think in Mac's thread I asked or stated the studs should be marked as well as the nuts so you can see if there is any twisting of either afterward. That's actually common practice on critically tensioned components. In my first professional job, I used to work with guys that built the hatches on the Space Shuttles - that's critical fastening.
One thing I was planning on talking to ARP about which relates to this is to not lube the threads in the block for higher frictional loading within the threads, and the possibility of using low or medium grade Locktite in the block threads to "plant" the studs. You don't know if the release of the twist is occurring at the block or at the nut.
Some engineers state 40% of the torque is used by the thread friction, and 50% used in the nut to washer friction. This is why I've always been amazed that ARP uses a torque value, not even putting into the equation of torque wrench inaccuracy. This is why angular tensioning was put into practice; you know the thread pitch, so with an angular rotation it's easy to determine the degree of stretch (clamping force) you have achieved by rotating 360º or whatever. It's doesn't matter the frictional forces or the accuracy of the torque wrench.
Can you provide links to where this discussion has come up before in your research?
I never understood the need to lube the threads in the block. And what's the rationale behind backing the stud out an eighth of an inch? Is it simply a difference in expansion coefficients between cast iron and steel?
Hotshot
Joined: Dec 2014
Posts: 17,762
Likes: 3,053
From: Jersey Shore
The problem with the studs bottoming in the block is if the studs turn you will start to also be applying a force pushing the studs upward, not just the tension force across the body of the stud. Now you can exceed the threads capability with the potential to strip out the block threads.
Thread engagement theory is (to me) interesting. In the typical hard metal materials, you only stress in some cases the first four threads. It can vary depending on the stiffness of the metal, there is always distortion. With more compliant metals, like our rocker boxes or manifold, more threads will engage due to the distortion.
It depends on how deep the rabbit hole you want to go. Fastenal has some good data.
Also briefly - https://fieldfastener.com/2018/03/13...ad-engagement/
But there also effects with temperature .... deep rabbit hole......
You can develop very high yield point studs and nuts, the weaker link, but the block threads are what they are. The 6.0 blocks so far haven’t been an issue, but when ARP first came out with studs for the 6.4L, they had to back off the torque values as the blocks were starting to crack by the lifter bores due to the stress.
People usually don’t think about the block upwelling around the head bolt locations and stress within the block. And what they use to clean the block threads with. The International service manual says to use a tap, but most consumer taps have a poor grade thread. It should be a thread chasing tool, or a modified bolt to not tear out more metal.
ASTM has the best studies and standards when it comes to strength. You know, the bridge and pressure vessel/piping guys.
Thread engagement theory is (to me) interesting. In the typical hard metal materials, you only stress in some cases the first four threads. It can vary depending on the stiffness of the metal, there is always distortion. With more compliant metals, like our rocker boxes or manifold, more threads will engage due to the distortion.
It depends on how deep the rabbit hole you want to go. Fastenal has some good data.
Also briefly - https://fieldfastener.com/2018/03/13...ad-engagement/
But there also effects with temperature .... deep rabbit hole......
You can develop very high yield point studs and nuts, the weaker link, but the block threads are what they are. The 6.0 blocks so far haven’t been an issue, but when ARP first came out with studs for the 6.4L, they had to back off the torque values as the blocks were starting to crack by the lifter bores due to the stress.
People usually don’t think about the block upwelling around the head bolt locations and stress within the block. And what they use to clean the block threads with. The International service manual says to use a tap, but most consumer taps have a poor grade thread. It should be a thread chasing tool, or a modified bolt to not tear out more metal.
ASTM has the best studies and standards when it comes to strength. You know, the bridge and pressure vessel/piping guys.
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Joined: Mar 2020
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When you pull heads off an active motor coolant and oil go everywhere. It's all about the cleanup afterward. You do as much as you can beforehand.
Before I put my studs in, I'll be talking to ARP.
The term scattering typically means inconsistent tension between all the fasteners. I've never heard it used for the release of a fastener twist. Unless they meant the release of the twist was causing scattering.
The release of the twisting does reduce tension, it's backing off the threads and it's well known. Ideally, you want to minimize twisting of the fastener, which is what I thought this ARP lube was supposed to do, better than any other. I think in Mac's thread I asked or stated the studs should be marked as well as the nuts so you can see if there is any twisting of either afterward. That's actually common practice on critically tensioned components. In my first professional job, I used to work with guys that built the hatches on the Space Shuttles - that's critical fastening.
One thing I was planning on talking to ARP about which relates to this is to not lube the threads in the block for higher frictional loading within the threads, and the possibility of using low or medium grade Locktite in the block threads to "plant" the studs. You don't know if the release of the twist is occurring at the block or at the nut.
Some engineers state 40% of the torque is used by the thread friction, and 50% used in the nut to washer friction. This is why I've always been amazed that ARP uses a torque value, not even putting into the equation of torque wrench inaccuracy. This is why angular tensioning was put into practice; you know the thread pitch, so with an angular rotation it's easy to determine the degree of stretch (clamping force) you have achieved by rotating 360º or whatever. It's doesn't matter the frictional forces or the accuracy of the torque wrench.
Can you provide links to where this discussion has come up before in your research?
Before I put my studs in, I'll be talking to ARP.
The term scattering typically means inconsistent tension between all the fasteners. I've never heard it used for the release of a fastener twist. Unless they meant the release of the twist was causing scattering.
The release of the twisting does reduce tension, it's backing off the threads and it's well known. Ideally, you want to minimize twisting of the fastener, which is what I thought this ARP lube was supposed to do, better than any other. I think in Mac's thread I asked or stated the studs should be marked as well as the nuts so you can see if there is any twisting of either afterward. That's actually common practice on critically tensioned components. In my first professional job, I used to work with guys that built the hatches on the Space Shuttles - that's critical fastening.
One thing I was planning on talking to ARP about which relates to this is to not lube the threads in the block for higher frictional loading within the threads, and the possibility of using low or medium grade Locktite in the block threads to "plant" the studs. You don't know if the release of the twist is occurring at the block or at the nut.
Some engineers state 40% of the torque is used by the thread friction, and 50% used in the nut to washer friction. This is why I've always been amazed that ARP uses a torque value, not even putting into the equation of torque wrench inaccuracy. This is why angular tensioning was put into practice; you know the thread pitch, so with an angular rotation it's easy to determine the degree of stretch (clamping force) you have achieved by rotating 360º or whatever. It's doesn't matter the frictional forces or the accuracy of the torque wrench.
Can you provide links to where this discussion has come up before in your research?
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