head studs
- Thread starter crash86
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david85
Full Access Member
Short answer yes, long answer no....(bear with me)
Short answer: To install the studs you have to drop them on the engine at the same time as the heads in the case of the rear most studs that are tucked against the firewall. Basically its a clearance issue that needs to be worked around.
Long answer: ARP recommends going through the torque sequence 5 times before finalizing the job and leaving them on. After each tightenting sequence, they are loosened off (again in proper sequence) and completely removed from the block. This repeated process seats the threads of the studs in the block and also allows the threads on the top ends to smooth out on the tightening nuts. The proceedure is indended to reduce friction on the bolts as much as possible and also by removing the studs every time, you help eliminate the possibility of the studs shifting up slightly as they settle over time. A lot of work, but this way as much torque as possible from your arm goes to clamping down the head and not defeating friction in the threads. I don't remember for sure, but I think the repetative process also helps to initially stretch the studs.
The proceedure as recommended by ARP is basically impossible to perform with the engine in the truck, but even if you were to just do the head torque sequence several times with the engine in the truck, it would probably hold well enough (way better than stock bolts). It won't be pleasant to get at those rear bolts though.
If you have the equipment, it would probably not take you much longer to do a head gasket job with the engine pulled.
Short answer: To install the studs you have to drop them on the engine at the same time as the heads in the case of the rear most studs that are tucked against the firewall. Basically its a clearance issue that needs to be worked around.
Long answer: ARP recommends going through the torque sequence 5 times before finalizing the job and leaving them on. After each tightenting sequence, they are loosened off (again in proper sequence) and completely removed from the block. This repeated process seats the threads of the studs in the block and also allows the threads on the top ends to smooth out on the tightening nuts. The proceedure is indended to reduce friction on the bolts as much as possible and also by removing the studs every time, you help eliminate the possibility of the studs shifting up slightly as they settle over time. A lot of work, but this way as much torque as possible from your arm goes to clamping down the head and not defeating friction in the threads. I don't remember for sure, but I think the repetative process also helps to initially stretch the studs.
The proceedure as recommended by ARP is basically impossible to perform with the engine in the truck, but even if you were to just do the head torque sequence several times with the engine in the truck, it would probably hold well enough (way better than stock bolts). It won't be pleasant to get at those rear bolts though.
If you have the equipment, it would probably not take you much longer to do a head gasket job with the engine pulled.
david85
Full Access Member
Not really. What you have to remember is that even though these are not "stretch" bolts in the normal sense of the word, they do still stretch slightly as they are torqued. They have to.
The head gasket and head do not stay completely rigid to the engine block, but instead dance around slightly as the engine runs and vibrates. that means the bolts have to have loads of clamping force, but they also have to be flexible to stand the test of time. If it wasn't for this flexibility, the threads would either shear out of the block, or the bolts would break. This is why you don't want to use aircraft grade fasteners that can't stretch when you torque them down because their yeild strength is so high. The bolt will hold too rigidly and something else will have to yield instead.
By increasing the torque on the ARP bolt, you are going past the optimal loading/flex of the bolt even though you may technically still be within the safe limit of the bolt (all that means is it won't break when you torque it down). Also since the threads might not be at the ideal seating in the block of the engine, the stud may settle after the engine is run for a little while and loose some of the clamping load. Retorquing later on may be needed, but by then the nuts will have more friction in the threads after having sat for a while and this is still not ideal.
You can get away with not following these all exactly to the letter, but understand that every corner you cut will come at a cost. If you want to get every dollars worth out of your studs set, then its good to understand the whole story behind the head bolts. And what a story it is.....
The head gasket and head do not stay completely rigid to the engine block, but instead dance around slightly as the engine runs and vibrates. that means the bolts have to have loads of clamping force, but they also have to be flexible to stand the test of time. If it wasn't for this flexibility, the threads would either shear out of the block, or the bolts would break. This is why you don't want to use aircraft grade fasteners that can't stretch when you torque them down because their yeild strength is so high. The bolt will hold too rigidly and something else will have to yield instead.
By increasing the torque on the ARP bolt, you are going past the optimal loading/flex of the bolt even though you may technically still be within the safe limit of the bolt (all that means is it won't break when you torque it down). Also since the threads might not be at the ideal seating in the block of the engine, the stud may settle after the engine is run for a little while and loose some of the clamping load. Retorquing later on may be needed, but by then the nuts will have more friction in the threads after having sat for a while and this is still not ideal.
You can get away with not following these all exactly to the letter, but understand that every corner you cut will come at a cost. If you want to get every dollars worth out of your studs set, then its good to understand the whole story behind the head bolts. And what a story it is.....
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