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Old 01-19-2011, 07:58 PM
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ARP head stud torque in stock sbc block

ARP head studs 134-4001 call for 80lbft using ARP Ultra Torque lube. That torque reading is based on 75% of the yield strength of the fastener (190,000PSI). So, the ARP studs have a greater tensile strength than stock head bolts allowing more torque to be applied to them. HOWEVER, what about the strength of the stock block head bolt hole threads? These were designed to withstand 65lbft from stock head bolts, not 80lbft.

With the above in mind, what do you guys think? I've had a previous bad experience with pulling threads from a seasoned stock block using STOCK bolts at 65lbft, so I'm more than a little nervous about torqueing the studs to 80lbft.

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Old 01-19-2011, 08:53 PM
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Studs aren't supposed to put as much pressure on the threads in the block as regular bolts do.
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Old 01-19-2011, 09:07 PM
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The stud isn't putting any twisting force on the threads in the block like the bolt does, so the stud is easier on the threads in the block.
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Old 01-20-2011, 09:59 AM
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If you torque them to 80, the next time you take the heads off, you will see quarter-sized wear marks at the top of the cylinder next to every stud, caused by the deflection. That is too much torque! Studs and 60-65 is fine, even with ARP lube. We torque 15:1 sprint car engines at 60 with studs, ARP lube, and aluminum blocks. The only one we go 65 is the one right in the center.
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Old 01-20-2011, 10:35 AM
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OK, I just got off the phone from ARP Tech Support on this and the guy said he's never known of anyone pulling threads from a block (well, happened to me on the last engine I worked on using stock bolts!) He did say I could torque the studs to 70lbft if I'm worried about it and it should be fine.
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Old 01-20-2011, 10:45 AM
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I should add that I did the exact same thing you did-saw 80 in the ARP booklet-only I didn't question it like you did. Wish I would have. I don't know why they say to use more torque than the stock GM torque settings, when their lube is slipperier than oil, which is what GM (I believe) based their settings off of. Maybe because the threads are fine, not course, at the top of the studs. When I did 80#- it was on a 400 block, and the same stud kit as you have-and you could clearly see the wear spot next to every stud on every cylinder the next time I had the heads off. 65 & oil, or 60 with ARP lube is more than adequate on a sbc.
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Old 01-20-2011, 10:53 AM
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That's what I'm thinking too... ARP are doubtless 'covering all bases' by specifying 80lbft; the studs can take it and 80lbft will doubtless apply greater clamping force and seal better, but ONLY if the block can take it. A good proportion of folks using studs probably use aftermarket blocks, but not all. As my motor is only a street engine with 10:1 CR and not running spray or a blower, I think I'll torque to 60lbft and see how it goes. I can always retorque to a higher value if I encounter any sealing problems.
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Old 01-23-2011, 11:18 AM
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Iīve just taken the heads off my motor equipped with ARP studs and they were torqued to ARP specs.
I noticed as I torqued them down it was getting pretty tight but I thought,
"they know".
Taking the heads off was tough, they were really stuck to the block, and there was a lot of "wet" there when they came off, the wet being the reason for the teardown.
Iīm pretty sure one of the nuts had a stripped thread as it released way too easy, very fine threads hard to tell with the naked eye.
I didīnt see or feel any distortion in the block deck, but if you check out the cylinders at the top it seems there was distortion there.
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Old 01-23-2011, 01:37 PM
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Bore distortion will surely occur if the block was not finished w/deck plates using the same studs at the same torque.

Threads will pull w/bolts many, many times easier than if using studs. The main reason bolts "pull" threads in the first place, is because somewhere along the line, the threads were "cleaned" w/a tap- not a thread chaser. This removes metal, so do not ever clean threads w/a tap.

I would not hesitate to use ARP's specs. The thing is, you're dealing w/a different alloy (having a higher tensile strength), and a different design (stud vs. bolt). This means that the stud- in order to stretch to the recommended percentage of its yield strength- needs the cited torque.

If you choose for whatever reason to use a lesser torque spec, I would be damn sure to go back several times and re torque the nuts after several heat cycles. Oh, and there is no going back and retightening the stud nuts after the head-to-block seal is lost. Once the seal has been lost, you have to replace the gaskets.

ARP usually recommends burnishing the stud/nuts by cycling several times before the final tightening in steps to the final spec. If you use 60 ft/lbs w/the ARP 134-4001 head studs and don't burnish, even using ARP moly lube, do not be surprised when the head gaskets do not hold a seal.

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Old 01-23-2011, 03:52 PM
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ARP usually recommends burnishing the stud/nuts by cycling several times before the final tightening in steps to the final spec.

Can you explain "burnishing in this application please ?
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Old 01-23-2011, 04:30 PM
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Quote:
Originally Posted by malc
ARP usually recommends burnishing the stud/nuts by cycling several times before the final tightening in steps to the final spec.

Can you explain "burnishing in this application please ?
Malc, the burnishing involves torquing to the specified torque, then loosening and repeating 4 more times. This is necessary to achieve proper bolt (or stud) stretch. If the burnishing isn't done, the clamping force won't be what it should be, even though the proper torque value has been used. I suppose it would be roughly the equivalent as burnishing the threads, then torquing to 1/2 the required value. This is only a required step when using the 'old' ARP lube though (ARP Moly Assembly Lube). If you're using the new stuff (ARP Ultra Torque Lube), you don't need to burnish.
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Old 01-23-2011, 04:34 PM
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Quote:
Originally Posted by malc
ARP usually recommends burnishing the stud/nuts by cycling several times before the final tightening in steps to the final spec.

Can you explain "burnishing in this application please ?
The stud and nut threads "polish" each other smoother at a very microscopic level, taking all the tiny irregularities that come from the manufacturing process and crushing them smooth.

Almost all ARP hardware has instructions to cycle the nuts 3 times to smooth the threads out so that the torque achieved is consistant. It's in the instructions that most never read...
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Old 01-24-2011, 02:12 AM
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Quote:
Originally Posted by v8hed
Malc, the burnishing involves torquing to the specified torque, then loosening and repeating 4 more times. This is necessary to achieve proper bolt (or stud) stretch. If the burnishing isn't done, the clamping force won't be what it should be, even though the proper torque value has been used. I suppose it would be roughly the equivalent as burnishing the threads, then torquing to 1/2 the required value. This is only a required step when using the 'old' ARP lube though (ARP Moly Assembly Lube). If you're using the new stuff (ARP Ultra Torque Lube), you don't need to burnish.
I must have done that, memory fails me as they were first installed seven years ago.
Iīm going with a new set of studs, but I canīt get any type of ARP lube, Summit wonīt ship it by air.
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Old 01-24-2011, 04:16 AM
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BTW,
Malc, the burnishing involves torquing to the specified torque, then loosening and repeating 4 more times.
Wonīt that compromise my new head gaskets ?
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Old 01-24-2011, 06:04 AM
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Quote:
Originally Posted by malc
BTW,
Malc, the burnishing involves torquing to the specified torque, then loosening and repeating 4 more times.
Wonīt that compromise my new head gaskets ?
Use an old gasket for the burnishing process.

Or, use the new Ultra Torque lube
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