Studs aren't supposed to put as much pressure on the threads in the block as regular bolts do.

 

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.

 

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.

 

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.

 

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.

 

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.

 

I´ve 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.
I´m 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 did´nt 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.
Click here for the BIG pics.

 

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.

 

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 ?

 

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.

 

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...

 

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.
I´m going with a new set of studs, but I can´t get any type of ARP lube, Summit won´t ship it by air.

 

BTW,
Malc, the burnishing involves torquing to the specified torque, then loosening and repeating 4 more times.
Won´t that compromise my new head gaskets ?

 

BTW,
Malc, the burnishing involves torquing to the specified torque, then loosening and repeating 4 more times.
Won´t that compromise my new head gaskets ?

Use an old gasket for the burnishing process.

Or, use the new Ultra Torque lube

 

I must have done that, memory fails me as they were first installed seven years ago.
I´m going with a new set of studs, but I can´t get any type of ARP lube, Summit won´t ship it by air.

I found a UK supplier... will PM details.

 

Right, got that, now;
my Chiltern manual for Camaros tells me 68ftlbs(92Nm),
that´s what I´ll torque them to.
Oh, need a new torque wrench.

 

You DO realize that the torque spec you cite is for OEM bolts, using motor oil as the lube?

 

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.

I saw 60ftlb mentioned as well, so 70 is splitting the difference.
Are we agreed 80ftlb is too much or not ?

 

I saw 60ftlb mentioned as well, so 70 is splitting the difference.
Are we agreed 80ftlb is too much or not ?

The official answer is that 80lbft is not too much... this is the value specified by ARP when using Ultra Torque lube and confirmed with their tech dept. HOWEVER, anecdotal reports point to 80lbft being too much for stock block (probably esp. true of an older block with somewhat weaker threads). So, torque to 80lbft and hope your block threads hold-up, or torque to 68lbft and hope your gasket seal holds-up. The words 'rock' and 'hard place' come to mind. Personally, I'd rather deal with a blown head gasket than wrecked threads in my block (been here, done that), so I'd recommend being conservative with the torque. JMHO.

 

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.

Ahh, yep! This is a place where there's lot of misunderstanding. Torque values are used as a second order means of determining how much preload stretch is applied to a fastener where that stretch cannot be directly measured, the example of direct first order measurement would be stretch measurement in rod bolts using a micrometer while tightening the nut.

The threads in the block must react the forces carried in the fastener period there is no way around this. Thisw happens regardless of fastener type, bolt or stud. If these forces exceed the strength of the threads in the block, they will fail. It doesn't matter if the studs are epoxied into the block's threads, the load reaction from tighening the nut is the same on the block's threads as would come from a bolt at the same torque. It doesn' matter if the stud's twisting force is between the the top block thread and the nut. In the end any and all force put in the nut has to be reacted into the threads of the block, these forces have no where else to go and must react out to a net zero sum between the fastener and the casting's threads. That's not to say the forces dissappear, they must be equal between fastener and fastened.

It doesn't matter if the fastener is stronger than the block, in the end it will be the strength of the threads in the block that will determine how much force can be carried in the fastener because the block or any other casting, will fail if excessive forces are put on the threads. Typically an engineer designs such that the fastener will fail before the casting, this is done because it's less difficult and less expensive to replace the fastener than the casting. Buy using a stronger fastener you risk failing the casting before the fastener.

Unless you're racing and have need to take the casting's threads to the ultimate they can tolerate to restrain combustion pressures and or need the fast R&R time offered by studs, or need to reduce the insertion and removal casting thread wear from repetitive cycles of assembly, dis-assembly, and re-assembly there isn't any justification for the use of studs other than the usual hot rodders routine of "Monkey See, Monkey Do".

Bogie

 

Bogie, you echo my thoughts exactly on this... my application (10:1 383) doesn't require studs from a sealing standpoint and I won't be subjecting the motor to repeated heads-on / heads-off procedures. However, I've been frightened-off using bolts since my prior bad experience where the bolt hole threads pulled-out on me (and they were properly prepped before torquing the bolts). The problem with using any seasoned block is that, in most cases, you have no clue as to its history and, therefore, have no idea how many times those threads have seen action. You also don't know if everyone who has previously had occasion to pull the heads off the block in the past has used the correct (or any!) sealer on the bolt threads, which would also considerably weaken the threads in the block due to corrosion. So, with all this in mind, I personally think it safer to use studs purely and simply to exert the minimum stress on the block threads as possible... the fact that the stud is not twisting into the receiving threads as the torque is applied and the fact that the threads are fully-engaged right off the bat should result in minimum stressing of the block threads. To anyone else using studs for this reason (rather than their potential for greater sealing ability due to their increased tensile strength), I can't really see any reason why 65-70lbft shouldn't be sufficient to provide a close-to-stock clamping force.

 

I use studs to preserve what I have, oil pan, headers, carb, thermostat housing.Especially in aluminum I think they are thread savers if you´re not helicoiled.
I even use them on both sides of my intake manifold, one side I install them first, the other by hand, if the threads are chased clean they go in easily
with thread sealer, and I´ve had no trouble removing them.
I did email ARP to make studs for the intake like the head studs, with the Allen
wrench facility, they never took it up so fingers do the job.
For us in Europe parts costs are high with shipping and import duties.

 

I don't know what has been done to your engine. If it was honed with torque plates I would use whatever the machinist used then. Studs distort the block in a different way than bolts do when torqued. Just some food for thought!

 

You can debate this torque discussion all you like but I will say this, if you stick with the stock torque you will have no problems and unless your doing some ultra high compression or high boost on the engine with some custom build that is not typical there is no reason to stray from the factory torque value.

Studs or not, they engineered the head/gasket interface for that torque value for a reason...going outside their recommendations now makes you the engineer and you best know what your doing.

Not saying it shouldn't be strayed from, just have a good reason to do so and have thought out the consequences of your actions and make allowances for them.

Personally I love studs at stock torques, they stretch less and retain torque far better....think of it as extra heavy valve springs to ensure good gasket sealing.

 

"I can't really see any reason why 65-70lbft shouldn't be sufficient to provide a close-to-stock clamping force."

I have just looked through a load of CarCraft and CHP mags, wherever head torque is mentioned it´s 65ftlbs.

I think 4Jaw hit the nail on the head.