[v8hed]

Originally Posted by malc

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.

[malc]

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.

[cobalt327]

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

[malc]

Originally Posted by v8hed

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 ?

[v8hed]

Originally Posted by malc

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.

[oldbogie]

Originally Posted by v8hed

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

[v8hed]

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.

[malc]

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.

[RippinRon]

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!

[4 Jaw Chuck]

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.

[malc]

"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.

[v8hed]

Originally Posted by malc

"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.

There's no question over the torque for BOLTS... 65lbft is definitely correct. The problem with that is you can't compare the torque for bolts with the torque for studs; it's an apples to oranges comparison as they're two totally different fasteners. Also remember that torque isn't directly related to the resulting clamping force applied... it's just an easy and convenient method of estimating pre-load / stretch in the fastener. This is why the torque is different for different lubes (eg. 30w engine oil vs moly lube). Now factor in that fact that studs use a fine thread pitch and bolts use a coarse thread pitch the issue is complicated even further (fine threads = greater surface area = more friction = more torque). Now ALSO factor-in that head bolts are a steel fastener going into cast iron threads and that studs involve using a nut torquing-down onto a chrome moly steel stud and now you have differences in the friction coefficient due to the differing materials.

Bottom line: ARP say to use 80lbft with ARP Ultra Torque lube. That's their black & white statement and what their techs will also say to use regardless of application. It would be useful if ARP published torque figures for their head studs that would equate a torque figure (with their lube) to STOCK clamping force. In the meantime, it's down to personal judgment as to what torque value to use that would result in a stock clamping force. That figure (with moly lube) might be 65lbft, but it might be higher. Personally, I suspect a tad higher, so I'm sticking with 70lbft (which is also that ARP tech support told me I could use 'off the record' if I'm worried).

[cobalt327]

Originally Posted by v8hed

There's no question over the torque for BOLTS... 65lbft is definitely correct. The problem with that is you can't compare the torque for bolts with the torque for studs; it's an apples to oranges comparison as they're two totally different fasteners. Also remember that torque isn't directly related to the resulting clamping force applied... it's just an easy and convenient method of estimating pre-load / stretch in the fastener. This is why the torque is different for different lubes (eg. 30w engine oil vs moly lube). Now factor in that fact that studs use a fine thread pitch and bolts use a coarse thread pitch the issue is complicated even further (fine threads = greater surface area = more friction = more torque).

Bottom line: ARP say to use 80lbft with ARP Ultra Torque lube. That's their black & white statement and what their techs will also say to use regardless of application. It would be useful if ARP published torque figures for their head studs that would equate a torque figure (with their lube) to STOCK clamping force. In the meantime, it's down to personal judgment as to what torque value to use that would result in a stock clamping force. That figure (with moly lube) might be 65lbft, but it might be higher. Personally, I suspect a tad higher, so I'm sticking with 70lbft (which is also that ARP tech support told me I could use 'off the record' if I'm worried).

I agree- and along w/the above explanation of why it's an apples to oranges comparison, add to the facts that the steel alloy of the studs is different from that of the OEM bolts. Because the tensile strength is greater, MORE torque is required to stretch the stud to the same percentage of yield as an OEM bolt- thus the higher torque recommendation.

I think everybody can agree that if there isn't enough torque applied to the studs to maintain a clamping effect, the seal will be lost. Insufficient torque can also cause a loss of sealing when the gasket "takes a set" over a period of heat cycles, for example, because the amount of stretch that was induced in the studs by under torquing was insufficient to compensate for this.

My bottom line: If a torque less than that recommended by ARP is used, at least go back after several heat cycles and retorque the studs.

And I cannot see going one bit less than 70 ft/lbs under ANY circumstance (I'm already on record as saying to use the recommended specs), and I'm a bit surprised an ARP tech went out on a limb like that. But then, HE isn't the one who will be picking up the pieces, either.

[malc]

The BIG pic.

[cobalt327]

Those are general guidelines. They are superseded by the specific recommendations for the exact fasteners in question.

FWIW, below is another ARP torque chart:



You might notice there are discrepancies between it and the other chart. For me, this is yet one more reason the specs for the exact fastener and that fastener's application needs to be taken into account.

Just as going outside the engine manufacturer's torque recommendations "makes you the engineer", so does going outside the fastener manufacturer's recommendations make you the engineer. In this case, I trust that ARP's engineers have taken GM's torque recommendations fully into account and that's exactly why ARP came up w/the torque specs that they have recommended.

This would have been based on what clamping force was specified by the OM by their bolt size and material and torque spec. From that, ARP deduced how much torque would be needed, when using their studs.

Look- you can use whatever torque spec/lube/torque method you're happy with. It's YOUR engine, YOUR time and YOUR money riding on this- not mine. I can only say what I have done and will continue to do- and that is to follow ARP's recommendations.