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Tightening Cylinder Head Studs


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Over the next few weeks I am planning to lift the head on my TR3a to deal with a suspected head gasket blow.  It has been an ongoing problem and I am thinking of moving to ARP studs and have been doing a bit of reading up on them including the instructions for installation. Yes I know it's boring reading the instructions first but I am an engineer and old habits die hard!

Anyway, does anyone on here know why the conventional studs should be torqued up un-lubricated whereas the instructions for ARP studs are quite specific about the need to use their preferred lubricant on the threads prior to torquing to same 110 lbs ft as the regular studs?  The introduction of the lubricant will make a hell of a difference to the stud tension and its clamping force.

Rgds Ian

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Yes, the TR wet liner engine is a 1950s engine that harks back to the designs of the 1930s, lubricating threads wasn't done then, these "new fangled" ideas hadn't arisen, or been applied to mass car production anyway.

The lubricating of threads (and bottom of the washers or nuts applying the clamp) obviously alters the stiction (sticking and turning friction) so that the same torque applied in real life will increase markedly.

If you have a head gasket blowing the standard TR studs will do a good job for you and I'd dare to suggest that lack of clamping force is not the problem. As always it will be down to the last 50 years of stress relieving that has been carried out diligently to the block (we call it driving) where the multiple thousands of hot/cold cycles and the clamp of the studs has warped or twisted the block.

The block doesn't remove heat in a uniform fashion, not many engines do, but in this case No 4 cylinder runs hottest being furthest from the water pump and receiving water preheated by passing cylinders 1/2/3. Then number 1 cylinder runs hottest, contrarily being too close to the water pump the full force and flow races the water past it and doesn't allow the extra milliseconds required to lift the correct heat sink from the metal. You'll be relieved to hear that at least some of the cylinders run OKish with number 2 and 3 running at a median or thereabouts engine temperature, the sum of all the individual cylinder temperatures gives us our generic engine temperature which hopefully reassures you when you look at the gauge. Despite all these disadvantages the engine runs excellently and is a design classic being ultimately rebuildable even at the side of the road ( a number of us in times gone bye can attest to that) with individual cylinders being able to be replaced and even crankshafts along with the even more major components (although if you try and replace an engine block at roadside I'd suggest "you are aving a laff " !  it's easier to remove the engine and do in a garage).

Fitting the ARP studs to an engine which has blown a head gasket without investigating and diagnosing what has caused it risks you paying a large amount of money out purely to say you have ARP studs (and very nice they are too, fine fastenings ...just not essential).

If you measure the liner height when you take the head off no doubt you'll find a variation across and around some of the liners at least, and I'd suggest that would be where your problem would lie.

Why do you quote using a torque figure of 110 lb ft when the workshop figures are 105 maximum ? don't get me wrong I've used 110 but when I did I knew I was "stretching the envelope" of the engine block cast material near to where I believe it's limits are. If you use a lubricated thread on the ARP I fear you risk stripping the block.

If you use lubricated ARP bolts the applied torque will be something in the order of 15% more (there are tables which will tell you how much) than the standard applied dry torque even though it will be more evenly achieved across the block. If you wanted it to be even more evenly applied of course you would measure the stud lengths used (the TR OE stud lengths aredifferent) and mathematically vary the applied torques so the longer studs have more torque applied because of course they stretch, (you want to see what torques I use on my Stag with 11" studs with 5" Setbolts and 3" Setbolts  all on one head ! no they are not all set the same...now). But of course this myriad of torques then also need applying consistently which would mean lubricating the threads first then tightening by torque levels to say 80 lbft and then applying final clamping by angular measurement turning the bolt head a set number of degrees which will increase the torque to the numbers required. Without recommendation from ARP this would need defining using an old actual block and head and trial and error because you risk stripping the block threads whilst carrying it out.

This is gilding the lily, I've built over 20 of these 4 cylinder engines and in the TR Register race series  achieved HP figures right at the limits of 4 cylinder technology (1989) and to my shame I've never yet used ARP studs on one of my engines, I've never felt the need. I use old fashioned toolmaker engineer methods of inspecting the threads in the block with Mk 1 eyeball and cleaning them carefully with a tap to smooth out any drag marks.

For the studs I clean the threads in thinners, wiping dry and again checking with eyes that all is well and with a scriber inserted into the thread face run it down and along the thread faces to pick up any "galling" (thread material pickup) which I clean up and smooth with a needle file. If I find a stud which after treatment I deem not satisfactory I exchange it with some of my many spares (who do you think buys the scrap engine bits for pence at the internationals ?). Then after drying off the threads in the block and on the studs I torque them up dry. We have empirical evidence over the last 50 years that these engines do NOT blow head gaskets if built correctly and the engines when stripped have maintained their interior dimensions and specifications.

Your head blown gasket fault lie elsewhere rather than not enough torque from the standard fittings. If you want to talk it through drop me a PM and we'll discuss.

Mick Richards

 

Edited by Motorsport Mickey
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Ian

Having discussed this at length with a well know supplier  when i last refreshed the engine, i concur with Mick, ARP fasteners are lovely but not essential, even for a high performance 4 pot engine.

Iain

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Mick & Iain,

Thks for taking the time to reply and I recognise that the standard OE studs were / are fit for purpose and the cause of my problem is probably the liner heights.

My only reason for looking at ARP studs was because if I am going to go through the faff of lifting and replacing the head and probably dropping the sump to replace a FO8 gasket or three,  I don't want to be revisiting the same job again.  I know from the last time I lifted the head at least two of the studs are a bit corroded so they will need replacing anyway and for what ARP studs cost, (it's not necessary to pay Moss prices) I was thinking belt and braces.

My reference to 110 lbs ft comes from the ARP instructions that are very specific about the torque values to be used, even underlining them.  I was going from memory regarding the TR WM figures but if they are 105 lbs ft then that is even more of a discrepancy.

Rgds Ian

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Hi Ian,

 ;looking at Mick's explanation that lubricating the threads increase the torque value then your 110lbs ft with grease will be well over the torque for the block threads.

The bolts may well survive such a value but will a corroded 50 year old block.

 

I know what I would do and it would not involve the ARP bolts.

 

Roger

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Something I've often wondered about "dry" torque figures: how dry? When I've been in engine assembly lines, all the parts seem to have a coating of oil, presumably to resist corrosion. Should we degrease fasteners before torquing them up?

Pete

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1 minute ago, stillp said:

Something I've often wondered about "dry" torque figures: how dry? When I've been in engine assembly lines, all the parts seem to have a coating of oil, presumably to resist corrosion. Should we degrease fasteners before torquing them up?

Pete

It all depends what covers the threads and what you call degrease.

As you observed assembly lines call off their parts straight from parts stillages where they will have a coating of the manufacturers anti corrosion gunk. Because it's a controlled environment the torques of ALL fastenings will have been defined and if they can get away with it the manufacturer will include any torque variation required to allow for involuntary lubrication of threads. So their own torqueing regime unless requiring the use of sticky bolts where fastenings are cleaned and a Locktite or other proprietary locking agent fitted (these days bolts have the anti loosing agent impregnated by their manufacturer). So their interpretation of dry is not strictly without any trace of anti rust residue.

My interpretation is cleaning block threads and stud threads with thinners to degrease, wiping dry and then a wet clean of WD40 to displace anything a wipe can't get with a blow out with airline of block threaded holes thrown in. I again wipe the threads with a non fluffy cloth and that's as good as it gets, no doubt there may be a residue in microns on the thread surface but I'm satisfied the torqueing operation is not adversely affected.

As an aside on competition engines with standard race prepared conrods, ( I guess I'm a dinosaur, I have used Carillos for another persons build, their request)  I replace the standard conrod bolts with Unbrako cap head bolts fitted with a smear of Blue Loctite on the threads (no washer) and use the standard torque values...no problems.    

PS: I use Unbrakos fitted the same way for flywheel fitment also, I like my ankles.

Mick Richards 

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On the subject of stripping the thread in the block, I notice that Don H and Stan (Foster461) have both fitted ARP studs to their TR3a engines. Presumably they didn’t strip the block but maybe they didn’t use the recommended ARP torque. 

Rgds Ian

Edited by Ian Vincent
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Hi there,

how do you put the head seal and the cylinder head on the engine?

With the studs in the engine already? Or first seal and cylinder head and second the studs through head and seal?

My father worked as a truck mechanic for a decade and told me they always did it the second way.

This because the first way it can happen, that the threads on the studs work like files and dust/coal in the drills of the cylinder head will fall on the seal.

I did it anyway the first way, with the result that I had to make it a second way with another new seal the way he recommended me,

because coal was falling on the seal and water came out. (I guess I still should have the first seal in my Workshop...).

Ciao / Cheers, Marco

 

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A very good thought Marco. I certainly remove the studs first when taking the head off but that’s because it’s easier. And I put the new gasket in place before I replace them but I hadn’t thought about putting the head back before inserting the studs. Is there anything that you’d need to look out for doing it this way?

rgds Ian

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Unfortunely the original studs are a little bit short to lock a second nut the get them out with the head still on the engine.

But when you remove the washer under the nut it works. I know on the ARP studs you can use a allen head tool.

That's lovely and tells me my dad was not wrong. But I used the original studs again.

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"Is there anything that you’d need to look out for doing it this way? "

 

I fit my 4 cylinder engines head gaskets with a covering of Wellseal (both sides) and on the block and head, so 4 surfaces all of them sticky. There are no dowels on the block surface to locate the head gasket without studs and no way of locating the head onto the gasket accurately when fitting from above, beyond about a quarter of a hole without placing the head onto the Wellsealed gasket and squirming the head around to try and line the holes up.

That risks moving the headgasket position and especially where I may be using cut gaskets with only half a compression ring sealing where perfect positioning is essential.  Fitting the studs with a wrench by winding it in gives you no feel of when the stud has reached the end of it's thread and risks the stud being forced into the block surface under further tightening when torqueing up, that risks starting cracks in the block surface, it also risks nipping the gasket around the stud holes when wound in from above unseen.

You have a cylinder head with dirty stud holes ?... Not on my heads, the holes are clean, rust free and have no debris to be scraped out of them, so no disadvantage to fitting the studs first using them for gasket location and then the head, ...you know, the way it says in the workshop manual. 

I was involved in truck workshops for 40 years and you can rely that mechanics working against the clock will always find a quicker way of doing things, but not necessarily the right way for overall engine reliability. 

 

Mick Richards

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23 hours ago, Motorsport Mickey said:

It all depends what covers the threads and what you call degrease.

As you observed assembly lines call off their parts straight from parts stillages where they will have a coating of the manufacturers anti corrosion gunk. Because it's a controlled environment the torques of ALL fastenings will have been defined and if they can get away with it the manufacturer will include any torque variation required to allow for involuntary lubrication of threads. So their own torqueing regime unless requiring the use of sticky bolts where fastenings are cleaned and a Locktite or other proprietary locking agent fitted (these days bolts have the anti loosing agent impregnated by their manufacturer). So their interpretation of dry is not strictly without any trace of anti rust residue.

My interpretation is cleaning block threads and stud threads with thinners to degrease, wiping dry and then a wet clean of WD40 to displace anything a wipe can't get with a blow out with airline of block threaded holes thrown in. I again wipe the threads with a non fluffy cloth and that's as good as it gets, no doubt there may be a residue in microns on the thread surface but I'm satisfied the torqueing operation is not adversely affected.

As an aside on competition engines with standard race prepared conrods, ( I guess I'm a dinosaur, I have used Carillos for another persons build, their request)  I replace the standard conrod bolts with Unbrako cap head bolts fitted with a smear of Blue Loctite on the threads (no washer) and use the standard torque values...no problems.    

PS: I use Unbrakos fitted the same way for flywheel fitment also, I like my ankles.

Mick Richards 

Thanks Mick. Half a lifetime ago I was involved in strain measurement, and I recall vaguely some tests we made on lubricated versus unlubricated fasteners. Compared to a degreased fastener (cleaned in an ultrasonic tank with Genklene followed by a vapour rinse), the tensile load achieved for the torque we were using increased dramatically with any lubrication, even a thin film of WD40. There was a much smaller difference when the WD40 was replaced by oil, and a further small difference when we tried Molyslip. These tests were done with stainless screws into an aircraft grade of aluminium alloy.

This would suggest to me that unless the fasteners are really thorougly degreased, it makes little difference if they are lubricated or not.

When I was tuning Imp engines Rootes used to advise that studs be lubricated with a Shell Ensys fluid, can't remember which one though.

Pete

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