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Cylinder Head Studs


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I`ve got a snapped cylinder head stud in a 4 pot block.  The 91/2 ins stud Item 14 on the MOSS Catalogue diagram.  Snapped at the top of the UNC thread deep in the block.

Machine shop proposes drilling for next higher thread diameter, then making a stepped bespoke stud to avoid any alteration to head.

Does any one know what grade metal the studs are made from please?

 

Grateful for any advice,

John

 

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+1 Can be done, the helicoil will allow even larger torque safely than the standard thread. And yes, I’ve drilled and tapped a 16mm hole and made a stud to fit it previously, so depending on which hole there should be material there.

Mick Richards

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1 hour ago, Bob Smith said:

John, The material for all the head studs is EN16 - do not know the modern equivalent specification

Do not forget heat treatment I suspect for the finished stud.

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To drill the broken bolt in the block for example 9 mm and use a Linksausdreher does not work?

Some heat, some WD40, some gentle hits with a hammer may help....

Did it ripped off because of too much tension or because fixed by rust in the block?

Perhaps you are a lucky guy in your bad luck.....

 

Edited by Z320
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Evening chaps,  thanks for the suggestions and data.  All much appreciated and providing a little more confidence there`ll be a solution.

The Forum came to the rescue again.

The stud was a re- used original stud and went in during a total engine rebuild about 12 years ago.  they all went in with a dollop of copper grease at the bottom, and the others came out freely.  I think this one may have turned down when torqueing the head and locked against the bottom of the hole.  Maybe assisted by some overstressing, earlier in life, it gave up the call to come out this time.

I shall be off to the machine shop early tomorrow to suggest they try to get a helicoil in to take the original size stud.

Thanks again. I shall report back the result in due course.

Stay safe,

John 

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WD40 useless as a penetrating oil - it's a Water Dispersant (No. 40 to be tried by NASA) 

"A dollop of copper grease at the bottom". - of the block hole, I presume.  Was there a groove in the threads, to release the hydraulic pressure as it was screwed in?  If no, no need to bottom, surprised they didn't all seize.

A machine shop should be able to drill it out, without damaging the thread in the block.    Or, WELD a bolt to the stub, if that is possible.  The localised heat will help release it, much more effectively than any gas axe.

John

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2 hours ago, Adrian Fuller said:

When fitting the cylinder head studs in the block is it a good idea to coat the unc threads with copper slip or any other grease? 

This question has been asked a number of times.

It sounds sensible to coat them to hold back any corrosion but!!!  A lubricated thread will cause the stud to have more load on it from the torquing process.

These studs have a torque load with a dry stud.  Have a look in the Work Shop Manual.

However I'm not sure what the difference in torque loading would be between dry and lubricated.

I would tend to lubricate but do NOT put excessive amounts of grease down the hole - you may end up with a hydraulic lock and cause issues.

 

Roger

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Hi Roger,

currently on my old engine all studs I found easy to spin out and more or less "oil wet".

Only the one on the right side on the front was not possible at all to move and I stopped far before I stressed it or ripped it off.

Some heat with the propan flame helped LOVELY, it moved with a "dry clonk" and I found only this thread dry.

All of them have been slotted, to brake the hydraulic lock, as I learned from John above.

I always thought (I've never been told this) the studs are UNC down in the block and UNF on the top because when this is torqued up

only the UNF nut on top will move and not the coarse end in the block - to keep us free from problems with studs locked in the block?

Have I always been wrong?

Ciao, Marco

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There's always a concern with studs, they do transfer part of the torque load down from the head nuts into the block. This is why the recommendation is to only screw the head studs in by hand and NOT to tighten them into the block to avoid further possible torque transfer causing shear problems.

Mick Richards

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I've been looking at this issue as I have been putting the head back on the Midget. The problem is that there are as many different opinions out there as there are forums and posters!

After advice here and from MG forums, and talking to a very good engine builder I know I decided that a very light oil of the end threads on both the UNC end of the stud and UNF nut was the way to go and, because 5 of the 9 studs (the short ones) on an A series engine go into threaded holes that go right into the water channels and as recommended by the engine builder, I also used a small amount of sealant around a couple of the top threads on each of those 5 studs. He also said that the stud should be lightly torqued into the block and not be only finger tight, so I did them to ~8-10 lb ft as I felt the 15-20 lb ft he recommended was too much. I then torqued the head nuts to 40 lb ft as per the book. I've still to refit the carbs and before that whilst the manifold connection is accessible, I'm going to fit a new stainless exhaust. Hopefully all will be OK when I do run the engine.....

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  • 4 weeks later...

You may have already solved your problem, but another way to approach this is to get some copper pipe with an OD similar to the ID of the hole in the block (a tight-ish fit is good), lightly drive it into the block and drill the seized stud. Once you have a small hole drilled through the stud, you can go up a size at a time until you can get a suitable EZ-Out into the stud.

Another alternative is to drill through an old stud to use as a guide in a similar way.

Left-hand drill bits can also help, as the slug will sometimes unwind itself once the remaining 'walls' are thinned out..

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Any engineering firm will remove this cheaply. Even yourself if you have a largish drill stand machine or a miller with enough space between block deck and drill chuck face to set it up.

 OR buy (or you maybe have) the old fashioned hand drill stands where the hand drill is converted into a small drill stand.

Z320 ....Marco is good at this (and lots of other things also). As long as the drill will pass through the drill stand base (if solid...drill it out...using the hand drill until big enough with ample clearance 5/8th dia maybe, turn a drill bit down on a lathe).Fit the drill to stand and clamp the drill stand to the block deck (using the head studs with clamps or across lock straps or whatever). Position the drill and stand roughly over the stud hole and pinch a knob of plasticine or your choice of soft slightly sticky retaining dough onto the chuck jaws (closed together). Then insert a small knob pin or needle into the plasticine and start the drill at a couple of hundred revs or whatever speed, press the bottom spinning end of the pin outwards (finger/pen/knife edge ...whatever) so it describes a spinning circle (the same dia as the stud hole in the block) then position the spinning needle point directly over the circumference of the hole (slide the entire drill stand and spinning drill around by hand until you centralise it over the studhole) and clamp the drill stand in position. 

That should then have a centralised drill within a few thou of centre directly over the stud hole, and using a suitable small dia drill (or centre drill if you can get one long enough) spot a centre hole onto the stud and open it up with subsequent dias until you drive a flanged stud remover NOT an easy out (they are too hard and the left hand thread is a stress raiser almost guarenteed to shear) This is the sort that works well

The nut slides onto the fluted shaft which you can use a socket and wrench on, no stress raiser and the larger size can accept lots of torque...it will come out.

Mick RichardsStud extractor.jpg

Edited by Motorsport Mickey
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Mickey,

Two interesting ideas!  Your method of centralising a drill stand understood.

But "flanged stud remover" gets nothing on Google that lloks like your picture.     How does it work?

John

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1 hour ago, john.r.davies said:

Mickey,

Two interesting ideas!  Your method of centralising a drill stand understood.

But "flanged stud remover" gets nothing on Google that lloks like your picture.     How does it work?

John

Hi John,

Check on Amazon, there are normally 2 or 3 different sets of differing qualities here is one

HAZET 841/25 Stud Extractor Set - Burnished/Oiled : Amazon.co.uk: DIY & Tools

1865021704_Flangeextractorset.thumb.jpg.bde904194b3dabb6fa41d75f6c7a507f.jpg

Sorry can't get the link to copy but you should find it under the name.

mine is a Neilsen set also from Amazon which cost £30 ish about 3 years ago...works fine.

Product description

Product advantage 2 / application: - For turning out broken bolts and screws 6 to 15 mm ∅. Plastic box. Surface: burnished, oiled. 25 pieces, in plastic box. Net weight: 0.66 kg. For turning out broken bolts and screws. Application: - 1. Bore up with drill and tapping sleeve - 2. Insert grooved stud extractor - 3. Put on union nut and screw out broken bolt or screw. Number of tools: 25 Stuck.

The method is the set is a collection of supplied drills with slip over centralising sockets if the stud is sticking up, you use the socket to drill through centralising the drill bit with it.

1598057520_Drillingthroughsocketintostud.thumb.jpg.0873bb702a6099e38d7c010fbb8ef3d6.jpg

When the appropriate hole size is selected and drilled into the broken stud use the appropriate fluted extractor (set of 4 supplied) which core dia suits the hole drilled (all are marked) and drive it into the drilled hole.

 

The flutes supply good drive and torque is supplied by using a slip over fluted drive nut (as shown in the photo in the last post) and then a wrench on the nut.

414895691_Slideflangednutoverstud.thumb.jpg.b4200287709f2cdf5083094ed12ab6cd.jpg

If the broken stud is really tight I've even used a torque wrench to apply the torque to the slip over fluted nut at a suitable torque to the fluted stud dia, just as you would if it was a threaded fitting.

The fluted stud is cunning, the flutes run the full length of the stud parrell with it's core...no change of direction stress raisers like the accursed and falsley named "Easy outs" ha, they bloody explode when torque is applied to them unless the broken stud is only finger tight. A broken Easy Out is harder than the hobs of hell and needs stellite drilling out or spark eroding...don't go there.

1590226750_Studextractorfinish.thumb.jpg.47af8e759298ce64861d6ccffeea7ea7.jpg

So far I've 100% success bringing out broken studs with my fluted set.

Mick Richards 

Edited by Motorsport Mickey
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Stud update.

 

So far sorry to say I have no update, the first machine shop prevaricated for a couple of weeks and after a number of prompts and a further couple of weeks decided, "we have`nt the machine that can do it."  This is a business long established, 60 years that I know of, and that I have used several times before.  I interpret this as that they can no longer be bothered with small, one off jobs.  However they are still happy to do heads, valves, and cranks!

The block has now been left at a small one man machine shop very local to me, and from where I have had work in the past.  He seemed very sure that he would provide an answer, but I`ll have to wait in the queue!  I am leaving him in peace with space to work and keeping fingers crossed.

I will report back when I have good news, I hope.

John  

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