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MG MGA - Head Studs GRRR!

Well, I knew I probably shouldn't have tested my luck but I did. I went to retorque my head studs down and on #11 on the second pass, JUST TO MAKE SURE, it snapped.

I just ordered new head studs and as of right now I'm faced with two scenarios.

#1: Take the head off, get a tap and stud installer, clean the threads in the block (which wasn't done when I first installed these studs) and then reinstall the head.

The problem I have here is that I really don't want to install a new head gasket. I have another copper head gasket but it got dinged up in the packaging (i.e. not necessarily as flat as I'd like it to be). SO, is reinstalling the not so mint condition new head gasket better than trying to reuse the other head gasket or should I just try to use the old gasket?

I really think this is the best option, but I guess what the real question is how good does a 'new' head gasket have to be (i.e. how flat) to not fail prematurely? I don't want to go through all this stuff only to have to redo this another 1000 miles an then chance snapping head studs after retorquing again...

#2 option is try to get the end of the head stud out and then just install a new head stud into the hole. Hardest part here will be getting the old broken stud out. Then I have 7 tried to get a stud that will torque down.

What do you guys think is the best idea? Only last question I have is do you have to drain the coolant to remove the head? I was going to change the oil before the head sheared so I guess changing coolant would be good anyways? Thank a bunch in advance. -Jamie
Jamie

Hi Jamie. You need to drain the engine coolant from the block, if you intend to loosen or remove all the cylinder head nuts. Coolant gets pumped through the engine block and cylinder head, so if not drained prior to loosening or removing the cylinder head nuts, antifreeze will leak into the oil pan, and contaminate your motor oil. If you can get the busted stud out without removing the cylinder head, then yes, you can safely re use the old head gasket with no problem. If you have to take the head off the block, then as a precautionary measure, I would definitely use a new head gasket. Cheers and Merry Christmas! GLenn
Glenn

As Glen said use a new head gasket. How much is your time worth and the inconvenice of another blown head gasket.
JEFF BECKER

Jamie,

In addition to the sage advise above, don't forget to use antisieze on the threads when replacing the studs. Have the threads so very clean that you can bottom out the stud in the block,turning them by hand. For final reassembly, back stud off 1/4 turn from dead bottom. This way, if a stud does break in the future, it is easily removed with fingers.
Paul Hanley

If the new head gasket I have is copper but has a few handling dings or has been bent in the middle (while in the cardboard) is that still ok to use?

I definitely didn't know about cleaning threads 5 years ago and I have a feeling that is why I'm having so many problems. I think that while I'm waiting for the new studs I'll try to get that old one out and if I do, then great, but if not I'll just use that new headgasket and hope that between the gasket dressing and the weight of the cylinder head it will flatten the imperfections out.

Thanks so much for the great advice. -Jamie
Jamie

Hi Jamie. Is your other head gasket solid copper, or is it copper sided with an asbestos center section laminated in? A few tiny dents, or a slight bend in a solid copper gasket might be acceptable. Such defects in a head gasket of laminated construction could well cause problems though. Since pulling the head is labour intensive, I would take no chances with a potentially defective head gasket! If there is ANY doubt as to it's integrity, please purchase and install a new head gasket! The aggravation of doing this job a second time easily justifies the purchase price of a new head gasket! Cheers! GLenn
Glenn

And buy a Payen gasket - more expensive, but MUCH more reliable, and they only need one torque down!

Did I just hear "sold"?
dominic clancy

These engines often 'pull' the top thread in the block, which means that you won't get a good clamp on the new gasket.

Remove all of the studs and very slightly countersink the holes in the block - a cone reamer in an electric drill works well for this.

Then reinstall the studs as Paul suggested and you should be fine. As others have stated, the cost of a new gasket is pretty minor compared to the aggravation of having to pull the head again.

As for crimped gaskets, I recall routinely buying the special competition composite head gasket from Leyland ST for the race car (when they were still around) and one of these very expensive geaskets showed up at my local dealer in a rather interesting form. The moron in shipping in Burlington ON had obviously lacked a proper shipping container, so he simply folded the gasket in half so it fit what he had.....at least I didn't have to pay for that one!
Bill Spohn

Payen gasket...one torque down?

My question now is what is the point of retorquing head studs. I know this topic has been debated on many different forums by many different people, but was just curious as to what the arguments for one side or another is.

I keep talking to my parts supplier and he says, "These new studs are Rover studs." Well, Rover studs can't take 45 ft-lb is what I'm finding out. I'm thinking that what I should do is just pull the head, clean the threads out (which should have been done in the first place), and put everything back together.

I need to get a tap and die set in my collection anyways...
Jamie

Hi Jamie. As I understand it, the head nuts are torqued a second time to make up for gasket "squish" When you initially tighten the head nuts, the head gasket gets compressed. Even after the nuts are fully tightened the gasket still continues to be compressed a bit, and "beds into" the surface of the engine block and cylinder head. As this gasket continues to compress and bed in, and the engine is run, it leaves the head nuts a bit looser than when they were first tightened. So then you retorque the head to ensure that the gasket is fully compressed thereby ensuring that the gasket will hold the necessary cylinder compression, and that it does not leak coolant. Since the gasket does compress , that means that valve adjustment changes a bit also. Therefore, the valve clearances need to be checked, and adjusted again (if necessary) after the head is retorqued. Hope this helps! GLenn
Glenn

I believe the correct way to clean the threads in the block is with a thread chaser, not a tap. The thread only cleans and straightens the threads. A tap cuts a sharp groove in the block and can cause weak points. You can get a thread chaser at Sears, Napa, or any decent tool supplier.

If I recall, didn't the factory recommend oiling the studs before installation? Definately back them out 1/4-1/2 turn from fully seated! Or you can spend big $$$ on the ARP studs and not ever have to worry about them again!
Jeff Schlemmer

Dominic...the reason you heard "sold" on the Payen gasket is because the 'spare' gasket I have is a Payen!!! I didn't know until I looked at it's condition. This is the gasket that is 'a little beat' and that after looking again, I feel can more than likely be used without having much trouble.

I always refer to a tap as something that either makes or cleans threads. If the threads are already there and you don't crank down on the tap, it should 'chase' the threads instead of cutting new threads. Do they actually have tools that distinguish one from the other?
Jamie

Jamie. I, too, have questioned the "thread restorer" when I have seen it recommended. There is such a tool for bolts and studs--it forces the deformed metal back into the threaded area.

I cannot, however, find a "thread restorer" for internally threaded holes. The Rutland Tools catalog does not list such an item. Nor do J&L Tools. They only list a variety of standard taps for threading holes, all of which are capable of removing metal (as is their design). Thus, among the catalogs for professional machinists, an internal "thread restorer" is not recognised. I have always used a regular tap, taper, plug or bottoming, as the job required and have had no problems.

I have had one problem with a Rover brand head stud breaking. Chris Betson, who posts on the MGB boards and owns Octarine Services, sells the custom made head studs he uses in his engines through his website. Do not have the url to hand, but a Google search for Octarine Services should take you to the website. I have purchased a number of parts from Chris and have been very happy with the quality of parts, service and the prices.

Les
Les Bengtson

Both Sears and Snap-On sell thread restorer sets that include taps and dies. Both are about $40. Not sure what makes them different from those for cutting new threads. Perhaps the material spec is relaxed a little, or maybe 2-flute vs 3-flute for chip removal.

G Goeppner

G. The only difference I can think of between a "tread restoring" tap and a standard tap would be the tolerances. Taps are made in three styles--taper, plug and bottom which differ in the number of tapered flutes at the bottom of the tap. More taper makes it easier to align the tap in the hole when tapping by hand. But, depending on how deep the hole is and how far the stud/bolt has to go into the hole, a taper tap might not cut threads deeply enough. Hence, the plug tap which has significantly less tapered front end and the bottom tap which only has the lower two threads tapered. You can, if careful, use a plug tap to tap a hole, but a bottom tap is only used to clean up the bottom most threads of a hole already tapped with a taper or plug tap.

Taps are made of either carbon steel (normally blackened) or High Speed Steel (HSS). The carbon steel is less expensive, breaks more easily and, if broken, is easier to break out. HSS taps are somewhat less likely to break, cost significantly more and are normally silver in color. HSS taps may be had with certain coatings applied which make production work go a little faster. Taps are available with no flutes, two flutes, three flutes and four flutes depending on how large the tap is in size and the material it is designed to be used in. For automotive use (i.e. cleaning out existing holes which have already been tapped before) the carbon steel taps, with two or more flutes, will work just fine. Get the collet type tap holder in the 0-1/4" and 1/4"-1/2" size and most projects can be accomplished. A good tap handle will make tapping, or retapping, a hole much easier with less possibility of damage to the hole or existing threads.

On dies, the normal die is designed to be used in a handle, called a die holder, and the die is adjustable. By being able to adjust the die, you can cut a minimum depth of thread on the workpiece, test fit it to the hole, then, if necessary, cut the thread deeper to produce an exact fit between the threaded piece and the hole it is to go into. There are various dies made for "rethreading" with are either a round die (used in a die holder) or a die having a hex shaped exterior. This type of die is non-adjustable and is normally made to cut the deepest thread allowable. This way, it will clean up any existing thread of its size. Both of the "rethreading" dies can be used to cut threads in a non-threaded workpiece, but the fit will be somewhat looser than would be had if an adjustable die were used to cut the threads.

Thus, while it is perfectly possible to purchase a kit for "thread restoration" all of my available information is that the "thread restoration" taps are exactly the same as the thread cutting taps and the dies only differ in that the restoration dies are non-adjustable. Standard taps and dies will work just fine for thread restoration in automotive use.

I am neither an engineer, nor a machinist. I have, however, been a "machine tool user" for over 20 years. (A machine tool user is someone who performs a number of different mechanical operations only some of which require the use of machine tools. A machinist will, normally, focus on the use of the machine tool to produce parts with others doing the gauging, finishing, and fitting of the parts made.) Thus, these "thread restorers", of magical properties, seem to exist more as a marketing scheme than as a real object.

Les
Les Bengtson

Jamie,

I'd recommend replacing all of the studs. Over time and after several installations they become brittle and stretch. Remove them all, clean the threads and countersink all the holes. A new set of studs is less than $40 and replacing them all will save you the headache of having to do it all again. After all, if one was old and brittle enough to snap, assume they all are.
Craig Cody

Hang on just a moment before you go tearing the motor apart again. Has anyone thought of trying to take the remaining part of the stud out without removing the head as it will probably come out fairly easily. Get a fairly long drill and put it into a tube sleeve which is a fairly good fit in the head and also a good fit on the drill. Make sure that the tube protrudes above the head face. Now gently drill down into the stud stump for say 1/2" then remove the drill and the tube and blow out any swarf. Now using an easy out of sufficient length remove the stub which should come out fairly easily. Now fit the new stud and retorque. All studs can be renewed and replaced using locknuts to remove them. If only one is removed at a time there is no need to drain the coolant and as the head is not being disturbed then the gasket is no longer an issue.
Iain MacKintosh

Hi Les. I stopped at Sears last night to look at their thread restoring kit. The taps are like a bottom tap, and have 4 reliefs for chip clearance. The dies are not adjustable (not for $40 the set!), and also have 4 chip clearance slots. I say "chip clearance", but there can't be much residue during use, except that they are suggested for rusty/painted thread clean up. I suspect you're right in that they probably have a looser tolerance specification, a slightly different dimension to avoid thread cutting, and a bit of marketing hype to sell more product!

George
G Goeppner

I suspect that the taps you have seen George are Carbon Steel which would have a very short life if actually used for tapping new holes. But for thread cleaning and minor repair work they will be just fine. Taps are all made to cut an exact thread form and there is no tolerance variation catered for.

Additionally what you have seen included for external threads is what is called a Die Nut which once again just cleans up the thread profile. Sets of cutting dies usually have a split incorporated so that when fitted into a handle and cutting a thread in stock bar this can be adjusted by means of grubscrews to give the exact size / profile of the specified thread. Alternatively a die nut can be used for the final cut on smaller diameters to ensure that the thread is cut accurately. With larger diameters hand cutting dies are usually in two parts which assemble into an adjustable hand lever
Iain MacKintosh

This thread was discussed between 24/12/2005 and 04/01/2006

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