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MG Midget and Sprite Technical - Head studs

Head studs.

I have 4 (long) with drill points on the top of them, and 5 (short) without drill points on them.

The WSM says to torque head studs to 42lb unless with drill point then it's 50lbs.

I was expecting them to all to be with or without drill points.

So can those that know about these sort of things please tell me which get torqued to what please?
Nigel Atkins

There were various different studs produced, over the years.

Some of the short studs - possibly A+ - had a letter Y stamped on them.

Do yours have anything at all? Are they new studs, or what you already have fitted to your engine?
Dave O'Neill 2

Hi Dave,
I've only noticed the drill points, no '22' or 'Y'.

All the studs are in there now, I assume they've been there since I got the engine (car).

I bought the car for the Heritage shell and the engine in it that was supposed to have only 50 miles from a lot of engine work being done but it was without it's number so who knows what it is and where it came from. I treated the engine as such and ran it in progressively over 2,000 miles. At some point I checked the torque on head studs nuts, noticed the drill points - and then I can't remember, did I check the other studs for drill points, can't remember, were there weren't there drill points on the other studs, can't remember. IIRC I checked all studs at 50, I don't remember having to tighten them.

12 years ago, after 7,000 miles on the engine I had a HGF, so perhaps I did wrong by checking the torque, or torquing all to 50 or perhaps it was just bad luck. HGF happened on our way to a weekend tour of Norfolk/Suffolk but I carried on I'd had HGFs before and knew we could make the tour.

Gasket replacement (and head skimming) was carried out by a local motorsports place and IIRC I had them checked the torque after x-miles/cycles.

Actually Dave you might be one of the very few to know the place that done the engine work (assuming it was on this engine which most things points to it is) -
Autosprint, Duke End Farm, Coleshill.
Nigel Atkins

I know of them, but never really had any dealings with them.

I know they were in Birmingham city centre about 35 years ago, but moved away.
Dave O'Neill 2

Dave,
there was no details on the paperwork I had other than 'Autosprint' and at the time I tried to look them up and eventually found an address but they seemed to be out of business.

Just now I done a web search and to my great surprise there's a web site - http://www.autosprint.co.uk/
Nigel Atkins

Nigel, so your engine was built with both types of studs? Its important that they are all to the same torque so you would need to do them all to the lower 42 ft/lb figure. Uniformity is more important than just a high torque setting and its very easy to overtighten and crush the fire rings in the gasket.

I was going to ask if the shorter dimple-less studs were fitted upside down, but the threads are different, aren't they?

Or get a complete new set of studs.

I cannot believe that you have taken the rocker cover off to check the studs! That involves holding a spanner and getting hands oily. Doesn't fit with your usual attitude to car work. Perhaps you can be excused if it was only as part of a 12,000 mile service to check tappets as listed in The Handbook.
GuyW

Guy,
I don't really know and can't remember about the studs, as you can imagine I personally have never changed them. I did consider getting a new set, but too late now.

Studs are coarse thread to block fine for nut, I know as one came out.

I could say I took the engine apart to see how it operates and have the 'fun' of taking it apart and 'fun' of putting it back together again but it was because of (yet another) HGF.

I of course willingly do whatever service work the 'good book' decrees and check the valve clearances every 12 months (or 12k-miles) even if I'm not the most consistent with my results.

It was suggested I get the Metro Turbo gasket so that's what I did, Payen BK450, got it from Mini Spares as they had it in stock and at a good price (apart from their P&P).

On looking at the gasket that had failed guess what, it is a Payen BK450.

On the new gasket packaging was a sticker which by the look of it *I guess* Mini Spares put on, see below.


Nigel Atkins

Nigel, you can at least check if the studs have 'drawn' the block surface up. Clean the block ready for fitting the gasket but then stand a steel rule in its side along the head, against the line of studs. Check to see that it is in uniform contact with the head and that no gaps are showing. If necessary, shine a torch at the ruler/ head contact from the other side and look for light escaping under the ruler edge.

It won't fix the problem, but hopefully will eliminate that as a source of your repeated HGF.

I am still a great believer in NOT overtightening head bolts. Its so easy to be tempted to ' add a bit for good measure' This then crushes the fire rings and spreads the pressure of the head over the whole surface of the gasket, instead of concentrating it on the fire ring areas where it is needed. It actually reduces the clamping pressure.
GuyW

Thanks Guy, checking with torch would be a waste with my eyes, feeler gauge if they go thin enough perhaps.

The gasket very obviously blew between 2 and 3, why this happened on "an exceptionally good gasket" as Mini Spares describes it, I've no idea. It blew enough to mark the cylinder head so that needed skimming (or whatever the correct technical term was), that makes twice with me plus when the engine was done (block was also skimmed then).

I'm with you thinking that the studs should be all at the same setting and not overtightened, I've no idea what the previous gasket was set at, the 50 I done was for the original gasket that I done 13 years ago. This time I've borrowed a torque wrench from someone that works at an engineer place. 12 years ago I borrowed my neighbours torque er, can't remember what they're called, not wrench, not (torsion?) bar, I suppose it is a wrench but I'm sure they were called something else.
Nigel Atkins

This thread was discussed between 16/08/2020 and 17/08/2020

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