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MG Midget and Sprite Technical - Head Stud Woes

Hi, for the first time in ages I had a couple of hours in the garage to refit the head after a gasket change.
Sods law after tightening the last nut I heard a sickening crack, you guessed it, snapped stud (why is it always the last one?).
Luckily it snapped just under the nut so I was able to remove the stud. I did torque them up in stages 25, 35, 50 (I do have the dimpled studs) but they were existing ones.
Do you think its worth the £100 or so for the uprated studs and would I really benefit from them as I only have a mild spec, MG Metro head, twin Hs2's (with a little bit of Vizard) LCB/K & N and an RC40 box or would I be as well to go for the standard studs.
This is all new territory for me so any help/advice would be appreciated.
Mark

Mark Whitmore

Hi Mark,

I am a fan and convinced Gary to get a set the last time his head came off. Two main reasons: they don't stretch (ok they do but not enough to notice) and they are a fit once and don't worry ever again.

I don't even bother to re tighten mine after 500miles...and have never had a head gasket fail on me in 10 years (and 5 years before that in my mini).

you pays yer money etc...
Toby Anscombe

I think it depends on the quality of your car


For my work truck, Id be tempted to go ebay direction myself, if all I needed was a good used cheap one, But on my car, thats a differant story, Ill eat peanut butter and oinion sandwhichs in order for my midget to have the best.

If you have a nice car in great shape, then I would invest in a nice set of ARP studs....if its a friday night beer runner...then ebay baby, or try a MG repair shop, they always have stuff lying around.
and most likely free.

prop

Prop

As Toby said, I didn't bother to retorque mine and had 7000 miles of trouble free motoring including thrashing it as hard as I could around a track.
Same old Gary

It is amazing how tough these engines are and the abuse they can take....


prop
Prop

Mark.

I would certainly go for the better quality ones. I think Swiftune carry the ARP ones in stock or MiniSpares stock their own (which are still very good but not as expensive).

As Cosworth ALWAYS specify, lubricate....!

I use engine oil on the threads and an anti scuffing paste (usually supplied by ARP) on the contacting faces ie washer to nut. Torque in equal stages and re-torque after the engine has been thoroughly warmed up and cooled overnight. To re-torque, simply slacken each nut (or bolt) by 1/4 of a turn and bring back to it's correct torque setting. Do this in the correct sequance and you should have no more worries.

Mark.
Mark Boldry

First check that torque wrench ! It's reasonably common for them to vastly under or over-read after a few years of abuse, which includes not zero-ing them after EVERY use. Always assuming it was accurate in the first place which the cheap ones often aren't.
David Smith(davidDOTsmithATstonesDOTcom

Which is why when I lent my 3/8 and 1/2" snap-on torque wrenches to a friend and they came back after a week wound right to the top, I wasn't happy.

Nick

NEVER lend your 'Good' tools out....!

Mark.
Mark Boldry

Well I think thats sold me on that one, uprated studs it is!!
I did find that the one of the 4 smaller rocker studs had the threads stripped whilst torquing up to 25 lb ft(these didnt have a dimple on them if that makes a difference) so I'm wondering if its a case of poor quality studs or a torque wrench thats out of whack? after all I dont want to strip/snap the new studs.
I did pick the wrench up from an autojumble and it is an older one suppose I thought that if it was made back in the day that it would be made well.
Mark
Mark Whitmore

Mark,

Just to give a contrary view I have built 4 A series engines and have always used the standard head studs. Never had any problem with them. I wasn't building race engines but fast road engines which did get hill climbed and weren't given an easy life on many occasions. Maybe the quality has dropped in recent years though as the engine has gone out of production and other suppliers are producing substandard parts, the last engine I built was around 1988.
David Billington

David.

1988 is 20 years ago...! The studs that were made in the 1960's and 70's are now very old and fatigued, back then they probably still had some 'life' in them. I still think that taking the risk is not an option, just think of all the cursing and hassle IF another stud broke just because we (as the BBS) suggested that Mark used crap studs....

Mark.
Mark Boldry

Mark,

I didn't necessarily recommend reusing the standard studs, although I have done, I was just commenting that I have never had an issue with a standard one new or used. The longest I have had a set in use holding down a head was about 55k miles then the head failed, same studs used then to hold down a different head.

I have read recent comments on poor new fasteners which is why I mentioned the year of the last build.
David Billington

I have used standard studs on race engines without problems.

They were original equipment, though. I bought a load from Roversport in the early 90s. Still have a few ;o)
Dave O'Neill 2

David, I have to admit I have used standard studs many times on engines without problems, but given the choice (and budget) I would always prefer to use ARP but at over £100 per set, I think a lot of folk would stick with the originals. One more thing that nobody has mentioned and fair enough, it is not stud strength related, is the head and block faces should be clean and flat, preferably newly machined, but that's not essential.

Mark
Mark Boldry

Well all the boxes arrived this morning, I opted for the ARP studs as a late Christmas bonus came through and I thought what the hell!! (I also ordered an oil cooler/ stat kit as I do a fair few motorway miles)

My second question (the second of many I presume) is that the instructions with the stud kit give torque recommendations which state:

'Torque values are based on 75% of the fasteners yield strength. Use the manufacturers torque sequence but NOT the engine torque specs. Torque the nuts to 40 ft. lbs for ARP moly assembly lubricant or ARP thread sealer or 60 ft. lbs with 30wt motor oil.'

I thought these studs were designed to use a higher setting as per drilled or 22 marked studs?

Now I am confused!

Mark

Mark Whitmore

I think (but I may be wrong) that as the ARP studs stretch less, that there is no need to tightenen them as much as the others.
Same old Gary

Maybe I have been doing it wrong for all these years, but having built many successful racing engines I would like to think not. I use 'manufacturers' torque settings with the ARP molly on the thrust face of the nut (or bolt head) and engine oil on the threads. Always seems to work for me.

Mark.
Mark Boldry

As per Mark - use oil to lube otherwise your torque settings will be all over the shop.

I can't remember exactly but I think that I tend to use the Hanyes settings rather than working out in my head. This assumes that you have a good wrench!
Toby Anscombe

I reckon it's down to the efficiency of the ARP lube as a lubricant and being much better at its job in this case than the 30wt oil. Part of the torque normally applied is just to overcome the friction in the threads and the nut face and doesn't go to stretch the bolt, if you use a good lubricant then less torque is required to impart the right "stretch" to the stud. In the case ARP mentions 75% of yield strength so the stretch in the stud is not permanent, I think the standard stud is the same in that it should not be yielded by the tightening torque and both ARP and standard should go back to their normal length once the load is removed. As to ARP stretching less for a given applied load that would only occur if the stud was physically larger, if the ARP and standard stud have the same dimensions then for a given load they will stretch the same, the strength of the steel having no effect.

Mark Whitmore, I would suggest if you query the instructions, having spent the money on ARP then I would ask ARP to verify them and explain why.
David Billington

I have ARPs on my engine much to many people's recommendations. I would personally use them everytime because I've never heard a bad word said and it's just not the bit of the engine you want to 'shake apart'! It's funny that whilst many of us insist on the use of ARP bolts for the engine, many of us are still coping with the frankly appauling engine mounts that the Midget has.
Rich Amos (1330cc Blaze Red '72)

This thread was discussed between 04/02/2008 and 06/02/2008

MG Midget and Sprite Technical index

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