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MG Midget and Sprite Technical - Cylinder head re-torque

Hi all.

Just fired up the engine for the first time.
Noticed some leaks around the studs and nuts, have them torqued to factory spec at 42lbft. Am wondering if this is wrong for my cylinder bolts?

I have mounted a kit of these, have i misread the description?

http://www.minispares.com/product/Classic/Engine/Cylinder_heads/Studs_bolts_nuts/C-AHT280.aspx?100409&ReturnUrl=/product/Classic/Engine/Cylinder_heads/Studs_bolts_nuts/CAM150.aspxBack%20to

What should i re-torque with?

Thanks
Alex
Alexander Sorby Wigstrom

If you've fitted the ones shown surely you should be torquing them to 55 lbs with oil on the threads? Even the standard 1275 (with dimpled studs) are 50.
john payne

Are you sure you aren't seeing the bubbles of air and oil from the expansion of gases below the nuts? This is often blamed on gasket not sealing. I would tend to torque at 50 lbs ft when stone cold and lightly oiled threads.

Peter
Peter Burgess Tuning

From an engineering point of view their statement "These studs do not stretch, so they pull the head down, not the thread up, this vastly increases head gasket life" is pure marketing BS.
David Billington

As I was posting on a recent thread, over torquing is not necessarily a good thing even if your studs and nuts will take it. It can crush the fire rings, damage the gasket and actually reduce the clamping pressure on the parts of the gasket that matter. That's with a standard gasket. If you use a solid copper or a laminated steel gasket that may be a different matter.
GuyW

On the arp fasteners they state that the hardware must be pre stretched to work properly... considering these are basically knock offs of arp ... id check to see if thats the case also...i know the marketing says there non shrinkable but reality is normally a differant bed time story

42 ftlbs seems low to me also... the arp kit is 50 with there inhouse lube and i think 60 with motor oil...but dont qoute me on the motor oil as lube spec
Prop and the Blackhole Midget

My Haynes book said 42, or at least i think it did. I let the engine cool and re torqued with 50 lbs/ft. When i started it again just one of the studs were leaking. Am thinking of maybe removing the head and redo it all with a new gasket instead of risking this one blowing since i probably didn't set it up properly.

/Alex
Alexander Sorby Wigstrom

Does the stud bubble as soon as you start the engine or after it heats up a little?

Peter
Peter Burgess Tuning

Alex,

When you torqued the head, did you do it in increments? That is, for example, all bolts in sequence to 20 lbs, then all to 30, then all to 42. Then, did you continue to go around in sequence to make sure that all were at full torque?

Charley
C R Huff

Great pojnts both peter and charly

prop
Prop and the Blackhole Midget

I fitted these same head studs believing that they were more or less the same as ARP - they are not!

I had to remove the head and refit it a few months after the original fit, and during the routine 'oiled' re-torque to 55 lbf ft, one of the studs snapped. MS would neither supply a single stud, nor treat it as warranty, so removed them and fitted genuine ARP studs from Peter May and vowed not to use MS again. That was about 5 years ago now and the ARP studs are still fine.

Richard
Richard Wale

Peter, it comes after it heats up a little.

Charley, yes i did.

Richard, well that didn't sound all to nice thanks for the warning!
Alexander Sorby Wigstrom

I think it is just air bubbling through the oil around the studs from what you describe, maybe keep it idling for a good long while, take it for a gentle drive and see how it progresses?

Peter
Peter Burgess Tuning

I think Peter could well be right. I have certainly had the same thing happen, and it is surprising how long it goes on showing signs of bubbling before it fully dries out. But it does eventually.
GuyW

Alright, thanks for the input guys I hope you're right!
Alexander Sorby Wigstrom

Relevant message from a friend:

Head retorque. I'm just doing the H/G on the Capri as it happens, -- sprung an oil leak out the side.

Anyway, in sourcing a h/g, I found a NOS Payen kit.

A-series are Cast iron heads, as are Ford Kent engines.

You may remember in the payen H/g sets you used to get instructions. I do. These instruction apply equally to any C/I head.

It's a bit blurry, but you can just make it out.

CI head /block. It is essential that the C/H nuts/studs be retightened to recommended torque immediately the engine is HOT.

Ally head block. --- bla bla ---- COLD.

GuyW

Just be cautious with gasket material, we have been instructed by Payen the black composite ones are single torque. To be honest we still retorque copper gaskets ( a must) after they are stone cold. I am always wary of distortion when things are hot and the difference in effect of torque when the head cools down again. I suppose the problem with retorqueing ally heads its like when spark plugs are fitted hot in ally and they can pull the threads when they cool down!

Peter
Peter Burgess Tuning

I suppose, that just because it is of Payen manufacture, that doesn't mean they only do the one type. Or do they?

Since so many folk advocate and use different techniques it would suggest to me that the gaskets are actually fairly tolerant of different treatments.

I had a newly replaced head gasket on a 1500 blow within 100yds. But I suspect that my technique was somewhat to blame which is why I haven't recommended it to others.


(I trapped the advance vacuum pipe under the rear of the head when I lowered it onto the studs)
GuyW

This thread was discussed between 27/03/2016 and 31/03/2016

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