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Grahamgl

Angle torque

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Gentlemen,

I have had new pistons and liners fitted to my 4A and have now done 500 miles and was told the head would want re-torquing when the car had done 500 miles.

My grandson who is an HGV mechanic is coming this weekend to bring me his certified torque wrench to use to do the job. He has just asked me what the angle torque is for the car as well.

Can anyone help me with the information please?

Thanks

Graham

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Graham,

 

I think only some moderns have a Torque angle, never heard of it for a TR.

 

Cheers

Graeme

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Normally a torque angle is used where a lubricated or stretching fastening is in use.

It's arrived at by a given torque being applied to the nut or set bolt ie 50 lb ft and then a further set angle of 60 deg for example, being measured of continuing movement. The angle measurement ensures a relatively accurate torque is applied to each fastening especially usful where a bolt is encouraged to stretch to apply a " fixing" force to it to prevent it loosening, often used these days on more modern designs as Graeme says. This " angle" torque application allows the fastening to apply torque unencumbered by many of the competing forces that can cause a variance, and give a more even clamp across the item being torqued.

However when these engines were designed and built ( 1950s for the builds starting, and the design is a throwback to an earlier age) the thought of angle torque application was something that woke engineers up with a start from their sleep after a particularly heavy drinking bout accompanied by some rich cheese, a bit like the present occasion actually !

All TR torques are quoted "dry" ie not lubricated, and although from memory some of the later TR4a con rod bolts were of the stretch variety (although reusable a limited number of times) the cylinder head nuts and studs, if original and not some of the very nice ( and expensive) ARP fastenings sometimes offered, are fitted dry and with a side order of " clamp that you bugger" of your very best 105 lb ft torque applied to it.

It's to be hoped the original torque was applied in at least 3 separate and graduated clampings something like 30-80-105 to help prevent gasket shuffling and build up of stiction ( sticking friction) causing a torque variance of the clamp. However the method for a retorque remains as follows, release the torque on the fastenings ( nuts) by one flat using the torquing sequence (that's to prevent any stiction giving a false reading) and then retorque the head up in the approved torquing sequence in one movement back up to 105 lb ft. If you mark the nuts with chalk prior to releasing the torque you'll find the finished position after torquing back up may be in order of a flat or two more than it's original position where you marked it. It's not unusual to find the amounts vary over the fastenings on the head ( that's because the torque us applied dry and not as an angled torque, who said modern engineering practices were crap ?) however Triumph designed it as a dry torqued clamp and considering many engines happily perform over decades giving good power and reliably it gets a big thumbs up from me !

 

Mick Richards

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