16 replies to this topic

[flamenco]

Hi boys (& girls )

So, I replaced my mini's head gasket last febuary. I torqued the nuts to 50lbs ft and after about two journeys, I checked them again with a torque wrench at 50, but none of them needed retorquing, none of them moved before the wrench clicked.

Last wendesday I was talking to a local mini engine expert, and he hold me that the correct way to re torque the head nuts is to first slacken the nut, and then torque it again, doing them one by one. I.e slack one nut, and re torque it, obviuiosly according to the sequence.

What's your opinion regarding this? Will I distort the gasket by slackening the nuts? Or is this the correct way to re torque the head?

thanks in advance

Jeremy

Edited by flamenco, 05 April 2010 - 06:07 PM.

[L400RAS]

No, dont undo the nuts, not even slighly. Composite gaskets do not like this metod one bit.

If you didnt re-torque after 2 mins of running and letting it go cold, i wouldnt bother re-torquing at all now.

[HARBER07]

I just do mine to 60lbs and leave it. Never been a problem for me.

[samsfern]

i usually get it up to temperature, then i slacken them a quarter of a turn, then retorque, one by one, to 55ftlbs, whilst its warm, never had a prolem. different people have different ways of doing it though.

[Surfbluegarage]

i do it exactly the same as samsernie never had a problem. run it up to temp then let it go stone cold then do that. only one by one tho.

[flamenco]

mm don't know what to do.

Still confused!

I think I'll just leave it, and hope it doesn't blow again!!

[samsfern]

i retorque mine whilst its still warm.

although, i just had a look in the haynes manual and it doesnt say anything about retorquing it. Should be fine just as long as your not using new elastic headstuds.

[dklawson]

Sorry, I agree with the builder. I was taught to loosen the nut about 1/4 turn, then go forward again until the desired torque is reached. This is done one at a time following the normal tightening sequence/order.

For other A-series discussion on this see the link below:
http://www.british-c...90242562912.htm

[bmcecosse]

Sorry - don't agree - re-torque when the engine has been first run - but while it is still hot! And DO NOT slacken off - just pull the wrench round to the desired setting. However - that 60 ft lbf is FAR too much (and 55 is too much too) - 50 ft lbf is plenty, and even then - only with either the later flanged nuts or with the early plain nuts with the 'competition' washer set under the nuts, and oiled threads of course.

[HARBER07]

As said above, people do things differently. I've done many head gaskets and none have ever failed.

[dklawson]

If you are going to retorque at all, you need to loosen just slightly first. It's a matter of dealing with the static friction of the threads vs their running friction. Failure to back the nuts off just a touch will result in exactly what was reported by Flamenco in his first post... the torque wrench will reach its setpoint without moving the nuts at all.

[samsfern]

ill stick to my way, get it warm, slacken a 1/4 turn, then retorque back up to 55ftlbs, in the normal order, whilst its warm. never failed on me. each to there own though

[MRA]

Of course it would be interesting to check everybodies torque wrenches as I have seen more than 10% error across a collection of so called "professional" wrenches

Depending on the model some will be between plus / minus 2 & 5 % tolerance and that's for the wrenches that come with a calibration certificate....... Hands up all those that have a certificate for the torque wrenches they use for cylinder head studs / nuts ?

Torque settings are important, as they load a stud & nut (in this case) combination within their "Elastic" deformation, a bit like a bungy cord, if you don't pull it enough then it will be loose, and if you pull it too much it will enter the "plastic" deformation range and stretch past the yield point, so you have a range that you must stay between.

As long as your method keeps the stretch (preload) on the fixings within this range, and the gasket, block or head are not damaged by an overely high preload all should be ok

It appears that as above several variations along the same theme are being used..........

[dklawson]

My wrench is, sort-of (he says raising his hand).

We have a torque wrench calibration box at work and I take my "good" wrench in periodically. I don't have a certificate for my wrench but I am checking my wrench against certified test equipment.

[HARBER07]

I know torque setting are important, this is just the way I've always done head gaskets on A series. And yes I do have a calibration certificate for my wrench and It will get checked every 12 months (due soon!)