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MG TD TF 1500 - Retorque Options - cylinder head

Which method do you recommend when retorquing a cylinder head?

1) Torque without loosening the nuts.
2) Loosen one nut at a time and torque.
3) Loosen all nuts then torque.
4) Other

XPAG = 600 in-lb (50 ft-lb)
XPEG = 500 in-lb (42 ft-lb)

All nuts tightened and torqued in the recommended order. see image below.

Thanks,

Lonnie
TF7211

LM Cook

The studs and nuts should be lubricated then tightened in two or preferably three steps. All to step 1, then all to step 2 and finally all to step three in the order given.
Dave H
Dave Hill

Thanks Dave -

Should I loosen only one nut at a time, lube the stud, and torque?

or -

Should I loosen all of the nuts then lube, and torque?

Lonnie
TF7211
LM Cook

Fair question Lonnie. I'd never considered loosening before re-torquing & planned to simply re-tighten to the recommended figure, (which does seem to differ depending on the source), from the centre out. This way you get a feel for any difference between each of the studs. I have three different recommended sequences in the various manuals in my possession, all are similar however, suggesting working from the centre to the outside. Cheers
Peter TD 5801
P Hehir

Hi Lonnie,
I use method N°2
Method N°1 necessitates an additionnal torque to overcome the static friction of the nut. The specified torque does not take it into account. But just loosen the minimum amount to unlock those frictions. 1/8 of a turn or less.
That way, the gasket does not expand between head and block.
Method 1 does not release the static friction.
Method 3 allows the gasket to expand.

Laurent.




LC Laurent31

Personally I would use method 1 if the nuts are already tight and had been lubricated to start with.
Dave H
Dave Hill

I do one at a time. I slightly loosen the nut first, just to ensure that the nut is turning when the torque wrench clicks. There is always a bit of "sticking" when you first try to turn a nut, and this can cause an immediate click when the nut is still in fact too loose. I do NOT however, loosen the nut all the way. Maybe 5-10 lbs/ft under, then torque up to full again.
Steve Simmons

Thanks everyone for your responses. I don't feel so bad for asking ... seems like there are a number of ways to do the job and obviously all of them work.

I have used "method #2" the few times that I have retorqued the head on my TF for the reasons stated. This time I'll loosen each nut a little less than in the past as Laurent and Steve suggested.

Lonnie
TF7211
LM Cook

Any nut that is to be retorqued should be loosened a bit before retorquing to prevent "stickshon" Steve as Steve stated. This even applies to bearing cap nuts even though they are bathed bathed in oil constantly. Cheers - Dave
DW DuBois

This makes me want to go retorque mine.
Alex Waugh

whoa - trying to type with one's right arm in a sling (shoulder replacement surgery) produces some interesting results - in my last post, it should read ... to prevent "stickshon" as Steve stated. Cheers - Dave
DW DuBois

I agree with Laurent and Steve. Their method is the one I always use.

Bob Schapel
R L Schapel

Stickshon? I Googled it & it means "the grease sticks to the body" in gun speak. I guess it's a term used in ice bound areas. One that I'd not heard of before. Cheers
Peter TD 5801
P Hehir

It's generally spelled as 'stiction'. Try Googling that one. Bud
Bud Krueger

Thanks Bud. I welcome the orthographic advice & I'll add it to my lexicon. Cheers
Peter TD 5801
P Hehir

I thought it was a rare event to lube threads prior to torquing ...

"The biggest danger in lubing threads (when the torque spec is for dry threads) is that the fastener will be over-torqued. Thread friction is somewhere around 60%-80% of the resistance when tightening fasteners, so the thing will be a lot tighter with lubed threads for the same torque reading."
I'll have to reread the shop manual to see if it states to lube the threads ... If it does not specify lube.. The torque values are for dry installation.

Regards, tom
tm peterson

Retorgue hot or cold? Forrest TDC/22679
Forrest Rubenstein

Tom - this is an interesting point about dry or lubed specifications. I don't believe the factory shop manual specifies dry or lubed - so it is an open question.

I was told at a tech session this weekend that the threads should be lubed prior to torque. This was information provided by a well respected, knowledgeable machinist/mechanic. I wonder what the correct answer could be based on - since we lack any factory references.

Does anyone have a factory reference they can cite?
DLD

For my ARP rod bolts and head studs I consulted with their engineers, who recommended using engine oil to LIGHTLY lubricate the threads, and then they based their torque values on the materials used to make the studs and bolts. Even with lube, they are slightly higher than stock.

ARP also sells their own proprietary lube with is somewhat slipprier than oil, but there seems to be no reason to use it.

Tom Lange
MGT Repair
t lange

This thread got me thinking? Why do we retorque the head say after we replace the head gasket at say after 100 miles or so of driving or after one minute blipping the throttle a few times as WKF Wood says in his book THE XPAG ENGINE.

Is it to ensure that there is uniform correct torque after the head has been stressed and put under pressure on the head studs and nuts. I think that is the reason.

If I am correct then why would you loosen the nuts and retorque them if after that, you would have to keep this cycle up because you loosened the nuts each time. Seems like you would be caught in a infinite loop of torque, loosen and having to retorque, etc.

So I would suggest option 4. Retorque if necessary WITHOUT loosing.

Joe
JWP Policastro

Retorque is mostly to account for the head gasket compressing. It will only compress so far under a given torque, so after a short time the nuts need to be returned to their proper tightness. The studs will also stretch a bit but mostly the first time they are pulled tight. Subsequent tightening to the same torque will not stretch them as much.
Steve Simmons

I just called my rep at ARP, and he told me their re-torque recommendation:

1) ALWAYS torque on a cold engine

2) Slightly loosen head nuts before re-torquing them.

3) If using their assembly lube, reduce the torque from standard; if using engine oil slightly increase the torque.

Tom Lange
MGT Repair
t lange

When lubing bolts like this, whether it is a generic torque lube or official ARP assembly lube or oil, I make sure it gets applied everywhere on the threads, then gently wipe most all of it off. Doesn't take much to lube the bolt. A case where less is more.
D mckellar

I agree - my instructions say to "LIGHTLY" apply the same oil you will be using in your engine.

Like selecting engine oil, there are differing choices and opinions. But as someone who uses and sells their bolts and studs, I trust the experts. I have never blown a head gaskets in many engines I have rebuilt, by re-torquing (cold) after running the engine for a few minutes and blipping the throttle, after the first run (again, cold), and after 100 and 500 miles. I will from now on follow ARP's recommendation and slightly loosen the nut and then re-torque. I suppose it can't hurt!

Tom Lange
MGT Repair
t lange

Tom:

Thanks for relaying ARP's recommendations. I have been waiting to retorque my head until I had time to run the car to full operating temp. Based on ARP, I'll do the job with the engine cold. Then I'll run to full op temp and set the rockers.

This is a good thread. I am saving it as a PDF and filing in my "engine" folder.

Lonnie
TF7211
LM Cook

I use a trick to adjust the valves after a re-torque: I don't.

I use a short 19/32" socket that fits the head studs perfectly (I did cut it down), and that slips under the rocker shaft for torquing the head nuts. That way I can re-torque without removing the rocker assembly.

You do need to remove the clips on the rocker shaft to do those head nuts, but they clip right back on.

Tom Lange
MGT Repair
t lange

I've never noticed any clearance issues with sockets and torque wrenches. The front and rear can be a little tight but the socket always goes on. Maybe this is one of those long vs short rocker shaft issues.
Steve Simmons

This thread was discussed between 14/01/2016 and 20/01/2016

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