(T) Retorqueing cylinder head nuts.

Haynes or one of my other manuals says you have to do this after the engine has been run for a while following rebuild.
I assume you perfectionists out there have also done that...or have you found it unnecessary?
To retighten I think you're supposed to slacken them a little first , but is that done one by one or slacken the lot and start from scratch?

Having just recently put my engine back together, I noticed that more than half of the nuts were surprisingly loose after only running the car a couple times while setting the timing and tuning. So, I did re-tighten. Once it's run in, I'll check again. I did install a new head gasket (and cylinder base gaskets), so this could explain why things were slightly loose.

I loosened them all a little because, as I understand it, having them all loose and one tight puts an inordinate amount of pressure on the head in the area of the one tight nut. Being super anal, I tightened in 4 passes versus the two suggested by Haynes.

But, you pose an interesting question that if all the nuts are tight, is loosening only one at a time and retighten it OK? I'll look forward to posts by others.

If my memory serves me correctly, depending on what the manual says.
First off the manual tells you to re torque the nuts either hot or cold. It makes a difference so do what it says.
No you don't need to loosen them as the whole point is the head gasket usually compresses more once it has been through a heat cycle. So if you checked the torque on each one you should find they are slightly less than when you set them first off.
So just go through the sequence & torque them to the correct setting.

Tighten bolts to recommended torque and follow the sequence. Do this in 3 stages.
For 650engine:


1st stage: 15ftlbs
2nd stage: 20ftlbs
3rd stage: 29-30 lbfts


set tappets roughly as you'll need to remove again. Don't bolt up the tin ware to the block - as this will prevent the head from "settling" and remove the 2 banjo bolts (bolts with holes in them)


Start engine and run it until hot (20 mins at least). Let it cool down and the following day WHEN ENGINE IS STONE COLD retorque and you'll be surprised at the results! The head will come loose as I was told.


Retorque again at approx. 1000kms (600 miles).


I didn't do this first time and had to buy a new head. Live and learn.

Yes retorquing is definitely required if you have replaced the head gasket- we used to do it as part of a service when checking the tappets and they were often loose.
If you keep the head tight on a 500 it should never need a head gasket replacement, I have never had one fail in any of my cars over the last 20 years but have seen plenty of them fail. How many miles have you done since your rebuild?

Yikes! All makes sense but that's quite hard work. On the same line of thinking you could argue that the exhaust systen will brace the head against accurate torqueing to some extent. Must get round to that. Still got time because the Authorities are still messing me about with registering the car.
At least it's not a 126 Bis. The head on that seemed genetically designed to fail.

Yes, forgot to add that you should loosen the exhaust from the engine block brackets also.