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cylinder head torque

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I've tried to torque head nuts before without taking them down a hair first, and found the wrench would click without moving at all. Loosening the same but and torquing again resulted in turning the nut beyond where it was before. Since that day I've always cracked them loose first, but only the smallest amount possible which seems to be about 1/8 turn.
 
tony barnhill said:
If you back them off before using your 'click' torque wrench, you'll never know if there was a problem with the initial torque 500 miles earlier.
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Agreed, but that's the whole point of retorquing!
 
Yup... all it has to do is "snap" and you've broken the bond and can then get a true torque setting.
 
DrEntropy said:
Yup... all it has to do is "snap" and you've broken the bond and can then get a true torque setting.
Click to expand...

... using your carefully stored Snappy wrench backed down to zero each time.
 
I use my 'point' torque wrench for initial torques & my 'click' for retorques....& I've had it move before clicking....now, that might be because my initial torque wasn't as accurate; or it might be because the torque had changed.

Interesting concept though, loosening a torque to retorque....I'd think you'd need a third 'retorque' after another 500 miles to verify the new 'retorque'! Because, that's what it is: new. If you break the torque to retorque, are you retorqueing? Or are you just torqueing?

Edit: I think we're getting into another 'shim' discussion."
 
There is no "one correct way" for any repair. It depends on many factors. But that doesn't make anyone else wrong either.

Fastener manufacturer's specs only give you torque values, not procedures. If your head stud nuts move freely then there is no reason to back them off slightly first. If they are sticky then it is likely that your torque wrench will reach the specified torque value before the nut breaks free. In this case the proper way to set the torque accurately is to first back it off.
 
tony barnhill said:
I'd think you'd need a third 'retorque' after another 500 miles to verify the new 'retorque'!
Click to expand...

No sir. The retorque is to account for the studs and nuts stretching, head gasket compressing, etc. Once that's done, you need only retorque once. Even if you took the head completely off and reinstalled with the same gasket, it is possible that the studs would not need a second torque. (I wouldn't count on it but you get the idea!) /bcforum/images/%%GRAEMLIN_URL%%/smile.gif
 
Where the heck is Hap when we need a professional engine builder opinion.

I think it is a decient question and can understand both answers/methoids but am unsure which is correct or are both?
 
I can see that if a nut is sticking, you might want to back it off a tad as sometimes lock washers dig into things & keep nuts from moving easily (just had that happen on an exhaust system I'm working on).....if its not sticking, I don't see a reason to do so....simply a matter of technique & what each of us is comfortable with.

Now, lemme toss a real quirk into this bed of worms: when I install head studs into a block, I bottom them out & then back them up about a turn-or-so so that, when I apply torque, they don't bottom out in the hole in the block. Any controversy there?
 
Noop, that's the way.
 
Well it's time for me to chirp in and back up the whole level of conversation to mechanics 101. I thought I was retorquing my cylinder head today, when all I was doing was overtightening and ultimately stripping the nuts on my ROCKER BRACKETS!!!!!!! Exactly where are the nuts located that I would use my handy dandy new torque wrench on? I'm learning as I go along, and putting Tony's grandkids through college in the process. It's a true win-win.
 
19_again said:
Exactly where are the nuts located that I would use my handy dandy new torque wrench on?
Click to expand...
Perhaps this photo will help; 5 down the side, 1 in front, 1 in rear, 4 at rocker pedestals:

1060.jpg


Oh, gotta givecredit where credit is due...I found that photo on the Chicagoland MG Club's site.
 
Why yes indeed that helps a lot. When I started the post regarding alloy head covers someone said you may as well retorque the head while you're in there, so I figured that they must be within the cover area. Now I know and can advise the next guy who shouldn't be doing this unsupervised by a grownup.
Thanks Tony.
 
<div class="ubbcode-block"><div class="ubbcode-header">Quote:]I can see that if a nut is sticking, you might want to back it off a tad as sometimes lock washers dig into things & keep nuts from moving easily.....if its not sticking, I don't see a reason to do so[/QUOTE]
Exactly right. Most of the time they stick a little bit, which is all it takes to keep the torque wrench from doing its job. They would have to be really loose to overcome the stickiness and still turn to the appropriate torque value.

<div class="ubbcode-block"><div class="ubbcode-header">Quote:]where are the nuts located that I would use my handy dandy new torque wrench on? [/QUOTE]
Remember that the four buts you torque under the rocker cover are the long ones. Short ones are for the rocker assembly.
 
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