Re-torqueing head bolts

[frilaens]

My workshop manual says the head bolts should be torqued again after 20 hours operation. What exactly does this mean? That they should be undone, tightened up to the intermediate 20N and then up to the full 70N in the required pattern or that you should just check that they are 70N?

Andy

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[sailorman]

it means just use the torque wrench to "check" by putting it back on the bolts& tighten to set limit ie 70 N.
they may not have changed, certenly DONT LOOSEN THEM AT ALL
U will also have to re-check the tappet clearances as well after the head bolts R done

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[johnsomerhausen]

According top the auto engineers´ "rukes", you should take off the nuts, clean their threads and those of the studs and then retighten in two stages, as you mentioned. But I´ve had a reputable mechanic just checking whether they were at the right torque. The problem with that last method is that some dirt may introduce extra friction and thus give you a false reading. By all means check the valve tappet clearances again
jiohn

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[chippie]

These days , with overhead camshaft engines , torqueing the head nuts shouldnt change the tappet clearances in the way that it would on a pushrod engine. Is your engine pushrod or OHC?

I suppose it doesnt hurt to check them anyway.

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[DJE]

I did mine a few months ago. I torqued them to 70Nm when I re-assembled the engine and then after 20 hours running just put the torque wrench back on them and tightened it. They all went about a quarter of turn before they reached 70Nm again. I think it is something to do with the gasket compressing and everything just bedding down. It is a bit of a pain on the Volvo 2002 because you have to take off the valve rocker gear to get at some of the head bolts.

<hr width=100% size=1>Better to keep one's mouth shut and be considered a fool than open it and remove all possible doubt.

 

[paddywackcocker]

I agree that the torques should be checked just by useing a good torque wrench but at no point should they be loosened to do so arfter engine rebuild/runup.
If the engine was put back together proply there should be no reason for any dirt/rust to be near the head bolts/nuts interface.
Threr are a few engines that require you to slacken and retorque but this is done on the bench and not ounce insalled and engine has had use.

<hr width=100% size=1>Sorry for the spilling

 

[Heckler]

ahem,
if you do as you suggest you cock the whole job up and have to start again. just set the wrench at 70 nm and you will find the nuts will go down a bit further.
stu

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