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Re: Head bolts

To: John Mitchell <jmitch@snet.net>,
Subject: Re: Head bolts
From: "Jack W. Drews" <vinttr4@geneseo.net>
Date: Tue, 29 Nov 2005 09:00:46 -0600
When you further tighten a bolt or nut that is already tight, like a 
head nut, there are two things that take place. First, the nut has to 
start to move -- and oftentimes this takes more torque than what 
you're going to apply for tightness. This is called 'breakaway 
torque". Second, you want to apply the torque required to keep the 
parts together.

So...it's safest to back off the nuts a little bit and then 
re-torque. Don't back it off with the click-type torque wrench, 
though, as this reduces the accuracy of your torque wrench. It is 
also most accurate to do this one nut at a time rather than loosening 
them all. It is also possible to re-torque without backing off the 
nut, if you're sure that the nut actually rotates before coming to 
the full torque you want.

I also find that the valves need to be re-set after the head is re-torqued.

I also find that this can all be done after the engine has been 
started and shut off several times, giving it several heat cycles, 
rather than waiting until the end of the full break-in period. This 
reduces the possibility of the gasket developing a leak during break-in.

At 07:36 AM 11/29/2005, John Mitchell wrote:
>    What is the procedure for re-tightening the head bolts after 
> break in..  Do I back off on the nuts first?  Thanks John Mitchell   76 TR6


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