If your head bolts are of the "torque to yield" or "stretch" head bolts,
they should be used once and replaced when removed.  They are designed to
actually stretch once the torque value is achieved and once used, their
clamp load will be compromised when used again.  I don't believe the WBX
head bolts are torque to yield but most modern diesel engines use them.
JB

George Averill wrote:
Does this mean that the torque should be increased to allow for this?
----- Original Message -----
From: "Larry Alofs" <lalofs@enteract.com>
To: "George Averill" <averill@LDL.NET>; <vanagon@GERRY.VANAGON.COM>
Sent: Saturday, August 03, 2002 8:49 AM
Subject: Re: Do head bolts have to be replaced?

> George Averill wrote:
> >
> > Have had a discussion with a friend this week about head bolts and
thought that some of you might be able to shed some light on the question.
> >
> > One time I was replacing the head on my engine and experienced a strange
thing.  When I tightened the head bolts to the correct torque, and then
removed the tension, the bolts would untighten on their own.  They would
move.  The friend said that he thought that this was due to the fact that
head bolts stretched and should always be replaced when replacing the head.
> >
> > Anyone have any thoughts on this?
> > George
>
> The head of the bolt may turn backward a little as you release the
> tension if it is a long bolt.  The shaft of the bolt is twisted
> elastically as you are tightening it and it springs back when you stop
> twisting, especially if the surface beneath the head of the bolt is
> lubricated with fresh sealant.
>
> Larry A.