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.