Why is it necessary to use new cylinder head bolts every tim

[Dannyboy]

Hi,

Can anyone also explain to me why, when replacing the cylinder head gasket, it is essential to use new cylinder head bolts when my Bongo Service Manual indicates that if the bolts are within their tolerances they can be reused?

Thanks.

[westonwarrior]

the bolts are stretch bolts so weaken if reused, when spending so much on a rebuild its worth getting new ones.

[maxheadroom]

As above really plus this link

http://www.gomog.com/allmorgan/stretchbolts.html