I am reading that the head bolts should be replaced to do a head gasket job. Can anyone explain why this is a recommended procedure?

Thanks,

C:>

Depends on the car, but most modern head bolts are designed to stretch when they're torqued to spec. The stretching lets them hold the torque better than a hardened bolt, but means they need to be replaced after each use. It's usually not that big an issue since they aren't (shouldn't be) very expensive and these days not that many cars ever get their heads removed and replaced before they hit the scrapyard.