I have been driving and working on Volvos for 35 years and have probably
built up at least 15 engines. I have never bought a new headbolt, and the
only failures I have experienced were on installation. I torque them just
a little tighter than the manual says, 70 ft-lb the last time around, although
the one that failed failed at about 55. I always run a tap into the threads,
clean the bolt threads on a wire wheel, clean everything out of the holes and
grease the threads of the bolts so that more of the torque is used in clamping
force, rather than trying to screw the threads together. A little grease under
the bolt head is a good idea too. (This relates to cast arn blocks and heads,
NOT aluminum!!)
--
George Downs, The "original" Walrus3, Bartlesville, Oklahoma