Head bolt torque is determined by the yield point of the bolt material and they arein tension. If the bolts have been over torqued they may be, beyond the yield point. Over time due to heat and vibration a material in tension will normalize and relax. This lowers the yield point. Good practice to replace an older set of head bolts.
Can you get away with reusing the old bolts? Sure, most of the time, but there is always the acceptation.
Denny Graham
Sandwich, IL
