One thing we engine builders tend to overlook when building up our engines are those 70-something year old head bolts, and also the main bearing fasteners. These fasteners have been subjected to hundreds of thousands of heat/cool cycles, with the corresponding stretch/shrink situation. On a lot of the racing engines I've built, we usually discarded the OEM head bolts and other critical fasteners in favor of new, high strength studs. One critical advantage is the fact that once a stud is threaded into the block, it remains stationary- - - -all the torque is applied to the nut at the top, and the only load on the block thread is a straight up pull. On a racing engine that gets dismantled and reassembled frequently, that protects the block threads. That's not as critical on a street engine, but it's still a factor to consider. Ford 351 Windsor head studs have the same block threads as stovebolts- - - -1/2"-13. The top thread is 1/2"-20, and the head stud kits sold online include new 12 point nuts, and hardened steel flat washers. It's worth considering an upgrade, particularly considering the cost VS benefit comparison considering the overall cost of a rebuild.
Jerry
