Back in the 50's when we used GMC's hard in commercial service, grinding valves was an annual thing or oftener. We would have never dreamed of buying new head bolts every time we had a head off. Of course we didn't look at books much in those days. I thought I was real "up town" when I bought a torque wrench and it came with a free little pamphlet with torque values and tightening sequence of then popular engines.