Thread inserts/ lessons the hard way
Clymer warns not to over tighten the valve cover bolts, which I did. I then repaired the stripped out bolt hole with a helicoil. It lasted for a couple of years. However, don't use a helicoil for anything that has to be tightened much more than finger tight. The helicoil failed, and I took the head to a shop to see what other options I had. The mechanic used an insert called Rockmount. It appears to be a much better, though more expensive, option. There are other options out there, but my experience with hilicoil has not been the best, at least not for this application.