I was an idiot and overtightened one of my valve cover bolts. It snugs down but not to torque spec and it is causing a slight valve cover gasket leak. The bolts seems ok but I will likely get a new one. My question is, What is the best way to repair the threads in the aluminum head. time-sert? helicoil?

 

You might be able to get away with just using a slightly longer bolt, as the thread in the cylinder head usually goes a little deeper than the length of an OEM bolt.