Small hole in head at bottom of valve cover bolt!

I don't know how the myth got started that JB Weld is good exposed to gas. It's not. JB Weld is not impervious to gasoline and that's not where you want it. I would switch to valve cover studs. They are neater in appearance and hold the gaskets on when you replace them. Coat that stud with a good coat of red high temp RTV and let it ride.