Valve cover gasket bolts loose

[slvr00gt]

I finally got around this weekend to fix leaking valve cover gaskets and found that the reason for leaking gasket were loose bolts. Head gasket in the truck was replaced before I bought it a few years ago. Mechanic at that time used cork based valve cover gasket. Is it possible that cork gasket shrunk, or mechanic simply forgot to tighten some bolts to spec?

BTW: I used Ford's metal/rubber gaskets this time around...

 

[hondaxr650]

Pretty common for the cork gaskets to shrink up and cause loose bolts. They get hard and crack on the lower edge too because they are so close to the exhaust ports. The metal/rubber ones last a lot longer.