The thick valve covers on my '13 were leaking oil, so here is how I fixed them. I got a spare two hole block, and put a gasket over the opening so the paint wouldn't get messed up, and put the valve cover on backwards. I used three flat washers under the nut so I could push the valve cover down far enough. The distance at the center should be 1/4" more than the edges. That brought them back to standard. Another thing I don't like is the new type gaskets weep, meaning they act like a wick. Wouldn't it be nice if they were to use cork again! And, if you are wondering how thick those early valve covers are, they are between .095-.100. I haven't seen any thicker, and they got considerably thinner every year after that.