No, its the stock covers. I removed the covers one at a time and checked the rods and tightened the rockers back to 22. When I started the truck with either cover off you couldn't hear the knocking. Seems likes its echoing off the covers.

Quote Originally Posted by gagliano7 View Post
You said the rockers are hitting the valve covers. Are they aftermarket? That could be your sound. Check and make sure they are tight. Rockers shouldn't be touching the valve cover.