No oil to rockers.

x2 Rustyratrod. Also, you may have installed the rocker shaft upside down. This will burn up a set of rockers in no time. The shaft really needs a through cleaning by removing the end caps (replacements are cheap) and scrubbing shaft(s) with a bore brush. As Rusty said the oil feed hole in block may be plugged. Get some stiff wire and a lot of Brakleen and keep at it. Good luck