hello modelman.i went way back in the lounge section to look at the pictures of your engine and see what kind of rocker arms it has. i would loosen up those rocker shaft supports and lift them up a little to see if there is oil supply holes in them to feed the shafts. some times oil is delivered through the supports to the shafts, sometimes the supports that supply oil have special skinny bolts to allow oil to flow.try turning the oil pump with these supports lifted a little. you'll have to readjust the valves later , but i think it's worth a look. maybe a bolt is in the wrong place,or the supports are a little clogged. you mentioned media blasting some parts, is it possible a little media got trapped inside? just a few more ideas. hope this helps. good luck.
