[James]

Remove the rocker arm shaft assemblies from both side of the engine. Disassemble the shaft but keep the assembly order. There is two way the shaft can be assembled, which is why you need to keep in place. The drill passageway in the shafts makes a difference. Cleaned out the inside of the shaft, the end mounts passageway, and the squirter holes in the arms (see attachment). It might be plugged up with sludge. The rear mount in the right head and the front mount on the left head supply oil to the rocker arms. Clean out the supply holes in the heads the best that you can. Lubricate everything with fresh engine oil and assemble it to the head. This would also be a great time to check valve clearances. Once everything is assembled, run the engine. It will take some time to fill up the shafts, but you should see oil flowing out of the rocker arms.