One of the troublesome areas of the Y-Block V8 is the rocker arm shaft assemblies. Due to poor oiling conditions in the past, it is common for them to have excessive wear. When rebuilding your Y-Block V8 it is important to pay close attention to this area. New rocker arm shafts are readily available for you to overhaul your own assemblies. I personally like to convert them to full pressure oiling by deleting the overflow tube when performing this process. After discarding the tube, you will need to tap one of the rocker towers for a 5/16 X 1/2 bolt that has been shouldered approximately 1/16 back from the tip to locate and center the new shaft, then cut a slot across the tapped hole with a hack saw to bleed off air trapped in the
Also it is a good idea to cut a small groove across each oil hole on the shaft for better oil dispersion.
Please view the below video for further instruction