There's a sneaky way to clean out a gummed up internal oil passageway on the later model engines that don't have a steel oil line going to the oil connector at the center of the rocker shaft. Remove the head bolt adjacent to the middle of the rocker shaft, and make a hardwood dowel that's a snug slip fit in the bolt hole. A piece of broomstick whittled down and sanded down in a drill press works well. Fill the bolt hole with oil, slip the dowel into the hole, and smack it HARD with a BFH. The hydraulic pressure will blow sludge and debris out of the oil passage under the head bolt, and improve oil flow to the rocker shaft. Back in the dark ages, Lisle used to sell a tool to do that, but a piece of broomstick was cheaper and did the same job. They also work well for clutch disc aligning tools. No wonder all the brooms in my shop had short handles!
Jerry
