Back in the good ol' days, sights like that were common. We'd drain the oil. fill the crankcase with kerosene and run it until the rods started knocking.Drain, Refill with oil. Run it for a couple hundred miles, pull the valve cover and check. If it was reasonably clean that was it. If not, then another kerosene treatment. Then that miracle treatment, STP came along and kind of reduced it a little. For now I got to go along with the Seafoam treatment. I've used it and was happy with the results. The biggy to watch for is don't let any globs get in the oil system. It'll clog up the oil gallerys and or any little hole it gets to.