"Oiler kits" once were in common use on some valve in head engines that were prone to plugging the oil channels to the overhead.The stovebolt was one of these as was the trashy old "Y"
block v-8 from the blue oval.Often the pluggage was where the oil was passed around the cam bearing between it and the block.Detergent oils changed on a appropriate frequency helps prevent this but the old engines with the old oils in the hands of operators who are frugal and/or ignorant of what they are doing makes some terrible muck in the oiling system.We could talk a lot more on this subject.
