Jon, look at the cam shaft. Note that it is hollow. The oil pump pushes oil down from the back end. There are little holes that point at the crank shaft mains and rod bearings. They are spray lubed from the cam. About 75% of the availabler oil goes thru the cam and to the bearings in this fashion. On the outside of the engine, back corner you will note a couple small oil lines the lube the rocker arms and valves and a dribble on the governor bushing. About 15% of the total flow is routed thru the oil filter and dumps back into the oil pan. The filtered oil does not go to the bearing like a car motor. The motor is big, heavy, well designed and built to run for 50 years. Dont drill the crank, spend your time getting the proper clearance on the bearings.