Motor oil will drain off of cylinder walls, cam lobes, and out of bearings over time. If this is a newly built engine, use of an assembly lube would have been good although this can be applied to the cam lobes at any time. If it is a used engine, the oiling system can be filled by turning the auxiliary shaft with a drill. A bit of oil in the cylinders and turning the engine is good. If the fuel system has old gas in it, pumping a product like STA-BIL Fuel Stabilizer thru the lines and injectors will prevent corrosion.