combustion passages 57 and 58 and absorb the heat from these walls the coolant flow past these walls and between said cooling fins extracts from the engine head excess heat coolant circulation passage 23 is radially positioned around partial cylinder 50 and axially aligned with the axis of said partial cylinder coolant passage 123 is radially positioned around partial cylinder 150 and axially aligned with the axis of said partial cylinder gear shaft 24 is axially aligned with the axis of partial cylinder wall 50 and the interior surface said wall of said partial cylinder 50 is very closely spaced from the outer diameter surface of the gears of gear shaft 24 gear shaft 124 is axially aligned with the axis of partial cylinder wall 150 and the interior surface of said wall of said partial cylinder 150 is very closely spaced from the outer diameter surface of the gears of gear shaft 124 identical gear shafts 24 and 124 are divided by five bearing sections on each shaft 25 29 on gear shaft 24 and bearing sections 125 129 on gear shaft 124 into four gear sections on each shaft two positive displacement oil pump gears 30 and 33 located near the ends of said.