An engine is disclosed having a water cooling system allowing efficient cooling of the exhaust valves to prevent temperature gradients from building in the engine. Water is therefore pumped through the engine though first and second water cooling cores which discharge through the head. A water manifold is positioned over the discharge opening and includes couplings for the radiator supply, radiator return, water pump supply, oil cooler supply and oil cooler return. The engine has separate chambers to isolate the pistons and cylinders, and reed valves cover the chambers and allow the blow-by gases and oil to enter the oil pan during the power stroke of the engine cycle.