[wolf k]

Water leaves the two discharge ports from the pump equally and enters both banks of the block at the front. There it flows around the cylinders and then up into the heads. The size of the holes in the head gasket are designed to equalize the water flow so that all cylinders get the same flow rate (that is why installing the gaskets in the correct orientation is important). Water then flows through the heads and exits at the crossover in the intake manifold where it combines from both banks. It then encounters the thermostat, which if open, leads water to the radiator, or if closed, slows down the water flow tremendously, allowing the engine to warm. The small by-pass hose allows a small amount of flow back to the suction side of the pump when the thermostat is closed to prevent dead-heading the pump. Water from the open thermostat to the radiator from top to bottom and back to the suction side of the pump. Again it is the size and orientation of the holes in the head gasket where all the heavy engineering is. These equalize flow so that all cylinders and heads run at near the same temperature. And what Jerry said about the rear block-off, it there because the heads are reversible, thereby allowing for one casting.