Water Jacket

The water passages in the cylinder block and cylinder head form the engine waterjacket (fig. 6-4). In the cylinder block, the water jacket completely surrounds all cylinders along their full length. Within the jacket, narrow passages are provided between the cylinders for coolant circulation around them. In addition, water passages are provided around the valve seats and other hot parts of the cylinder block In the cylinder head, the water jacket covers the combustion chambers at the top of the cylinders and contains passages around the valve seats when the valves are located in the head.

The passages of the water jacket are designed to control circulation of coolant and provide proper cooling throughout the engine. The pump forces coolant directly from the lower radiator tank connection into the forward portion of the cylinder block. This type of circulation would, obviously, cool the number one cylinder first; causing the rear cylinder to accept coolant progressively heated by the cylinders ahead. To prevent this condition, the L-head block is equipped with a coolant distribution tube that extends from front to rear of the block, having holes adjacent to (and directed at) the hottest parts of each cylinder. I-head engines are equipped with ferrule type coolant directors that direct a jet of coolant toward the exhaust valve seats.