This cylinder head seals the combustion chamber at the top of the engine block. It houses the intake and exhaust ports, valve guides, and injector or glow-plug bores, and it contains internal coolant passages that direct flow around the combustion area. The head gasket surface must remain flat within specification; warpage from overheating can cause compression loss, coolant leakage into the cylinders, or cross-contamination between passages. As an original-manufacturer component, the casting and machined surfaces match the block's deck geometry and the fastener thread pattern, which eliminates the need for shimming or reaming on installation. When replacing the head, always install a new head gasket and torque the fasteners in the sequence and to the value specified for the application.