Cylinder heads on the 6.4L Powerstroke (2008–2010) are key to airflow, combustion, and engine performance. They hold the intake and exhaust valves, valve springs, and injector ports. The heads seal the top of the cylinders to contain combustion pressure. Built from strong materials like iron or aluminum, they handle high heat and boost. Over time, they can warp, crack, or develop valve seat damage under stress. Replacing or upgrading the heads restores compression, improves airflow, and boosts engine durability.