Head gaskets on the 6.4L Powerstroke (2008–2010) seal the engine block and cylinder heads, keeping combustion pressure in and fluids from mixing. These multi-layer steel gaskets handle the high heat and pressure from the twin-turbo setup. When a gasket fails, it can cause compression loss, overheating, and leaks. Replacing damaged gaskets helps protect the engine, restore performance, and ensure long-term reliability.