Install reliable sealing new cylinder heads on your performance built 2008-2010 Ford 6.4L Powerstroke with the Powerstroke Products Loaded O-Ring 6.4L Cylinder Head PP-6.4HeadLHDVSO. The O-Ringed design provides a positive seal around the cylinder which keeps in compression. These heads are assembled using heavy duty valve springs to keep the valves under control when used in high performance builds. Each head is built from a new casting and is assembled with brand new valves, seals, and HD springs. No core required, sold individually.