The OTR Cylinder Head Assembly for Caterpillar 3406E/C15 ensures Expertise Built In , featuring 30% more coolant flow for superior engine cooling in harsh environments. This heavy duty engine cylinder head assembly is essential to the airflow in and out of the cylinders as well as fuel deployment. This replacement cylinder head provides your heavy duty truck with new parts, including an all new valve train, cam bearings, injector tubes, and valve guides, providing you maximized performance with a smooth ride on the road ahead. FleetPride is your First Click in Heavy Duty .