PROFessional Powertrain 2313 Nissan E16 Remanufactured Cylinder Head All cylinder heads are both vacuum and pressure tested to verify valve seating, and integrity of water passages. All cylinder heads are packaged in environmentally safe and recyclable containers that are the perfect size for returning your original core. All threads and machined surfaces are and repaired with technology that exceeds the original metal Non-sealing iron surfaces painted to prevent oxidization.