Abstract: Apparatus for pressure testing of a cylinder head for leak detection is disclosed. A clamping plate, crossbar members, clamping members connected to the crossbar members, and clamping screws threaded onto the clamping members clamp the plate towards the crossbar members compressing water passage port sealing plugs positioned between the machined surface of the cylinder head and the clamping plate, thereby sealing the water passage ports. An air pressure source, liquid source and a pump connect to a diversion valve, the outlet of which supplies air pressure or liquid as selected to cylinder head inlet tubes at a water passage port. Cylinder head outlet tubes with an outlet valve are connected to another water passage port.