Abstract: Testing apparatus which permits precise determination of the existence and location of possible fractures and cracks in the cylinder head of an engine. In a preferred embodiment, the apparatus comprises a plurality of individual test plates which are specially designed for the particular engine desired to be tested. The plates include at least one planar surface having one or a plurality of generally circular recesses formed therein for holding and retaining O-ring seals. The position of the recesses on the plate corresponds to the position of water conduit outlets in the cylinder head. The preferably transparent plates, along with the O-ring seals, are bolted onto the cylinder head, and water under pressure is then applied. The reverse side of the plates may conveniently include a different arrangement of recesses to accommodate a different engine cylinder head design.