David Vizard's How to Port and Flow Test Cylinder Heads

Book excerpt: Porting heads is an art and science. It takes a craftsman's touch to shape the surfaces of the head for the optimal flow characteristics and the best performance. Porting demands the right tools, skills, and application of knowledge. Few other engine builders have the same level of knowledge and skill porting engine heads as David Vizard. All the aspects of porting stock as well as aftermarket heads in aluminum and cast-iron constructions are covered. Vizard goes into great depth and detail on porting aftermarket heads. Starting with the basic techniques up to more advanced techniques, you are shown how to port iron and aluminum heads as well as benefits of hand and CNC porting. You are also shown how to build a high-quality flow bench at home so you can test your work and obtain professional results. Vizard shows how to optimize flow paths through the heads, past the valves, and into the combustion chamber. The book covers blending the bowls, a basic porting procedure, and also covers pocket porting, porting the intake runners, and many advanced procedures. These advanced procedures include unshrouding valves, porting a shortside turn from the floor of the port down toward the valve seat, and developing the ideal port area and angle. All of these changes combine to produce optimal flow velocity through the engine for maximum power.