When serious engine builders in.blueprintin. an engine, they'll in.portin. or smooth off rough head castings around the intake and exhaust ports for better air flow. This makes it easier for the engine to in.breathein. resulting in greater power and efficiency. Using the Porting Kit, you can perform this professional technique at home. The Porting Kit contains 80 grit abrasive rolls: 20 tapers for reaching into tight spots and 20 cylinders for flatter areas, two 4in. and two 6in. mandrels, and complete illustrated instructions. For best results use a high speed grinder. To remove more, try carbide burrs.