9. Here's a look at what goes on in the porting/polishing room. Porting is the shaping of the combustion chamber and ports to increase the amount of air passing through the ports. This doesn't make the port bigger, but it improves the shape for optimal airflow dynamics. Branch's "bathtub" design makes the air flow more completely and thoroughly. John ported with a solid-carbide burr bit on an air gun, and then changed to 80-grit cartridge roll, then to a 120-grit, 180-grit, and finally a 240-grit (John emphasized the importance of the porting prep work for polishing. Polishing could take roughly 30 seconds if the heads have been thoroughly ported). After porting, it was time for polishing. Polishing is important because a stock head's chamber builds up with carbon due to its rough, cast material. With a lot of carbon buildup, detonation is affected and causes a spike in performance. John removed all of the carbon and polished the chamber with a Canton flannel wheel and a jeweler's rouge compound so that no carbon builds up on the ports, therefore increasing airflow. After the port/polish process had been completed, it was time to move onto lapping the valve.
9. Here's a look at what goes on in the porting/polishing room. Porting is the shaping of