Side by side, 351C high- and low-compression chambers are easy to spot. On the left is the open 73-77cc chamber (low compression). On the right is the 61-67cc wedge chamber (high compression). The most basic choice facing 351C builders is chamber and port size. Strictly street engines may opt for open chambers and small 2V ports for good low-end torque. Street/strip engines may go with open or closed chambers depending on the compression desired. Large ports may impress people, but they do their best work at high rpm. They offer limited torque on the street unless you plan on leaving the light at 7,500 rpm.