Small Block Ford 351W Pro Billet Distributor with Mechanical Advance. The Pro Series Pro Billet Distributor is for the racer who needs added spark and precision for their high performance power plant. It features a high quality, fully adjustable mechanical advance and an accurate magnetic pickup trigger. The CNC-machined aluminum body and hardened steel shaft, guided by a sealed ball bearing on top and a sintered steel bushing on the bottom, ensure stability up to 10,000 RPM. The distributor can be locked out and features solid brass terminals with a color-matched wire retainer. Another important feature on all Pro Series distributors is the fully adjustable mechanical advance. This allows you to easily modify the distributor to achieve a variety of timing curves. Included with all Pro Series distributors are four bushings of varied size. The bushing determines the mechanical advance the distributor can achieve. Also included are six springs, with two at each level of tension. The springs control the rate at which the distributor reaches the advance.