Proform Harmonic Balancer Cover 66517BKC; 6.750 in. Aluminum Black Powdercoat 60 BTDC to 0 TDC-A for Chevy 262 to 400

These patented harmonic balancer covers offer improved readability, more stable Top Dead Center indication and timing accuracy, enhanced appearance for a previously ignored underhood area, and the elimination of timing tapes which are inevitably flung off. They are available in chrome and black, resulting in parts with the appearance of $200 balancers. Each cover is distinctively marked with Top Dead Center and the proper timing degrees. Using this cover improves timing accuracy because over time the etched outer inertia ring of a typical harmonic balancer may slip in relation to the center hub of the balancer, causing the etched markings to provide an inaccurate indication of Top Dead Center for the #1 piston. Mounted directly through the center hub, this cover eliminates the affect of any outer inertia ring slippage. Aluminum. U.S. Patent 5,675,078