For a crisper, smoother running engine, replace your stock HEI module with the Dyna-Mod. The Dyna-Mod has more "electronic dwell" in it to provide more coil saturation time. The additional saturation time allows the coil to produce a more intense spark. All D.U.I. distributors are built with this module. The Dyna-Module has more electronic dwell in it to provide more coil saturation time. The additional saturation time allows the coil to produce a more intense spark, improving throttle response and low end power! Installation is easy as the Dyna-Module mounts in the stock location of an HEI module with no modifications. Fits all V8, 6 Cylinder and 4 Cylinder DUI / HEI Distributors. Also fits Performance Distributors Chevrolet, Pontiac and Dodge Tri-Power Ignition Systems. Fits 1974-Up (w/o computer) GM HEI distributors. Some parts are not legal for use in California or other states with similar laws/regulations