Allows you to change the amount of ignition vacuum advance for maximum part-throttle performance while preventing the harmful effects of spark knock (detonation) Dial in as much spark advance as conditions permit—add more advance under light load conditions to improve throttle response and fuel economy, or limit spark advance in high compression engines and high load conditions to eliminate knock Built-in stop prevents the adjustment screw from "backing out" like other designs Includes 3/32" Allen wrench and easy-to-follow instructions Perfect companion to Moroso H.E.I. Advance Curve Kit No. 72300