Oil restrictors for use in Dart SB Chevy shape blocks are specifically designed for the priority main oil system to reduce the amount of oil flow to the top of the engine, reducing the risk of evacuating the oil pan in continuous high RPM engines. Kit includes two restrictors, an extra O-ring and detailed installation instructions. The key to success in a car building project is access to high quality, reasonably priced parts that get the job done right. Each Allstar part is the result of our dedication to research and development. Once a need is established, parts are designed and manufactured by talented craftsmen, many of whom are racers and hot rodders themselves. Many Allstar Performance parts are one-of-a-kind; you won't find them anywhere else