Manley Valve Spring, SPRING-DODGE SRT-4 Manley Performance was founded by Hank Manley in 1966, his desire for speed and to win led him to build his own racing engines. Since that time Manley has continued to evolve, using the knowledge they have gained since the beginning and building on that to continue to bring the best engine components to the market. The goal at Manley Performance remains laser focused on designing and producing the highest quality internal engine components at extremely competitive prices coupled with excellent customer service.