Fits Evo VII HKS valve springs are stiffer springs specifically designed for use with HKS camshafts. As valve train dynamics change with the use of high performance cam profiles and greater lift, stiffer valve springs are needed to optimize valve movement. When changing to a high lift cam, stock springs cannot match the increased valve train movement. Therefore HKS engineered valve springs that are precisely matched to the characteristics of HKS camshafts. A stringent shot-peening and heat treatment process is applied to the HKS valve springs to provide durable and consistent spring rates over time. Applications with high revving engines will benefit from HKS valve springs, as the risk of valve-float and coil-bind is greatly reduced due to their specific design and construction.