When upgrading your valves it is a must to also upgrade the valve springs and retainers. Manley's valve springs are wound using the cleanest alloy available and are also heat treated to allow for durability. They are specifically designed to be used in high revving applications and are made to take whatever you can throw at them.
Manley titanium retainers are made of rugged and certified, heat treated aerospace grade titanium. They are a must for any high performance engine revving past the stock limits. The light weight mass allows the motor to rev higher safely, but still keeps dangerous valve float in check. Manley has designed these with the highest quality standards and it shows in every aspect.