These stiffer valve springs alone will extend the revving capabilities of your valvetrain to the 8,000 rpm mark. In addition, the SportTuned valve spring set will eliminate potential coil bind on high lift cams. When properly installed they will allow up to 0.500 inches of cam lift. A good idea for any high performance engine. Designed to fit stock retainers. Remember: Always keep the lower valve spring seats in your cylinder head to prevent damage to the aluminum casting. 12V VR6 spring sets include required shims (to be installed beneath the springs) for proper installation.