KPMI choose to use C630 nickel bronze as a material to make valve guides because of its ideal characteristics for the application. The 4 to 5 percent nickel content provides superior resistance to wear, and the approximately 80 percent copper content delivers outstanding heat conductivity. Guide profiles are designed to have minimal effect on the airstream while maintaining critical cross sectional thickness in high temperature areas, promoting high performance and endurance. The top portion of the guides are shortened when cam lift information is available at the time of design shows that an additional retainer to seal clearance is required. C630 nickel bronze material valve guides. The 4 to 5-percent nickel content provides superior wear resistance. Approximately 80% copper content for outstanding heat conductivity.