C630 is a blend of copper, nickel and aluminum. The high copper content gives excellent thermal qualities, the nickel makes the guide tough and wear resistant, and the aluminum brings work hardening characteristics. This bronze alloy allows for tighter clearances than other materials, creating better valve and seat sealing, as well as superior oil control. The expansion qualities of C630 aluminum cylinder heads.
All valve guides are made of Ampco-45, a high-performance compound with 80 percent copper content to provide great heat conductivity and 4-5 percent nickel content for wear resistance