C630 bearing bronze is a tough nickel-aluminum-bronze alloy. It is not as durable as cast iron but typically used in high performance and racing applications where rapid heat transfer from the valve to head is important. Note: Standard non-oversize dimensions (for reference only) are 0.5620″ O.D. (14.27mm); 0.3090″ I.D. (7.85mm); 2.00″ OAL (50.8mm).
