20-4321 KPMI, intake/exhaust valve guide. C630 bronze. +.001"

This Kibblewhite valve guide is made from C630 bearing bronze, a specialized nickel-aluminum-bronze alloy that excels in high-performance and racing environments. Its primary advantage is rapid heat transfer, helping to keep valve temperatures under control in high-output engines. This guide features a .001 inch oversize outer diameter, providing a precise press fit for 1984 to 1999 Evolution Big Twins, 1999 to 2004 Twin Cam models, and 1986 to 2003 Sportster XL models. While not quite as long-wearing as cast iron in touring applications, C630 is the professional choice for performance. For reference, the standard outer diameter is 0.5620 inches. Sold individually, these guides are essential for any top-tier engine build where thermal efficiency and precision are the goals.