Tomei decided to make their Valve Guides from Phosphor Bronze (Cn-Sn-P alloy) for it's high tensile strength and superior heat transferring ability which is vital in high power and high RPM engines. Since race engines these days require more power at higher RPM use with leaner AFR mixtures, these engines now experience more extreme heat conditions which risk with the rapid deterioration on these valve train related components. The Phosphor Bronze material has exceptionally lower friction and the best possible clearances can be maintained which will in effect reduce stress on the valve train, prevent seizures and cracking under high stress loads.
