MAN L58/64 Valve Guide

1. Material: GG25(standard), Alternatives: High alloy cast iron, Broneze, etc...A). Mechanical properties(GG25):Tensile strength: 250MPa min. Hardness: HB220-260B). Matrix: Perlite, ferrite 10% max.; Graphite: Preferably lamellar and uniformly distributed; Phosphide eutectic: Preferably continuous network.2. Guide bore to be gun drilled and plateau honed for excellent bore diameter and straightness and achieving cross hatch pattern for better running-in;3. Fitting diameter to be ground, and achieving max. 0.0008' concentricity between guide bore and fitting dia.4. Surface treatment: Phosphating or Tufftriding.5. Casting defects and welding repair are not allowed.