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These days, nickel-base superalloy has been applied to reduce the valve weight of motorcycles. Inconel 751 is excellent in performance but expensive in cost. Therefore, we verified the constituents of nickel-base superalloys corresponding to the requirements of valves and we succeeded in developing a new superalloy and applying it to motorcycle exhaust valves. The characteristics are summarized as follows: 1. The basic composition is Fe-46Ni-18Cr-4Ti-1Al-0.3C-0.004B. It is a precipitation-hardened nickel alloy characterized by precipitation of Ni3 (Al,Ti) and, crystallization and dispersion of fine TiC. 2. It has the following distinctive features. (1) Superior to Inconel 751 in wear and heat resistance. (2) Superior to 20-11P steel in resistance to lead oxide corrosion. (3) Applicable to both unleaded and low-lead gasoline. 3.

There are several all-aluminum cylinder blocks. A typical example is a mono-block cylinder of alusil alloy produced by low pressure die casting. This material's resistance to abrasion and seizure, however, is not satisfactory for motorcycle; in addition, long processing time is another disadvantage. To cope with these problems, the authors developed a light and highly productive all-aluminum cylinder block with a cast-in liner through die casting. The liner is made from powder metallurgy composite (PMC) with 3 to 5 % alumina and 0.5 to 3 % of graphite additives. The PMC reconciles abrasion resistance and machinability. The hardness deterioration of the composite due to the heat at die casting is avoided by using heat-resistant rapidly-solidified powders, made from an aluminum-silecon-iron alloy, for the matrix.

In Japanese automotive industry considerable changes have been done in not only design of exhaust train but also materials to be used due to non-leaded gasoline as well as emission controls. Especially application ratio of heat-resisting and stainless steel has increased rapidly and at the same time manufacturing technique and performance improvement of raw-materials have been made for heat-resisting steel for passenger cars. We have explained for the current trend in materials used for exhaust train such as reactor, catalytic convertor, other part of exhaust train, engine valves, valve seat inserts.

A new heat resistant steel wire was developed for automotive valve springs. The purpose of the development is to apply a high temperature carbo-nitriding process to the springs to have a longer fatigue life. The valve spring processed at an optimal temperature was found to have a fatigue life about five times as long as the conventional Si-Cr oil-tempered wire springs processed at a conventional low temperature.