| 摘要 |
A valve assembly (10) for use in an engine (12), comprising a valve stem guide (14) and a valve seat insert (40) mounted within the engine (12), the valve stem guide (14) and the valve seat insert (40) being provided with a solid film lubricant (30) impregnated therewithin. A valve (20) is reciprocatingly received within the internal bore (16) of the tubular valve stem guide (14). The valve (20) includes an axially extending valve stem (22) which is received by the solid film lubricant (30) within the valve stem guide (14), thereby reducing friction therebetween. The valve stem (22) and the valve stem guide (14) are formed so as to cooperate with associated components within narrowly defined dimensional tolerances in a manner which has the characteristics of reduced friction and lessened passage of oil to the exhaust system of the engine (12). The valve guide assembly (10) thus has the characteristic of being operable in an oil-starved state. The invention comprises the valve assembly (10) itself, the method of preparing it, and the composition of matter of which it is made.
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