Speaking of the valve core, it must start with its intake valve. The intake valve generally uses alloy steel, that is, chromium steel and nickel-chromium steel, and the exhaust valve uses heat-resistant alloy, that is, silicon chromium steel. Sometimes in order to save heat-resistant alloys, the exhaust valve head is made of heat-resistant alloy, and the rod part is made of chrome steel, and then the two are welded together.
The shape of the valve head of the valve core includes a flat top, a spherical top and a horn top. Flat tops are usually used. Flat top valve head has simple structure, convenient manufacturing, small heat absorption area, small mass, and can be used for both intake and exhaust valves. Spherical top valve is suitable for exhaust valve. It has high strength, low exhaust resistance and good exhaust gas elimination effect, but it has a large heating area, large mass and inertia, and complicated processing. The horn type has a certain streamline shape, which can reduce the intake resistance, but its head has a large heating area, which is only suitable for the intake valve.
The cone angle of the valve core is the angle of the valve sealing surface, which is generally 45 degrees, and some are 30 degrees (CA1091 type car 6102 engine). However, in the case of a 30-degree valve, considering the same lift, the valve taper is small, the valve passes through a large end face, and the intake resistance is small. Because of its performance, it relies on this performance and it is generally used for intake valves.