Engine cylinder seal needs three places: piston, piston ring and cylinder seal; Sealing of cylinder pad; Seal of valve and valve seat.

Valve:

The valve is composed of a rod part and a head part: the rod part moves in the catheter to guide the movement of the valve; Head and valve seat close to ensure the cylinder seal.

Valve seat:

The valve seat has two structural types, one is made into a separate seat ring, inserted into the cylinder head; One is directly hinged pin forming on the cylinder head.

For a valve seat shaped directly hinged pin on the cylinder head, the valve seat has three cones: the outer cone, the inner cone, and the valve seat working cone. When the valve is seated, it is in contact with the valve seat working cone, forming a ring contact surface on the valve working cone, the width of the contact surface is 1.2-1.8mm, and the position of the contact surface is in the middle of the valve working cone.

The contact surface is too wide (that is, the valve seat working cone is too wide), easy to stick on the debris, affecting the sealing performance of the valve; If the contact surface is too narrow, the sealing performance will also decline.

Note:

In the process of work, with the impact of the valve on the valve seat, high temperature ablation, the valve and the valve seat working cone surface pitting, ablation, depression, valve sealing performance decline. Therefore, in the process of engine "overhaul", in order to ensure the sealing performance of the valve, the valve should be replaced, and the valve seat for hinge pin and grinding (if it is the valve seat type, directly replace the valve seat), to ensure the width and position of the valve contact surface is appropriate to ensure the sealing performance of the valve.