What is the purpose of adjusting valve clearance in a car engine?
1 Answers
The purpose of adjusting valve clearance in a car engine is to compensate for the thermal expansion of the valves. When the engine is running, the valves expand due to the increase in temperature. If there is no gap or the gap is too small between the valves and their transmission components in the cold state, the thermal expansion of the valves and their transmission components will inevitably cause the valves to not close tightly in the hot state. Valve clearance is divided into cold clearance and hot clearance. Hot clearance is slightly smaller than cold clearance, and the clearance measured in the cold state of the engine is the cold clearance. Generally, the cold clearance of the intake valve is between 0.08 to 0.10 millimeters, and the cold clearance of the exhaust valve is around 0.10 to 0.12 millimeters. Adjustment should be strictly carried out according to the clearance specified in the manual. The inspection and adjustment of valve clearance must be performed when both the intake and exhaust valves are completely closed. When the piston is at the top dead center of the compression stroke, the intake and exhaust valves are exactly completely closed, so the valve clearance must be adjusted when it is at the top dead center. The adjustment of valve clearance should be performed when the engine is in the cold state. It is strictly forbidden to adjust the clearance when the engine is running. For a twin-cylinder engine, inspection and adjustment should be carried out cylinder by cylinder.
