What are the symptoms of excessively small valve clearance?

[LeHaley]

The symptoms of excessively small valve clearance are valve leakage and erosion of the valve seat. The function of the valve is specifically responsible for introducing air into the engine and expelling exhaust gases after combustion. Structurally, the engine is divided into intake valves and exhaust valves. The intake valve's role is to draw air into the engine to mix with fuel for combustion; the exhaust valve's role is to expel the burned exhaust gases and dissipate heat. The valve consists of a valve head and stem. The valve head operates at very high temperatures and also withstands gas pressure, the force of the valve spring, and the inertial force of the transmission components. Given the poor lubrication and cooling conditions, the valve must possess certain strength, stiffness, heat resistance, and wear resistance.