What is the standard valve clearance of b 12 engine?

According to the manufacturer's standard data, the intake valve is 0.075~0. 125mm, and the exhaust valve is 0.245~0.295mm.

Because the valve works at high temperature, the valve and other parts are extended due to thermal expansion, so it is necessary to reserve a certain valve clearance when the valve is cold, so as to ensure that the valve and the valve seat can cooperate closely when the valve is expanded and extended by heat. But because the valve works for a long time, it will change the original valve clearance.

If the engine directly driven by the valve tappet can't adjust the valve clearance like the engine with rocker arm or swing arm structure, it is necessary to choose a valve tappet with appropriate thickness to replace the original one, and adjust the appropriate clearance according to the distance from the base circle of camshaft profile to the top of the valve.

Extended data:

The influence of too large or too small valve clearance;

Excessive clearance: After the intake valve and exhaust valve are opened late, the intake and exhaust time is shortened, and the valve opening height is reduced, which changes the normal valve timing and makes the engine power drop due to insufficient intake and unclean exhaust. In addition, the impact of valve train parts increases and the wear accelerates.

Too small clearance: after the engine works, the parts are heated and expanded, pushing open the valve, which makes the valve not close tightly, causing air leakage, reducing power, causing serious carbon deposition or burns on the sealing surface of the valve, and even the valve hits the piston.

References:

Baidu encyclopedia-automobile engine b 12