What is the standard valve clearance for b12?
3 Answers
According to the manufacturer's standard data, the intake valve clearance is 0.075~0.125mm, and the exhaust valve clearance is 0.245~0.295mm. 1. Valve clearance: Since the valves operate at high temperatures, components such as the valves elongate due to thermal expansion. Therefore, a certain valve clearance must be reserved when the valves are cold to ensure tight contact between the valves and valve seats when they expand due to heat. However, prolonged operation of the valves can alter the original valve clearance. 2. Adjusting the proper clearance: For engines that use direct valve tappet drive, unlike those with rocker or swing arm structures, the valve clearance cannot be adjusted directly. Instead, based on the distance from the base circle of the camshaft profile to the top of the valve, a valve tappet of appropriate thickness must be selected to replace the original one, thereby adjusting to the proper clearance.
Adjusting the valve clearance on the B12 engine is something I'm very familiar with. When the engine is cold, the intake valve clearance should be between 0.20-0.30 mm, and the exhaust valve needs to be 0.25-0.35 mm. These values aren't arbitrary—they're determined by the engine's thermal expansion characteristics. When the engine heats up, component expansion consumes the clearance, so measurements must be taken when cold. I always use a feeler gauge for precise measurement during adjustment. If set too tight, it can burn the valve seats and cause the engine temperature to skyrocket; too loose and you'll hear a tapping noise with poor acceleration. Last time when helping a friend adjust his Jinbei Haise, I found the valve rocker arms were excessively worn—the clearance wouldn't stabilize no matter how we adjusted it. We had to replace the parts to fix it. Remember to adjust each cylinder in firing order sequence, and always use a torque wrench for the locknuts, otherwise you might have to redo the work.
The B12 engine in my car has been used for eight years, and the valve clearance has been adjusted three times. The standard is 0.20-0.30mm for the intake and 0.25-0.35mm for the exhaust when the engine is cold. When I tried to adjust it myself, I realized there's a lot to learn—you have to remove the valve cover first and wait for the engine to cool down completely before starting. Once, I was in a hurry and adjusted it while the engine was hot, resulting in the exhaust valve not sealing properly during high-speed driving, and the tailpipe even turned red. Now I've learned my lesson and keep both 0.25mm and 0.30mm feeler gauges in my toolbox. Additionally, I found that wear on the hydraulic valve lifters can cause the clearance to gradually increase, so older cars need to be checked every 30,000 kilometers. After adjustment, remember to let the engine idle for ten minutes and listen to the valve noise to ensure everything is fine.
