What is the intake and exhaust valve clearance?
2 Answers
Intake valve clearance is generally within the range of 0.20mm to 0.25mm. Due to thermal expansion, the exhaust valve clearance is larger than that of the intake valve side, so it naturally requires a larger clearance, usually between 0.29mm and 0.35mm. Here is some related information about intake and exhaust valves: Effects of excessive clearance: Excessive clearance can lead to incomplete valve closure, affecting engine performance, causing insufficient intake and incomplete exhaust, and easily resulting in collisions between the valve and valve seat, as well as valve noise. Effects of insufficient clearance: Insufficient clearance can cause incomplete valve closure (no space), leading to noise, increased wear, and phenomena such as engine power loss.
After all these years of repairing cars, I've found that valve clearance generally ranges between 0.1 to 0.4 millimeters. The exact values depend on the vehicle manual—for example, some older Japanese models have intake clearance around 0.15mm and exhaust around 0.25mm, while German cars might be closer to 0.20mm intake and 0.35mm exhaust. Clearance is critical because engine components expand when heated during operation. Without proper space, valves can seize or burn out, leading to costly repairs. Adjustment must be done on a cold engine using feeler gauges and wrenches, step by step. Too loose, and you'll get excessive noise and poor acceleration; too tight, and you risk air leaks and reduced fuel efficiency. Beginners shouldn't attempt this themselves—leave it to professional shops for peace of mind. Last time I helped a friend adjust a car with 0.6mm excessive clearance, the engine was rattling badly. After adjustment, it ran as smoothly as new. Though a small job, regular checks can significantly extend engine life.
