How to Adjust the Valves of a Four-Cylinder Engine?
2 Answers
To adjust the valves of a four-cylinder engine, first rotate the first cylinder to the compression top dead center (there is a scale on the crankshaft pulley or a mark on the crankshaft flywheel) and align it with the 0 mark or the pointer in the timing gear chamber. Adjust the intake and exhaust valves of the first cylinder, the intake valve of the second cylinder, and the exhaust valve of the third cylinder. Then rotate the engine 360 degrees and adjust the exhaust valve of the second cylinder, the intake valve of the third cylinder, and the intake and exhaust valves of the fourth cylinder. Below are some important considerations: 1. When the engine is running, the valves operate at high temperatures, causing thermal expansion and elongation of the valve components. Therefore, a certain valve clearance must be reserved when the valves are cold to ensure that the valves and valve seats remain tightly sealed even when the valves expand due to heat. Over time, the original valve clearance may change. Thus, if you hear a "clicking" noise from the valves, you should check and adjust the valve clearance. 2. When adjusting the valve clearance, it is essential to follow the manufacturer's specified values and ensure the valves are fully closed during the adjustment. The adjustment locations for valve clearance are: on the tappet for side-valve engines and on the rocker arm for overhead-valve engines. Common valve adjustment methods include: single-cylinder adjustment, two-step adjustment, and expression method. However, due to the wide variety of engines and the different sequences of intake and exhaust valves, these methods can be cumbersome and hard to remember. Moreover, if the engine's firing order (or injection order) is unknown, the adjustment process becomes even more complicated.
When I first bought my car, I learned to adjust the valves myself. This job must be done when the engine is cold to avoid burns. First, find a quiet place, turn off the engine, and wait for about an hour until the temperature drops to a safe level. I usually remove the spark plugs first, then rotate the crankshaft to find the top dead center of the compression stroke, ensuring the pistons and valves are stationary. Next, use a feeler gauge to measure the gap between the valve rocker arm and the cam—typically, the intake valve clearance for a four-cylinder engine is around 0.15mm, while the exhaust valve might be slightly wider. If the gap is too large or too small, use a wrench to loosen or tighten the adjustment screw, or replace the shim with the appropriate one. Don’t forget to measure again after adjustment to confirm. The key is not to rush; take your time. Incorrect adjustments can lead to burnt valves or engine knocking. I’ve seen beginners rush and set the wrong gap, ending up with repair bills over a thousand dollars. For regular maintenance, it’s best to check every 20,000 kilometers to prevent issues. You don’t need many tools—just a feeler gauge and a wrench. Doing it yourself saves money and helps you learn new skills.
