Adjustment method of valve clearance of automobile engine

How to adjust the valve clearance of automobile engine When the engine is working, because the valve works at high temperature, the valve and other parts are extended due to thermal expansion, so a certain valve clearance must be reserved when the valve is cold, so as to ensure that the valve and the valve seat can still cooperate closely when the valve expands and extends when heated. Because the valve works for a long time, the original valve clearance is changed. Therefore, when you hear the abnormal sound of the valve, you should check and adjust the valve clearance.

1. A simple method to determine 1 cylinder compression top dead center

If the ignition sequence (or fuel injection sequence) of the engine is known, the compression top dead center position of 1 cylinder or cylinder 6 should be found accurately when adjusting the valve clearance. At present, the method of determining the compression top dead center of 1 cylinder or cylinder 6 is complicated and troublesome to operate (that is, remove the spark plug of 1 cylinder, plug the spark plug hole of 1 cylinder with thumb or cotton ball, and then crank the crankshaft. When the thumb feels pressure or the cotton ball jumps out, it is the compression top dead center position of cylinder 1). According to the author's maintenance experience, this paper introduces a simple and practical method: the pistons of 1 cylinder and cylinder 6 (cylinder 4) are on the same plane, and when the compression of 1 cylinder ends, the valves of cylinder 6 or cylinder 4 overlap to determine. That is, 1 cylinder compression TDC, the exhaust valve of cylinder 6 (cylinder 4) is closed, and the intake valve has just been pushed up, so it is difficult to grasp the descent of the exhaust valve, and it is easy to observe the upward push of the intake valve. As long as the ejector pin of the intake valve is slightly upward, the cylinder 1 will be in the compression TDC position. Similarly, when the intake valve push rod of cylinder 65438 is +0 inch, cylinder 6 (cylinder 4) is in the compression top dead center position.

2. Skills for determining adjustable valves

Taking a 6-cylinder engine with 1-5-3-6-2-4 power sequence as an example, the simple adjustment method and formula are explained. When it is determined that engine cylinder 1 is at compression top dead center, the valve of cylinder 1 is fully adjusted, and the exhaust valves of cylinders 5 and 3 are adjustable at the beginning of compression and intake process. No.6 cylinder can be adjusted when the intake air overlaps. At the end of exhaust and work of cylinders 2 and 4, the intake valve of cylinder 2 is adjustable. After adjustment, all the remaining valves can be adjusted in turn after the crankshaft is rotated by 360.

It can be summarized as the formula: full harmony and non-harmony. It can also be summarized as: take the first cylinder, remove the middle, adjust the front row, adjust the rear row, 360, and the rest cylinders are carried out in turn. That is, the intake valve is adjusted for the cylinder before the cylinder 6 and the intake valve is adjusted for the cylinder after the cylinder 6. If cylinder 6 is at the compression top dead center (6-2-4- 1-5-3), its reasoning method is the same, starting from cylinder 6, it is also fully harmonious and uncoordinated. That is, the intake valve of the cylinder before 1 and the intake valve of the cylinder after 1.

This method can also be used for 4-cylinder and multi-cylinder engines. Taking a 4-cylinder engine with the working sequence of 1-3-4-2 as an example, the formula is still full harmony and non-harmony. That is, the intake valve of the cylinder before cylinder 4 and the intake valve of the cylinder after cylinder 4. The intake valve and exhaust valve of cylinder 4 are not adjusted.

The above reasoning shows that as long as you remember the formula and know the working order of the engine, you can easily determine the adjustable valve.