The thermal clearance of the valve and its adjustment

In any ICE for the organization of normalValve mechanisms are applied. A small part of the torque is taken to the crankshaft drive. During heating, the metal has properties to expand. Consequently, the dimensions of the motor parts change. The dimensions of the timing elements are also changing. If the valve thermal gap is not provided in the timing gear, the valves will not close tightly when the engine is heated to its optimum operating temperatures. As a consequence, they will not provide the required tightness.

For this reason, the engine performancemay deteriorate. But that's not all. The resource of the valves decreases - the edges of the plates are often burned. During operation of the valve, its surface wears out, and the thermal gaps increase. This leads to a more noisy motor operation. To avoid this, and the engine always worked smoothly and quietly, it is necessary to periodically adjust the thermal gap of the valve. For this, the engineers have provided a special mechanism or washers for adjustment.

Importance of adjusting the clearances

After starting the engine and all its elementswarm up and, as follows from the school course of physics, are expanding. Also rubbing elements wear out for natural reasons. This makes it necessary to have an exact gap between the elements of the timing system. And the distance between the cam on the camshaft and the valve is one of the most important factors.

When the thermal gap of the valve is less than necessary,the motor will not be able to maximize the potential built into it by the manufacturer. This will necessarily affect the dynamics and speed characteristics of the machine. At the same time, the intake valves will overheat. Their edges are melted.

If the gap is increased, the car owner willhear the knocking of the valves. It will disappear as the engine warms up. At large distances, the camshaft cam knocks on the rocker rod rocker, instead of pressing on it.

Signs of need for setting

The fact that the thermal gap of the valve is setincorrect, some signs will say. So, the first symptom is characteristic ringing sounds in the area of ​​the head of the cylinder head. Another sign - reduced engine output, and with it a high fuel consumption.

Also adjustment of gaps is necessary, ifany repair of the gas distribution mechanism was carried out. It is necessary to perform the adjustment, if the last clearances were exposed more than 20 thousand kilometers ago.

There are other signs. This is increased oil consumption, shots in the silencer or intake manifold, an error in the rich or too lean mixture. The state of the spark plugs will also tell about incorrect thermal gaps. They will be raided.

How often should I adjust?

On cars VAZ thermal clearances of valves onthe manufacturer's regulations must be regulated every 45 thousand kilometers. But often the need for tuning appears much earlier. Experts recommend to adjust the timing elements at least 20 thousand kilometers. And if the engine operates under maximum loads, then 15. This figure is also due to the quality of spare parts for domestic cars, which quickly wear out even under ideal operating conditions.

Measuring thermal clearances

It is also possible to make sure that theaid measurements. Checking the thermal gaps of the valves are always carried out on a cold motor. To perform the operation, you will need a measuring probe and a set of tools. What will go into this kit depends on the type of valve pusher.

If the gaps are adjusted by means of a screw, thena spanner, a hammer and a hammer. If the adjustment of the valves in the engine is carried out by means of washers, then a set of washers must be purchased. The latter must be of different sizes. You will also need a micrometer, puller, tool for replacing washers and tweezers.

To adjust the clearance, crankshaft should be crankedso that the cam on the camshaft for the selected valve is facing away from the pusher. At the latter, light punches are applied with a hammer. Then the valve is swung with your fingers.

Then use a feeler gauge to measure the gap.Do this between the pusher and the valve. The measurement values ​​are verified with nominal dimensions. They can be found in the instructions for the car. If the value is different, then it should be adjusted. How to change thermal clearances on the motor, whereadjustment is carried out with the help of washers? The crankshaft should be cranked so that the cam on the camshaft looks up towards the pusher. Then, using a set of probes, the gap is measured. Values ​​are compared with nominal values ​​and adjusted if necessary.

Technology settings

Let's look at how to adjust the heatvalve clearance on the example of VAZ engines. The very first thing to do is put the piston of the first cylinder in the position of the top dead center. This is done very simply. The crank is cranked to the point of coincidence of the marks on the camshaft star with the crankshaft pulley and on the cylinder block. After that you can proceed with the adjustment. The scheme for adjusting the thermal gaps of valves on diesel engines is similar to this.

The touch probe is inserted between the workersThe cam and lever surfaces on the corresponding valve. If the probe comes with small difficulties, then the gap is OK. If it does not go or enters too tightly, then the distance must be adjusted. To do this, hold the head on the adjusting bolt with a 13-key. At the same time, the key is released on the 17th counternut and turn the bolt in the required direction. Twist until you get the right clearance. Then you need to check the parameter, then tighten the nut. In which order should the valves be adjusted? The technology of tuning is discussed below.

The order of adjustment of thermal gaps of valves

The first to adjust the eighth valve,located on the fourth cylinder. After it - the sixth valve of the third cylinder. The gaps are adjusted in pairs. For each engine crankshaft is rotated by 180 degrees. For each of the subsequent turns, adjust the fourth and seventh valves, the first and third, fifth and second, respectively.

Control measurement

Even professionals can not always adjustthe gaps are correct the first time. Therefore, the control measurements of the thermal gaps in the valve actuator are mandatory. If there is a discrepancy, then you need to adjust again. After such adjustment the engine will work much more silently, more stable and will please its owner.

So, we found out what the thermal gap is, and how to properly adjust it yourself.