Valve clearance and adjustment

2024 Author: Erin Ralphs | [email protected]. Last modified: 2024-02-19 11:41

In any internal combustion engine, valve mechanisms are used to organize normal gas distribution. A small part of the torque is taken to the crankshaft drive. In the process of heating, the metal has the ability to expand. Consequently, the dimensions of the motor parts change. The dimensions of the timing elements also change. If the timing drive does not have a thermal valve clearance, then when the engine is heated to its optimum operating temperatures, the valves will not close tightly. As a result, they will not provide the required tightness.

For this reason, engine performance may deteriorate. But that's not all. The life of the valves is reduced - the edges of the plates very often burn. During operation of the valve, its surface wears out, and thermal gaps increase. This leads to a noisier operation of the motor. To prevent this from happening, and the engine is always runningsmoothly and quietly, it is necessary to periodically adjust the thermal clearance of the valve. For this, engineers have provided a special mechanism or washers for adjustment.

Importance of setting clearances

After starting, the motor and all its elements warm up and, as follows from the school physics course, expand. Also, rubbing elements wear out for natural reasons. This necessitates the presence of an accurate gap between the elements of the timing system. And the distance that there is between the cam on the camshaft and the valve is one of the most important factors.

When the thermal clearance of the valve is less than necessary, the motor will not be able to maximize the potential inherent in it by the manufacturer. This will definitely affect the dynamics and speed characteristics of the car. At the same time, the intake valves will overheat. Their edges are melted.

If the gap is increased, the car owner will hear the sound of valves. It will disappear as the engine warms up. At longer distances, the camshaft cam taps on the valve stem rocker instead of pressing on it.

Signs for tuning

There are some signs that the valve clearance is set incorrectly. So, the first symptom is the characteristic ringing sounds in the area of \u200b\u200bthe cylinder head cover. Another sign is reduced engine output, and with it high fuel consumption.

Also, clearance adjustment is necessary if any repair of the gas distribution mechanism was performed. Requiredadjust if the gaps were last set more than 20 thousand kilometers ago.

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

How often should I adjust?

On VAZ vehicles, according to the manufacturer's regulations, thermal valve clearances must be adjusted every 45 thousand kilometers. But often the need for tuning appears much earlier. Experts recommend adjusting the timing elements at least after 20 thousand kilometers. And if the engine is running under maximum load, then 15. This indicator is also determined by the quality of spare parts for domestic cars, which wear out quickly even under ideal operating conditions.

Measurement of thermal gaps

You can also verify the need for adjustment using measurements. Checking the thermal clearances of the valves is always carried out on a cold engine. To carry out the operation, you will need a measuring probe and a set of tools. What is included in this kit depends on the type of valve lifter.

If the gaps are adjusted by means of a screw, then you need a ring, open-end wrench and a hammer. If the valves in the engine are adjusted using washers, then a set of washers should be purchased. The latter must be of different sizes. You will also need a micrometer, puller,washer replacement tool and tweezers.

To adjust the clearance, the crankshaft should be rotated so that the cam on the camshaft for the selected valve faces the other way with respect to the tappet. The latter is lightly hit with a hammer. Then use your fingers to rock the valve.

Next, use a feeler gauge to measure the gap. This must be done between the pusher and the valve. The measurement values are compared with the nominal dimensions. They can be found in the owner's manual. If the value is different, then it should be adjusted.

How to change the thermal gaps on the motor, where the adjustment is carried out using washers? The crankshaft should be rotated so that the cam on the camshaft is facing up in relation to the tappet. Next, using a set of probes, the gap is measured. Values are compared with nominal and adjusted if necessary.

Tuning technology

Let's look at how to adjust the thermal clearance of valves using the example of VAZ engines. The very first thing to do is to set the piston of the first cylinder to the top dead center position. This is done very simply. Turn the crankshaft with a key until the marks on the camshaft star coincide with the crankshaft pulley and on the cylinder block. After that, you can start adjusting. The scheme for setting thermal valve clearances on diesel engines is similar to this one.

The measuring probe is inserted between the working surfaces of the cam and the lever on the corresponding valve. If the probe goes with little difficulty, then the gap is in order. If it does not go or enters too tightly, then the distance must be adjusted. To do this, use a 13 key to hold the head on the adjusting bolt. At the same time, with a key of 17, the lock nut is released and the bolt is turned in the required direction. Twist until the desired clearance is obtained. Then you need to check the parameter, and then tighten the nut. In what order should the valves be adjusted? We will consider the tuning technology below.

Procedure for adjusting valve clearances

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

Control measurement

Even professionals can't always get the gaps right the first time. Therefore, control measurements of thermal gaps in the valve drive are mandatory. If there is a discrepancy, then you need to configure it again. After such an adjustment, the engine will run much quieter, more stable and will please its owner.

So, we found out what a thermal gap is and how to properly set it up with your own hands.