Why do I need valve adjustment and how to get rid of it? What causes valve clearance to increase. Consequences of incorrect valve clearances

01.10.2019

5 years ago

Welcome!
Valve adjustment - most people, of course, know what this process is and why it needs to be done regularly on some cars, for example, on the Classic, but there are people who don’t know anything about it and want to understand this issue, therefore, especially for such people this article was prepared from which you will learn a lot. And if something becomes unclear to you, then in this case, write a comment with your question at the very bottom of the site and we will answer it as soon as possible.

Note!
And in addition, at the end of the article, an interesting video clip awaits you, thanks to which you will understand a lot for yourself in adjusting the valve drive!

Why do you need to adjust the valves?

Their adjustment is necessary in order for the machine to work more stably both at high and at low engine speeds. Because, as a rule, due to improper valve adjustment, the gaps that should be between the camshaft cam and the valve itself are violated, which leads to too much valve opening during engine operation and as a result, depressurization will occur in the cylinder, which in turn can adversely affect the engine life .

Note!
In the event that the gap between the valve seat and the side particles of the cylinder has become very large (see photo below, this gap is marked there), then in this case the valve may burn out, and also if the piston stroke is very large, then meeting of valves with the piston itself during engine operation. Therefore, the valves must be adjusted periodically and with great care, since incorrectly set gaps during adjustment can again adversely affect the life of the motor!

How will the valves work if the clearance is incorrectly set?

In this case, as mentioned earlier, the operation of the valves is disrupted, in connection with this, the valves either start to open a little more than it should be, or they start to be in a constantly open position, due to which the sealing in the cylinder disappears, for clarity, look at the photo below on which the valve adjustment is broken and in connection with which the valve is in a permanently open mode.

How to get rid of valve adjustment?

Have you ever asked yourself: “Why, for example, on a 16-valve prior, do you not need to adjust the valves?” And the thing is that in the priors engine, instead of the “Pusher”, due to which the camshaft cam pushes the valve, there are “Hydro-compensators”, which, in turn, due to the high oil pressure, find the optimal gap between the cam and the “Hydro-compensator” itself valves and therefore valves always operate at optimum clearances.

Note!
By the way, "Hydro-compensators" can be installed on almost any car, and therefore you can forget about valve adjustment, but there is one But! "Hydro-compensators" can only be installed on cars in which the "Gas Distribution Mechanism - aka Timing" consists of a camshaft, crankshaft, as well as valves and a piston group - in fact, this is the main part of cars!

On the engines of many modern cars, valve clearance adjustment is not necessary due to hydraulic lifters. If there are none, then the manufacturer must indicate in the repair manual the exact dimensions of the engine valve clearances, non-observance of which leads to:

to reduce engine power;
its unstable idling;
increased fuel consumption;
premature wear and failure of timing parts and some others (we will consider later).

Valve clearance measurement

When the engine is running, the parts of the gas distribution mechanism become very hot. Because of this, there is a linear increase in their size. Therefore, when assembling, it is important to observe the thermal clearance of the valves, which compensates for such an increase. This will prevent increased friction between parts. But the increased valve clearances do not allow the drive mechanism (which includes the camshaft, rocker arms, pushers, etc.) to open them to the required amount. Let's see what this leads to.

An insufficiently open intake valve will prevent the combustion chamber from filling with a fuel mixture, which will adversely affect engine power.
Graduation in such a situation will prevent the removal of combustion products, due to which soot appears on the parts, which will be deposited on:

the bottom of the piston and the surface of the combustion chamber, impairing heat dissipation and thereby contribute to overheating of parts;
a spark plug of a gasoline engine or a glow plug of a diesel engine, which will fail prematurely because of this;
the working surface (chamfer) of the valve and its seat, which will prevent their tight fit to each other and cause a decrease in compression in the cylinder.

In addition, large valve clearances increase the shock loading of interacting parts and can cause:

hardening of the upper ends of the valves;
saddle deformation;
breakage of springs;
pusher damage;
rocker breakage.

On a running engine, excessive clearances give themselves out as a sonorous characteristic knock.

The reduced clearances of the engine valves can prevent the latter from fitting tightly to the seats, due to the fact that the valve “elongated” from heating will be pressed from the seat by the pusher. In this case, a significantly overheated edge of the outlet may burn. In addition, the compression naturally decreases.

Gap between valve and guide sleeve

Excessive increase in the diameter of the guide sleeve hole due to wear leads to the fact that the valve-sleeve pair begins to work like a vacuum pump, “pumping out” oil from under the valve cover into the combustion chamber. We have already talked about what the formation of soot leads to. Another unpleasant consequence of bushing wear is oil consumption.

Measurement and adjustment

Valve clearance adjustment

A detailed description of these procedures will take up the size of a brochure, since along the way one would have to go into the technical terminology and details of the timing device of various designs.
The basic and necessary rules relating to all internal combustion engines without exception:

valve clearances should be measured and adjusted only on a cold engine;
these actions should be carried out only when the valve is closed, for which you need to know the order of operation of the cylinders and the location of the alignment marks on the sprockets (gears) of the camshaft (or camshafts) and crankshaft;
the marks on the sprockets and gears must be exactly aligned with the marks on the engine housing by turning the crankshaft in the direction of rotation. For two revolutions of the crankshaft, the camshaft makes one revolution.

The simplest measuring tool is a valve gauge. For classic Zhiguli, for example, it is sold separately (0.15 mm), but on some engines not all valves have the same gap size (for example, on ZMZ-402) and a set of probes is required. Using a micrometer will give you greater accuracy, but you must use it in conjunction with a gap gauge.

Special tools are used to adjust valves.

For the same Zhiguli, it is a rail that is installed on the studs for fastening the “bed” of the camshaft. It shows the angles of rotation corresponding to the closed position of a valve.

In addition to measuring tools, sometimes you need devices for adjusting valve clearances.
For example, on engines of the VAZ 2108 family, this is a set of two tools. With one valve follower (“glass”) is pressed from the camshaft cam, with the other this position of the follower is fixed, which allows you to replace the adjusting washer.

In any case, if you decide to make the adjustment yourself, auto parts stores will not leave you with your bare hands.
For more information about adjusting valve clearances (for example, VAZ cars), see the video on our website!

Simple in appearance, the valves of an internal combustion engine perform the most important work in it: they control the processes of supplying the fuel-air mixture and removing exhaust gases from the engine cylinder. The efficiency of the engine depends on how timely these processes take place: its power, efficiency, toxicity, and even the very ability to work.

How ICE valves should work

The working cycle of a four-stroke engine consists of four strokes: intake, compression, power stroke and exhaust. Based on the purpose of these cycles, one can understand how the gas distribution mechanism should work: on the intake stroke, the intake valve is open, allowing the fuel-air mixture to enter the cylinder; on the compression stroke, both valves are closed (otherwise you won’t compress); during the working stroke, the valves are also closed so that all the expansion energy of the burning mixture is directed only to moving the piston; during exhaust, the exhaust valve is open and the exhaust gases leave the cylinder through it.

Exactly the way it would be if the valves were able to open and close instantly, while the piston is in its dead center, top or bottom. To imagine what a moment is for a period of time during which an engine cycle occurs, we must remember that modern engines easily achieve six or more thousand revolutions of the crankshaft per minute. In one working cycle, the crankshaft makes two revolutions, which means that each of the valves opens and closes three thousand times per minute. And the piston is in its dead points six thousand times! For comparison, the rate of fire of the legendary Kalashnikov assault rifle is only six hundred rounds per minute, exactly ten times less! Under such conditions, even a few milliseconds of engine operation is a noteworthy time period during which very important processes take place.

In theory, during the compression and power strokes, both valves are closed. In the figure: I - intake stroke, intake valve is open; II - compression stroke; III - working stroke; IV - exhaust stroke, exhaust valve open

And even if modern valves can move much faster than their ancestors a hundred years ago, the properties of the combustible gases they control have not changed much. They are also easily compressed when exposed, and also stubbornly continue to strive in all directions equally, obeying Pascal's law, which means they are in no hurry to move where they are asked. And in order to ensure that the cylinder fills as much as possible in such a short period of time, the intake valve begins to open before the piston completes the exhaust stroke. And the exhaust will begin to open before the end of the stroke, so that the hot gases under pressure in the cylinder do not create excessive resistance to the movement of the piston when the exhaust stroke begins.

The moments of time when the opening begins, the duration of their stay in the open and closed states, form the valve timing of the engine. The camshaft controls the movement of the valves, in the form of the cams of which the information about the valve timing of your engine is “encrypted”. The phase values are selected when designing the engine, depending on its design, purpose, and operating conditions. In the most advanced engines, these phases can change for specific operating conditions and loads at a given time. In conventional engines, the only effective way to change the valve timing is to replace the camshaft. Changing the valve timing by installing the original camshaft is one of the advanced engine tuning methods. When agreeing to such a procedure, we must understand that an increase in engine power will occur due to a deterioration in efficiency and a decrease in the resource of its parts. Therefore, such a setting, as a rule, is used on sports cars, where the resource, efficiency and environmental friendliness of the engine are of secondary importance.

In a real engine, when the piston is near its top dead center (TDC) and bottom dead center (BDC), the intake and exhaust valves are open at the same time.

Where to install the camshaft

There are different options for the location of the camshaft in the engine and the design of the mechanisms that transmit pressure from the surface of the camshaft to the valve stem. However, the increase in the speed of modern passenger engines has led to the fact that everywhere they have a fixed scheme with the location of the camshaft in the engine head - the upper structure. The proximity of the camshaft to the valves allows you to increase the rigidity of the system, and therefore increase the accuracy of work.

The prototype of the first Zhiguli VAZ-2101, the Italian Fiat-124, had a solid and reliable, but already outdated engine design with a lower camshaft. Soviet engineers decided that the engine of our new car should keep up with the times, and together with the Italians they modernized it by moving the camshaft to the block head.

Why gaps are needed

The valve closes under the action of a special spring. So that the profile of the cam under no circumstances could prevent the complete closing of the valve, a strictly defined gap is set between it and the pusher. Moreover, this gap should also take into account the increase in the length of the rod during heating. And the valve heats up during operation can be very strong.

The intake valve head of an automobile engine heats up to a temperature of 300-400 degrees Celsius. And the exhaust, which is "washed" by hot exhaust gases - up to 700-900 degrees, while becoming a dark cherry color.

Ways to provide a thermal gap

In the overhead scheme, the camshaft acts on the valve stem either directly or through a rocker arm. The use of a rocker arm makes it possible to reduce the difference in the camshaft profile relative to the value of the maximum valve movement during opening. With the direct impact of the camshaft on the valve stem, the stem perceives a significant lateral force, which leads to increased wear. To avoid this, the end of the rod is covered with a special glass, which takes on the lateral force, moving in its own guide socket, and transfers the axial force to the valve. Adjusting washers are installed between the glass and the camshaft cam. If there are rocker arms in the design, then special adjusting screws with lock nuts are installed on them.

Many modern engines, especially those with more than two valves per cylinder, are equipped with hydraulic valve clearance compensators. In these designs, adjustment of thermal gaps is not required.

Valve adjustment: when and how

As a rule, the gap is checked and adjusted at each maintenance. The procedure is performed on a cold engine. To do the job, you will need a feeler gauge and normal hand tools, depending on the fasteners used on your vehicle. For valves with shims, tweezers are also useful. Before starting, be sure to read the repair manual for your car, which indicates the clearance values, engine design features, and describes the sequence of its disassembly and assembly. In general, the workflow is as follows:

remove the valve cover;
look for marks on the engine block and crankshaft (usually on the timing belt pulley);
turning the crankshaft with a suitable key (but in no case with a starter!) in a clockwise direction, when viewed from the front of the engine, align the marks with each other. In this position, the piston of the first cylinder is at top dead center, both valves are closed;
check the gap between the first - from the side of the pulley - the camshaft cam and the adjusting washer (rocker striker);
if the gap is greater than required, the washer should be replaced with another one of greater thickness; if the gap is smaller, then, accordingly, the thickness of the washer must be reduced. The nominal thickness of the washer is usually marked on the washer itself. If the thickness of the washer is unknown, then you will need a micrometer to properly select a new washer. In designs with a rocker arm, the procedure is simpler, since we achieve the required clearance by screwing in or out of the adjusting screw. Be sure to tighten the locknut after adjusting the screw.
After adjustment is made, the clearance check must be repeated. Tolerance: plus or minus 0.05 mm.
Pay attention to the fact that the clearance for the intake and exhaust valves is usually different. This is due to the different heating temperatures, as mentioned above. So, for an eight-valve VAZ engine, the clearance on the intake valve is 0.20 mm, and on the exhaust valve - 0.35 mm.
Repeat the work for all cylinders, determining their sequence and the angle of rotation of the crankshaft in accordance with the recommendations of the engine manufacturer.

Video: how to adjust clearances on front-wheel drive Frets

In general terms, the design of the gas distribution mechanism and the procedure for adjusting the valve clearance on a diesel engine is the same as on a gasoline engine.

There is an opinion that after installing gas-balloon equipment on the engine, it is necessary to change the thermal clearance in the valves in the direction of increasing. This is explained by the higher combustion temperature of the gas. Actually, this is not required. The features of ignition and combustion of the gas mixture in the cylinder are taken into account by changing the ignition angle, and the process of filling and removing gases from the cylinder does not differ from that when the engine is running on gasoline.

When the gap is not only seen, but also heard

Valve clearances are often audible, especially in cold weather. This is expressed in a slight metallic click when the engine is cold. As it warms up, the sound weakens. If it is also heard on a warm engine, then most likely all or some of the gaps are larger than normal. An increased thermal gap reduces the time the valve is open, which reduces the efficiency of the engine, it starts to work intermittently, starts poorly, and detonation combustion may occur, which adversely affects engine parts. The reduced clearance is even more dangerous, because it completely disappears in the engine warmed up to operating temperature and the valve stops closing completely. As a result, the power and economic indicators of the engine also decrease, but the most unpleasant thing is when the conical chamfers on the valves and on their seats burn, and this problem cannot be corrected by simply adjusting the clearance.

The engine is the heart of the car, so any signs of deterioration in its performance should put you on your guard and, at the first opportunity, start diagnosing it. If power has dropped, fuel consumption has increased, if the engine “troits” or pops are heard in the exhaust system, check the spark plugs and check the valve clearances.

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 provide for thermal, 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 be degraded. But that's not all. The resource of 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 always runs smoothly 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 Clearance Adjustment

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 exists 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 it. It will disappear as the engine warms up. At longer distances, the cam hits the valve stem rocker instead of pushing against it.

Signs of a need for customization

Some signs will tell you that the thermal clearance of the valve is set incorrectly. So, the first symptom is the characteristic ringing sounds in the cylinder head cover area. Another sign is reduced engine output, and with it high fuel consumption.

Also, adjusting the gaps is necessary if any was performed. It is imperative to perform the adjustment if the last time the gaps were set more than 20 thousand kilometers ago.

There are other signs as well. 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 do you need to adjust?

On VAZ vehicles, according to the manufacturer's regulations, the thermal clearances of the valves 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 a box, open-end wrench and a hammer are needed. 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, a puller, a washer replacement tool and tweezers.

To adjust the gap, the crankshaft must 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 swing the valve with your fingers.

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 looking up in relation to the tappet. Next, using a set of probes, the gap is measured. The values are compared with the nominal values and adjusted if necessary.

Customization 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 the thermal clearances of valves 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 we consider the tuning technology below.

The procedure for adjusting the thermal clearances of valves

The first to be adjusted is 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 are not always able to set the gaps correctly the first time. Therefore, control measurements of thermal clearances in the valve drive are mandatory. If there is a discrepancy, then you need to configure again. After such an adjustment, the engine will run much quieter, more stable and will delight its owner.

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

The smooth operation of an internal combustion engine requires periodic adjustment of its valves. They are located in the cylinder head and belong to the gas distribution mechanism. We will tell you how to adjust the valves yourself.

Preparing for engine valve adjustment

The operation of adjusting valve clearances is included in the maintenance of your car. On domestic cars, it is carried out every 15 thousand km, for foreign cars - every 30 thousand or 45 thousand km. The fact is that when the gaps change, the gas distribution phases shift. The engine in this case starts to work intermittently due to a lack or excess of fuel. In the most advanced cases, compression will disappear (the motor simply will not start) or the valves will meet the pistons (a major overhaul of the device will be required). The latter is true for both gasoline and diesel engines.

How to determine if adjustment is required

Professionals identify the following symptoms of improperly adjusted gaps:

The engine is troit, the compression in the cylinders is noticeably different or completely absent. If the gaps are too small, the valves do not close completely, therefore, the tightness of the combustion chamber is violated.
There is an extraneous knock in the upper part of the engine. This can be caused by both too large (knock pushers on the valves) and too small (valves rest against the pistons) gaps.

If any of the listed symptoms are present, the gaps in the valve mechanism should be checked.

Adjustment of gaps is always carried out on a cold engine. At the same time, the cylinder head with camshaft is installed and tightly tightened. The dependence of the size of the gaps on temperature is given in the table.

Table: dependence of the size of the gaps on temperature

Standard 0.15
Temperature degrees	mm	indicator
-10	0.128	44.1
-5	0.131	45.4
0	0.135	46.8
10	0.143	49.4
20	0.15	52

From the table it follows that the optimum temperature for adjustment is 20 degrees.

Clearance adjustment is mandatory:

after the engine overhaul;
after removal and installation of the cylinder head.

When replacing equipment with a gas-balloon one, it is not necessary to adjust the valves.

Valve adjustment on domestic cars

The most simple adjustment is carried out on domestic cars of the VAZ family.

Video: how to adjust valve clearances on a VAZ 2106

Clearance adjustment is made using a flat probe. First, set the piston of the first cylinder to top dead center (TDC). Then we adjust the gaps according to the table.

Table: valve clearance adjustment sequence

The adjustment process varies depending on the VAZ model. So, on the VAZ 2106, the gaps in the valve mechanism are adjusted using a screw with a lock nut.

On the VAZ 2108-09, shims are used for this, and the clearance is determined using flat probes.

Previously, in the days of the USSR, a special rail with an indicator was used to accurately adjust the valve clearances.

Previously, a rail with an indicator was used to control valve clearance.

Adjusting the clearances of the VAZ 2106 engine is carried out immediately, without intermediate measurements. On the VAZ 2108–09, a set of shims should be used. After measuring the clearance, the old washer is pulled out, and in its place, taking into account the measurements taken, a new one is selected.

To replace the washers, you need a special puller.

When adjusting the clearances, the valve cover is first removed, and then the puller is installed.

When adjusting valve clearances, the type of engine (gasoline, diesel or gas) is absolutely not important. Only the design of the “valve - pusher - camshaft” assembly matters. By changing the gaps, it is possible to shift the valve timing by several degrees (the opening and closing moments, expressed in degrees of rotation of the crankshaft).

Phase shift occurs when the camshaft is displaced relative to the crankshaft by rearranging the timing chain or belt. Usually, such an adjustment is needed only when boosting engines or chip tuning, so we will not consider it here.

Modern engines often use hydraulic lifters. With their help, the valves are adjusted under the action of a spring and oil is supplied from the engine lubrication system. In other words, hydraulic lifters automatically adjust clearances while the engine is running.

How to adjust valve clearances on foreign cars

First of all, using the instructions for the repair and maintenance of your car, we determine the type of engine. The fact is that some foreign cars can have up to ten types of engines on one car model. The tool required for adjusting and setting the timing marks is also indicated there. However, in most cases a set of wrenches and flat feeler gauges will suffice. Consider the features of adjusting clearances on the Mitsubishi ASX 1.6 with a gasoline and diesel engine.

Gas engine

To do this, follow these steps:

We remove the plastic casing of the engine (it is held on by rubber latches).
We dismantle the ignition coils and valve cover.
We set both camshafts according to the marks (the nominal gaps of the intake and exhaust valves are also indicated here).
We measure with the help of probes the gaps “Second and fourth cylinder - inlet valves”, “First and third cylinder - exhaust valves”. Record the measurement results.
Rotate the crankshaft 360 degrees. Then we combine the marks on the camshafts and measure the clearances of other valves.
We remove both camshafts, take out the adjusting cups and, using the above formula, calculate the size of the new cups.
We install new cups and install the camshafts in the cylinder head.
We apply sealant to the indicated places and twist the valve cover.

diesel engine

Sometimes Mitsubishi ASX 1.6 can be equipped with a diesel engine. In this case, the valves are adjusted using bolts in the pushers.

The main signs of improperly performed work

If the valve clearances are set correctly, the engine will run quietly and smoothly. With increased intervals, it will emit extraneous knocks and noises, with reduced intervals, it will work unevenly. Further operation of such a car is impossible, it is necessary to repair it yourself or contact a service center. Otherwise, you may lose your car.

The trouble-free operation of your vehicle is largely determined by regular valve clearance adjustments. The frequency of these operations is set by the manufacturer, and the adjustment technology is quite simple and does not require special knowledge and skills. Good luck on the roads!