How to adjust valve clearances, signs and symptoms of improper adjustment, work procedure, etc.

Depending on the type of engine, different cars may have two or more valves on a cylinder. Some, inlet, are used to admit a mixture of fuel particles with atmospheric air, and others, exhaust, are used to release used gases. A special mechanism leads them to the required action. There is a lot of debate today about how valves should be adjusted correctly.

Misregulation and consequences

When the thermal clearance of the valve changes during long-term operation or when individual elements of the system break down, the efficiency of the engine and the service life of the parts are significantly reduced. This is also accompanied by increased fuel consumption and a characteristic knocking noise in the engine compartment. If, for example, the gap is larger than normal, the element cannot open completely, and this contributes to a drop in power characteristics. Burning of the valve and its seat is possible if the gap is very small. In any case, these faults have a bad effect on the engine's response when you press the accelerator pedal.

Gap function

There are at least 2 valves in a car engine cylinder (maybe more depending on the car model). Through the inlet valve the combustible mixture enters the cylinder, and through the outlet valve the gases are removed. The part is driven by a gas distribution mechanism.

During operation, the motor heats up, resulting in expansion of all its elements. Therefore, when the motor is not running (in a cold state), there must be a gap between some parts sufficient for thermal expansion of the metal.

The role of valves and valve timing in an engine

One of the most important characteristics of an engine when it comes to its maximum power output with acceptable fuel consumption is filling the cylinders with fresh mixture. It enters the working volume through the valve system, and they release the exhaust gases.

When the engine operates at significant speeds, and with some assumption they can be considered both maximum and minimum idle speeds, the masses of gas passing through the cylinders begin to manifest their aerodynamic properties, inert and others related to the efficiency of combustion and thermal expansion.

The accuracy and optimality of selecting fuel energy and converting it into mechanical energy depend on the timely supply of the mixture to the working area, followed by its equally prompt removal.

On the subject: PCV valve or how crankcase ventilation works

The moments of opening and closing of the valves are determined by the phase of movement of the piston. Hence the concept of valve timing.

At any time, and for a motor this means the angle of rotation of the crankshaft and a specific stroke of the engine within the cycle, the state of the valve is determined quite clearly. It can only depend on the speed and load within strictly standardized limits set by the phase adjustment system (phase regulators). They are equipped with the most modern and advanced engines.

How should the elements work?

The operation of a 4-stroke engine includes 4 cycles.

Each cycle has its own purpose:

1. Intake - the intake valve opens and the fuel mixture is supplied to the cylinder.
2. Compression - the valves are closed, the fuel mixture is compressed.
3. Power stroke - the valves are closed, the burning mixture expands, its energy is directed to move the pistons.
4. Exhaust - the exhaust valve opens, exhaust gases are removed.

For the motor to operate efficiently, the clearances must be properly adjusted.

The importance of adjusting engine valve clearances

After the start, the engine and all its parts begin to heat up, and therefore expand. At the same time, we should not forget about the natural wear and tear of rubbing and contacting parts. This necessitates strictly defined gaps between certain components. And the thermal valve clearances (between the camshaft cam and the valve stem) are among the most important.

If the gap is too small, the engine will not be able to fully realize its potential, which will immediately affect the dynamic and speed characteristics of the car. At the same time, the exhaust valves will overheat and their edges will melt.

If the gap is larger than required, the car owner will be alerted to the characteristic “clatter” of the engine, which can sometimes go away as the car warms up. With increased clearance, the camshaft lobe begins to "knock" against the rocker of the valve stem instead of pushing through it.

Valve mechanism in section using the example of an engine with two camshafts

The need to adjust the valves is ripe if the following signs are visible:

• there is an extraneous, slightly ringing sound in the area of ​​the cylinder head cover;
• the gas distribution mechanism was repaired;
• the last adjustment of the valve thermal clearances was carried out more than 20 thousand km ago;
• engine output has dropped noticeably;
• As a consequence, high fuel consumption is possible.

Most modern engines use hydraulic compensators to adjust thermal clearances. It is convenient and does not require third-party intervention, although there is an opinion that components still wear out a little faster. The engines of many cars, in particular VAZ classics, require manual adjustment of thermal clearances. Some people consider this a simple matter, others, on the contrary, consider it a responsible and serious job. It all depends on experience, variations of techniques, dexterity and patience. It is recommended to carry out work after approximately 20 thousand km since the last adjustment.

Also, there is not much difference whether you have to deal with a gasoline or diesel engine. There are no significant or fundamental differences in the valve adjustment process.

It’s even better to combine adjusting the valve clearance with changing the engine oil. And exactly in this sequence. This will allow dirt, dust and sand that may get into the engine during adjustment to then leave along with the old oil and oil filter.

Preparation

Before starting work, it is better to thoroughly wash the car body and clean the engine compartment from dust and dirt, so that nothing unnecessary gets into the engine after removing the cylinder head cover. Then it is very advisable to place the car on the most flat surface possible, tighten the parking brake and place chocks under the wheels. It would be useful to have good and uniform lighting. If the latter is not enough, get additional light sources.

It is not at all necessary to buy such stops; you can easily make them yourself

Next, you need to wait until the engine cools down to the recommended temperature (usually 15–25 °C) so that the measurements are as accurate as possible. Sometimes experienced craftsmen undertake “hot” adjustments, taking into account certain corrections for the increased engine temperature. But engines are different, with their own nuances and amendments, so it’s better to wait. Free time can be used to replace filters, check optics, etc.

The thermal clearances of the valves can also be adjusted with the cylinder head removed. Here, for whomever which scheme of work is more convenient, this method cannot be considered wrong. Just remember that when installing the cylinder head on the machine and broaching, the gaps may shift either to the plus or minus of the required values. Therefore, it is better to play it safe and double-check.

Why are valve clearances necessary?

Answering the question why engine clearances are needed, it can be noted that for normal operation of the motor, the thermal gap is quite important. Due to it, the closing and opening times of the valves are observed, and the preservation of the optimal level of tightness when closed is ensured.

If the gaps are set in accordance with the rules, after warming up their parameters are reduced to minimum values. This ensures regulation of gas distribution phases and long service life of parts.

During the operation of the car, the gap changes up or down. Depending on such deviations, certain problems appear. In most cases, this leads to a decrease in the service life of the valves, a decrease in the engine power level, the filling of the cylinders with the fuel and air mixture becomes worse, the overall combustion efficiency decreases, and so on. It is for this reason that it is so important to adjust the gaps from time to time.

It is necessary to check and, if necessary, adjust the gaps every 20 - 30 thousand kilometers. You need to rely on the standards prescribed in the repair manual for a car of a particular brand.

What should it be like?

The piston has two types of rings: compression (prevent burnt gases from passing through) and oil scraper (remove excess oil from the cylinder walls). By design, they are not solid, but have a cut that allows the rim not to jam when heated. The cut also promotes elastic pressing against the cylinder walls. The presence of thermal space in the locks plays a very important role in the operation of the rings and cylinder. Its permissible range is from 0.3 to 0.6 millimeters. Failure to comply with the range may result in missing or severe damage to the cylinder.

An oblique cut is much better valued. Since the pressure on the walls occurs more evenly due to the fact that its edges are slightly thinner.

It is useful to know about the gaps in the locks. Sometimes mechanics try to make the thermal space in locks as small as 0.2 millimeters. This often leads to scoring of rings and cylinders. And this is natural, since when the part is heated, the space in the lock becomes smaller (or completely absent) and it crashes into the walls of the cylinder.

The simplest lock with a straight cut has one drawback - its ends have high pressure on the cylinder, or rather on its walls. This leads, first of all, to oil leakage and premature wear of the walls.

In order to summarize the above, we list what characteristics the piston rings should have and what the thermal clearance of the piston rings should be:

1. Temperature regulation. This is one of the most important functions, since a large mass of heat that is absorbed by the piston during the combustion period will be removed. If there is no such heat removal, the piston will melt in a matter of seconds.
2. Pressure. The main function is to compact. And full implementation of this characteristic is possible only with appropriate pressure. When pressure appears, it affects the piston circles, and they, in turn, are pressed against the cylinder walls. In order for the pressure to be uniform, uniform distribution and correct clearance in the piston rings are necessary.
3. Reliability and oil supply - oil scraper. They have two oil scraper bridges, which are responsible for the required amount of oil supply in the amount of 1-2 microns. If the oil is supplied correctly, then its consumption is not high, as is the fuel consumption. In this case, the wear rule will be observed as much as possible and the service life will increase.

As a result, I would like to wish every motorist and driver, regardless of whether he has diesel or gasoline, to check on his own or contact specialists in this matter. Especially when it comes to cars with high mileage and more than 5 years of constant driving.

Valve clearance adjuster

A more effective and efficient way to adjust the valve mechanisms of the power unit is to adjust them using a device, which is a special rail with an indicator attached to it. This adjustment is much more accurate manually, since when using the device, it detects and takes into account all defects on the surface of the adjustable parts.

For mechanical adjustment, in addition to dismantling the cylinder head cover, you will additionally have to remove the accelerator drive, the protective shield on the ignition distributor, the exhaust hose from the crankcase, and for carburetor cars, the carburetor “pan”.

Using a special wrench, you need to rotate the crankshaft until the marks on the camshaft sprocket align (this is described above). To make this process easier, you can use a bright marker to mark the camshaft sprocket every 90 degrees. After that, we install the device rail on the valve being tested and fix it in a stationary state. We put an indicator on it and place its foot on the edge of the adjustable valve. To correctly perform this procedure, you will need a special grip, with which you need to clamp the cam and pull it up (a simple wrench will do). As a result, the indicator readings should deviate by 52 divisions. If they are slightly too low or too high, the valve needs to be adjusted. And then everything is extremely simple:

• using a 17mm wrench, loosen the locknut on the adjusting screw;
• the gap is adjusted with a key of 13, and all readings are clearly reflected on the indicator scale;
• the adjustment is checked and the locknut is tightened;
• At the end of the stage, it is again necessary to check the correct settings of the valve mechanism.

As you can see, this adjustment is much more accurate and simpler. But we should not forget that a highly qualified specialist will perform it at a high level and using a standard set of probes. In conclusion, it is worth emphasizing that most sets of feeler gauges contain an adjustment diagram that contains data on the angles of rotation of the camshaft and crankshaft, indicating the numbers of cylinders and valves.

How to adjust using the rack and indicator

To adjust the thermal clearance of the valves, a special rail paired with an indicator can be used. This set helps achieve greater accuracy than using a feeler gauge or washers.

Set with rail and indicator for adjusting valve thermal clearances

The work order is as follows:

1. After the preparatory procedures and removal of the valve covers, the engine is cranked until the mark on the camshaft gear matches the body mark.
2. Using a marker on the back side of the gear relative to the factory mark, you can put your marks every 90 degrees.
3. Using three bolts, fix the rack on the protrusion of the bearing block.
4. A dial indicator with a scale set to “0” is placed in a special slot on the bar.
5. A special device is used to take the cam and pull it upward, after which the indicator needle moves by 50–52 divisions. If the numbers obtained are different, then the valve is adjusted according to the scenario described when working with the dipstick.

Video about the sequence of work

How to ensure the required clearance

The required clearance can only be obtained through properly carried out adjustment work. When carrying out this process, the main gas distribution mechanism is adjusted, especially the gap located between the camshaft cams and the valve lever.

There are special instructions on how to make the adjustment. It is not enough to ensure that the valves are pressed more tightly, since as the temperature rises, all parts become larger in size. Such an expansion automatically leads to various negative consequences.

The intake and exhaust valves should close the seat tightly, but with a small gap. It is necessary to ensure that the valve stem does not rest rigidly on the top of the device.

In the process of self-regulating gaps, you need to strive for strictly established values. They should not be more than 0.15 mm. The maximum permissible error level is 0.05 mm. These parameters should be checked only with a cold engine.

By ensuring the correct clearances during the adjustment process, the driver will receive stable engine operation, significant fuel savings, and increased service life.

How will valves operate if the gap is incorrectly set?

The engine operates under severe temperature conditions; metal expands due to high temperature. Therefore, if the tappet is pressed tightly against the camshaft cam, the following happens:

1. When heated, the intake valve will not be able to fit tightly into place, and part of the ignited mixture will be thrown out through this gap.
2. Due to the loose fit of the wide part of the valve to the block, its cooling is disrupted and it collapses faster. This is especially true for exhaust valves operating in more severe temperature conditions. The intakes are cooled by the incoming mixture.
3. Compression is disrupted, power drops noticeably, and wear of parts is greatly accelerated.

The same thing will happen if the exhaust valves do not close tightly.

The gap may decrease due to wear of the chamfer on the wide part of the valve - the “plate”, and its “seat” also wears out due to constant impacts and high temperatures. Therefore, the “plate” gradually sinks into the “saddle” a little deeper, and the pusher moves closer to the cam. Of course, these values ​​are very small - microns, but still gradually begin to affect the operation of the engine.

The opposite situation also happens when the gap is too large. For example, wear of the camshaft cams and the tappet surface inevitably occurs. The gap between them increases. As a result, engine operation is disrupted - the intake valves open a little later, and the mixture does not have time to enter the combustion chamber in sufficient quantity. As a result, the engine power drops, and it runs noisily due to the knocking of the camshaft on the pushers. The situation is aggravated by the later opening of the exhaust valves, as a result of which the exhaust gases are not completely removed from the cylinder.

In any case, as soon as the engine begins to pull worse, especially when running with a lot of noise, it’s time to go to a service station. Otherwise, one day the trip will end with a call to a tow truck, and then the replacement of some engine components. Thus, saving several hundred rubles and an hour of time leads to lengthy and expensive repairs.

The best prices and conditions for the purchase of new cars

Simple in appearance, the valves of an internal combustion engine perform the most important job 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 occur: its power, efficiency, toxicity, and even the ability to operate.

When to adjust valves

If your engine does not have devices to maintain the required clearance automatically, then you need to be prepared for the fact that every 30-35 thousand km. the indicated gaps must be checked.

Let us add that many car enthusiasts, especially owners of domestic VAZ models, determine the need for adjustment based on the appearance of noise during operation of the valve mechanism.

On foreign-made cars, the need to adjust the valves may arise after 60-80 or even 100 thousand km. mileage, since the engines have a longer service life and the set gaps on such internal combustion engines remain more stable.

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 a scheme with the location of the camshaft in the engine head - an overhead design - has become established everywhere in them. The proximity of the camshaft to the valves makes it possible to increase the rigidity of the system, and therefore improve the accuracy of operation.

The prototype of the first Zhiguli VAZ-2101, the Italian Fiat-124, had a solid and reliable, but no longer modern 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 head of the block.

Signs and consequences of improper clearance

After starting the engine, it itself and all its parts begin to heat up significantly and automatically expand. It is also worth taking into account the natural wear and tear of the elements in contact with each other. All this is the basis for ensuring strictly established gaps between certain parts. Deviations from the norm can lead to certain problems. The list of them depends on which direction the gaps have changed - more or less.

Gap too big

If the gap is larger than the required size, the driver will begin to hear the characteristic clatter of the engine, which gradually goes away as the car warms up. With increased clearance, the camshaft fist does not push through the rocker of the valve stem, but simply begins to knock on it.

Such long-term shock load leads to such unpleasant consequences as:

• significant reduction in valve life;
• riveting;
• chipping of the end, which further increases the gap;
• increased noise during engine operation.

At the same time, engine power decreases due to serious disruption of gas distribution processes.

Gap too small

With a very small gap, the car engine will not be able to fully realize its functionality. This will automatically affect the overall speed and dynamic characteristics of the vehicle. At the same time, there will be significant overheating of all exhaust valves with melting of their edges. Among the main consequences of a reduced gap size are the following factors, based on the loss of combustion chamber tightness:

1. Reducing compression due to the release of the air-fuel mixture.
2. During the working stroke, exhaust and hot gases break through and lead to severe burnout of the valves.
3. The plates no longer touch the seats, which disrupts heat transfer.
4. The valves are heated to temperatures that significantly increase corrosion and oxidation.
5. Increased load on timing belts.

Based on everything said above, we can conclude that adjusting the gaps must be done without fail. The process must be carried out if the following signs are present:

in the upper part of the cylinder head of installed cylinders there is an extraneous, slightly ringing noise;

repair of the gas distribution mechanism;

the adjustment was made more than 20 thousand kilometers ago;

a clear decrease in engine output;

increased fuel consumption.

The engines of modern cars are designed in such a way that thermal clearances must be adjusted manually. For some it may seem simple, while others consider this process serious and responsible. It all depends on the driver’s experience, the availability of certain skills and tools. Moreover, there is no difference between diesel and gasoline engines. The adjustment process is carried out here according to the same scheme.

Why is adjustment necessary?

Correctly adjusted clearances decrease after the engine warms up, providing precise adjustment of valve timing, which contributes to a long service life of the parts. As operation progresses, the depth of valve subsidence in the seats increases, the rocker arms and the cams themselves wear out, which means that the valve timing is disrupted and wear increases.

Large gaps lead to the appearance of extraneous noise during operation of the internal combustion engine and, if they are not brought back to normal in time, they will continue to increase, which will negatively affect the condition of the components and parts of the power unit, for example, valves or pushers may be damaged.

The opposite situation is even more dangerous, when there are no gaps or are critically small. In these cases, serious interruptions in the operation of the internal combustion engine occur with the possible occurrence of malfunctions, such as broken parts. If there are no gaps, the valves are not completely closed, the fuel mixture does not burn completely, and hot gases break into the resulting space, damaging the parts. These processes are irreversible. Even if you adjust the gaps after this, sooner or later a major overhaul is inevitable.

All malfunctions that may arise due to incorrect clearances can be summarized in a table.

Table of gaps and faults

Gap size Consequences Large gaps - reduced service life of parts; – riveting; – appearance of chips at the ends; – damage to the pushers. Small gaps or their absence - burnt valves; – depressurization of cylinders; – damage to the plates; – increased loads on the timing belt; – activation of corrosion and oxidation processes.

Operating principle of internal combustion engine timing valves

An ordinary ordinary driver, when it is necessary to adjust the valves, does not do it himself, but goes to a car service center. Because this requires certain skills and time. To teach yourself how to adjust valve clearances, you need to know the principle of their operation. An internal combustion engine has two shafts: the crankshaft (crankshaft) and the camshaft (camshaft). They are connected to each other through pulleys and a belt, through sprockets and a chain. The most common option is a timing belt driven engine. The crankshaft to camshaft transmission ratio is 2:1 (two to one).

The cams have a special irregular smooth shape that closes and opens the valves so that they correspond to the position of the crankshaft and camshaft, the engine stroke and valve timing.

When the internal combustion engine is running, it heats up accordingly, its parts heat up and expand due to high temperature. Because of this, the distance between the camshaft and the valve tappet changes slightly.

Question: why does the engine run differently when cold and when hot? Answer: because when the engine warms up to operating temperature, the valve tappet is pressed tightly against the valve and camshaft. This ensures efficient operation of the internal combustion engine.

And, if the valve end stops above the pusher, then a gap appears between the seat and the plate, and this leads to a decrease in compression in the cylinder.

It’s easy to check the compression: turn off the engine, unscrew the spark plug, screw in a special pressure gauge instead, turn the ignition key, get out and see what pressure the pressure gauge of a given cylinder shows.

And, if the end of a closed valve is located below the pusher, then during a certain valve timing phase, the valve will not open to the full distance it should. And this leads to a loss of power due to the slow removal of exhaust gases.

Design and principle of operation

The design of the compression ring is simple: it is a ring that has a gap so that its elasticity allows the ring to diverge and maintain the pressure of the working edge against the cylinder walls. Material – high-strength cast iron, less often – high-alloy steel.

The operating conditions of the upper compression ring are harsh: high temperature and pressure. At the moment the mixture ignites, the pressure reaches 90 bar, the temperature approaches 1500 degrees. As the cylinder wears, it loses its uniform diameter, and with each up-and-down stroke of the piston, the ring has to compress and expand, which contributes to the accumulation of fatigue stresses. To increase the service life, at least the upper ring is coated with a layer of chromium, which has high hardness.

The second compression ring operates in lighter conditions - in this place the piston is already colder, and direct heat transfer from hot gases no longer affects it. Therefore, it may not be chrome plated.

Oil scraper rings were initially made of solid cast iron; they had two working edges with a groove between them. The oil that passed through the lower edge was collected by the upper edge into this groove, and through the radial holes in it fell into the holes in the piston skirt and was discharged inside it. This design had a serious drawback: both edges worked simultaneously; in worn-out engines, where the ring was warped along with the piston, oil leaked past the ring. Therefore, composite structures were invented: in them, two thin rings are pressed against the edges of the groove with a spring expander, through which the collected oil flows into the piston. Due to the small width of the individual rings and their operation, this design remains effective when the piston is misaligned.

Preparatory work

So, the engine is cooled down, and the car itself is placed on a flat surface and immobilized. You can start working:

1. Remove the carburetor air filter cover and remove the filter;
2. We unscrew the filter mounting bolts and remove it, having first disconnected the pipes going to it;
3. We remove the cable for manual control of the air damper (choke) and disconnect the throttle linkage;
4. Unscrew the bolts securing the valve cover and dismantle it;
5. Check the chain tension (it must be normal, otherwise you will have to adjust the tension first);
6. Remove the distributor cap.

Now you need to set the TDC of the piston in the 4th cylinder and the marks on the knees will help with this. camshaft drive shaft and cover. shaft, as well as on the camshaft gear and its cover.

To do this, you can use a key of appropriate size, which you need to rotate the knees. shaft for the drive pulley bolt. Or use one of the drive wheels. To do this, you need to hang it with a jack, engage 4th gear and slowly turn the raised wheel. In this case, the transmission will ensure rotation of the crankshaft. But with the second method, you will need an assistant, since it will be difficult to check the coincidence of the marks.

What types of adjustments are there?

Automatic gap setting

Most modern cars are equipped with hydraulic compensators. These are devices that are responsible for maintaining the thermal gap by using engine oil pressure. The hydraulic compensators themselves do not require any adjustments. The main thing is to ensure that they are not clogged with dirt and are always in working order. You must understand that if the malfunction of this device was not detected in a timely manner, then it is assumed that the gap adjustments could have gone wrong, so it is better to check them and, if necessary, restore them.

Adjustment with screws

A method of adjustment using special screws without using any additional parts, and in the vast majority of cases, disassembling the cylinder head is not required.

Adjustment with washers and pushers

A common, but rather complex method of adjusting gaps. The problem is that in order to set a new gap, the pusher must be removed and a new one of the appropriate size installed in its place. This may require disassembly and removal of the camshaft.

What are valve clearances for?

In order for the engine to work at its best and develop all its performance characteristics to the maximum, the valves must move clearly and synchronously. The valves should fit tightly into their seats and open to the maximum.

With correctly set valve clearances, a hot engine works almost the same as a cold one, that is, the loss of power is minimal.

When the car is used a lot, for example, working in a taxi around the clock, the valves quickly lose their settings. Many people have probably heard, they say that the valves are knocking. This is just the time to adjust the valves.

Advice from auto experts: It is necessary to check and adjust the valves every 25 thousand kilometers of actual mileage. Of course, there are many modifications and brands of engines. It would be better to read the operating manual for the specific engine. Maybe there's no need to adjust at all.

Sequence for adjusting engine valve clearances

Before making adjustments, set the cylinder piston to TDC (top dead center) on the compression stroke. In this position, both valves of the adjustable cylinder must be closed, and the rocker arms of these valves must swing freely within the clearance.

After this, slowly loosen the locknut on the adjusting screw or bolt. Use a feeler gauge and adjusting screw to adjust the required clearance, then tighten the locknut.

“Be careful not to change the set clearance when tightening the locknut.”

After tightening the locknut, the thermal clearance must be checked again. Use a feeler gauge to check the gap. The feeler gauge should fit into it with little effort; if this feeling does not occur, but it passes very easily or very hard, you need to adjust the gap again.

To adjust the thermal clearance in the remaining valves, it is necessary to turn the crankshaft half a turn. During adjustment, the operating order of the engine cylinders (1-3-4-2) should be taken into account. Turn the crankshaft by the bolt securing the generator drive pulley.

Why do you need clearance in a bearing?

The clearance in the rolling bearing is needed to prevent jamming of the rotating bodies (balls, rollers) of the bearing with rings during operation. This clearance compensates for the reduction in distance between the inner and outer ring of the bearing.

Read also: ✅ What does the phase regulator affect?

• when the bearing assembly heats up significantly during operation and parts expand or contract
• when landing with interference
• to compensate for some bearing displacement relative to other parts

Clearance is one of the important factors affecting the longevity of a bearing. At the same time, in radial (non-adjustable) bearings it is customary to consider radial clearances, and in angular contact bearings, where the radial and axial clearance are adjustable, it is customary to consider only the axial clearance. Selecting a bearing with a radial or axial clearance that is optimal for given operating conditions allows for rational load distribution between the rolling elements, maximum reduction of bearing vibration during operation, and reduction of noise arising during bearing operation.

Adjustment of valves

First of all, on a carburetor car we remove the carburetor and air filter, and on an injection car only the pipes, which will prevent you from removing the valve cover.

Then we unscrew all the nuts around the perimeter by 10 using a socket wrench, be sure to collect the washers in containers so as not to lose them, since they are quite specific. Of course, you can later purchase them in the store, but this can significantly delay the work process.

Now we take a crooked starter or key, then rotate the crankshaft clockwise until the mark on the pulley coincides with the last ebb on the front cover along the way. With this action we set the pistons of the first and fourth cylinders to top dead center. It is at this very moment that the valves in these cylinders should be completely closed; accordingly, it is in this position that the adjustment is carried out.

The VAZ 2106 engine works according to the 1-3-4-2 scheme. That is, when the pistons of the first and fourth cylinders are at top dead centers, the pistons of the third and second are at the bottom.

So, after we have aligned the pistons as needed, we proceed to adjusting the valves. We can determine the ones we need by simply shaking the rocker arms - a light tapping sound will be heard. We need valves 8 and 6, counting from the front of the car.

To adjust, insert a feeler gauge between the camshaft cam and the rocker arm. If the probe enters with tension and comes out the same way, then nothing needs to be adjusted. If it passes easily, then you need to unscrew the locknut and unscrew the adjusting bolt. At this time, while we are unscrewing, we fidget with the feeler gauge to find the optimal position.

Once it is determined, tighten the locknut. It is very important to ensure that the adjusting screw does not turn even a degree. In any case, we need to check. To do this, we fidget with the probe again. If this is not possible, or vice versa, the probe moves without effort, repeat the procedure.

At this moment, if you look at the camshaft gear, the mark on it coincides with the cast on the camshaft housing. So, this is the best guide, because the crankshaft will need to be turned exactly 180 degrees, while the camshaft will turn 90 degrees. We adjust valves 4 and 7. Next, we turn the crankshaft again and adjust the valves in accordance with the table.

There is no point in discussing the assembly. The only thing worth paying attention to is the flatness of the valve cover plate. Over time, it is pushed through by washers, so it requires editing. If indentations are visible in the tightening areas, then it must be corrected on an anvil.

Useful tips

To avoid “pinched” valves on classic VAZ models, you need to take into account that the back surface of the camshaft cams may not be ideal. This shaft runout is sometimes about 0.04 mm. For this reason, it is necessary to additionally check the gap. This is done when the cam is in the following positions

• before the valve opens;
• after the moment of its closure;

To solve the problem, you will need to install the camshaft in a position where the mark on the gear is in the upper direction. Then the clearances at valves 4, 6, 7 and 8 are checked. Then you need to rotate the crankshaft 180 degrees, that is, the camshaft will rotate 90 degrees. After turning, you can check valves 7, 4, 3 and 1. The 3rd, 1st, 2nd and 5th valves are checked in the same way, and then the 2nd, 5th, 6th and 8th. Please note that all valve measurements must have the same end result. If the results differ, then when setting the gap it is necessary to take as a basis the place where the gap is minimal (the most “squeezed”).

I would also like to know that VAZ has a special device with a dial indicator for adjusting the valves. It is assumed that such a tool makes it possible to achieve higher accuracy compared to using a feeler gauge, and also allows you to easily adjust the valves “hot”. Unfortunately, in practice such solutions have certain disadvantages and errors. As a result, the measurement accuracy is often far from ideal and may even be inferior to the usual method using a probe.

Some craftsmen can easily adjust valves on imported cars using special tools for VAZ, making certain changes to the design of the device. It is also common practice to use only one pusher clamp, which is selected according to size. The procedure boils down to cranking the crankshaft until the pusher “sinks” the camshaft cam.

Then the clamp is inserted, after which the camshaft rotates until the cam comes off the washer. After removing the old washer and checking/replacing it with a new one, the camshaft rotates back again. Note that the camshaft must be rotated using a wrench that turns the camshaft gear. The crankshaft should not be turned, since the timing belt must be properly loaded when rotating.

If you set the valve clearances incorrectly

After 5-10 minutes of operation, the motor reaches operating temperature (this is about 90-100 degrees). According to the law of physics, all parts begin to expand. Engine wear will vary depending on whether the valve clearances are too large or too small.

Gap too big

If the gap is larger than the nominal one, the sound of the engine will be different. As the engine gradually warms up, this unusual sound (clunking) will disappear.

If the valve clearance is large, then the camshaft fist does not press on the valve drain rocker, but knocks on it.

If the engine runs in this mode for a long time, then:

• valve service life is reduced;
• the end of the valve stem may break off;
• riveting;
• there will be an increased noise level of the internal combustion engine.

Since the gas distribution phases are disrupted, engine power may drop by half.

Gap too small

In this case, the valve does not open completely, the exhaust gases do not have time to escape completely, hence the loss of engine power. Valve plates will burn out due to increased overheating.

Consequences of low valve clearance:

1. Low compression in cylinders.
2. The exhaust gases do not have time to escape through the small gap and the edges of the valves burn out.
3. The valve plates do not fit tightly into their seats.
4. High load on the timing belt or chain drive.

It is necessary to adjust the valve clearances as soon as possible if the following symptoms appear:

1. A ringing sound appeared in the upper part of the cylinder head (cylinder head).
2. If the timing belt has been repaired.
3. If you have driven more than 25,000 km since the last adjustment.
4. If the engine does not pull. Neither uphill nor in a straight line.
5. If gasoline consumption has increased.

Adjusting the thermal clearances of the valve mechanism

Let's start with the fact that although different engines may have certain differences, the general principles of gap adjustment are similar for the vast majority of engines.

1. The first nuance is that adjustments must be made at the internal combustion engine temperature specified for a specific engine type in the maintenance and repair manual. The average is about 20°C. This requirement must be carefully observed by those who do not have sufficient experience and strive to achieve maximum measurement accuracy. As for a qualified craftsman, it is no secret to a specialist that at a higher temperature of the unit, the gaps will initially increase. For this reason, valve adjustment on a warm engine is possible, but is carried out taking into account a number of amendments. It is worth adding to this that different motors may have parts made of different alloys and materials. As a result, thermal gaps may differ, and the cooling process may proceed faster or slower. For this reason, corrections for each internal combustion engine are individual.
2. Now about the gap itself. The indicated gap on many motors is measured under the adjusting screw. You need to measure the gap using a set of special feeler gauges; the main one is the feeler gauge, which has a width of 10 millimeters. A number of nuances should also be taken into account. For example, consider VAZ cars. When making adjustments on classic models, there is a need for a wide feeler gauge. The fact is that the use of standard narrow probes leads to an error. This error is caused by the fact that the valve lever on such units is slightly beveled. Let us add that the optimal gaps on the “classic” are 0.15 mm. This clearance is the same for both intake and exhaust valves. It is quite obvious that it is quite difficult to accurately determine the indicated gap with one simple feeler gauge. The task is even more complicated, since it is not always possible to purchase a complete set of probes. In such cases, the experience of the master plays an important role, who actually tactilely determines the gap. To do this, take a 0.15 mm probe, after which its passage in the gap is assessed. If the indicated probe goes too “tight”, then the valve is clamped. Free passage of the feeler gauge will indicate increased clearance.
3. It should be understood that it is not possible to set the gap perfectly right away, since after tightening the locknut it still gets a little off. For this reason, an amendment is made, the gap increases slightly. As for reducing the gap, such manipulation is not recommended. Note that there is a so-called table that contains various corrections in the case of valve adjustments on a hot engine. If you look at such data, then you can see the dependence of the increase in gaps on the degree of heating of the motor. In other words, the gaps should be larger when the engine is warmer. In this case, one should take into account the fact that the gaps are indicated for an idle internal combustion engine. After starting the unit, they will decrease, since the valves themselves will heat up the most and will be increased in length compared to other timing structural elements.
4. Many people strive to minimize the noise from the operation of the timing belt. For this reason, there is a misconception that a slight reduction in clearances has a positive effect without harm to the engine. Actually this is not true. Indeed, if the valves are “clamped”, then the engine can run quieter when “cold” and/or “hot”. But reduced noise does not mean minimized wear due to the absence of audible impacts. The fact is that under certain conditions the valve stops closing completely. A loose fit of the plate disrupts heat transfer; the valve does not transfer excess heat to the cylinder head. The result is overheating and burnout of the valve. It turns out that incorrect valve adjustment with a decrease in clearance can lead to engine failure and the need for further repair. A clear sign of “pinched” valves is the condition of the camshaft, as the back of the camshaft cams will have noticeable wear.

Adjustment using a feeler gauge

• Remove the cover and ignition coil. We unscrew the soured bolts without serious effort so as not to strip the threads.
• The adjustment should begin with the least tightened one. Its cam will be in the “away from the rocker” position. Place the head of the key on the bolt holding the crankshaft pulley and turn it 180 away from the rocker arm, if possible. If it is not possible to take such an angle, then we turn to the largest possible.

Remember that the bottom valves (those closest to you) are exhaust valves. The gap in them should be within 0.20-0.25 mm.

• You should loosen the nut, take a 0.20 mm feeler gauge and tighten it by screwing in the rod. Put on the locknut, pull out the dipstick and tighten the nut completely. Check the gap by comparing how the feeler gauge passes 0.20 and 0.25. The latter will not go in completely. We mark the adjusted mechanism with a marker. We alternately adjust all the exhaust valves in the same way.
• Now we’ll find out how to adjust the intake valves on our own. This is done according to the same principle as the bottom row, only the gap size is smaller - from 0.10 to 0.15 mm.
• We check the dimensions of the set gaps with feeler gauges again and tighten the nuts tightly.
• We clean the valve box, armed with a utility knife and No. 0 sandpaper. Perform all movements from the valve to the edge to avoid litter getting into the box. We also first rough clean the lid with a blade, then carefully clean it with sandpaper.
• We change the gasket and, in a strictly defined order, following the manufacturer’s instructions, tighten the cover bolts.
• All that remains is to connect all the wires, hoses and pipes, and reinstall the air filter housing.

Adjustment using rack and indicator

To adjust the automotive thermal gap, a special rail is often used, along with an indicator. These devices allow you to achieve maximum accuracy, which cannot be obtained with the method described above. The order of work here is as follows:

• after carrying out the preparatory work and removing the valve covers, the engine must be turned until the marks on the camshaft gear and the marks on the housing coincide;
• You need to put your icons on the back of the built-in gear with a marker. This must be done every 90 degrees, relative to the mark set by the manufacturer;
• using three bolts you need to fix the rack on the protrusion of the block of installed bearings;
• You need to insert a dial indicator into a special slot on the bar. In this case, the scale should be set to zero;
• Using a special device, take the cam and pull it up a little. In a normal situation, the indicator needle will move by approximately 50 - 52 divisions.

If, as a result of the measures taken, the obtained parameters are slightly different, you will need to make adjustments using the method described above.

At the end of the adjustment process associated with setting the clearances in the valve mechanism, you need to start the engine and listen to how it operates in different modes. If the manipulation was carried out after the head was restored, it is necessary to ensure that the valves are properly ground in.

An example of valve adjustment on a VAZ 2108–2115

How to adjust a 6-cylinder in-line engine: video

The thermal clearance of the valve ensures its tight fit on the seat during thermal expansion of parts during engine operation. For each engine model, the optimal value of the thermal clearance in the valve mechanisms is established.

During operation, due to wear or improper adjustment, the size of the thermal gap may change and deviate from the optimal dimensions. Both an increase and a decrease in the thermal gap negatively affects the operation of the timing belt and the engine as a whole.

With a very large thermal gap, shock loads increase, and wear of valve drive parts also increases. The valve timing is disrupted (the moment of the beginning and end of the opening and closing of the valve), which leads to a loss of engine power and efficiency.

Small thermal gaps do not ensure the tightness of the combustion chamber, causing the engine to lose compression, not develop full power, and the valves overheat, which leads to valve burnout.

The gaps are checked and, if necessary, adjusted during maintenance. in the timing belt is performed on a cold engine - 15-25 degrees Celsius. The clearance is adjusted using a feeler gauge, the thickness of which must correspond to the required clearance in the valves of the car engine being adjusted. The feeler plate, the thickness of which is equal to the required gap, should fit into the gap when pressed lightly.

Sequence of work when adjusting the thermal clearance of valves.

Remove the valve covers. We install the piston of the first cylinder at TDC during the compression stroke; for this it is necessary that the mark on the pulley coincides with the mark on the timing gear cover. The compression stroke can be determined in this way: unscrew the spark plug and insert a paper plug into the hole for the spark plug. Rotate the crankshaft with the crank until the paper plug comes out.

Using a feeler gauge, check the size of the thermal gap in the valves between the valve stem and the toe of the rocker arm. If the gap is not within the acceptable range, it must be adjusted. To do this, you need to loosen the lock nut of the adjusting screw; if the gap is small, unscrew the screw; if it is large, screw it in so that the feeler gauge of the required thickness can pass freely. While holding the screw, tighten the locknut. The dipstick that corresponds to the lower value should pass freely with little effort.

Rotating the crankshaft to an angle of 720/i, where “and” is the number of cylinders, adjust the valves in the other cylinders in the order of engine operation.

Reinstall the valve cover.

Start the engine, warm it up to 80-90 degrees Celsius and listen to its operation. If adjusting the thermal clearance of the valves

done correctly, there should be no knocking in the valves.

While the cars that were included in the VAZ classic series, and these are models from 2101 to 2107 and Niva, will drive on the country's roads, their owners will have to learn how valve clearances are adjusted. These new machines are equipped with self-regulating hydraulic compensators, which independently adjust the operation of the gas distribution mechanism. The good old Zhiguli cars need more attention.

Why are valve thermal clearances set?

One of the most common types of adjustment work is adjusting the gas distribution mechanism, in particular the gap that should exist between the camshaft cams and the rocker (valve lever).

Many people have a question about what this gap is for? Wouldn't it be better to adjust the parts so that they just fit together as tightly as possible? The answer to this question is found in school physics textbooks, and more specifically in the section that talks about the thermal expansion of solids.

The fuel mixture, burning in the cylinder, heats all parts of the engine to a very high temperature. Naturally, all parts increase slightly in size. For the gas distribution mechanism, such an expansion can lead to negative consequences. The inlet and outlet valves must close the seat very tightly. If the valve stem rests rigidly in the upper part, then during thermal expansion, its plate will move down and the channel will be slightly open, and this leads to an undesirable result, namely:

• reduction and loss of engine power;
• increased fuel consumption;
• overheating and destruction of timing parts (valves, etc.) by escaping flames.

To ensure that the valve always remains closed during expansion, the thermal clearance of the valves is calculated. The gap is present when the engine is cold, but when its temperature reaches operating parameters, the gap gradually decreases. Naturally, the driver is interested in what valve clearance is set during adjustment. The gaps have a strictly established value - 0.15 mm. An adjustment error of 0.05 mm is allowed. This value is calculated for a cold engine. Adjustment on a hot engine is possible, but such adjustment is considered inaccurate.

• sustainable;
• fuel economy;
• increasing motor life.

What you need to prepare for regulation

Fearing that they will do something wrong, many car enthusiasts head to a car service center if they need to adjust the valves. Considering that such a procedure should be carried out, on average, after every 15-20 thousand kilometers, you have to pay a significant amount from the family budget. In addition, a lot of time is spent waiting in line at the service center, and the engine must cool down to the required temperature. Therefore, it is better to adjust the valve clearances yourself in a garage. This work is not difficult and you will need a simple tool for the operation:

• probe 0.15 mm thick;
• wrenches.

In order to begin work, you need to install the car in a well-lit place or install artificial lighting in the engine compartment. Next, you should disconnect the air filter housing, timing cover, and remove the oil dipstick.

Adjusting valve thermal clearances

To begin the process of adjusting the clearances, you should set the piston of the first cylinder to top dead center on the compression stroke. It's simple: use a wrench to turn the crankshaft until the drilling on the camshaft drive sprocket with welding and the marks on the crankshaft pulley and the engine block coincide.

Now you can start directly adjusting the gaps, and this is done like this:

• the probe is inserted between the working parts of the cam and the lever of the corresponding valve;
• if the feeler gauge enters with slight difficulty, we can assume that the gap is in normal condition;
• if the feeler gauge does not fit in, fits in very tightly or passes without any effort, you need to start adjusting: holding the head of the adjusting bolt with a 13 wrench, release the lock nut with a 17 wrench and turn the bolt in the desired direction until the required gap is obtained, check the height of the gap with a feeler gauge, then then tighten the locknut.

The first valves to be adjusted are the 8th valve (4th cylinder) and the 6th valve (3rd cylinder). The valves are adjusted in pairs, and for each of them the camshaft must be rotated 90° (crankshaft 180°). With each subsequent turn, the following valves are adjusted:

• No. 4 (2nd cylinder) and No. 7 (4th cylinder);
• No. 1 (1st cylinder) and No. 3 (2nd cylinder);
• No. 5 (3rd cylinder) and No. 2 (1st cylinder).

Perhaps on the first try you, as a novice auto mechanic, will not be able to make a perfect adjustment of the valve drive, but after some time, the adjustment skills will come by themselves. It is advisable that the work, especially for the first time, be supervised by an experienced mentor.

Even an experienced car enthusiast should definitely check the compliance of the technology for adjusting thermal gaps. This is done after all valves have been checked and adjusted. Using a wrench or hanging the rear wheel, you need to turn the crankshaft several times. After this, you should install the crankshaft and camshaft at the same marks and check the gaps according to the algorithm described above. If necessary, repeat the gap adjustment.

This article on valve adjustment will also be useful to motorcycle owners.

The need to adjust the valves, or rather their thermal clearances, may occur at different times for different cars; for foreign cars a little later, for domestic cars earlier (after about 10 - 15 thousand km. And for modern cars with hydraulic compensators, there is no need to adjust the valves at all. But Most older cars still periodically need such adjustment, and we will look at how to do it correctly in your garage, and what you will need for this, in this article.

The fact that it is necessary to adjust the valves on your car can be determined by the mileage, by an extraneous knocking sound in the area of ​​the cylinder head (although with low thermal clearances there is no knocking, but engine power is lost), and by loss of compression (read how to check compression) and, accordingly, engine power.

Why is it necessary to adjust the thermal clearances of the valves?

In general, correct adjustment of valve thermal clearances, that is, setting the required gap between the end of the valve stem and the cam (or rocker arm on older machines), is a very important operation. After all, valves are made of metal, which, as is known, expands when heated, which means that the valve stem lengthens by several fractions of a millimeter with increasing temperature. In addition, the camshaft cam, which presses on the valve stem, expands (becomes thicker) (or the rocker arm becomes thicker, on older machines).

The degree of elongation of the valve stem (and other parts) depends on the grade of steel and that is why different engines have different clearances (as recommended by the manufacturer), depending on the grade of steel. Therefore, before you start adjusting the valves on your engine, you need to check in the manual of your particular engine the exact size of the thermal clearances recommended by the engine manufacturer, and from this value select the value with which the adjustment will be made. On many engines, the size of the thermal clearances is written on a sticker that is glued to the valve cover.

And if the thermal gap is less than required for your engine, or there is no gap at all, then when the valve stem heats up and lengthens, the valve will no longer be able to close completely (tightly) during engine operation and provide compression in the combustion chamber, since it will rest against its end into the cam (or rocker pad).

The fact that from a loose closure of the valve disc (loss of tightness between the disc and the seat) compression will “float away” and engine power will be lost (and the car will start worse, and the diesel engine may not start at all) is half the problem. But the worst thing is that the valve plate and its seat will quickly become covered with soot due to a loose fit and begin to burn and deteriorate.

After this, naturally, such a motor will no longer work normally, even if the valves are subsequently adjusted. Removal and, that is, restoration of the surface, and subsequent valves will be required. Although it also happens that the valves will have to be changed.

If the thermal gap is larger than required, then during engine operation, as the valve stem heats up and lengthens, the gap between the end of the stem and the cam (or rocker arm) will not be completely selected. As a result, the valve stem and cam (rocker arm) will experience shock loads and wear out quickly, and the knocking of valves in the head area will be heard.

Therefore, both increased thermal clearances and decreased ones are harmful for any engine, and therefore you should always strive to adjust the thermal clearance recommended by the factory, and periodically adjust the valves, according to the manufacturer’s recommendations, and even earlier - if extraneous knocks appear in the cylinder head area .

Naturally, different engines may have slightly different designs of the gas distribution mechanism, and it is impossible to describe the adjustment of valve clearances on absolutely all engines in one article. But as a rule, there are only three main designs - with hydraulic compensators, with valve opening using a camshaft cam and valve opening using a rocker arm.

As I wrote above, valve adjustment is not required on engines with hydraulic compensators. And on such engines, if there is some kind of malfunction, the parts are simply replaced with new ones (or the problem with oil pressure is solved). Therefore, below we will describe the adjustment of valves on a design with a rocker arm, where adjustment is carried out using special bolts, and on a more modern design, where the cam itself directly presses on the end of the valve stem, and a special cemented adjusting washer is installed between them, which is simply replaced with another washer , that is, the required washer of a different thickness.

Adjusting valves on an older rocker arm driven design.

On engines with this design, adjusting the thermal clearances is the simplest operation, and below we will consider its sequence. You can also read about this. But before that, buy a set of feeler gauges and prepare a set of wrenches. Well, wait until the engine cools down to 20 degrees, or better yet, in order not to wait, make adjustments on a cold engine, before the trip, and not after it. Further:

Adjusting valves on a more recent design (with shims).

• Install a device on the valve cover studs (see figure and photo) to recess the valves and their pushers.
• Rotate the engine crankshaft (clockwise) until the piston of the first cylinder approaches TDC of the compression stroke - this corresponds to the moment when the marks on the camshaft pulley and on the crankcase or rear cover of the belt housing are aligned (check in your engine manual where this mark is located).
• After the marks match, tighten the crankshaft a little by about 2.2 - 3 teeth of the camshaft pulley (corresponds to a rotation of 40-50°).

Valve drive types

During vehicle operation, as a result of wear and heating of the mechanical parts of the gas distribution mechanism, the gap between the valve levers (rocker arms) and the camshaft cams changes (in other types of engines - between the camshaft and pushers, between the rocker arms and valves). Therefore, periodically (after about 30 thousand km), as well as during any repairs of the mechanism or removal of the cylinder head, this gap should be checked and, if necessary, adjusted in engines with mechanical valve drives.

The size of the thermal gap for each engine is individual and ranges from 0.10 mm in Volkswagen GT cars to 0.60 mm in Ford Fiesta cars. In the technical characteristics of engines, thermal clearances can be given for both a cold and a hot engine, and for a hot engine the gap can be either larger or smaller, depending on the design of the gas distribution mechanism.

Cold

An engine in which the coolant temperature is below 35° C is considered, which is achieved by cooling the engine after warming it up for at least 4 hours at an ambient temperature of 20° C.
hot
if the coolant temperature in which is about 80° C (moment turning on a large fluid circuit).

Check and adjust the thermal clearances of the valves with the valves closed, i.e., at the maximum distance of the top of the camshaft cam from the rocker arm (pushrod, pusher) of the valve. This shaft position can be achieved in various ways. Checking the gaps is done using a feeler gauge (Fig.)

Fig. Adjusting the gaps in the gas distribution mechanism:

1 - rod; 2 - lock nut; 3 - adjusting screw; 4 - screwdriver; 5 — rocker arm; 6 - dipstick; 7 - valve

The most common method is to first adjust the valve clearances of the 1st cylinder; at the same time, its piston is at TDC on the compression stroke.

The compression stroke is determined by the increase in air pressure in the cylinder as the piston moves to TDC. To determine this stroke, it is necessary to unscrew the spark plug (injector), close its hole in the cylinder block with a special whistle, plug, or simply with your finger, and turn the crankshaft until a whistle occurs (the plug is pushed out, the pressure on the finger sharply increases).

For gasoline engines, the position of the piston on the compression stroke near TDC can be determined by the position of the breaker slider - the ignition distributor, if the breaker was not removed and the engine was not disassembled (assembled). When the distributor cover is open, the slider should be located near the high-voltage terminal going to the spark plug of the 1st cylinder.

The piston is near TDC and when a spark jumps at its spark plug (in gasoline engines). To determine TDC, turn the spark plug out (or disconnect the high voltage wire from it and connect it to a “spare” spark plug or spark gap), turn on the ignition and turn the crankshaft until a spark appears on the spark plug. After finding the desired position of the piston, align certain marks on the crankshaft pulley and the cover of the gear (sprocket, pulley) of the camshaft drive, marks on the flywheel and other parts.

After adjusting the thermal clearances of the valves of the 1st cylinder, the clearances in the remaining valves are adjusted in the order of their operation, each time turning the crankshaft by 180 (for 4-cylinder engines), 120 (for 6-cylinder engines) or 144 (for 5-cylinder engines).

For some engines (for example, VAZ), it is recommended to align the marks on the camshaft cover and its drive pulley, which corresponds to the end of the compression stroke in the 4th cylinder. In this position, adjust the thermal clearance of the exhaust valve of this cylinder and the intake valve of the 3rd cylinder, and then of other cylinders, in the order of their operation, each time turning the crankshaft 180 degrees.

The less precise position of the cams relative to the tappets or their rocker arms can be determined visually by the rotation of the camshaft. In this case, the shaft cam should be as far as possible from the pusher (rocker arm), i.e., facing the pusher with its back side, and the valve is closed.

The engines of modern passenger cars do not have a crank for manually cranking the crankshaft. Therefore, turning it to determine the moment of closing the valves in the cylinder, in which it is planned to adjust their thermal clearances, can be done using a key or a special device that is put on the central bolt of the shaft belt pulley. It is not recommended to turn the crankshaft by the camshaft pulley bolt, as this can damage the bolt or stretch the drive belt. If such a bolt is missing, the crankshaft can be turned by turning the wheels of the drive axle, hanging the car wheels and engaging direct transmission. To make this operation easier, it is advisable to first remove the spark plugs (in gasoline engines).

In practice, a method of cranking the crankshaft using a transmission has also been used - by rolling the car with direct (overdrive) gear engaged. With this method, the moment of valve closure is determined visually. After adjusting the thermal clearances of the valves of a certain cylinder, the car is rolled again until the camshaft cam, abutting the adjustable valve, is as far as possible from the pusher (rocker arm) of the latter.

There are several options for transferring force from the camshaft cams to the valve stems (i.e., types of valve drives), and therefore, methods for adjusting thermal clearances.

1. Drive through a rod and rocker arm (Fig. 4.44) for Renault, early Ford, Volga, Gazelle cars. With this drive option, the thermal gap is checked between the rocker arm and the valve. If the gap deviates from the nominal one, unscrew the nut of the adjusting screw and, turning the screw with a screwdriver, set the required gap according to the laid feeler gauge. After this, holding the adjusting screw with a screwdriver, lock it with a nut and check that the gap is set correctly.

Rice. 4.44.

Valve drive via rod and rocker arm:

1

- valve seat;
2
– valve;
3
– oil deflector cap;
4, 5
– valve springs;
6
– spring plate;
7
– cracker;
8
– rocker arm;
9
– adjusting screw;
10
– adjusting screw nut;
11
– pusher skirt;
12
– spring support washer

2. Drive through a rocker arm (Fig. 4.45) for Mazda-626, ZAZ-1102 cars. With this design, the camshaft cam acts on the rocker arm, at the end of which a roller bearing can be installed to increase service life. At the other end of the rocker arm there is an adjusting screw with a lock nut that acts on the valve stem. To adjust the gap, you need to loosen the lock nut and rotate the adjusting screw to achieve the required gap between the end of the valve stem and the adjusting screw, then tighten the lock nut.

Rice. 4.45.

Valve drive via rocker arm:

1
2
– rocker arm;
3
– adjusting screw;
4
– lock nut;
5
– gap

3. Drive through a rocker arm and an adjusting eccentric (Fig. 4.46) for BMW-518, BMW-520. With this drive option, the cam acts on the rocker arm, which comes into contact with the valve stem through an adjusting eccentric. The gap is measured between the eccentric and the end of the rod. If the gap does not correspond to the required value, use a screwdriver or a special rod (2 mm thick) to turn the eccentric so as to obtain the required gap, and then tighten the lock nut.

Rice. 4.46.

Valve drive via rocker arm and adjusting eccentric:

1

– adjusting eccentric;
2
– rocker arm;
3
– camshaft cam

4. Drive through a lever (Fig. 4.47) for Mercedes-Benz 123 and Suzuki cars. With this design, the camshaft cam acts on the arm of a special lever, the back surface of which transmits force to the adjusting nut located at the end of the valve stem and locked with a locknut. If it is necessary to adjust the thermal gap, loosen the lock nut, set the required gap by rotating the adjusting nut (by placing a feeler gauge of the appropriate thickness between it and the lever) and tighten the lock nut.

Rice. 4.47.

Valve drive via lever:

1

– camshaft cam;
2
– probe for adjusting the thermal gap;
3
– lever;
4
– adjusting nut;
5
– lock nut;
6
– valve spring plate;
7
– valve spring;
8 9
– cylinder head;
10
– valve stem;
11
– valve guide sleeve

5. Drive through a rocker arm having 4 supporting surfaces (Fig. 4.48) for VAZ-2101...VAZ-2107 cars. With this drive option, the thermal clearance is checked directly between the rocker arm and the camshaft cam. To adjust, loosen the locknut, rotate the adjusting bolt to set the required gap (by placing a feeler gauge of the appropriate thickness between the camshaft cam and the rocker arm) and tighten the locknut.

Rice. 4.48.

The valves are driven through a rocker arm having 4 supporting surfaces:

1

– cylinder head;
2
– valve;
3
– valve guide bushing;
4
– rocker arm;
5
– camshaft bearing cover;
6
– camshaft cam;
7
– adjusting bolt;
8
– lock nut;
A
– thermal gap

6. Drive through a cup pusher (Fig. 4.49) for Ford, Opel, Volkswagen, Audi, VAZ-2108...VAZ-2110 cars. This type of drive is most common in car engines from the 1980s to the 1990s. release. The camshaft acts on the cup pusher, the force from which is transmitted through the adjusting washer to the valve. This drive does not have rocker arms, which increases the reliability of the gas distribution mechanism.

Rice. 4.49.

Valve drive via cup tappet:

1

– cylinder head;
2
– valve;
3
– cup pusher;
4
– camshaft bearing housing;
5
– camshaft cam;
6
– adjusting washer;
7
– valve oil scraper cap;
A
– thermal gap

The thermal gap is adjusted by selecting the thickness of the adjusting washer. If the clearance is different from the nominal one, use a screwdriver to turn the cup pusher to a position that allows access to the adjusting washer through the slot in its upper part. The pusher is recessed using a special device (if it is not available, use a screwdriver) and fixed in the lower position (Fig. 4.50). After this, using another device (a steel plate with a flat magnet), or, in its absence, using pliers, a magnet or compressed air, the adjusting washer is removed. Use a micrometer to measure the thickness of the washer, and then determine the thickness of the new washer using the formula

H = B +

(
A – C
)
,
where H

– thickness of the new washer;
B
– thickness of the removed washer;
A
– measured gap;
C
– nominal gap.
So, for example, let A
= 0.29 mm,
B
= 3.75 mm,
C
= 0.20 mm. Then

N

= 3.75 + (0.29 – 0.20) = 3.84 mm.

Within a tolerance of ±0.05 mm, take the thickness of the new washer equal to 3.85 or 3.80 mm.

A new washer is installed in the valve pusher with the marking towards the pusher. During assembly, the washer and pusher are lubricated with oil. After adjusting the thermal clearances of the valves of such a drive, it is necessary to pour oil into the oil baths of the cylinder head.

Spare parts are supplied with adjusting washers with a thickness of 1.65 to 4.00 mm in increments of 0.05 mm.

When checking the thermal clearances of valves in any type of valve mechanism drive, the feeler gauge should enter with a slight pinch. In order to ensure the accuracy of the test, you can use probes a little thicker and a little thinner than the nominal one. A probe with a larger thickness should not enter the gap, and a probe with a thinner thickness should enter freely.

Since the 80s, most foreign-made car engines began to use hydraulic pushers to drive the valve mechanism, which do not require adjustment during operation.

Rice. 4.50

.
Recessing ( a
) and fixing (
b
) the valve pusher to replace the adjusting washer:

1

– device for recessing the pusher;
2
– cup pusher;
3
– device for fixing the pusher;
4
– adjusting washer

How to adjust valve clearances on foreign cars

First of all, using the repair and maintenance instructions for your car, we determine the engine type. 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 installing timing marks is also indicated there. However, in most cases a set of wrenches and feeler gauges is sufficient. Let's look at the features of adjusting clearances on a Mitsubishu ASX 1.6 with a gasoline and diesel engine.

Gas engine

This is what a Mitsubishu ASX 1.6 engine with a gasoline engine looks like

To do this, follow these steps:

1. Remove the plastic engine casing (held on by rubber latches).
2. We remove the ignition coils and valve cover.
3. We set both camshafts according to the marks (the nominal clearances of the intake and exhaust valves are also indicated here).

   
   We set the engine camshaft marks

4. Using feeler gauges, we measure the gaps “Second and fourth cylinder - intake valves”, “First and third cylinder - exhaust valves”. We record the measurement results.
5. Rotate the crankshaft 360 degrees. Then we align the marks on the camshafts and measure the gaps of the other valves.

   
   Checking the size of the engine valve clearances

6. We remove both camshafts, take out the adjusting cups and use the given formula to calculate the size of the new cups.

   
   Adjusting valve clearances

7. We install new cups and install the camshafts in the cylinder head.
8. Apply sealant to the indicated places and tighten the valve cover.

   
   Apply sealant and tighten the engine valve cover

Diesel engine

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

This is how valve clearances are adjusted on a Mitsubishu ASX 1.6 with a diesel engine

The main signs of incorrect work

If the valve clearances are set correctly, the engine will run quietly and smoothly. With increased intervals, it will make extraneous knocks and noises; with decreased intervals, it will work unevenly. Further operation of such a vehicle is impossible; you must carry out repairs yourself or contact a service center. Otherwise, you may lose your car.

The trouble-free operation of your car is largely determined by regular operations to adjust the valve clearances. 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!

Sources

• https://FB.ru/article/226876/zazor-klapana-kakim-on-doljen-byit-instruktsiya-po-pravilnoy-regulirovke-klapanov-vaz-i-inomarok
• https://autochainik.ru/regulirovka-zazorov-klapanov.html
• https://pol-z.ru/regulirovka-teplovyih-zazorov-klapanov-v-pomoshh-avtolyubitelyu/
• https://mtz-80.ru/bez-rubriki/regulirovka-zazorov-klapanov-dvigatelya
• https://scart-avto.ru/remont/kak-otregulirovat-zazory-klapanov-priznaki-i-simptomy/
• https://KrutiMotor.ru/regulirovka-klapanov/
• https://VmyatynNet.ru/avto-rf/nastrojka-klapanov.html
• https://gp-prsmah.ru/tyuning-remont/na-chto-vliyaet-regulirovka-klapanov.html
• https://delis-avto.ru/obzory/proverka-zazorov-klapanov.html
• https://autostuk.ru/regulirovka-zazorov-klapanov-2-varianta.html
• https://4x4privod.ru/regulirovka-klapanov-poryadok-proved/
• https://auto-gl.ru/regulirovka-klapanov-dvigatelya-sovremennogo-avtomobilya/

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Screw adjustment procedure

In order to explain how valves are adjusted, you can turn to the classics and consider adjusting the valves of the VAZ2107.

Typically, the need to regulate valves arises when there is a sharp drop in the power of the internal combustion engine and the appearance of characteristic metallic knocks at low or high speeds. Allow the engine to cool before starting the activity. All work must be carried out on a cold internal combustion engine. The valves in the power unit of this model are opened by transmitting pressure to the lever rod, which is moved by the camshaft's eccentric cam. The gap that is subject to regulation is the gap formed between the cam in the place opposite the eccentric and the lever itself.

When carrying out work, follow the table.

Direct adjustment begins with setting the piston of the fourth cylinder to TDC. This is a state of compression. At this point both valves are closed. Then the crankshaft is rotated until the mark on the sprocket meets the mark on the body. For control, a 0.15mm probe and two keys are used - 13 and 17.

Work order:

– the probe is inserted into the space between the cam and valve lever No. 6 in turn; – if it is inserted with force, then this is normal; – if it dangles or, on the contrary, gets stuck or it is impossible to push it in at all, then adjustment is required; – decreasing or increasing the size of the gap is carried out by fixing the adjusting bolt, releasing the lock nut and turning the bolt. In this way, valves No. 6 and 8 will be adjusted.

The same manipulations are carried out for each valve by turning the crankshaft each time at an angle of 180° from the previous point, which corresponds to turning the camshaft by 90°. At each such turn, the following valves are measured and, if necessary, adjusted:

The regulation procedure is observed in strict sequence. If it is violated, then all settings of the gas distribution system will be lost. If you have sufficient skills, adjusting the valves yourself does not cause any difficulties. The issue price is 0 rubles.