»Breaking the timing belt and possible consequences - causes, symptoms, repair

In most cases, when the timing belt breaks, a clap is heard and the engine stalls, although all other automotive components continue to function normally. Restarting the engine in this case is most often accompanied by a metallic knock and ease of rotation by the starter, due to the lack of compression in the cylinders.

At the first suspicion, you should stop the car and raise the hood to inspect the condition of the belt, if there is such a possibility with quick access, as a rule, this is not possible.

Consequences and causes of a broken timing belt

How serious the consequences of a timing belt break are for your car is directly related to the engine design, the simpler it is, the less likely it is to damage it.

Most often, they can lead to:

• Engine overhaul.
• Restoration of the gas distribution mechanism.
• Bending of the valves - Occurs when the timing belt breaks when they are lowered to release gases or inject fuel. In this case, the crankshaft continues to rotate by inertia and is met by the pistons, which in turn can inflict a strong blow on the valves. However, this problem is typical only for cars with a specially reduced combustion chamber or in the absence of a recess on the pistons. To determine the degree of damage, it will be best to transport the car to a service station, since it will be necessary to dismantle the cylinder head and diagnose the engine using special equipment. It would be best to replace the entire set of valves, even if during a break, the engine was idling and only 3-4 of them were damaged.
• Piston Failure - Most often occurs on Japanese cars and occurs from a strong blow to the valve heads. If the belt breaks at high speed and all the valves are bent, the bushings will burst and the pistons will be punched by fragments. In this case, a very expensive repair will be required, including head replacement.

The most serious consequences of a timing belt rupture are observed in diesel engines, the design of which practically does not allow the valves to move, therefore, in the event of a break, when they are in the top dead center position, they can simultaneously become unusable:

• Camshaft with bearings
• Cylinder head
• The connecting rods are deformed
• Valves bend

The nature of the timing belt break

No less influence on the consequences that a timing belt breakage entails, is also borne by its nature, because in some cases it does not break, instead one or more teeth are cut off on it. In this case, both the crankshaft and the camshaft continue to rotate, striking pistons on all nearby parts.

Similar damage can occur even if the belt teeth remain intact but jump over the timing sprocket teeth.

Potential Costs and Belt Replacement Procedure

The cost of one valve, excluding additional costs, is on average one thousand rubles, and given that all 16 may need to be replaced, one can imagine how much the repair will cost.

In addition to the accompanying little things, you will need to purchase:

• New belt, or timing kit with tensioner and idler roller.
• Gaskets for intake and exhaust manifolds.
• Gaskets for cylinder head and valve covers.
• Set of fixing bolts.
• Possibly a water pump (pump) if wear is suspected.

The replacement operation is easiest to carry out on a lift. To work you will need:

• a set of keys
• screwdriver
• timing pins
• in some cases special. tool.

To dismantle the old belt, follow the steps below:

1. Remove the timing case - secured with several bolts.
2. Unscrew the crankcase bolts.
3. Next, remove the compressor belt. To do this, dismantle it, remove the belt and reinstall the compressor.
4. Remove the alternator belt.
5. To de-energize all contacts, remove the terminal from the battery.
6. Unscrew the mounting bolts from the engine and remove the generator, terminal and pump pulley, remembering to first remove the bolts holding them.
7. It may be necessary to remove the engine mount
8. Remove the protective cover from the timing belt

Now proceed with the direct replacement, for which you will need to remove the toothed pulley covers and pull out the old timing belt. Put a new one in its place and tighten the tensioner. If the rollers have become unusable, they should also be replaced. Next, assemble the structure in reverse order. Keep in mind that each brand of car has its own characteristics of dismantling and installing the timing belt, however, in general, they are very similar.

Timing belt break video

Preventive measures

To avoid the need to replace the timing belt on the road due to an unexpected breakage, it should be replaced at least after a run of 60 thousand km, using only original spare parts and without waiting for the belt to fail itself.

Do not be lazy to periodically check the degree of its tension and the condition of the pump and all the rollers. The tension should be done evenly, without sagging in certain areas.

Also, in order to avoid breaking the timing belt, you should pay attention:

• To the emergency lamp showing the degree of oil pressure
• On the condition of the oil seals - If they become unusable and pass oil to the timing belt, it will quickly fail. The main evidence of leaks is oil stains on the asphalt or engine surface.
• Avoid starting the car "from the pusher", as such jerks can provoke a break after 20 thousand kilometers.

Even if you follow all the tips, you cannot be sure that it will not break on the road, therefore, it will be useful to have a set of tools and a new belt for quick replacement.

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The cause and mechanism of the problem

In the first VAZ cars, it was impossible to imagine the problem of valve bending. However, the situation changed fundamentally after the transition to front-wheel drive. If earlier the timing chain performed its work, then the drive belt and the transverse aluminum block immediately led to problems.

First of all, the timing belt was much less reliable than the chain. That is, a break at almost any moment could lead to the fact that the piston in its movement rests against the valve, leading to the bend of the latter. The problem was defined in the professional environment of auto mechanics as a "stick problem".

However, in the very first engines of the Euro 2 class, this problem was practically not encountered, and all thanks to the rather spacious engine compartments. Anyway, the distance between the pistons and valves was sufficient so that even a belt break would not produce unnecessarily destructive consequences. However, the desire of manufacturers to maximize the compactness of the engine and the Euro 3 requirements negatively affected the performance of the latter. Now the compression ratio began to increase sequentially, which brought the piston closer in its movement to the valve. An imbalance in the system almost inevitably leads to direct contact between the piston and the valve. When the timing belt breaks, the crankshaft continues to rotate, and the camshaft gradually stops. As a result, the movement of the piston towards the valve leads to a shock, to which the valve reacts by bending of varying degrees of intensity.

As a rule, the "butt problem" leads to the valve bending under the "poppet", in the most vulnerable place. In turn, this leads to immobility of the car, even if “only one” valve is damaged.

Most often, the valve kink problem affects one or two valves. However, there are situations when all the valves may suffer, and then you will have to at least sort out the engine and change the valves, or even decide on more significant expenses in the form of engine overhaul or even its replacement. There is simply no other way to "cure" the problem.

Preventing valve bending

However, any problem can be avoided and valve kinking is no exception. The first and foremost rule for those who wish to avoid this problem is to monitor the condition of the timing belt. Its good condition and timely replacement is the main rule of prevention. Moreover, it is recommended to do this with a slightly higher frequency than the manufacturer advises, and the more

You can also use another method - use non-standard pistons, the bottom of which is specially machined with cutters in the shape of a valve. They can be installed as "non-native", that is, created by other manufacturers, and "native", VAZ. For several years AvtoVAZ has been producing special engines with pistons that are protected from valve bending in this way - through the use of pistons treated in a special way. Such engines are eight-valve, and these modifications are well-respected by motorists. While they certainly do not provide a 100% guarantee on valve kink, they significantly improve engine safety.

Continuous improvement of the internal combustion engine in order to increase and improve fuel efficiency forced engineers to seriously redesign the design of modern diesel and gasoline engines. The changes also affected the device of the piston group and the combustion chamber. These modifications were made for the most efficient filling of the cylinders and their high-quality ventilation, that is, to obtain an improved gas exchange.

If in the early stages of development the most common was the engine with two valves per cylinder (1 inlet and 1 outlet), today there is an increase in the number of valves per cylinder. Such changes are well illustrated by the most common version of the automobile with four cylinders. Previously, such motors were often 8-valve, with one. Today, such a unit is often a 16-valve version with two camshafts (for intake and exhaust valves), can be equipped with a variable valve timing system, etc.

Read in this article

Broken timing belt / chain: main causes

If we compare modern motors with their predecessors, today motors have more power and less resource. As for the problem of bending the valves, it is to achieve greater recoil from the motor that the distance from to is minimal. Even a slightly open valve bends during the lift of the piston at TDC. It turns out that various technical innovations in engine building did not affect the well-known problem that is inherent in the vast majority of engines, regardless of the type of engine and manufacturer. We are talking about the bend of the valves when the drive belt breaks or.

An important rule during the operation of the car is to monitor the condition of the timing belt and its timely replacement. The belt should be free of delamination, cracks or other defects. Also, it is not allowed to get various technical liquids on its surface. The appearance of a squeak, squeak and other extraneous sounds will require the owner to check the tension and condition, as well as the tension and other rollers.

To answer the question when you need to change the timing belt, you need to study the operating instructions for a particular car. Often, on new cars, the belt changes after 60 thousand kilometers traveled or after 2-3 years (whichever comes first). A planned replacement with an original belt involves the next replacement every 50 thousand km. It is advisable to choose non-original belts with care and change every 40 thousand km.

Now a few words about the chain drive. The timing chain requires less attention, since the replacement of the chain is, on average, necessary once every 150-200 thousand km. and more. In this case, it is necessary to monitor the chain tension, the condition of the tensioner and chain damper. Increased noise during engine operation, the appearance of a metallic clang and other signs will indicate the need for immediate verification of these elements.

So, back to the less reliable belt compared to the chain. The timing belt most often breaks for the following reasons:

• belt wear as a result of long-term use or use of a poor quality product;
• jamming (water pump);
• wedging of the crankshaft, camshaft;
• malfunction of the tension roller, jamming of the timing rollers;
• destruction of the timing belt as a result of engine oil getting on its surface;
• mechanical damage after contact with sharp edges, camshaft gears;

Why do the valves bend when a belt or timing chain breaks

Despite the improvements, the general traditional principle of the timing and valve train of the engine remains unchanged. As you know, raising the piston at TDC (top dead center) means that at the specified moment and the valves are closed. This is necessary to create pressure and seal the combustion chamber.

If the timing belt breaks, then the valves simply do not have time to close, which means they collide with the rising piston. When the timing belt breaks, the camshafts stop immediately. This immediate stop occurs for two reasons:

• since the driving force from the belt or chain disappears;
• the camshaft cams themselves are retarded by return springs;

As for the crankshaft, this element continues to rotate by inertia. The inertial rotation of the shaft does not depend on what gear and at what speed the car was moving, at what speed the engine was running, etc. cranks the crankshaft anyway. In other words, if the timing belt is cut off, then the gas distribution mechanism stops immediately and the valves remain open, while the crankshaft continues to rotate and the moving pistons hit the open valves at this time.

The result of a broken belt is that the piston meets the valves, after which the valves are immediately bent. The valve stem is often bent, although sometimes various deformations of the valve disc are also possible. Less commonly, damage to the piston itself can be found, which is also a consequence of the belt breaking and bending of the valves.

Engineers and automakers are familiar with this problem. To prevent the consequences of breaking the timing belt / chain in some old ICEs, special grooves for the valves were made on the piston. These grooves actually provided the necessary free space, which allowed the open valves not to collide with the upward moving piston. In such motors, after a break in the drive, the valve did not bend.

Modern engines also have distinctive piston notches. It is worth noting that these grooves avoid the risk of damaging the valve while the engine is running. If the timing belt breaks on such motors, these grooves do not save from bending the valves, that is, the valve still bends even if there are special grooves on the piston.

On which engines the valve bends: how to find out

Due to the severity of this problem and the high cost of subsequent repairs, many motorists are concerned about the question of how to find out if the valve motor is bending or not bending when the timing belt breaks. To more accurately find out and determine whether the valves bend on a particular engine, you can use the following recommendations:

1. Study in detail the technical documentation for the engine from the manufacturer. We add that a visual inspection, as well as various data from the tables, still do not give 100% confidence that when the drive belt breaks, the valve does not bend. It is also not recommended to blindly trust the statements on the specialized auto forums or rely on information from other more or less authoritative sources. In other words, the accuracy of any data must be questioned and rechecked.
2. Another method is the so-called "physical" check, which allows you to find out yourself if the valves are bent. This method allows you to determine the likelihood of valve bending, that is, to confirm or deny the possibility of contact between the valve and the piston.

In order to find out whether the valve bends or not, you will need to remove the timing belt. Further, the piston in the first cylinder is set to the TDC position, after which the camshaft of the gas distribution mechanism is rotated 720 degrees. If in the process of turning the camshaft no stop is observed, then it is necessary to make a similar check by alternately raising the pistons in all other cylinders of the internal combustion engine to TDC. If the camshaft does not rest anywhere, then there is a high probability that the valve on this engine does not bend when the belt breaks.

With regard to various technical information, which is given in the tables, as well as referring to the experience of auto mechanics and ordinary drivers, the summary data allows us to note:

• often the valve does not bend on simple 8-valve motors;
• usually valves bend on 16-valve and 20-valve engines;
• valve oppression on almost all diesel engines;
• bending of the valves occurs on most engines in the event of an open timing chain, that is, on engines with a timing chain drive;
• valves usually bend on engines of small cars with a displacement of 1.1 to 1.4 liters;

Read also

The machine will not start after replacing the timing belt, timing chain, or other work on the timing mechanism drive. Main reasons, recommendations.

When buying a car, not all motorists are interested in whether the power plant installed on the car is "plug-in" ie. whether the valve bends on it when the timing is broken. And this question is quite important and the answer to it depends on how laborious and how much it will cost to repair the engine in the event of such a breakdown.

What is a plug-in motor?

This concept characterizes the likelihood of collision of pistons with valves, as a result of which the latter are damaged - they bend.

This situation arises when the timing drive is broken, when the gas distribution mechanism stops, and the crank continues to operate by inertia.

"Plug-in" and "non-plug" power units are in the lineup of almost all car manufacturers, including VAZ. In this case, the second option of engines, of course, is a higher priority when choosing a car.

If we consider AvtoVAZ products, then this manufacturer has a fairly extensive line of power plants, and in some motors, when the timing drive is broken, the valve bends, while in others such a breakdown does not occur.

The problem when choosing a VAZ car for purchase is the fact that both "plug-in" and "non-plug" units can be installed on the same model, which can confuse the buyer.

What engines are on some VAZ models, see below.

It is worth noting that the type of timing drive affects the likelihood of valve bending. For example, on the VAZ of the classic family (VAZ-2101-2107) as well as the "Niva", only "plug-in" engines were installed. But on the motors of these cars, a timing chain drive is used, which is highly reliable. Therefore, on classic VAZ and Niva, the problem with valve bending due to a collision with the piston is, in fact, not relevant due to the low probability of its occurrence.

Starting with the VAZ-2108 and ending with the latest models - Priora, Grant, Kalina, etc., only the timing belt drive is used. Here it can break off and the damage that the motor will receive depends on whether it is "plug-in" or not.

Why do engines bend valves?

One of the ways is to ensure the most efficient filling of the combustion chambers with a fuel-air mixture and the removal of exhaust gases. And this is done in two ways - by increasing the number of valves per cylinder and increasing the throughput of the intake and exhaust ports.

The second method is realized by increasing the distance of the valve exit from the seat, and it is this that causes it to collide with the piston and subsequent bending.

Thanks to the drive of the gas distribution mechanism from the crankshaft, synchronous operation of the timing and KShM is ensured. During normal operation of the power unit, on the approach of the piston to the TDC, the valves are in the closed position, which excludes their contact.

If the drive of the gas distribution mechanism is cut off, the connection between the mechanisms is lost, and the timing stops immediately, and the KShM continues to function (due to the inertia of the flywheel). In this case, the return valve springs set the camshaft in a position in which most of the camshaft cams do not press on the valves (they are closed), but some of them still rotate so that they act on the valves and the latter are open.

In "non-stick" engines, it is structurally provided to maintain the distance between the valve plate and the piston crown, which is at TDC, therefore, even with the valves open, no contact occurs.

On these power plants, a break in the gas distribution mechanism does not lead to any internal damage to units and parts, and to restore the power unit's performance, it is enough to install a new belt and perform adjustment work (set everything according to the marks).

But if the power plant is "plug-in", strongly protruding valves collide with the piston, which leads to their bending. On such motors, a break in the timing drive is usually accompanied by a strong single knock. Engine repair in this case is laborious and expensive, since it is necessary to change damaged parts and restore the cylinder head.

On VAZ power units subject to valve bending when the drive is broken, timely and periodic diagnostics of its condition, checking and adjusting the tension are especially relevant. Such measures are practically the only ones to prevent valve breakage.

VAZ engines - "non-stick" and "risky"

Since several power plants are installed on each of the VAZ models, it is important to know which of them are "plug-in".

As already noted, on the classic VAZ (2101-2107) and VAZ "Niva" power units were installed, in which the valves bend. But since the timing drive on these motors is a chain drive, "sticking" can be ignored.

Samara

On cars of the "Samara" family (VAZ 2108-21099) were installed:

1. Units marked VAZ 21081, 2108 (carburetor and injection);
2. Motors 21083, 21091;
3. 8-valve VAZ-2111 (models of later years of production).

Of these, units 21083 and 2111 did not bend the valves when the timing belt broke, but versions 21081 and 2108 were "risky".

VAZ 2110-2112

On the models of the 10th family (VAZ-2110-2112), the line of power plants is even more extensive. Some units were installed on all cars of this family, and some were offered only for certain models.

The engines with the indices VAZ-2110, 2111 (8-valve), 2112, 21114, 21124 were common to all models. Of these, the VAZ-2112 and 21114 engines are "plug-in", and the rest of the valves are not bent.

Additionally, the VAZ-2112 model car was equipped with a VAZ-21128 power unit, which is also "risky" and when the timing belt breaks, the valves bend.

Samara-2

Cars of the Samara-2 family, which include the VAZ 2113-2115 models, are equipped with units of the VAZ-2111, 21114, 21124 and 21126 brands. Of these, only the VAZ-2111 and 21124 engines are “risk-free”.

Also, for the VAZ-2113 and 2115 versions, a motor with an index of 11183 was offered, in which a broken belt does not lead to bending of the valves.

"Granta", "Kalina", "Priora"

Lada "Granta" is equipped with a line of installations of the following brands: 11183, 11186, 21126 and 21128. The latter two of them are also equipped with the version of "Grant Sport". Of all the motors, only version 11183 is "non-stick", the rest are bent valves.

For Lada Kalina, engines of the brands VAZ 11183, 11186, 11194, 21126 and 21127 are offered. The latter two units are also installed on the Kalina Sport model, and the Cross version is equipped with engines 21127 and 11186. Of the entire line, only the VAZ-11183 engine does not bend the valves when the timing belt breaks.

Lada "Priora" is equipped with installations with indexes 21114, 21116, 21126 and 21127. All these motors are "plug-in".

Note that only the main brands of power plants with which certain models are equipped are indicated above. But AvtoVAZ almost always "sins" with experimental small-scale production, when units that are not typical for it are installed on some cars.

For example, an engine with an identical index was installed on the VAZ-2109, which differs from version 2108 in a lightweight design, and a small series of VAZ-2108 was completely equipped with a rotary installation marked VAZ-415.

READ BY TOPIC: Other characteristic and other models in the series.

Foreign cars

Let's touch on the topic of foreign cars a little. Below is shown on which engines from Toyota, Suzuki, Daewoo, Chevrolet, Citroen, Hyundai, Renault, Volvo, Kia, Fiat, Mercedes, Peugeot, Honda, Ford, Geely, Mitsubishi, Nissan, Audi, Volkswagen, Skoda, Opel, Lifan, Chery, Mazda, Subaru bending the valve.

Determine which engine is risky

A large number of VAZ power units and the likelihood of falling into an experimental model makes it difficult to determine whether the engine on a particular car is "plug-in". Moreover, even studying those. the documentation does not always give a reliable answer.

To determine whether the valve bends on the engine, it is only possible to physically check it. This operation is not entirely simple, especially for 16-valve units, but it allows you to accurately establish their susceptibility to valve bending.

This method is suitable for checking cars from other manufacturers.

The verification algorithm is very simple:

• Remove the timing belt from the engine;
• Install the piston of the first cylinder at TDC;
• We turn the camshaft (16-valve version - two) two turns;
• We set the TDC on the second cylinder and again make two turns.

If, during the check, the camshafts rotated without stopping, the engine does not bend the valves.

Although this method of verification is laborious - it is necessary to disassemble the timing drive, then reassemble, set according to the marks, but it gives an exact answer.

Ways to solve the problem

Since the collision of pistons with valves has rather serious negative consequences, many motorists are interested in whether this situation can be influenced.

There are several methods that make it possible to turn a valve-bending motor into a "plug-free" one.

The simplest of these is the installation of grooved pistons. By the way, on some VAZ engines this is exactly how the problem with "sticking" is solved.

On the bottom of such pistons there are special recesses for valve discs. Due to this, the latter in the open position do not come into contact with the pistons installed at TDC.

But not all motors can be modernized in this way, for the reason that it is not always possible to find pistons with factory-made grooves to replace the "family" ones.

The second method is to make the grooves on the piston yourself. This method is suitable for those who have not found "non-stick" replacement pistons. But this method has a significant drawback - it is very difficult to make the same indentations on all pistons. As a result, an imbalance of pistons by weight may form, which will affect the resource of the KShM. Also, grooves of different sizes can cause, and this problem cannot be eliminated.

The third method is to increase the height of the combustion chamber. This is done by installing 2-3 gaskets under the block head. This method has a negative side - an increase in the volume of the combustion chamber, which entails a fall, and as a result - a decrease in power and an increase in fuel consumption.

Tuning and its impact on "sticking"

VAZ is a great option for, which is what many owners use. One of the main types is to increase its power, and this is done in the same way that designers use - ensuring better filling of the cylinders with an air-fuel mixture. To do this, it is enough just to install a tuning camshaft instead of the standard camshaft - with a higher cam height.

But the increase in power with the help of the tuning shaft also has a negative side - the valves leave the seats to a greater distance, which means that they are more likely to collide with the pistons when the timing drive is broken. Therefore, such tuning makes even a "risk-free" motor "plug-in".

In order not to make the engine "risky", during tuning it is better not to make adjustments to the timing design, but if it is decided to make an upgrade, then you should be ready to constantly monitor the state of the drive.

Finally, we note that if the engine is "plug-in", it does not mean that it is very problematic. With timely maintenance of the timing drive, the likelihood of such a breakdown as valve bending is very low and it may not occur throughout the entire period of vehicle operation.

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Often in the conversations of motorists, phrases flash: “I got to be repaired, the belt broke, the valve was bent”. Of course, in such cases we are talking about the timing belt. In order to understand the causes of the "catastrophe", let us consider in general terms the interaction of the connecting rod-piston group and the gas distribution mechanism.

This interaction is strictly coordinated, otherwise the normal operation of the engine will not be ensured.

The principle of operation of the valve-piston system

Let's take a compression cycle as an example. When the piston, compressing the combustible mixture, approaches the top dead center, it almost comes close to the combustion chamber (on diesel engines - to the surface of the head). If at this moment any of the valves is not closed, then the loss of compression will be the lesser evil. Most likely, the valve, the rod of which is rigidly held by the rocker arm (or the cam of the camshaft) from above, will take the blow of the piston.

The valve bends in the event of a collision of the valve with the piston

In very rare cases, the piston crown has recesses in the piston crown to avoid collisions. From the above, I hope, it is clear why the valve bends when the timing belt breaks: the camshaft stops rotating, some of the valves remain in the open position, being a “convenient target” for pistons moving by inertia.

The coordination of the timing with the crank mechanism is ensured by the precise installation of gears or sprockets. For this, alignment marks are made on them and at certain points of the engine.

By the type of torque transmission, the drive of the gas distribution mechanism can be:

• Belt
• Chain
• Gear

Consider their common malfunctions, which can lead to bending of the valves.

Timing drive device

Consequences of a broken timing belt

Some curious motorists are interested in the question: is it possible to bend the valve with a starter? The answer is easy! Just do not set the sprockets or gears "according to the marks" - and the key is ready to start! If the engine starts, you will immediately learn to recognize the symptoms of kinked valves. Although, if you do not “miss” much, then everything can be fixed by assembling the timing drive according to the rules.
If only one valve is bent, the engine will run unevenly. Even if it's a V-shaped "six" - hear it.
If, after the restoration of the camshaft drive, the engine runs smoothly and develops the same power, then you are lucky and the manufacturer prudently supplied pistons with sufficient indentations in the bottoms. Unfortunately, this is not always possible. First of all, when designing a motor, the designer achieves a combination of many seemingly contradictory qualities of his "brainchild". Let's say such as economy and power. This can to some extent serve as an excuse for the fact that on 16-valve motors, the valve often bends when the timing belt breaks.

Such problems are especially acute for the creators of diesel engines, in which the compression and the necessary swirling of the fuel mixture set the power characteristics. Therefore, the combustion chamber is made in the piston crown and often has a whimsical shape.

On diesel engines, the valve bends more often than on gasoline

However, behind this is the accurate calculation and simulation of vortex flows on a computer. Such chambers are called undivided and making recesses for the valves is impractical from the point of view of high-quality atomization and the most efficient combustion of the fuel mixture. The piston comes very close to the block head. Therefore, it is not yet known for certain whether there are diesel engines that “do not bend the valve”. Although, perhaps, human genius coped with this disaster.

Repairs

Curved auto engine valves

Never try to repair bent valves in any way!
Replacement, and only replacement!

If you straighten the valve "by eye", then you risk making yourself more trouble. A hand-rebuilt valve is unlikely to be aligned with the guide bushing and will press tightly against the seat. And if you want to "slightly" trim the rod, then it will work like a pump, pumping oil into the combustion chamber - no cap will hold it.
It would be prudent to troubleshoot other parts as carefully as possible. After all, a blow can damage the guide bushings, valve seats. There are cases when the connecting rods were bent. Breakage of rocker arms is also not uncommon.

Models of VAZ engines, the valves of which are not “afraid” of breaking the timing belt:

VAZ 2111 1.5l; VAZ 21083 1.5L; VAZ 11183 1.6l (8 valve); VAZ 2114 1.5l and 1.6l (both 8 valve)

It is known that the old 8-valve "Opel" engines (such as on the DAEWOO Nexia and Chevrolet Lanos), also calmly endure this trouble.

As a rule, if a person in his favorite car bent at least one valve, even once, such a person already begins to understand that even “glands” do not have iron patience and will try to become a good master of their “horse”.

In conclusion, it will not be superfluous to add - watch your car, do not hesitate if there is a reason to “look under the hood”.