DIY 402 cylinder head repair

Actually indications for overhaul 2 - this is an increased consumption of gasoline and / or oil. In principle, everything. Any engine malfunction (and not only, as well as chassis, for example) one way or another will lead to an increase in fuel consumption. At the same time, the car will not lose in dynamics (well, unless everything is extremely neglected, like a burnt-out valve piston). For any car, the manufacturer indicates the normal consumption of both gasoline and oil. In the case of the Volga with ZMZ 402, gasoline consumption in the city should be 13.8 liters per 100 km, and oil should be consumed no more than 250 grams per 100 km.

In my case, the consumption was 25-30 liters, while the oil had to be topped up by a liter per month, with a mileage of less than 400 km. Gasoline consumption was measured by the odometer. As further developments showed, in addition to the wear of the engine itself, a slipping clutch and a wedging brake pad, as well as a muffled EPHH system, also contributed to the increased consumption.

The capital was made a year ago, upon completion of the running-in, it turned out that in winter, with normal driving (without slipping), it fit into 20 liters, in summer the consumption was 14-16 liters when driving with a moderate degree of aggressiveness. During the run-in, the problem of oil leaks was actively solved and by the time the run-in was completed, the engine was switched to synthetics, which it still drives.

The oil pressure before the capital was satisfactory, so I did not plan to remove the crankshaft. Nor did I plan to change the earbuds. From the spare parts, I took a set of valves:

New valve springs. It is imperative to change them with capital, Evgeny Travnikov constantly repeats this, they say tired valve springs squander power at high speeds. It seems to be true, after 3000 the motor with new springs began to pull much more fun.

A re-turning was also planned, for which a set of bushings was purchased.

A set of gaskets was also purchased for the overhaul of ZMZ Zolotaya Series. This set turned out to be a rare gamma, so I advise you to buy separately the valve stem seals, the front crankshaft oil seal, crankcase cork gaskets, valve cover and pusher covers. For all other gaskets, I advise you to buy oil-resistant paronite and cut the necessary gaskets in place yourself.

From the tool you will definitely need:

Torque wrench for 12 and a head for 17 is required.

The mandrel for pressing on the valve stem seals will not interfere:

Be sure to need a 9mm sweep:

The valve dehydrator will make life easier and save the bushings:

One of the most expensive items is cutters:

To remove the cylinder head, first remove the axis of the rocker arms, then carefully unscrew 10 nuts. I had a couple of nuts creaking, so you need to unscrew it smoothly. Important! In order not to distort the cylinder head, the nuts must be unscrewed in the same order as when tightening, little by little. That is, first we pull off the nuts from their place. Then we sequentially unscrew all the nuts, unscrewing them by a third of a turn. Further, all the hope is that the collective farm with the previous installation of the cylinder head was not (such as a stuck solid oil). However, even in the absence of a stuck gasket, there will most likely be a problem with the penultimate hairpin on the passenger side:

The next stage of the overhaul is the removal of resinous deposits from the parts. This is how the cylinder head looked a year before the overhaul, after 1.5 years on semi-synthetics:

Washing was carried out with dishwashing detergent (any will do) using a toothbrush. The technology is as follows - we drip with dishwashing detergent and with three toothbrushes, wipe it dry like the slurry turns black with a paper napkin.And so on, so almost all the details were washed away:

First of all, the washed cylinder head must be sanded:

The combustion chamber was covered with a thick layer of carbon:

Next, remove the old valve stem seals. I didn't have much oak, and a couple were generally cracked:

The next step was to turn over. I wanted to use the technology of Evgeny Travnikov:

The next stage of cylinder head repair is the trimming of the saddles. It seemed to me that only a 45-degree chamfer was cut from the factory, but I cut all 3, which is why the valve should close more tightly and gas exchange should improve. I heard a lot about the hardness of the cylinder head ZMZ 402 saddles, but with the above set of cutters, my saddles were cut quickly and easily. The central chamfer was made in the region of 1 mm so that after lapping it would increase to the prescribed 1.5 mm.

The next step is lapping the valves - this is the most tedious step. I didn't bother much about checking with diesel fuel, etc. assessed visually by an even pattern around the circumference of the saddle. Do not forget to sign the valves so as not to confuse them during assembly.

Also, to improve gas distribution, I grinded down the steps at the valve seats:

At the end of the cylinder head repair, we press on new valve stem seals using a mandrel. IMPORTANT! Before pressing the MSC, put on the lower valve plates, then they will not fit 🙂... After that, you can dry out the valve. Let me remind you once again that the springs must be changed during a major overhaul. The old valves were dirty and worn out - they had both scuffs on the stem and did not protrude enough above the plate, that is, as the rocker arm wears out, it will begin to press not on the valve, but on the plate:

I started the assembly by replacing the tank with a new one from a gazelle, screwing a fitting 18 into it:

In the thermostat, I filed away casting defects with a file, which will improve the coolant circulation by a fraction of%:

I also slightly "screwed up" the oil supply channel from the hole to the support of the rocker arm axis (seen in the photo), there were small burrs:

Then he proceeded to replace the piston rings. Before that, I carefully scraped off the carbon deposits from the piston (it turns out to be aluminum):

Next, we change the gland packing. I bought a cheap one for 15 rubles, changed only in the lower holder, since I did not remove the crankshaft. Despite all this, this 15-ruble packing has been holding TNK 5v40 synthetics for a year with periodic engine promotion up to 5000 rpm. As far as I understand, the packing flows with large beats, with strong wear on the necks and liners.

The next step is to install the cylinder head on the studs, I wound fum tapes, due to the fact that it is Teflon (fluoroplastic), and it is extremely chemically resistant and quite heat resistant. In general, I wind fum tape on all pins / bolts prone to souring, in loaded places it will break and fill the cavities, which is why rust does not form in them. The fum tape itself is not going anywhere:

I put the gasket with triangular windows. From the factory there was the same:

I also applied a little know-how, wrote on my head the procedure for tightening the nuts 🙂:

The primary grinding of the rings was carried out with a barrel organ (crooked starter), that is, when the cylinder head was not yet installed, I poured oil from above into the sleeves and twisted it. That is, what a pause stood out, I approach - 50 revolutions. It became especially tight after replacing the packing, in total I did it with my hands in the region of 500-1000 rpm, as a result, the engine started with a starter without straining. I ran in the same oil that I drove to the capital - semi-synthetics TNK 10v40. While driving, I tried to keep 2100 rpm without spinning more than 2500. Without any dynamic overtaking. Having driven around the city for a week, then made a circle of honor around the city, about 80 km along the bypass road. At the same time, I was driving strictly 2100 rpm in 5th gear - this is about 80 km / h on the railway station, according to the speedometer it was 90. All the time I was running in I was at war with oil leaks, and by the time 1000 km was completed all leak channels were eliminated and I switched to synthetics with a clear conscience ...

Tightening threaded connections is critical. Loose or overtightened bolts and nuts can cause very serious damage. Therefore, it is correct to strictly follow the table of tightening force (torque) values ​​and use a torque wrench to control the force.

Timing gear cover retaining bolt

Timing gear cover retaining nut

Nut for fastening the cover of the pusher box

Cylinder head retaining nut

Rear cylinder head cover retaining bolt

1. After disassembling the block head, wash all parts in gasoline, wipe and dry. Remove carbon deposits from combustion chambers.

2. Inspect the block head. If there are cracks on the bridges between the valve seats or on the walls of the combustion chambers, traces of burnout, replace the block head.

3. Check with a metal ruler and probes whether the flatness of the head surface adjacent to the block is not broken. To do this, place the ruler with an edge on the surface of the head, in the middle along, and then crosswise and measure the gap between the plane of the head and the ruler with feelers. If the gap exceeds 0.1 mm, replace the head.

4. Inspect the valves. If cracks, warpage of the valve head, burnout, or deformation of the stem are found on the working chamfer of the valve, replace the valve. Minor marks and scratches on the valve chamfer can be removed by lapping. We look at the procedure for grinding the valves in the article - "Disassembly and assembly of the cylinder head".

5. Check the condition of the valve springs. Replace bent, broken or cracked springs.

6. Check the condition of the valve seats. The working chamfers of the seats should be free of signs of wear, cavities, corrosion, etc. Minor damage (small marks, scratches, etc.) can be removed by lapping the valves. More significant defects are eliminated by grinding. When grinding, observe the seat dimensions shown in the illustration. After grinding, check the runout of the seat chamfer relative to the hole in the valve guide, the maximum allowable runout is 0.05 mm. After grinding the seats, grind the valves. Then thoroughly clean and blow out the block head with compressed air so that no abrasive particles remain in the channels closed by the valves and in the combustion chambers.

7. Check the clearance between the guide bushings and the valves. The clearance is calculated as the difference between the bore diameter in the sleeve and the diameter of the valve stem. The maximum allowable gap is 0.25 mm. If the clearance is greater than the specified, the valve and guide bushing must be replaced. The old sleeve is pressed out with a mandrel on the side of the combustion chamber. Before installation, new bushings must be cooled in carbon dioxide ("dry ice"), and the block head must be heated to 160–175 ° C. Then insert the bushing into the block head so that it protrudes from the side of the valve springs above the block head by 20 mm. The sleeve should be inserted into the head freely or with little force. After installation, expand the hole in the bushing to a diameter of 9.0 + 0.022 mm. Then grind the valve seat by centering the tool against the bore in the bushing.

8. You can check the block head for cracks as follows. Connect a compressed air hose to one of the holes in the cooling jacket. Seal all holes in the block head with wooden plugs. Lower the head into a bath of water and supply compressed air at a pressure of 1.5 atm. Air bubbles will emerge where cracks are formed.

9. Clean the holes in the rocker arms, rocker arms and adjusting screws with a wire and blow with compressed air. Check the tightness of the bushings in the rocker arms. If the bushing does not fit snugly, it must be replaced, as while the engine is running, it can turn and block the hole for the oil supply to the push rod.

The sizes and fits of the cylinder head parts are shown in the tables.

Repair of ZMZ-402. Disassembly and troubleshooting

The internal cavities of the engine were heavily contaminated with a mixture of grease and soot, almost a centimeter under the valve cover.When opening the crankcase, the main nut was unscrewed.

The nut was stored in a pallet.

The stuffing was brought up in order, it was installed with a Christmas tree in rotation, i.e. vice versa.

The exhaust valves are flared with fungus.

The camshaft upset most of all, on 4 cams there are nicks, the cams are sharpened by 1 mm.

On the intake valves at the top of the cut.

To measure the stiffness of the springs, such a device was made.

Based on the results of parsing the camshaft for replacement, grinding the knee, valves for replacement. I will cut the head of the ZMZ-402 under 92 gasoline.
Internal springs are within tolerance, external springs are rather weak (46 mm, 23-25 ​​kg).
The piston is in the tolerance, at least not to change something, I will change the ring current.

So, at the moment, I have assembled a block. First of all, I eliminated factory errors in the manufacture of the block, the channel after the pump is clogged with flash and casting defects.

But after using the file, everything goes away.

Next, we unscrew the plugs of the oil channels, and clean the insides with a wire and a compressor; in three channels, the remnants of drilling were found, it looks like they are still from the factory.

We level the sharp edges on the oil channels of the crankshaft so that they do not cut off the liners, the main thing here is not to make a bump along the edge.

I spin the crankshaft, not over my head, but the crankpin plugs.

It got from the crankshaft.

We put a knee and drive in the piston, grease all the mating parts with oil, which I will then fill in for running in.

Tie on two clamps and strips of sheet metal 30 * 290mm

Installation of the ZMZ-402 camshaft.

I put the adapter on the Zhiguli filter, drilled out the oil channel, it was very small.

Adapter for Zhiguli filter.

The pulley spread apart had to be knocked down and grabbed.

I painted the covers from ZMZ-402.

On the left is the Volgovsky bracket, on the right is the UAZ one, for comparison

A Fenox basket was selected, driven by any UAZ one for the desired shaft (they are also different).

For comparison, on the left is an old Volgovskaya, on the right is a new one, at the back there is a lever. I will not say exactly where it came from from UAZ or GAZ, 6 springs, seemingly more powerful than from UAZ. I read from the reviews that the diaphragm link is weaker than the lever one, a small test stepping with the heel into the place of pressing the release bearing with my stunted body of 100 kg, I can say that the old Volgovskaya and the lever linkage bent 1-1.5 cm, and the new nifiga did not bend.

I read that the flywheel on the ZMZ-402 is lighter than on the UAZ (8 kg versus 13 kg), well, figs knows, maybe I have it from old age, but it weighs 13 kg.

And his diameter is like this.

It is desirable that the bell be universal, like mine.

Summarizing, we can say that to introduce the ZMZ-402 from the Volga to the UAZ, it is enough to buy a pressure plate and front engine mounting brackets. Well, the exhaust has to be altered, the gas pedal control… these are trifles.

I also had to change the ring gear, knocked down the old one with a hammer, put the new one in the oven for 10 minutes at 250 degrees, like ten minutes. I lubricated the flywheel with a thread lock in advance and put on a crown. Collected after cooling.

It happens that antifreeze runs away through a hole in the block along a hairpin, this one

Secret hole threaded at 10.

I did not check, but simply screwed a bolt in there.

Collected the cylinder head. The head was sanded under 92 gasoline, cut off 3.5 mm, the height of the cylinder head was 98 mm, it became 94.5 mm (standard 94.4 mm).

The outlet to the stove, the so-called tank, in the rear of the cylinder head rests against the wall of the engine compartment and needs to be removed, and the question arises where to get the outlet to the stove. Well, if there is a sensor in the upper part of the cylinder head, then the question disappears, but in this place I had only a technological influx of aluminum. In short, there is no hole. But the absence of a hole will not stop normal boys, I need to do it, I got married like that in general. Okay enough demagogy closer to the point.
The cylinder head was like this:

I took a 19mm drill bit (I had to take it for 18mm, but it worked out fine anyway) and half-inch taps for pipe threads, they can be seen in the photo, and rushed.

We drill and cut threads, everything is just enough space.

Then I checked the oil channel, it did not coincide a bit with the block, it was filed with a file.

Grinding the mating plane.

I checked the input-output channels for coincidence with the spider, sawed off.

Not a scratch remained on the valves from the purchased lapping, although the belt on the saddle was already packed almost 2 mm, I repeated it with a homemade one made of abrasive, it went a little.

But on the rest, I did not achieve the same effect, I spilled it with a solvent, it didn’t seem to flow and was dry.

In the set of gaskets there were gaskets for everything, I had to do it myself around the back plug of the cylinder head. It is convenient to hit holes with a sleeve 7.62,

For stuffing the caps, a brush came up clearly.

The passage diameter of the angle 15 is approximately 14.5 mm, the tank is 9.5 mm, i.e. the passage in the corner is more than 2 times.

I drove the holes for the engine studs with a 13 mm drill, cleaned out a lot of dirt and removed the aluminum flattened to the thread.

Ideally, the guides would be changed (clearance 0.5 with a max tolerance of 0.25 mm), but it is expensive, and there is no suitable set of tools. On sale, the scans are bad.

The engine is assembled and dries up. The head is screwed on, the valves are adjusted. I drilled a hole in the pump for a half-inch brush so that the coolant outflow from the stove was equal to the inflow.

I drove a sleeve from the shock absorber into the tee to reduce the flow of fluid in a small circle, so that the pump sucks more from the stove.

I screwed all the nuts, pins and bolts onto the thread lock, where it is red, where it is blue, something I like it very much lately.

Disassembly, assembly and troubleshooting of ZMZ-402 completed.

The ZMZ 402 engine, which was produced at the Zavolzhsky Motor Plant, became a real legend in the domestic automotive industry of an entire era. It was installed on many car models such as Volga, UAZ, Gazelle and others. But, since the power unit has ceased to be produced, and its operation is carried out to this day, then periodically these engines need to be repaired.

Any engine wears out during operation, and this happens not only with internal elements, but also outside. This indicator is influenced by many factors that destroy the engine. So, let's consider the reasons why the ZMZ 402 engine needs repair, especially with regard to capital restoration:

The process of carrying out repairs, including overhaul, for the ZMZ 402 engine and its modifications, is similar to other power units of the series. All power units manufactured and manufactured by the Zavolzhsky plant are similar in design characteristics, and therefore repairs are quite easy. So, let's look at how to repair the ZMZ 402 engine with our own hands.

Repair of the ZMZ 402 engine begins with the dismantling of the power unit. The process is fairly straightforward, but four-handed is recommended. But, there is one difference, if the internal combustion engine is removed from the Volga, then this is one sequence of procedures. As for the 402 Gazelle engine, here the dismantling technology is slightly different. In order not to get confused, consider the classic process of removing a motor from a Volga car.

So, what sequence of operations needs to be performed by the motorist, what to remove the engine from the vehicle:

1. First, the battery is dismantled and its shelf is unscrewed.
2. Next, you need to remove the air filter and carburetor.
3. Disconnect the front pipe from the exhaust manifold.
4. We unscrew the spark plugs, remove the wires and the distributor.
5. We drain the engine oil.
6. Disconnect the fuel system.
7. Remove the fan impeller.
8. We dismantle the starter and generator, as well as the wiring associated with them.
9. Disconnect the clutch from the gearbox.
10. Dismantle the oil filter housing.
11. We remove the radiator and pipes of the cooling system.
12. We dismantle the intake and exhaust manifolds.

Further, when everything is disassembled, we completely remove the hood so that you can be unhindered, pull out the engine. We dismantle the power unit by hooking it onto a hoist or winch. Now, we install the motor on a special stand, if there is none, then on pallets and proceed to disassemble it.The motorist needs to disassemble his engine completely.

To do this, remove the parts in the following sequence: clutch, valve cover, oil pan, cylinder head, oil and water pumps, pistons, yoke, crankshaft. Now you can start the procedure for diagnosing the condition of the parts.

Diagnostics of engine parts begins with an inspection of the integrity of the cylinder block and crankshaft. If necessary, the body can be welded with special welding. If the block is very susceptible to destruction, then it should be replaced with a new one.

The next step in the diagnosis is cylinder measurement. The standard for ZMZ 402 is the size of 92 mm. But, if there is an elaboration on the walls, scratches or shells, then you will have to sharpen it to the next size. And if the measurement showed that the walls have already been repaired, then it is imperative to sharpen it to the next one, since the cylinders have a depletion and it must be eliminated.

Consider a table of the dimensions of repairs for the power unit 402 and its modifications:

ZMZ 402 engine - these are several variations of four-cylinder gasoline engines. The release of this power unit began in 1968, but it was only in 1980 that it finally approved its design by the engineers of the Zavolzhsky Motor Plant. There are currently three main engine assemblies. The first one is ZMZ-4021.10which has a fuel compression ratio 6,7 and accordingly consumes A-76 petrol. The second is ZMZ-402.10, which has a higher compression ratio than the first. She makes 8,2 and therefore the car can be refueled with gasoline A-92... The last construct is ZMZ-4022.10which is designed to work with A-92 gasoline and differs from its counterparts in the type of ignition. Since GAZ cars with such engines remain popular in the vastness of our country, many are interested in how to modify (tune) the cylinder head of the 402 engine. In this article, we will try to reveal the main points of the rework, and also provide useful videos on this score.

What can be done:

Need to find lower camshaft numbered No. 2... It significantly increases the engine speed.

How exactly the power of the 402 engine will change from the operations performed in the table below:

The cylinder head (cylinder head) is an essential component of any automotive engine. It is in the combustion chambers of the head that the air-fuel mixture is compressed, then the mixture is ignited by the spark of the spark plug, and the working cycle is performed.

To create the required pressure in the cylinders, the cylinder head must be sealed; for tightness, a gasket is installed between it and the cylinder block. But it should be noted that there are designs of internal combustion engines (ICEs) in which the cylinder head is a single unit with the cylinder block, that is, it is a monolith. An example is the Austrian diesel internal combustion engine Steier, which was installed on GAZ vehicles in the late 90s of the XX century. In such an engine there is no head gasket, which increases the reliability of the connection, but complicates the engine repair.

The cylinder head of passenger cars is made of cast iron or aluminum, but recently cast iron is almost never used - metal has its drawbacks. In any block head, the number of combustion chambers is equal to the number of cylinders in the engine, and if there are 4 cylinders in the internal combustion engine, then there are also 4 combustion chambers in it.

• exhaust and intake valves;
• guide bushings;
• valve springs;
• crackers;
• valve stem seals;
• pushers;
• valve seats.

Almost all modern engines have an overhead camshaft, so there is a seat (bed) in the block head for the camshaft. Valves in the cylinder head are needed to fill the cylinders with a fuel-air mixture:

• through the intake valves, the mixture enters the cylinder;
• exhaust gases are discharged from the engine via exhaust valves.

The valves are raised and lowered using the camshaft cams and run along the guides pressed into the cylinder head. The clearance between the cams and valves is adjusted using pushers, which in turn can be hydraulic or mechanical.

The valve stem seals are needed to seal the connection, they prevent oil from entering the combustion chamber. There are seats under the valve discs, and when the valve is closed, the seat is used to seal the combustion chamber.

Modern passenger car engines can have two or four valves per cylinder, and if the internal combustion engine has 4 cylinders, such motors are called 8 or 16 valves.

Automotive engines tend to break down; ICE failure can occur for various reasons. Including various malfunctions occur in the cylinder head, the reason may be:

• burnt out valve;
• deformation of the cylinder head surface due to overheating;
• the appearance of cracks in the head;
• wear of the guide bushings;
• seat wear.

You can repair the cylinder head yourself - here a lot depends on the skills of the repairman and on the complexity of the engine itself. The least difficulty is the repair of an 8-valve block head, the simplest thing here is replacing the valve stem seals, except for adjusting the valves. On many car models, replacement of the caps can be done without removing the cylinder head, depending on the complexity of the engine, the work can take from several hours to one day.

Often, exhaust valves burn out on the block head, burnout can occur:

• due to low-quality gasoline;
• due to insufficient valve clearance;
• due to the formation of oil deposits in the combustion chamber.

In order to replace the valve, the block head must be removed in any case. If you have auto mechanic skills, the work of replacing valves is not particularly difficult, and in this case we do the repair of the block head with our own hands as follows:

• remove the cylinder head;
• we dry out the burnt-out valve and take it out;
• we take a new valve, apply lapping paste on its chamfer and rub the valve along the seat;
• The tightness of the valve seating is checked with gasoline or diesel fuel, which are poured into the combustion chamber. If the liquid does not leave the chamber, then the valve is ground well;
• after lapping, we dry out the valve, install the cylinder head in place.

Replacing the guide bushings is not an easy task, as the bushings are also changed using the repressing method. It is important to install the new guide in the center, if the bushing is installed crookedly, the valve will have to be ground in for a very long time. After the guide sleeve is in place, its inner diameter is machined using a reamer.

In the model range of VAZ cars there are front-wheel drive and rear-wheel drive cars, and if only 8-valve cylinder heads are installed on the VAZ-classic, 16-cl. block head. Such cars as Lada Kalina, Priora, Lada Granta, VAZ 2110-12 are equipped with 16-valve cylinder head.

Repairing a 16-valve block head is more difficult, removing and installing the cylinder head is also more laborious work. In order to remove the 16-cl. WHA, we do the following:

• merge antifreeze from the radiator;
• remove the decorative cylinder head cover;
• disconnect the air filter housing assembly with the mass air flow sensor and the air pipe;
• we unscrew the nuts of the exhaust pipe of the muffler;
• we disconnect all pipes going to the head of the block;
• dismantle the timing belt cover;
• unscrew the intake manifold nuts and dismantle the manifold;
• remove the valve cover;
• remove the fuel rail assembly with injectors;
• unscrew the fastening nuts and dismantle the thermostat;
• remove the camshaft gears;
• unscrew ten bolts of the block head;
• dismantle the block head.

On many 16-valve engines, valve replacement may be required if the timing belt breaks. Car owners can make such a repair of the VAZ block head on their own, but the replacement of seats and guide bushings should be entrusted to professionals.

On engines manufactured by ZMZ, 8 and 16 valve block heads can also be installed:

• A cylinder head with eight valves is installed on motors of the ZMZ 402 series;
• 16-valve cylinder heads are equipped with engines ZMZ 405 (406 or 409).

ZMZ 409 engines are installed on UAZ vehicles, this engine is highly maintainable, and auto shops always have spare parts for it.

Over the VAZ 16-valve engines, the ZMZ 406 series internal combustion engine has an undeniable advantage - there is no timing belt, a chain drive is installed instead, but even if the chain is broken, if the valve timing is violated, the valve does not bend. The main disadvantage of the head of the ZMZ 405/406/409 block is the curvature of the surface adjacent to the plane of the block, the plane is deformed from overheating of the engine. To bring the head of the ZMZ 406 unit into working condition, milling of the plane is required, but if the surface is curved strongly, the cylinder head has to be changed.

The heads of the ZMZ 402 block also have their own characteristic "sores":

• guide bushings wear out quickly enough;
• sometimes the seats can fly out from under the valves.

The guide sleeves can be replaced by yourself, and if done carefully, you can repress them without heating. But you can't do without a special tool here - you will definitely need special drifts, a 9 mm reamer, roller cutters for saddles.

Departure of the saddle from the cylinder head ZMZ 402 is an extremely unpleasant phenomenon, the saddles fall out due to a factory defect. If this defect occurs, the saddle crumbles into small pieces and scatters all over the cylinders. As a result, it is necessary not only to change the cylinder head, but also to repair the entire piston group. Any minor repairs to the heads of the ZMZ 402 unit (replacement of valve stem seals, inlet and outlet valves) are easy to perform, and many owners of Volga or Gazelle cars perform it on their own.

The cost of repairing a block head can be different, and it depends on various factors:

• the complexity of the car being repaired;
• the region in which the car service is located;
• car repair enterprise level;
• the complexity of the cylinder head repair itself.

The cost of repairing the block head will be higher if the repair is carried out in a specialized auto center with modern equipment and highly qualified specialists. Accordingly, it will be more expensive to work in Moscow or St. Petersburg than in some regional center.

The most expensive job is to replace cylinder head seats or guide bushings, and in some cases it is easier to simply replace the head than to repair it. But there are such cars when repairs are simply necessary:

• a new block head is very expensive, this is found on some foreign cars;
• a new part is difficult to buy and is in short supply.

The cheapest way is to replace the valve stem seals, and in many cases this work is done without removing the block head.