DIY car cylinder head repair

In detail: do-it-yourself car cylinder head repair from a real master for the site my.housecope.com.

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.

Video (click to play).

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 sludge in the combustion chamber.

In order to replace the valve, the block head must in any case be removed.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 over 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 grind 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 car dealerships 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 block 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.

Let's start by defining the concepts. The cylinder block of a modern car is the basis of the engine, on which the rest of the engine components are installed: cylinders, crankshaft, oil pan, cylinder head.

It is precisely the malfunctions and repairs of the cylinder head that are of interest to us. Is it possible to repair the cylinder head with your own hands in a garage-home? And craftsmen answer unequivocally - yes, repairing the cylinder head with your own hands is possible.

Let's start by clarifying that repairing a cylinder head is a complicated operation and will require from you: a little bit of understanding of the block device, the presence of a special locksmith tool and the ability to own it.

Basic tools required for cylinder head repair

Mandrel for pressing in valve stem seals.
Micrometer for measuring valves and guide sleeves.
Reamer for unrolling new bushings.
Mandrel for pressing out bushings.
Mandrel for pressing bushings.
Devices for drying valve springs.
Set of countersinks for restoration of valve seats.
Electric hotplate for heating the cylinder head during troubleshooting and before pressing the bushings.

Do not forget about the necessary spare parts and tags

As a rule, almost any repair of a cylinder head requires its dismantling. Exceptions are, for example, replacement of valve stem seals. Therefore, before starting to dismantle the cylinder head, think about purchasing the necessary set of spare parts.

Today's market provides Head Sets (or, in simple terms, upper sets), which include a cylinder head gasket and all the oil seals and gaskets located above the main gasket.

Well, the tool and the minimum kit are ready, we start troubleshooting the cylinder head.

Before dismantling, be sure to check the relative position of the crankshaft and camshaft according to the marks. Up to the point that we put additional marks on our own. Image - DIY car cylinder head repair

For specific car models, the technology for dismantling the cylinder head is described in the manuals. But the peculiarities of some operations are worth recalling.

We loosen the head mounting bolts from the middle by 0.5-1 turn, alternately. The bolts with internal slots must first be cleaned of carbon deposits, otherwise a loosely inserted key threatens to break off and problems during dismantling;
when dismantling the cylinder head, if there is no connection diagram for all kinds of vacuum tubes, then you need to sketch this diagram yourself, having previously applied the appropriate marks.
When removing the valve springs, use dryers, not the “strong hammer” principle.

Cylinder head condition monitoring

Basically, there are not many basic parameters in the cylinder head that need to be checked before you start repairing the cylinder head. So let's start looking for typical cylinder head malfunctions.

The lower plane of the cylinder head... It is checked using a straight edge and a set of probes. The ruler is placed along the diagonals of the head on a plane and the thickness of the gap is determined using a feeler gauge. If the clearance is more than the maximum allowable clearance of 0.05-0.06 mm, then grinding of the cylinder head is required.

Worn camshaft journal journals and bearings... All diameters are measured with a micrometer and compared with the maximum permissible values for a particular engine model. Based on the measurement results, a decision is made on the type of repair or replacement of parts. Do not forget to visually assess the external condition of the surfaces. They should not have obvious signs of mechanical damage: scratches, chips, scuffs, grooves, etc.

Wear monitoring of valve stems and bushings... It is made with a micrometer at several control points of the rod around the circumference. The valve is changed if the difference in diameter exceeds the maximum permissible parameters specified by the manufacturer.

If you do not have a device such as a bore gauge to determine the wear of the guide bushings, then it can be determined by the valve play (new) in the bushing. As a rule, bushings are replaced with new ones.

Wear of such parts, like: saddles, levers, rocker arms, cams are determined visually. If the chamfer on the valve is "failed", but the rod is in order, then it is processed, and the valve can be reused.

Other cylinder head defects can also be identified visually. The presence of burrs and serifs on the surface of the block head is eliminated by grinding the cylinder head to eliminate the leaky connection between the cylinder head and the block itself.

Thus, we carry out the repair of the cylinder head simultaneously with the troubleshooting, as they say, as soon as troubles arrive.

Good luck with DIY cylinder head repairs.

Has the engine lost its traction, throttle response, the oil level began to fall, the compression in the cylinders has fallen unevenly? It's time to start repairing the cylinder block.Checking and repairing the cylinder headWe remove the cylinder head, clean it with an iron brush on a drill from carbon deposits and assess the condition of the valves. If there is no wear on the valve stem and the plates have no visible cracks, we check the cylinder head for leaks. To do this, pour kerosene into the chambers and leave for a day. If after a day the kerosene is in place, then everything is in order with the head, and further repairs are not required. If kerosene leaves one or more chambers, the cylinder head must be dried and replaced. You also need to replace the valve stem seals. To remove them, there is a special puller, or you can use pliers. You will also need a special tool to fill the valve stem seals. We also check the condition of the valve guides - they should not have cracks or chips. If cracked, the bushings must be replaced. We knock out the old bushing with a hammer and a punch, and in its place we hammer in a new repair size (with a tolerance of + 0.3 mm) guide bush. The surface of the cylinder head must be sanded or milled (if there are deep scratches, or plans to increase the compression ratio of the engine).It's time to check the cylinder block. Visually inspect for cracks, scoring, chips. If the cylinders have an excellent surface, the hon is in place, the pistons are without chips and cracks, then everything is in order with the block and the problem will be eliminated with one cylinder head repair. If there are visible scratches, grooves on the cylinder walls, then the block must be taken to the factory, where the cylinders will be bored to the repair size. It is also necessary to check for runout and balance the crankshaft. When replacing the crankshaft, the new one must also be balanced with the flywheel. This will keep the engine running smoothly.The surface of the block must be sanded.After boring the cylinders, the block must be assembled on new oversized components. We buy new pistons, rings, connecting rods, crankshaft liners. For pistons and connecting rods, it is necessary to carry out weight distribution - the deviation in weight should not exceed 10 grams, otherwise the engine will be unstable. If the difference in weight is exceeded, the spare parts must be replaced at the seller.So, the crankshaft is balanced, the block is assembled. We buy a gasket between the cylinder block and the cylinder head, and assemble it. The assembly is best done with a torque wrench in order to maintain the required tightening torque.The cylinder head is the main element of the power unit and the engine cover, protecting its constituent components from external influences. Troubleshooting requires removal of the cylinder head.Dismantling, repair and installation of the cylinder head in the car may be required for the following malfunctions:The channel "Theory of internal combustion engines" spoke in detail about the need to repair the cylinder head.The purpose of the head is to form a combustible mixture of air and fuel, which is created in the combustion chambers. It is used to ignite and drive the vehicle. The cylinder head, like any other part of the machine, is not immune from defects. Malfunctions can occur spontaneously or as a result of a traffic accident or component wear.

marriage in the production of cylinder head;

high load on the node;

incorrect or insufficient maintenance;

poor-quality lubrication of the internal components of the device;

lack of protection against freezing or corrosion in the refrigerant circuit.

It is necessary to disassemble, replace and restore the cylinder head on an 8-cylinder or other engine after preparing the tools:

a special mandrel, required for pressing in the valve stem seals;

micrometer, necessary for measuring valves, as well as guide elements;

reamer will be used to unfold new bushings;

special mandrels for dismantling (pressing out), as well as installing new bushings;

a set of countersinks, designed to restore valve seats;

special devices for drying valve spring elements;

set of wrenches;

new cylinder head gasket;

an electric stove, used to heat the cylinder head, if its troubleshooting will be carried out, as well as to warm up the bushings before pressing.

Before repairing the cylinder head, it is imperative to prepare the necessary spare parts and tags, their composition depends on the car model and the type of defect.User Alex ZW talked about repairing the cylinder head, as well as what it will take to complete this task.To repair the assembly, you will need to dismantle it from the seat. The procedure for removing the cylinder head may have certain nuances depending on the type of device and car model.A universal algorithm of actions for dismantling the unit is considered: Image - DIY car cylinder head repair

Before the camshaft drive strap is installed, the crankshaft and camshaft pulleys are not allowed to rotate.

To carry out repairs, it is imperative to disassemble the cylinder head. Conditionally, the procedure for diagnostics and elimination of malfunctions can be divided into several stages.

Checking and repairing the cylinder head at the initial stage is carried out as follows:

User Alexander Skripchenko in his video using the example of a VAZ 2108 car showed what mistakes should not be made when repairing a cylinder head.

At the next stage of the repair, the following actions are performed:

The ICE Theory channel spoke in detail about the procedure for repairing and assembling valve elements of the cylinder head.

Algorithm of actions when performing the final stage of diagnostics and repair:

More details about replacing and installing a new cylinder head gasket were told by the user Avtoreanimator.

Installation of the cylinder head is carried out in the reverse order.When completing the task, it is imperative to change the cylinder head gasket, even if it was in perfect condition when dismantled. Experts advise, when replacing and repairing the cylinder head, to install new bolts that secure this unit, this is due to the design features of the fastening elements. When tightening bolts, you cannot be guided by the principle - the stronger the better.

The order of tightening the cylinder head bolts is individual for each individual car model.

Installation of all attachments, highways and branch pipes is carried out in accordance with the scheme drawn up by the car owner and the characteristics of the vehicle.

The process of tightening the bolts securing the cylinder head to the engine is described using the example of a VAZ 2109 car:

At the first stage, the fixing elements are tightened with a force of 2 kgcm or 20 Nm. A torque wrench is used to measure the tightening torque.
At the next stage, the force should be from 69.4 to 85.7 Nm. Or 7.1-8.7 kgms.
In the third step, all the bolts are extended 90 degrees.
At the last step, the fastening elements must be pulled again by 90 degrees.

After successful installation of the cylinder head, the unit is diagnosed for tightness, for this it is required to start the engine. If during the repair process the camshaft was replaced, then the operation of the power unit must be started at low speeds.

The Auto_Remont channel presented a visual instruction for installing the cylinder head using the example of a VAZ car.

As you know, the engine block is the basis of any internal combustion engine. In fact, the block is a three-dimensional part, inside which various assemblies and mechanisms are located (pistons and rings, as well as CPG sleeves, crankshaft, KShM connecting rods, etc.).

It is not surprising that damage to the cylinder block will not only disrupt the performance, but also disable the power unit. For this reason, the restoration of the block and its repair must be carried out efficiently and in a timely manner.

To begin with, there are two types of cylinder blocks:

cast iron BC;
blocks of aluminum alloys;

As a rule, cast iron blocks are additionally hardened with graphite, and lightweight aluminum products are made liner (a cast iron liner is inserted into the block). There are also aluminum cylinder blocks without liners. The alloy includes silicon, which significantly strengthens the block.

As for the sleeve blocks, the sleeves are "wet" and "dry". In the first case, the coolant is in direct contact with the sleeve, while in the second, the sleeve is tightly pressed into the block body during manufacture.

One way or another, each solution has its pros and cons, and during operation, various damages and defects of the cylinder block or defects of the block liners occur (depending on the type of BC).

Also, wear of the cylinders in the direction of the crankshaft axis often occurs. As a rule, cylinder damage on a "fresh" engine is caused by engine overheating or water hammer, as well as a decrease in the level or significant loss of the properties of the engine oil.

Less commonly, the cause of block defects is the unexpected destruction of the piston rings and other unforeseen breakdowns. We also add that in the BC there is often deformation of the crankshaft bearing bed, etc.

With regard to the wear of the cylinder surfaces, in this case, such wear is often "natural", that is, it is the result of operating the engine in normal operating conditions. The repair of cylinders itself in this case often involves boring and honing the cylinder (applying hone). This allows you to remove the ellipseness of the cylinder, remove scratches and scuff marks on the mirror.
A more difficult case can be considered a broken connecting rod,
as the damage is usually more serious. Also, the cause of block defects is valve breakage, destruction of the valve seat, etc. The result is scuff marks on the cylinder surface and other damage.Also, in the list of common malfunctions, cracks in the block or sleeve should be highlighted.
We also add that there are so-called "hidden" problems, that is, it can be difficult to identify defects visually within the framework of a superficial examination. At the same time, unqualified repairs, which are limited to the banal replacement of worn parts, will still lead to the fact that the engine will need to be disassembled again after several hundred or thousand kilometers.

By the way, this problem is more inherent in cast iron blocks. Also, overheating of the engine or its uneven heating during operation can lead to deformation of the block (both cast iron and aluminum).

So, the repair of the cylinder block and the restoration of the cylinders themselves involves:

thorough cleaning of BC surfaces;
then a check is made for the tightness of the channels of the cooling system in the block (cooling jacket);
also washed and cleaned, and then the oil channels are checked;
further, an inspection of the cylinders is carried out in order to identify various defects;
then the block is bored / bored, surfaces are ground, etc.

For many engines, cylinder boring is a mandatory procedure as part of an engine overhaul. To perform the procedure, a special machine is used for boring engine cylinders. The boring of the block itself should be understood as the processing of the inner surface.

Such processing actually represents the removal of a layer of metal to level out irregularities, remove scoring, smooth out cavities, etc. The main task of machining is to give the cylinders their normal shape (cylindrical).

Another cylinder block repair may involve liner or re-liner. In the first case, the installation of the liners should be understood, although the factory design does not initially imply this. In the second, the worn out sleeve is removed from the block, after which a new repair is installed.

Finally, we note that as part of the restoration of the block, it may be necessary to repair the crankshaft bearing bed. Also, in some cases, it becomes necessary to eliminate the deformation of the block. For this, the method of artificial aging is used, when the block is heated to a certain temperature, after which various areas are treated.

As you can see, there are many faults in the cylinder block itself. Some can be considered small (for example, if a bolt breaks off in a block, etc.), while others are serious enough (for example, wear on the cylinder walls, cracks, etc.)In practice, this means that in some cases it is possible to restore the cylinder block with your own hands even in a garage, while in others it will be necessary to have special equipment (machines for boring the block, honing, grinding). Also a very important aspect is the experience and qualifications of the master himself.In view of the above, it becomes clear that only experienced specialists should be entrusted with the performance of such work, and the engine itself should be optimally repaired at such service stations, where it is possible to perform all the necessary operations right on the spot. First of all, this will shorten the repair time, and can often serve as a quality guarantee.

Why a liner is installed in the cylinder block. Advantages and disadvantages of sleeve motors, aluminum alloy blocks, features, repair.

What is engine troubleshooting and in what cases it is necessary to carry out engine troubleshooting. Features of the troubleshooting of the power unit, recommendations.

Repair of a cast iron or aluminum engine block using a liner. Types of sleeves and how sleeves are inserted into the block. Tips and tricks.

How to determine when an engine needs to be overhauled: engine resource, the main signs of an imminent overhaul. How is the ICE repair carried out, tips

What does overhaul of a car engine mean, what work is being done. What determines the engine resource before overhaul and how to increase it. Helpful hints.

Users of our resource already know what a cylinder head is and what function it performs. But not every motorist knows in what cases a head repair is necessary and what is needed for this. From this article you can find out how the cylinder head is repaired and in what cases it is performed.

In principle, anything can happen to the cylinder head, from the breakdown of small parts to the appearance of cracks in the very structure of the head. But we will not consider all these nuances, but dwell on the most typical breakdowns of large units and elements.

Cylinder head assembly grinding process

There are several reasons due to which a breakdown occurs and, accordingly, the repair of the cylinder head.

regular driving on an overheated engine;
malfunction and breakdowns in the internal combustion engine lubrication system (meaning low-quality motor fluid, the ingress of antifreeze or fuel into the oil);
wear of components as a result of the used service life.

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In what cases is it necessary to repair the cylinder head?

Failure of the camshaft or other components associated with this unit.
Failure of the guide bushings.
Breakage of cast iron cylinder blocks and the appearance of cracks in the head. In this case, the home repair process is carried out only when you have welding equipment and you know how to use it.
Replacing the cylinders themselves. They may have seizures, cracks or cylinders simply could have "outlived" their term.
Broken valves or connecting rod. Such breakdowns of the cylinder head can subsequently cause the need for overhaul of the engine.
The appearance of cracks in the liner. Typically, such a problem arises in cases where a motorist or a repairman at a service station has incorrectly tightened the head mounting screws.
Punched gasket. It is also one of the most common breakdowns. Usually wears out due to the used service life.

Actually, this is only a small part of the reasons why it is necessary to remove the cylinder head and repair it. We will describe in more detail the most common methods of repairing faults below.

Any repair manual for this unit implies its dismantling and installation. If you do not know how to remove the cylinder head, you can read about it in more detail in our article. You can find out about all other repair methods below.

According to statistics, the procedure for drying out and replacing valves is most often carried out on old domestic cars and foreign cars. But it is also relevant for newer machines of both Russian and foreign production. To do this, you must know, at a minimum, how the cylinder head is removed and installed. To do the drying, you should buy a special device, which is called just that - the drying agent. It can have a different design for a particular machine model.

If you do not have a desiccant, you can use a regular metal tube. The pipe diameter should be about 2 cm. The valve should be supported in the combustion chamber. Place the BC head on the floor. Then place the tube on top of the valve and hit it with a hammer. After hitting several times, the so-called crackers will crumble and release the spring. The springs are dismantled, after which the valves themselves are removed. They are replaced and installed in the reverse order.

Replacement of bushings is carried out when these elements have worked out their service life. For dismantling, use a special mandrel.The bushings can be dismantled without any problems, we recommend buying new bushings with a diameter of 0.05 cm larger than the original ones.

To install new bushings you will need:

mandrel for installation;
lubrication (regular engine oil can be used);
hammer.

The cylinder head is installed on a stand, and the bushings are lubricated with grease. It is desirable to heat the cylinder head to 100 degrees, for this you can use an electric stove. To make the sleeves even easier to fit in, you can place them in the freezer for thirty minutes (before greasing them with oil). When all the bushings have been replaced, you need to wait a while for the head to cool down. It is necessary that the valves do not dangle, but do not jam, otherwise the cylinder head repair will be useless.

If you already know how to remove and install the cylinder head, then the final stage of the repair will be lapping the valves and checking the gasket for leaks. After replacing these elements, their lapping is done with the aim that these elements fit most closely to the seats.

You will need to purchase a lapping paste, then you need to treat the valve with this substance from all sides. After that, the valve is installed in the head.

Then the valve will need to be rotated, for this you can use one of the most relevant methods.

The first method is grandfather's. You can use a piece of hose that should fit the valve diameter. The hose is clamped between the palms and rotates first in one direction, then in the other direction, alternately. This method is not particularly convenient, because it was relevant at least 30 years ago.
Modern method. To facilitate this process, you can use a special lapping tool available at any automotive store. This will make it much easier to grind the valve.

To understand that the valve is worn enough, it is necessary to visually assess the surface of the installation site and the end of the valve. It should be matte and continuous.

Experts do not recommend doing such things if you do not know how to do it correctly, because you can grind and assemble, but it does not work, and you will have to change the valve seats. And when parsing, it turns out that it was only necessary to cut and grind.

As for the tightness of the cylinder head, after replacing the gasket, attention should also be paid to this point. The tightness is checked by pouring kerosene or fuel into the intake and exhaust manifolds. If everything is done efficiently, then within 5-7 minutes liquid will not flow out from under the cylinder head valves, this is an indicator.

You can learn more about how to replace a burned-out cylinder head component in this video.

The main thing to look out for is an inappropriate / inaccurate connection between the manifold valves and the cylinder head. The appearance of the slightest irregularities or steps can lead to undesirable consequences that begin to slow down the movement, partially blocking the channel and therefore must be removed. After removing areas with obvious inconsistencies, the manifold gaskets need to be modified, as they can also be an obstruction to the flow.

It is also necessary to fit the manifold onto the pins. This is extremely important for the reason that the fasteners holding the manifolds can stretch and as a result there is a slight change in the cylinder head planes relative to the manifold. If this is not done, then all the work to prevent inconsistencies will be useless.

I want to note that two pins must be placed on the collector (at the edges).

Before connecting the cylinder head and the manifold, you need to make a hole using cutters to refine the cylinder head. Then we put the pin on the head and put the collector on it. It is important that the second one sat down freely, but there should be no backlash. You can then ensure that the two elements are positioned accurately with great confidence. You also need to make some holes in the gasket.This is how optimal docking should be done.

The revision of the cylinder head also provides for the need to refine the channels, since a deformed shape, metal under the bushings, etc. can be observed in them. The channels are reworked by means of a ball cutter. It is better when you have more than one cutter, but several and with different parameters (sizes and shapes). Working with a milling cutter, you can achieve the removal of any irregularities, as well as increase the passable section.

It is extremely important to ensure that the channel bend is as smooth as possible and the corresponding curvature dimensions are observed. The surface on the intake ducts should be slightly rough - this contributes to good evaporation of gasoline from its walls. The outlet channel can be polished to a high shine. The channel section should not have a round shape, it has a slightly elliptical shape.
When performing an increase in the channels, it is important not to overdo it, you need to know the measure, since there is a possibility of touching the cooling channel or the oil channel. The cylinder head on classic engines allows you to increase and expand the channels, while on 8-valve VAZ engines, problems are inevitable.

Before you directly engage in the boring of channels, you should find out where to start this process - from a collector or a gas cylinder head. If you need to significantly increase the diameter of the valves, then it is better to start from the area where their walls are thinner. This will reduce the risk of accidental opening of the channels the next time you align. The parts of the bushings that protrude into the channels also need to be modified so that they do not interfere.

As a rule, they need to be either shortened or sharpened. There are situations when the bushings are grinded against the valve wall. Some motorists consider this method to be the best in terms of benefits, although, in practice, rarely does anyone do this, since it significantly reduces the resource of the guides. Correct modification of the valves is possible only under two conditions: experience and following the instructions.

Valve redesign is to reduce weight and increase flow. To lighten the valve, it must be reground or reground. Excess metal will then be removed from both sides. The valve stem is also being reworked - it needs to be narrowed. You can also choose the option without replacing the bushings, in which case you need to make the leg thinner all the way from the guide bush to the plate. A special result can be achieved by reducing the diameter of the stem. For example, reducing the leg from eight mm to seven helps to reduce the mass of the rod itself by 20%, increases the throughput (this is in 8-valve motors).

In reality, the valves are made of an alloy of titanium and aluminum and therefore have amazing lightness, which is combined with some unpleasant moments: high cost and fragility. Given this fragility, strong recommendations are made for valve springs and valve seats. The springs can be left at the factory or slightly loosened. It is advisable to change the saddles to others made of bronze.

The revision of the cylinder head also implies a change in the shape of the combustion chamber. In this case, three areas of work can be distinguished:

Reduced knock
Improvement for cylinder filling
Fulfillment of the conditions for optimal distribution of the mixture in the combustion chamber.

Detonation puts a heavy load on pistons and rings. It can be determined by the level of metallic sounds that propagate through the car engine. The sources of this phenomenon can be the most distant parts of the combustion chamber from the spark plug. It is solved like this:
· It is necessary to reduce to a minimum the work in the combustion chamber, which increases the spread of combustion.
· The number of compressor stations should be minimized. These areas include camera corners and sharp edges. To do this, you need to smooth the surface as carefully as possible.

The last two executions to improve the shape of the combustion chamber are very difficult to do on your own, since you need to have excellent knowledge in the field of physics.

The revision of the cylinder head is not quite complicated at some stages and is a fully justified procedure. Correct modification will increase the power of your vehicle's engine.

In the video, the auto mechanic talks about the nuances of the correct boring of channels in the manifold for the modified head.

Video (click to play).