Motor block head. Engine cylinder head: everything about it here

29.09.2019

A car engine is a rather complex and technological unit, consisting of many units, each of which performs its own narrow functions, in total leading to the conversion of the energy of the fuel combustion process into mechanical energy, capable of driving the car in one way or another. In other words, in order for the fuel poured into the tank to turn into movement, it is necessary to use a lot of mechanisms, assemblies and assemblies, which everyone who considers himself a motorist should know about.

In the photo, the cylinder head is the most important of the automotive components.

We will not delve deeply into the process of operation of the internal combustion engine internal combustion engine, as it is also called. Gearbox, cylinder head, ABS, timing - everyone who hears these abbreviations for the first time can get a little lost, because there are many abbreviated names of components, assemblies and processes associated with the car, and the decoding is always the same.

The cylinder head is the cylinder head, the most important of the vehicle components, responsible for controlling the process of fuel combustion in the engine and exhaust gases. Let's try to understand this issue in more detail, just as much as possible, so as not to switch to specific models, otherwise this topic risks becoming endless.

The design of the cylinder head and its main parts

The cylinder head covers the cylinders from above. It is attached to the block with powerful bolts or studs. Since the area near the landing plane of the head is quite large, in order to avoid deformation when attaching to the block, each threaded connection is tightened in a certain sequence and with a certain torque. The sequence and tightening torque of bolts or nuts is determined for each engine individually, since the design solutions for the cylinder head may be different.

Cylinder head video

Previously, the heads were cast exclusively from cast iron, but now it has been replaced by light aluminum alloys. It is not always possible to completely abandon cast-iron heads. This is due to the fact that the heads of engines operating in severe temperature conditions can undergo heat shrinkage and deformation, and cast iron is able to withstand this better. However, with the advent of new materials and the development of metallurgy, cast iron is slowly retiring.

In in-line engines, the head has a common housing for all cylinders, and in engines with a V-shaped cylinder arrangement, each row has its own head. For maximum sealing, a gasket of a simple design is used at the cylinder head to the cylinder block. It is made of reinforced asbestos, capable of withstanding high temperatures and high pressure, while ensuring the tightness of the channels of the cooling system, the oil pipeline, and, first of all, the tightness of the combustion chamber.

Thus, it is possible to distinguish the main mechanisms and parts of the cylinder head:

Crankcase, or block head housing, which houses all the mechanisms, channels of the cooling system, oil pipeline and combustion chamber.
Threaded holes or seating plane for mounting spark plugs or injectors.
Block head gasket.
The combustion chamber in which the ignition of the working mixture occurs.
Gas distribution mechanism.
Gas distribution mechanism drive.
Landing planes and threaded fasteners for intake and exhaust manifolds.

The non-removable parts of the block head include valve seats, which are necessary to ensure the tightness of the gas distribution mechanism (timing) and valve guides. These parts are pressed into the crankcase of the block head “hot”, and must be replaced only when using special tools and thermal equipment. In garage conditions, it is not recommended to replace valve seats and guide bushings, because due to uneven heating of the head, it can change its geometry, the plane of contact with the cylinder block will be disturbed, and the cylinder head will become unusable or serious restoration work will be necessary.

Repair and maintenance of the cylinder head

All components and assemblies of the car need maintenance, diagnostics, and sometimes repair. The block head is no exception. First of all, those parts that are loaded the most require increased attention. These are parts of the gas distribution mechanism - valves, valve seals, camshaft seals, head gasket. Many factors influence the wear of parts and the correct operation of the cylinder head, but the main ones relate to maintenance and diagnostics.

Tightening the nuts without observing the torque, which is controlled by a torque wrench, improper tightening of the head bolts or nuts - all this can lead to warping of the head body, which leads to engine failure. There are a number of operations involving the dismantling of the block head - cylinder boring, pressure testing of valve seats and valve bushings, replacement of the valves themselves or repair, refinement and grinding of seats, grinding of the mating surface of the head, and many other operations involving its dismantling.

If you have certain experience and knowledge, all these works can be carried out independently in garage conditions and with your own hands, with the exception of those works that require high-precision equipment. The most basic tool in the repair and maintenance of the cylinder head is an understanding of the process of its operation and knowledge of the design. Without knowledge, even the most perfect tool has no meaning.

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An internal combustion engine is a rather technologically complex unit, consisting of many parts that ensure the smooth operation of the entire mechanism. Some parts perform narrow technological tasks, others are given a “higher honor” - to perform functions leading to the conversion of one type of energy into another, that is, to convert the fuel in the tank into motion energy.

Of the large number of abbreviations that are found on the pages of technical documentation for a car, the cylinder head abbreviation is probably the most common. Why and what is a cylinder head in a car worth finding out more.

How is the cylinder head decoded

The abbreviation cylinder head stands for simply. This is the cylinder head - a detail that can be attributed to one of the most important in the entire internal combustion engine as a whole. It is this node that controls the process of fuel combustion and is responsible for the removal of spent elements, in this case gases, to the outside. To better understand what a cylinder head is in a car engine, you need to consider in detail its design and analyze the main functions.

Design features of the cylinder head and its constituent parts

For a long time, cylinder heads were made of cast iron, which is now being phased out in favor of aluminum-based light alloy products. Aluminum cylinder heads are being used more and more often, but cast-iron ones cannot be completely abandoned. There are types of engines where the temperature operating conditions do not allow the use of a light alloy, since the danger of thermal shrinkage and deformation is great, and cast iron heads resist such processes most effectively.

The cylinder head is superimposed on the cylinder from above and attached to its base with bolts or studs (the type of attachment depends on the engine modification and the address of its manufacture). The landing plane of the head is large enough in area, therefore, in order to avoid deformation of the structure, a certain sequence is used during fastening, the sequence of tightening each threaded connection, and certain efforts. The fastening scheme and the connection tightening sequence for each engine are developed individually, due to the difference in design solutions.

In so-called in-line engines, one block head covers the entire cylinder body, and in engines where the cylinders are arranged in a V-shape, each row has its own block head. To ensure effective tightness of the connection between the cylinder and the head, a gasket is placed, which has the exact shape of the head and cylinder, and all the necessary holes for fastening. Gaskets are made of reinforced asbestos sheet, which is a refractory material and, regardless of the level of heating, maintains the tightness of the combustion chamber.

The main mechanisms and parts of the cylinder head

The scheme of the main parts and mechanisms of the cylinder head includes:

block head housing (crankcase), where the system mechanisms are located;
a certain number of threaded holes into which spark plugs or nozzles are mounted;
asbestos gasket between the block head and cylinder;
a combustion chamber where the fuel ignites and turns into a working mixture;
gas distribution and exhaust mechanism;
planes and mountings for the intake and exhaust manifold.

In addition to removable parts, the head also has non-removable ones, which are necessary to obtain tightness of the gas distribution mechanism. These include valve seats. They are hot pressed into the crankcase of the head of the block. If necessary, you will have to use a special tool to replace them.

Repair and maintenance of the cylinder head

Like any part in a car, the cylinder head needs periodic inspection, diagnostics, and if serious problems are identified, it needs to be replaced. Usually, the parts that have to bear the greatest load fail first of all - valve seals, the valves themselves, the head gasket. The wear and tear of the head is most affected by the factors of improper diagnosis and maintenance. Violation of the necessary force when tightening the nuts and the order of tightening the bolts or fastening nuts leads to deformations of the housing, this disrupts the normal operation of the engine.

If these types of breakdowns are detected, the parts will have to be replaced, and this should be done according to a clear scheme, which is given in the technical description of the engine.

Whether it is necessary to change the oil when repairing the cylinder head of a car will show the final measurement of its level and analysis of its structural state.

The engine head, or cylinder head (cylinder head), along with the gas distribution mechanism (timing), is one of the important parts and not only the power and efficiency of the engine, but also its durability depend on it. In this article, designed more for beginners, I will try to describe in detail the device, maintenance and repair of the head, as well as all the nuances associated with it. Well, if one of the respected readers wants to get acquainted with some nuance in more detail, then for this I have installed several links in this article, by clicking on which you can get to a more detailed article.

Before proceeding to maintenance or repair, first consider the manufacture and design of the head of the simplest eight-valve motor. And only after studying the design of the cylinder head of the simplest engines, then there will be no difficulties in servicing more complex heads of 16 valve engines. Although, the head with 16 valves and another camshaft is not so complicated and in fact it is like a dual 8-valve "head", but let's not get ahead of ourselves. Having studied the device of the simplest head, any novice car owner or repairman can easily carry out its maintenance or repair on their own in their garage

Engine head - manufacturing and device.

The block head of most modern engines is a fairly thick plate cast from a light aluminum alloy (on some older engines, cast iron was used for the head material). After casting the billet of the future cylinder head, it is milled with the interface planes with the cylinder block and with the valve cover, and also bored with high precision the necessary mounting holes for the bed supports (most heads of four-cylinder eight-valve engines have five bed supports).

The camshaft bed supports are made detachable (from two halves) and the upper half is bored in the bed housings (sliding bearings), and the lower support is made as one piece with the engine head housing. Of course, in order to achieve the ideal accuracy of the holes for the camshaft bearings, the holes in the supports are bored in assembly with the bearing housings and therefore they are not interchangeable. That is, the cylinder head of any engine can only be replaced as an assembly with plain bearing housings for the camshaft.

Well, the gas distribution inlet and outlet channels are made initially at the time of casting the head body (modern ones are not cast, but milled from a single piece of material - see the video below), and then the planes are polished at their outlet, for attaching the intake and exhaust manifolds, well, holes are drilled and threaded, under the studs for attaching both manifolds (inlet and outlet). From the other end of the inlet and outlet channels, seats are bored (milled) for pressing valve seats, which are made of heat-resistant alloys.

In the area of the valve seats, spherical combustion chambers are first bored, the number of which depends on the number of cylinders in the engine block, and after the combustion chambers are bored, seats are already made for the valve seats and holes are drilled for pressing the guides. And the depth of the combustion chambers directly depends on the compression ratio of a particular engine, and the higher the compression ratio, the smaller the depth of the combustion chambers.

The very process of manufacturing an engine head from a solid aluminum alloy blank, on a modern milling center, those who wish can watch in the video below.

Engine head - valve drive VAZ 2108, 09, 10, etc.
1 - head housing, 2 - valve, 3 - pusher, 4 - valve cover, 5 - camshaft cam, 6 - adjusting washer, 7 valve seal.

Valve drive mechanism (gas distribution mechanism).

In any engine head there is a valve drive mechanism, or, as it is also called, a gas distribution mechanism (abbreviated timing). This mechanism serves to open and close the intake and exhaust valves at the right time. Valves 2 (see the figure on the left) on more modern machines (including our eights, nines and subsequent VAZ models) are actuated directly by the pressure of the camshaft cams, through cylindrical pushers 3.

And an adjusting washer 6 is inserted into a special pusher socket, with the help of which the valve clearance is changed (adjusted) - I wrote a separate detailed article about adjusting valve clearances using such washers, and those who wish can read about adjusting valve clearances on more modern engines with the VTEC system .

Removal and installation of the head of the car engine.

Before starting the repair of the engine cylinder head, it must be removed. As a rule, the head is separated from the motor block, if it is necessary to remove carbon deposits from the surface of the combustion chambers and valve plates, or to replace the valves or valve guides. I already wrote about all these operations on my website, for example, here in . Well, valve seals on most motors can be replaced without removing the head (it is described in detail about replacing valve seals).

Next, I will describe the sequence of actions when removing the engine head using the example of an eight-valve engine of domestic eights and nines, but on other cars with similar engines, the sequence of actions is not very different (well, except for some little things).

First you need to install the car on a lift (or fit it to a viewing hole in the garage) and, for safety, remove the negative terminal from.

the sequence of unscrewing the engine head bolts

After repairing the head, install it in place with a new gasket and assemble

everything in reverse order, pressing the cylinder head to the block with bolts and with the required torque indicated in the manual of your engine.

Before installing the standard head bolts to the block, I advise you to measure their length using a caliper and if the head bolts are extended so that their length exceeds 135.5 mm, then I do not recommend using such bolts, they should be replaced with new ones. Otherwise, any tired bolt during tightening (or after it) may burst at any moment and it will not be so easy to unscrew it.

But this is not the main thing, but the fact that a bolt (or two) may burst during the operation of the machine and the coolant may begin to seep into the crankcase and begin to mix with. And this can lead to sad consequences (who cares which ones -).

After installing the engine head in its place and tightening the bolts with the correct torque and in the correct sequence shown in the figure on the left, then you should adjust the belt tension using the special tool described in, and then you will need to check and adjust the valve clearances (about adjusting the valves) .

Well, below I will describe in detail the disassembly and assembly of the cylinder head of the front-wheel drive VAZ engine with eight-valve gas distribution, but of course, it is almost the same to disassemble and assemble the head on other cars with similar engines, including foreign cars.

Disassembly and assembly of the engine head.

Disassembly. Naturally, if you need to replace any one worn part, then you can not completely disassemble the cylinder head, but remove only the part that needs to be replaced with a new one. But still, I will describe a complete disassembly and assembly, as this may come in handy in some cases (for example, during a major overhaul).

We lay the engine head on a clean workbench, unscrew the mounting screws and remove the carburetor with a spacer, as well as the carburetor heat shield, if any. Next, remove the exhaust manifold, if it has not been removed beforehand even under the hood.

Also, if they were not removed in advance, disconnect the outlet pipe of the engine cooling jacket, unscrew the coolant temperature indicator sensor and, and also unscrew.

Then we take out their holes in the head of the valve lifters with shims. Pressing on the ends of the valves with the help of a cracker and compressing the valve springs, we remove the crackers, springs with plates, and spring support washers, and then turning the engine head over, remove the valves from the valve holes.

Cylinder head assembly. Having repaired the head (I will write about the repair a little lower), we assemble everything in the reverse order:

Install the spring washers in place.
lubricate the valve stems and new valve seals with engine oil.
we put new valve seals on the guides (on the back of the head) with the help of a mandrel (I wrote about this in detail in the article replacing valve seals - link above).
we insert the valve from the side of the combustion chambers into the holes of the guide bushings and new valve seals. New seals will keep the valves from falling out.
we install the springs and spring plates and then compressing the springs with the help of a cracker, we install the croutons in their seats.
further insert the valve lifters with shims into the holes of the engine head.
having cleaned the mating planes of the head and bearing housings from the remnants of the gasket, dirt and oil.
lubricate the support journals with clean engine oil and lay it in bed in such a position that the cams of the first cylinder are directed upwards.
we install the camshaft bearing housings (bed covers) from above in their places and tighten them in two steps, as shown in the figure below.
pre-tighten the fasteners until the surfaces of the bearing housings touch the planes of the engine head, while making sure that the mounting sleeves of the housings (if any) freely enter their mounting holes.
then, in the same sequence, we finally tighten the fasteners using a torque wrench with the prescribed torque (for VAZ eights and nines, the moment is 21.6 N m (2.2 kgf m)).
we install a new camshaft oil seal, having previously lubricated its working edges with clean engine oil - more on this.
install the rest of the attachments on the head in the reverse order of disassembly.

Engine head - technical condition diagnostics and repair.

I have already written several articles about repairing the engine head, links to which will be published below. And in this article I will write only the main thing with regards to checking the technical condition and repair, as well as about what I have not written about in other articles.

Before cleaning the head, thoroughly wash it with a brush and solvent. We remove carbon deposits from the valve plates and from the surface of the combustion chambers, using a soft brass wire brush nozzle, planted in an electric drill chuck. It will also be useful to remove carbon deposits from the walls of the exhaust channels.

Next, you should carefully inspect the engine head. On all supports (beds) under the camshaft journals and in the holes for the valve lifters there should be no cracks, scratches, burrs and other damage. In general, cracks in any part of the head are unacceptable. Well, if you suspect that coolant has entered the engine oil (of course, with a good head gasket), it does not hurt to check the tightness of the cylinder head.

To check the tightness, close all openings of the cooling jacket with plugs and then pump water into the cooling jacket with a pressure of at least 0.5 MPa (5 kg / cm²). At the same time, no water leaks from the head should be observed for at least two minutes.

Also, a leak test can be carried out using compressed air (for example). We also close the shirt holes with plugs or a sheet of thick plexiglass (I already wrote about this in an article about repairing a cracked head - link to the article above), and the pressure of compressed air supplied to the cavity of the shirt is at least 1.5 - 2 kg / cm².

Before supplying compressed air, we lower the head into a bath of hot water (temperature is approximately 60 - 80ºС) and then we supply air and note the time. For at least 1.5 minutes, no air bubbles should escape from the head anywhere.

Valve seats. We carefully inspect the working chamfers of the seats (the area of contact with the valve plates), which should not have pitting, corrosion or various damage. Minor damage can be eliminated by grinding (using a nozzle), but at the same time remove as little material as possible. But it is best to restore the chamfers of the seats using a special kit, which I described in the article on the restoration and repair of valve seats - link to the article above (in the list of links).

I also wrote a separate article about replacing the guide bushings and about the bushings themselves, the link to which is above.

Valves. We remove carbon deposits from the valves and check whether the valve stems are deformed and whether there are any cracks on the valve plates. Valves that are damaged, of course, are replaced with new ones.

It also does not hurt to check the condition of the working chamfers on the valve plates. In case of minor damage, they can be sanded, but it is important to maintain chamfer angles of 45º30'±5'.

In this case, the distances from the lower plane of the valve plates to the base diameters (34 and 30.5 on eights nines) should be within 1.3 - 1.5, and 1.8 - 2.0 mm.

Valve springs. We inspect the springs and make sure that there are no cracks on them, and also whether the elasticity of the springs has decreased by checking their deformation under load (shown in the figure on the right).

The main data for checking the valve springs of the VAZ 2108.09 engine: A - external spring, B - internal spring.
1 - springs in a free state, 2 and 3 - normal springs when compressed by force, 4 and 5 applied force in kilograms.

Valve lifters. We also inspect and check the condition of the working surfaces of all pushers, which should not have scuffs, scratches, and even more so cracks. If you find defects, then replace the defective pushers with new ones.

Also check the length of the head bolts to the block, and if they stretched out (I wrote the allowable length above), then change the bolts with new ones.

Adjusting washers. Inspect them, especially the work surfaces, which should be perfectly smooth, without scratches, nicks and scuffs, and even more so cracks. Also, on the surfaces of all shims there should be no stepped or one-sided wear or worn metal. Only concentric run-in marks with camshaft lobes are permitted.

I hope this article (and others, too, to which I have linked) about the engine head will be useful to novice car owners or repairmen, good luck to everyone.

The cylinder head (cylinder head) is the most important element of the internal combustion engine, which closes the cylinders from above and is attached to the cylinder block with head bolts or guide pins. The cylinder head, in fact, is a cover that covers the cylinders.

The cylinder head performs a number of important functions:

the cylinder head cover performs a protective function;
there is an oil filler neck in the cap;
the cylinder head gasket provides a seal where the cylinder head fits;
the block head is a place to place the chain tensioner and camshaft drive in a separate cavity in front of the cylinder head;
threaded holes for spark plugs and injection nozzles are located in the head housing;
combustion chambers are wholly or partially located in the cylinder head;
the head is the installation site of the gas distribution mechanism ();
holes are provided in the head housing for installing the intake and exhaust manifolds;

The cylinder head is made by casting from cast iron or aluminum alloys. After the casting is completed, the cylinder head is subjected to an artificial aging process using a special technology. This is done in order to remove residual stress from the element, since the cylinder head experiences serious loads during operation. For an in-line engine, one cylinder head is installed. On V-shaped engines, a head is installed on each row of cylinders. There are cylinder heads with lower valves, as well as heads with upper valves. The first type has a simplified design compared to the second.

Combustion chambers are partially or completely placed in the cylinder head. Inside the head there are inlet and outlet channels, "cooling jacket" channels for the circulation of coolant, as well as oil channels for the engine lubrication system. Inlet channels for supplying the fuel-air working mixture or only air to the cylinders, as well as channels for exhaust gases, lead to each individual combustion chamber. Each of the channels ends with valve seats that are pressed into the cylinder head. The valve seat is made of cast iron or other materials.

The lower plane of the cylinder head, which is adjacent to the cylinder block, is wider. This is done to get the best possible seal with the surface of the block. Additional sealing of the junction of the cylinder head and the block is achieved through the use of a cylinder head gasket. The fastening bolts have a strict sequence in the tightening process, and the tightening torque must also be observed. These bolts are tightened with a torque wrench.

The cylinder head is fastened and the bolts are tightened strictly according to the recommendation of the engine manufacturer. The main task is the need to avoid deformation of the cylinder head.

The upper part of the head of the block is closed with a cover called a valve cover and is attached to the head through a sealing rubber gasket. The cylinder head cover is made of aluminum alloys or sheet steel. The cylinder head of a modern car engine can have a complex design, depending on the characteristics of the gas distribution mechanism.

What is the function of the cylinder head?

Without too much pathos and exaggeration, we can say that the main one. This can be judged by the mechanisms and parts of the engine that the cylinder head houses.

The combustion chamber.
Place for timing (gas distribution mechanism).
Cooling jacket.
Places for injectors or spark plugs.
Lubrication channels.
intake and exhaust valves.

The cylinder head of the engine is made of aluminum alloy, and is attached to the cylinder block. There are certain requirements for the unwinding and tightening of the cylinder head bolts, since the tightness of the connection between the cylinder head and the block depends on the correct observance of the technology.

Taking into account the fact that cylinder head repairs are often done in garage conditions with your own hands, you need to know that a weak tightening of the cylinder head bolts leads to a breakdown of the gasket, which is fraught not only with loss of oil and coolant, but also leads to engine cylinders.

And too much force when tightening the cylinder head can cause deformation of the head housing, and then you have to restore the plane of the cylinder head.

The main requirements for tightening cylinder head bolts are technology and bolt torque. As a rule, each type of engine has its own tightening parameters, which must be strictly adhered to.

The placement of the camshaft chain drive and chain tensioner is provided in a special cavity in front of the cylinder head.

For spark plugs, threaded connections are made in the required quantity. On the right of the cylinder head, threaded holes are made for the studs for fastening the manifolds: exhaust and intake.

For parts such as camshaft bearing housings, arm bearing bushings, valve spring bearing washers and valve guide bushings, the cylinder head has holes and platforms on top.

At the junction of the cylinder block and the cylinder head of the engine is installed.

For single-row engines, one common cylinder head is provided, for multi-row cylinder heads by the number of rows.

The top of the cylinder head is closed by a cylinder head cover equipped with a rubber gasket.

Maintainability of the cylinder head

A certain part of the work on replacing or can be done without removing the head. The cylinder head cover is removed and the valves are adjusted, caps are replaced, etc.

The cylinder head is dismantled when the work does not require the removal of the entire engine from the car: replacing valve guides, removing carbon deposits, replacing bearing studs, lapping valves, etc. If or is required, then the engine is completely dismantled.

All repairs to the engine cylinder head must be carried out in strict accordance with the manufacturer's instructions. Self-activity can cost the failure of the entire engine.

The valve guides and seats must be inserted into the heated cylinder head when cold. This allows, after equalization of temperatures, to ensure high-quality tension in the connection.

In the engine cylinder head, it is possible to replace the bimetallic bushings of the oil pump drive shaft. Replacement is done by pressing out the old bushings and installing new ones.

Good luck with your practical understanding of the cylinder head.