Lapping valves

Lapping valves do-it-yourself - a simple procedure, provided that the auto-amateur had previously had experience in performing repair work. To lap valve seats, you will need a number of tools and materials, including lapping paste, a device for dismantling valves, a drill (screwdriver), kerosene, a spring that passes through the valve seat hole in diameter. In terms of time, grinding in the internal combustion engine valves is a rather expensive procedure, since in order to complete it, it is necessary to dismantle the cylinder head.

What is lapping and why is it needed

Valve lapping is a process that ensures the perfect fit of the intake and exhaust valves in the internal combustion engine cylinders on their seats (saddle). Typically, grinding is performed when replacing valves with new ones, or after an overhaul of the internal combustion engine. Ideally, lapped valves provide maximum tightness in the cylinder (combustion chamber). This, in turn, ensures a high level of compression, the efficiency of the motor, its normal operation and technical characteristics.

In other words, if you do not grind in new valves, then part of the energy of the burned gases will be irretrievably lost instead of providing the proper power of the internal combustion engine. At the same time, fuel consumption will certainly increase, and engine power will definitely decrease. Some modern cars are equipped with an automatic valve control system. It simply grinds off the valve, so there is no need for manual grinding.

What is needed for grinding

The lapping process is carried out with the cylinder head removed. Therefore, in addition to tools for grinding valves, the car owner will also need a tool for dismantling the cylinder head. usually, these are ordinary locksmith keys, screwdrivers, rags. However, it is also desirable to have a torque wrench, which will be needed at the stage of reassembling the head into place. the need for it appears, since the mounting bolts holding the head in its seat must be tightened with a certain moment, which can only be ensured with a torque wrench. Depending on which method of lapping the valves will be chosen - manual or mechanized (about them a little later), the set of tools for work is also different.

it is for lapping the valves that the car owner will need:

• Manual valve holder. In auto shops or auto repair shops, ready-made such products are on sale. If for some reason you do not want or cannot buy such a holder, then you can make it yourself. How to reproduce it is described in the next section. The manual valve holder is used when manually lapping valves.
• Valve Lapping Paste. In most cases, car owners buy ready-made compounds, since at present there are a lot of these funds in car dealerships, including at different prices. In extreme cases, you can produce a similar composition yourself from abrasive chips.
• Drill or screwdriver with the possibility of reverse (for mechanized grinding). usually, grinding is performed in both directions of rotation, so the drill (screwdriver) must rotate both in one direction and in the other. you can also use a hand drill, which itself can rotate in one direction and the other.

• Hose and spring. These devices are necessary for mechanized lapping. The spring should have low rigidity, and the diameter is two to three millimeters larger than the diameter of the valve stem. Similarly, the hose, in order that it could be put on butt on the rod. you can also use a small clamp to secure it. some short metal rod is also needed in diameter similar to the piston rod, in order for it to fit snugly into the rubber hose.
• Kerosene. It is used as a cleaner and subsequently to check the quality of the lapping performed.
• "Sharoshka". This is a special tool designed to remove damaged metal in the valve seat. Such devices are sold ready-made in car dealerships. Currently, in car dealerships you can find this part for almost any internal combustion engine (especially for common cars).
• Rags. Subsequently, with its help, it will be necessary to wipe dry treated surfaces (at the same time hands).
• Solvent. Needed to clean work surfaces.
• Scotch. It is a necessary component when performing one of the mechanized cleaning methods.

Valve Lapping Tool

If the car owner does not have the opportunity / desire to buy a factory device for grinding valves with his own hands (manually), a similar device can be produced independently using improvised means. For this you will need:

• Metal tube with a cavity inside. Its length should be about 10 ... 20 cm, and the diameter of the inner hole of the tube should be 2 ... 3 mm larger than the diameter of the internal combustion engine valve stem.
• An electric drill (or screwdriver) and a metal drill with a diameter of 8,5 mm.
• Contact or gas welding.
• Nut and bolt with a diameter of 8 mm.

The algorithm for manufacturing a valve grinding device will be as follows:

• Using a drill at a distance of about 7 ... 10 mm from one of the edges, you need to drill a hole of the diameter indicated above.
• Using welding, you need to weld the nut exactly over the drilled hole. In this case, you need to work carefully so as not to damage the threads on the nut.
• Screw the bolt into the nut so that its edge reaches the inner surface of the tube wall opposite from the hole.
• As a handle for the tube, you can either bend the opposite piece of the pipe at a right angle, or you can also weld one piece of the pipe or any other metal part that is similar in shape (straight).
• Unscrew the bolt back, and insert the valve stem into the tube, and use the bolt to tighten it firmly with a wrench.

Currently, a similar factory-made device can be found in many online stores. However, the problem is that they are clearly overpriced. But if a car enthusiast does not want to perform the manufacturing procedure on his own, you can completely buy a device for grinding valves.

Valve Lapping Methods

There are actually two ways to grind valves - manual and mechanized. However, manual lapping is a laborious and time-consuming process. Therefore, it is better to use the so-called mechanized method, using a drill or screwdriver. However, we will analyze one and the other method in order.

Regardless of the selected lapping method, the first step is to remove the valves from the cylinder head (it must also be dismantled beforehand). In order to remove the valves from the guide bushings of the cylinder head, you need to remove the valve springs. To do this, use a special device, and then remove the “crackers” from the plates of the springs.

Manual lapping method

in order to grind the valves of the internal combustion engine of a car, you need to follow the algorithm below:

• After dismantling the valve, you need to thoroughly clean it from carbon deposits. To do this, it is better to use special cleaning agents, as well as an abrasive surface in order to thoroughly remove plaque, grease, and dirt from the surface.
• Apply a continuous thin layer of lapping paste to the valve face (coarse-grained paste is used first, and then fine-grained paste).

• If the self-made lapping device described above is used, then it is necessary to insert the valve into its seat, turn the cylinder head over, and put the holder on the valve that is in the valve sleeve and lubricated with lapping paste. then you need to tighten the bolt in order to fix the valve in the pipe as tightly as possible.
• Then you need to rotate the lapping device together with the valve alternately in both directions by half a turn (approximately ± 25 °). After one or two minutes, you need to turn the valve 90 ° clockwise or counterclockwise, repeat the back-and-forth lapping movements. The valve must be lapped, periodically pressing it to the seat, and then releasing it, repeat the procedure cyclically.
• Manual lapping of valves is required perform until a matte gray even monochromatic belt appears on the chamfer. Its width is about 1,75 ... 2,32 mm for intake valves, and 1,44 ... 1,54 mm for exhaust valves. After lapping, a matte gray band of the appropriate size should appear not only on the valve itself, but also on its seat.
• Another sign by which one can indirectly judge that lapping can be completed is a change in the sound of the procedure. If at the beginning of rubbing it will be purely "metallic" and loud, then towards the end the sound will be more muffled. That is, when not metal rubs on metal, but metal on a matte surface. Typically, the lapping process takes 5-10 minutes (depending on the specific situation and the state of the valve mechanism).
• Typically, lapping is performed using a paste of different grain sizes. First, coarse-grained paste is used, and then fine-grained. The algorithm for using them is the same. However, the second paste can only be used after the first paste has been well sanded and hardened.
• After lapping, it is necessary to thoroughly wipe the valve and its seat with a clean rag, and you can also rinse the surface of the valve in order to remove the remnants of lapping paste from its surface.
• Check the quality of the lapping by checking the concentricity of the location of the valve disc and its seat. To do this, apply a thin layer of graphite to the chamfer of the valve head with a pencil. then the marked valve must be inserted into the guide sleeve, slightly pressed against the seat, then turned. According to the traces of graphite obtained, one can judge the concentricity of the location of the valve and its seat. If the lapping is good, then from one turn of the valve all the applied dashes will be erased. If this does not happen, grinding must be repeated until the specified condition is met. However, a full check is performed by another method, described below.
• Upon completion of the lapping of the valves, all working surfaces of the parts are washed with kerosene in order to remove residual lapping paste and dirt. The valve stem and sleeve are lubricated with engine oil. further, the valves are installed in their seats in the cylinder head.

In the process of lapping valves, you need to get rid of the following types of defects:

• Carbon deposits on the chamfers that did not lead to deformation of the chamfer (valve).
• Carbon deposits on the chamfers, which led to deformation. namely, a stepped surface appeared on their conical surface, and the chamfer itself became round.

Please note that if in the first case the valve can simply be ground in, then in the second it is necessary to make its groove. In some cases, lapping is performed in several stages. For example, rough lapping is carried out until all shells and scratches are removed from the surface of the workpiece. Often, paste with different grit levels is used for lapping. A coarse abrasive is designed to remove significant damage, and a fine one is for finishing. Accordingly, the finer the abrasive used, the better the lapping of the valves is considered. Usually pastes have numbers. For example, 1 - finishing, 2 - rough. It is undesirable for abrasive paste to get on other elements of the valve mechanism. If she got there - wash it off with kerosene.

Lapping valves with a drill

Lapping valves with a drill is the best option, with which you can save time and effort. Its principle is similar to manual grinding. The algorithm for its implementation is as follows:

• Take the prepared metal rod and put a rubber hose of a suitable diameter on it. For better fixing, you can use a clamp of the appropriate diameter.
• Fix the mentioned metal rod with the attached rubber hose in the chuck of an electric drill (or screwdriver).
• Take the valve and put a spring on its stem, then install it in its seat.
• slightly pushing the valve out of the cylinder head, apply a small amount of lapping paste to its chamfer around the perimeter of its plate.
• Insert the valve stem into the rubber hose. If necessary, also use a clamp of the appropriate diameter for better fastening.
• Drill at low speed start lapping the valve in its seat. In this case, you need to move it back and forth, in which, in fact, the installed spring will help. After a few seconds of rotation in one direction, you need to switch the drill to reverse, and rotate it in the opposite direction.
• Perform the procedure in the same way, until a matte belt appears on the valve body.
• Upon completion of lapping, carefully wipe the valve from the remains of the paste, preferably with a solvent. Moreover, it is necessary to remove the paste not only from the chamfer of the valve, but also from its seat.

Lapping new valves

There is also one lapping of new valves on the cylinder head. The algorithm for its implementation is as follows:

• Using a rag soaked in solvent, remove dirt and deposits on the chamfers of all new valves, as well as on their seats (seats). It is important that their surfaces are clean.
• Take a piece of double-sided tape and stick it on a plate of a lapping valve (instead of double-sided tape, you can take a regular one, but first make a ring out of it and squeeze it to a flat state, thereby turning it into a double-sided one).
• Lubricate the tip of the rod with machine oil, and install it on the seat where it is supposed to grind the device.
• Take any other valve of the same diameter and insert it into the chuck of a screwdriver or drill.
• Align the plates of the two valves so that they stick together with adhesive tape.
• Slightly pressing on the drill or screwdriver at low speeds, start grinding. The appliance will rotate one valve, and that, in turn, will transmit rotational movements to the lapping valve. Rotation must be both forward and reverse.
• The signs of the end of the procedure are similar to those described above.

Please note that many modern machine engines are not amenable to valve lapping. This is due to the fact that they are made of aluminum, and if the internal combustion engine elements are significantly damaged, there is a risk of frequent valve replacement. Therefore, owners of modern foreign cars should further clarify this information or better seek help from a car service.

Remember that after lapping, you can not change the valves in places, since lapping is performed for each valve individually.

How to check valve seating

At the end of the lapping of the valves, it is imperative to check the quality of the lapping. This can be done using one of two methods.

Method one

The method described below is the most common, but it will not always show the correct result with a 100% guarantee. also, it cannot be used to check the quality of valve grinding in ICEs equipped with an EGR valve.

So, to perform the check, you need to put the cylinder head on its side, so that the holes of the wells to which the manifolds are connected “look” up. Accordingly, the valves will be located in a horizontal plane, and their covers will be located vertically. Before checking the performed lapping of the valves, it is necessary to dry the valve outlets with the help of a compressor in order to provide visibility of the possible leakage of fuel from under them (that is, so that the vertical wall is dry).

then you need to pour gasoline into vertical wells (and kerosene is also better, since it has better fluidity). If the valves provide tightness, then poured kerosene from under them will not leak out. In the event that fuel even in small quantities leaks out from under the valves, additional grinding or other repair work is necessary (depending on the specific situation and diagnosis). The advantage of this method is that it is easy to implement.

However, this method also has its drawbacks. So, with its help it is impossible to check the quality of valve grinding when the internal combustion engine is operating under load (gas leakage under load). also, it cannot be used for ICEs equipped with an USR valve, since their design implies the presence of corresponding valves in one or more cylinders through which the fuel will pour out. Therefore, it is not possible to check the tightness in this way.

The second method

The second method of checking the quality of valve grinding is universal and most reliable, since it allows you to check the passage of gases through the valves under load. To perform an appropriate check, it is necessary to position the cylinder head “upside down”, that is, so that the outlets (holes) of the valves are on top, and the holes of the collector wells are on the side. then you need to pour a small amount of fuel (in this case, it doesn’t matter which one, and even its condition doesn’t matter) into the valve outlet cavity (a kind of plate).

Take an air compressor and use it to supply a jet of compressed air to the side well. Moreover, it is necessary to supply compressed air both to the intake manifold opening and to the exhaust manifold opening. If the lapping of the valves was done with high quality, then air bubbles will not come out from under them even under the load provided by the compressor. If there are air bubbles, then there is no tightness. Accordingly, the lapping was performed poorly, and it is necessary to refine. The method described in this section is extremely efficient and versatile and can be used on any ICE.

Hack and predictor Aviator

Lapping valves is a simple procedure that most car owners can handle, especially those with repair skills. The main thing is to have the appropriate tools and materials. You can make your own lapping paste, or you can buy a ready-made one. However, the second option is preferable. To check the quality of the lapping performed, it is desirable to use an air compressor that provides leakage testing under load, this is a better approach.