How to properly burnish valves with a drill

lapping valves with their own hands when repairing the engine head

During the repair of the engine of any of the classic models of VAZ, the car owner, accustomed to do everything with his hands, the question arises about how to lapping valves to the seats of the cylinder head. This problem is known to owners of other cars, developed by the Soviet car industry. New domestic and foreign machines do not allow mastering this process, as valve seats: either perfectly lapped at the factory, or lapped automatically during operation.

Why is valve lapping necessary?

One of the key indicators of the stable operation of the engine is the presence of a sufficient level of compression in the combustion chambers during the compression stroke. This indicator is influenced by such factors:

  • the condition of the piston, piston rings and the cylinder liner;
  • the quality of the gasket seal between the block and the cylinder head;
  • the degree of tightness of the intake and exhaust valve lumen sealing.

In addition to the fact that the compression must comply with certain parameters, its value for all cylinders must be the same. The piston group elements wear approximately equally and the valves can affect the difference in compression in the cylinders.

In order to ensure that each valve closes the channel as securely as possible in the closed position, the lapping paste is applied to the valve seating surfaces. This procedure should be performed each time the cylinder head or valves are replaced.

Proper valve lapping. manual lapping

In order to perform lapping of valve disks, you can use several ways. The simplest, most accessible, but very time-consuming is the manual lapping. For work it is necessary to acquire a special device in the form of a tube, one end of which has a T-handle, in the hole on the opposite side should enter the valve stem.

To hold the valve in place, a hole is made in the side wall of the tube, the thread is cut and a bolt is screwed in to hold the stem. Another important component of the process is the lapping compound. This is a mix of lubricants with fine abrasives, which is applied periodically to the lapped surfaces.

Procedure for manual lapping of valves:

  • the disassembled cylinder head is placed on the workbench and fixed;
  • the valve is inserted in its normal place and a fixture is attached to the end of the valve;
  • Apply a small amount of paste around the entire circumference of the valve at the point of contact with the seat;
  • holding the device by the handle, pull the valve toward you until the lumen is closed and perform circular movements to the right and to the left as far as the wrist joint allows;
  • after several movements, the valve is turned 180 degrees, opened, the paste is renewed and the lapping is repeated;
  • need to lapping until a homogeneous matte strip of at least 1.5 mm in width appears on the valve plate and the seat.
properly, valves, drill

Thus, knowing how to lapping the valves yourself, you can save a significant amount of money on paying for the services of a mechanic. The manual method, although it leads to fatigue, but it is considered the most correct, because the quality control of lapping is carried out constantly, and the person through tactile sensations controls the correctness of pressing, avoiding jumps and bumps.

How to properly lapping valves with the use of mechanical tools

For those who wish to accelerate the process of lapping the valves, there is a method that allows a significant reduction in physical labor to reduce the time and work. For this purpose it is necessary to have a mechanical or electric drill, which must meet certain criteria: the possibility of reverse rotation, the chuck speed regulation. Using drills, lapping is possible in two ways: from the side of the combustion chamber or from above.

Let’s see how to properly lapping the valves by the first method:

  • to work, you need to make metal heels smaller than the diameter of the valve plate, in the center of which a slot is made, as on the screw heads for screwdrivers;
  • After melting a little bit of bitumen, the pegs are glued to the valve plate;
  • after that the cylinder head is placed with the combustion chambers up, the valve is inserted and the lapping point is smeared with paste;
  • the metal rod, flattened at the end like the end of a screwdriver, is inserted in the drill chuck;
  • inserting the end of the rod into the cut of the nickel, start lapping the valve by rotating it with the drill. The rotation should be small;
  • after turning about 10 times in one direction, it is necessary to renew the paste and lapping in the opposite direction;
  • before installing the valve, a spring is put on the valve stem, which will lift it, but its resistance should be negligible;
  • the heel can be removed by heating the valve;
  • wash away the bitumen residue with petrol or thinner.

The second method of technology does not differ from manual lapping, the only difference is that the rotation is also performed with a drill. it is necessary to insert into the drill chuck a rod with the diameter similar to that of the valve stem, and also pick up a piece of rubber tube of length about 10 cm., which can be put on the flap and arrow on the chuck. The ends of the tube are crimped with pipe clamps for reliability.

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a few secrets for proper valve lapping

It is absolutely easy to master the process of lapping the valves. Once the coveted strip appears on the first valve disc, you will not have any more questions. Modern means of communication allow you to seek help from experts, because on how to lapping valves video clips posted on the Internet, there are thousands of.

Accepting the repair of cylinder head, particularly for lapping the valves, it is necessary to strictly follow certain rules:

  • each valve has its own location, valves should not be interchanged after lapping;
  • You should use a variety of pastes, from the coarsest to the finest abrasives;
  • After lapping it is necessary to thoroughly wash the head and the valves to remove abrasive particles.
properly, valves, drill

What is lapping and why lapping valves

Valve lapping is basically grinding on the surface of the valves (which allow fuel and air to flow freely) and where they contact each other. This is done by applying a special paste to the edges of the valves. The result is a perfect seal that will prevent gases from escaping during engine use.

The internal combustion engine works by reaching a certain compression ratio, which differs between models, and burning the air-fuel mixture, which is compressed to a certain volume, set by the compression ratio. And if the fuel-air mixture flows through the seat, the volume of the air-fuel mixture will change and the combustion process will not be accurate, resulting in poor engine performance.

  • Creates a maximum seal between the valve and the cylinder head that prevents the escape of gases during engine operation.
  • Large contact area ensures heat dissipation from the valves to the head, which will prevent valve combustion.

The entire process will result in finer surfaces, eliminate minor defects, and create a more reliable seal.

Standard tool set for lapping

The most important tool is the abrasive, or diamond paste. It must be applied to the valve lip. the paste creates a sanding effect and allows the disc to be lapped against the seat more quickly.

By the type of processing the paste composition differs in the size of the abrasive elements. from coarse to fine grained. Coarse abrasive is used for initial lapping. Finishing lapping is done with a fine paste. then the component head is firmly seated in its seat.

Pastes vary in price. from inexpensive pastes for personal use to proprietary formulations for professional lapping. Do-it-yourself work can be carried out with a medium-cost compound. It is important to observe the condition of the valves themselves and the correctness of the lapping process.

The next step is the choice of tools for work. The lapping can be done by:

  • Electric drill.
  • A wooden fixture with suction cups.
  • Pneumatic tool.
  • A special pneumatic tapping tool.

The electric lapping drill is most popular with hobbyists because of its accessibility and versatility. A special beveling machine can be used in repair shops.

Machining the seats and rebuilding them requires a special tool. This is a scraping block. a device made to the shape of the valve seat. The burr is put on the drill, since the drill bit is usually undersized.

The tool is used if valve heads are damaged due to bursting.

A strutting tool is also needed to remove the struts. the parts that connect the spring discs to the valve.

How to properly tap the valves

After the desoaking we carefully inspect the valve for blowholes. There is no sense in lapping a burnt out valve, it is easier to replace it. Also check the axial run-out of the rod in the bushing. If the valve is loose, check the valve stem. There must not be any visible wear on the stem. If the pin is intact, but there is still play, then the bushings need to be replaced as well. There is no point in lapping valves with broken valve sleeves.


Before lapping, the chamfer surfaces must be as free of carbon deposits as possible. After that we put a small layer of lapping compound on the valve chamfer. Insert the valve into the bushing on the block head and connect the stem with our tool from the back side. Put a little strain on the valve and begin to rotate it in the cylinder head. It is not necessary to apply too much pressure: you could cut too deep a chamfer in the seat.

Important point: Lapping must be done in both directions. If you work with a power tool, you need to change the direction of rotation at least once every 7-10 seconds. Otherwise the chamfer could be resharpened. When lapping by hand, simply rotate the valve 90 to 180 degrees and interpolate the tool periodically.

Do not lapping a chamfer in only one position. The valve should seat securely at any angle of rotation. The point is that when the valve train is running, the valves are constantly turning in their seats. And if the lapping is done without periodic turning, the drops will fit tightly and provide a seal in only one position.

How long to lapping? There is no definite answer to this question. It all depends on the initial damage to the chamfers, the granularity of the paste, the pressing force and the intensity of the process. The general recommendations are as follows:

  • every 2 to 3 minutes, stop, clean paste off the valve and block, and check the condition of the chamfers;
  • If you can see sinks on the machined surfaces. apply fresh paste and continue to work for 2-3 minutes more;
  • Once the entire valve circumference has a matte bevel, the lapping operation is complete.
properly, valves, drill

On average the entire process of lapping one valve takes from 5 to 15 minutes. In some cases, if there are deep grooves and cavities in the chamfers, one valve must be lapped for up to an hour. At the end of the procedure, be sure to thoroughly wash the head and the valve from the paste.

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What is needed for lapping?

Valves can be lapped in several ways, depending on which one is chosen, you will need the appropriate tool. This can be an ordinary electric drill, a special pneumatic tool, or a hand cutter. Accordingly special lapping paste is needed, which composition is similar to that used by jewelers for grinding metals.

There are several ways of lapping. Each of them has its own peculiarities which are described below.

Handheld cutters

The hand cutter is a stick with a suction cup on the end. The procedure is as simple as getting fire. The rubber suction cup is installed on the valve plate, the bevel of the plate and the seat are pre-treated with a special lapping paste and start rotating the strip between your hands. to the left, to the right. For a normal valve, it usually takes 15, to 20 minutes.

The most real connoisseurs of vintage cars use such way, getting moral pleasure from this process. With this type of lapping it is impossible to damage the disc itself, the valve stem or the seat. Visually, after machining the bevel becomes dull, like a seat.


There are special mobile valve lapping machines. They are used by professional mechanics in their workshops. These are devices like: VM1150, VM1200, VM1350, VM1500 or VM1600. They differ in the size of the pallets being machined and the plunging depth. There are also special stands for the lapping of valves, such as P-23.74, they can process 8 valves at a time, and are designed for the most different models of cars. from cars to large trucks.

Valve lapping explanation for not using a drill

Workbench and tube with a T-handle

T-handle tube. another device used for gentle lapping of valves of vintage cars. In this case, there is an attachment for a rod at the end of the tube and the handle is used to turn the valve in the seat. The method does not tolerate haste and force. It removes a minimal layer from the fragile and thin valve plate. But this method is time-consuming.

properly, valves, drill

Using a drill

Using an electric drill is the most controversial method among professional mechanics. In this method, the valve stem is clamped in the drill chuck itself or through a flexible rubber hose. A rotary drill must be reversible, with the ability to rotate the spindle in both directions at very low speed. Undoubtedly, this method significantly reduces time for lapping. for one valve, it takes from 1 to 2 minutes. But there is a risk of scratching the pallet or seat, leaving deep scratches on them or even breaking the valve stem.

Important! Lapping with an electric drill can only be performed by professionals who by eye can determine the quality and have a steady hand, accustomed to working with this tool.

What to prepare for valve lapping?

When you decide to do your own valve lapping, then you should prepare certain tools and materials. First, for the work you will need:

  • a special paste that is used for lapping valves. It is available under the index 1 and index 2 (which indicates the granularity of the granules present). Both options will be required;
  • valve tool. This is how the entire procedure is carried out.

In addition, it is necessary to check the condition of the valve itself. When the valve is deformed, you should not try to repair it, because without high-precision tools you will not be able to achieve a very accurate geometry. it is easier to buy a new valve.

What is needed for lapping

The process of lapping is performed with the cylinder head dismantled. Therefore, in addition to tools for lapping valves, the car owner will also need a tool for dismantling the cylinder head. As a rule, they are usual locksmith’s wrenches, screwdrivers, rags. However, it is also desirable to have a torque wrench, which will be needed at the stage of reassembly of the head in place. The need for it arises because the mounting screws that hold the head at its seat, should be tightened to a certain torque, which just can be provided only by using a torque wrench. Depending on what method of lapping of valves will be chosen. manual or mechanized (about them a little later), different and a set of tools for work.

Directly to perform the lapping of the valves the car owner will need:

  • Manual valve holder. Such products are available in car dealerships or workshops. If you for some reason do not want or can not buy such a holder, you can make it yourself. How to make it, told in the next section. The manual valve holder is used for manual valve lapping.
  • Valve lapping paste. In most cases, car owners buy ready-to-use formulations, as there are now many of these products in auto stores, including at different prices. In extreme cases it is also possible to make such a compound yourself from abrasive shavings.
  • Reversible drill or electric screwdriver (for mechanized lapping). As a rule, lapping is performed in both directions of rotation, so the drill (electric screwdriver) must rotate in both directions. You can also use a hand drill, which itself can rotate in one or the other direction.
  • Hose and spring. These devices are necessary for mechanized lapping. the spring should have a low stiffness, and a diameter of two to three millimeters larger than the diameter of the valve stem. Similarly, a hose so that it can be put on the rod. You can also use a small clamp to hold it in place. Some other metal rod of no length in diameter similar to the piston rod is necessary so it also fits snugly into the rubber hose.
  • Kerosene. It is used as a cleaner and then to check the quality of the lapping performed.
  • “ball socket.”. This is a special tool designed to remove damaged metal in the valve seat. Such devices are sold in ready-made form in car dealers. Nowadays you can find this part in auto stores for almost any engine (especially for common cars).
  • Rag. Subsequently with its help you will need to wipe treated surfaces dry (and your hands as well).
  • Solvent. Needed to clean the working surfaces.
  • Scotch tape. Is a necessary component when performing one of the methods of mechanized cleaning.
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Fixture for lapping valves

If the car owner has no possibility / desire to buy a factory device for lapping valves with their own hands (manually), a similar device can be made on their own using improvised means. For this you will need:

  • Metal tube with cavity inside. Its length should be about 1020 cm, and the diameter of the inner hole of the tube should be 23 mm more than the diameter of the valve stem of the engine.
  • Electric drill (or electric screwdriver) and metal drill bit with a diameter of 8.5 mm.
  • Contact or gas welding.
  • 8mm diameter nut and bolt.

The algorithm for making a device for lapping valves will be as follows:

  • Using a drill at a distance of about 710 mm from one of the edges you must drill a hole of the above diameter.
  • Weld the nut exactly over the drilled hole by welding. Care must be taken 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 to the hole.
  • As a handle for the tube, you can either bend the opposite piece of pipe at a right angle, or finish welding another piece of pipe or any other metal part, similar in shape (straight).
  • Unscrew the bolt back and insert the valve stem into the tube and use the bolt to clamp it firmly with a wrench.

Nowadays you can find such a factory-made device in many online stores. The problem, however, is that they are clearly overpriced. But if the car owner does not want to perform the manufacturing procedure himself. you can buy a device for lapping the valves.

What type of lapping compound to use?

In the early days of automotive engineering, diamond wheel dust mixed with machine oil was used for lapping valves. Today these blends are replaced by a variety of lapping pastes. They differ in m abrasive elements, sizes of fractions and, accordingly, the price.

The paste is selected according to the degree of contamination, quality and brand of valve metal, year of manufacture and engine model. The method of lapping. manual or mechanical. also matters.

An important factor in paste selection is the experienced technician. For example, a beginner using coarse paste can easily ruin a valve or seat. Therefore it is recommended to use fine-grained paste for beginners, and it will take more time for lapping with such means.

A coarse-grained paste called “Classic” or “Diamond” is available in car dealerships for the initial lapping. For finish lapping the paste “FABO” is used. the finish antifriction without abrasion. This paste is sold in a set of two tubes, with a coarse fraction and grinding.

There are also multifunctional pastes like “ABRO Grinding Paste GP-201. It can be used not only for grinding valves, but also for cleaning metal parts from rust, and even used for sharpening cutting tools, such as planers. Its price is much lower than the special “FABO”, so that, as they say, the economy is useful.

Pastes “PERMATEX” or “Done Deal” are also used for polishing chrome parts, since they do not contain diamond, but silicon carbide.

If the repair caught the driver without paste, and lapping impossible to postpone. the engine is already disassembled, you can mix with oil abrasive scraped from the usual, fine sandpaper, and for the final polishing paste used State Optical Institute or better known as, paste GOI.

To summarize

So, as evident from all above-stated, lapping is a responsible, labor-consuming procedure, but it is extremely necessary for good work of the engine not only after repair, but also after run more than 60 000 km. The only question that remains unclear is whether the valves on the new head need to be lapped.

As to such a case, there are two variants: if the head is brand new and was purchased fully completed, it is possible not to lapping. In any case, experts say that it is not necessary to do it. But if you bought the cylinder head separately from the valves, lapping is necessary. Again, in any case, before its installation, the tightness of the adjoining plates can always be checked in the already known way, that is, by pouring gasoline or kerosene in the cylinder head or manifolds.

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