When repairing the engine, lapping of the valves is often required . This is a responsible work, for the implementation of which it is necessary to have the appropriate tool at hand. Of course, you can do without it. So, how is valve grinding done by hand?
When lapping is required
Many use a special tool, paste and suction cup for grinding valves. However, not everyone knows how to properly carry out such a procedure. Seats and valves have only a few varieties of defects:
- chamfers are covered with shells or soot, but their shape is not changed;
- bevels are covered with soot and sinks, while their shape is changed.
In the latter case, something like steps can form on the surface of the part. In addition, the conical shape of the chamfer can change and become rounded.
Lapping features in both cases
If the shape of the chamfer is not broken, a regular grinding is carried out. If there are defects, the part is first processed using a lathe, and valve seats are trimmed with cones of conical shape. Moreover, the dimensions of the devices are of particular importance.
To begin with, valve seats are machined with a cone having an angle of 45 °, then the upper chord is cut with a cone with an angle of 15 °, and a chamfer with an angle of 75 ° is removed at the bottom of the seat. Parts can also be machined with abrasive wheels and a hand drill. In this case, the tools should have angles of 45 °, 15 ° and 75 °.
It is worth considering that grinding valves with a hand drill or screwdriver is time-consuming. To speed up the process, you can use an electric tool that can be checked in both directions, and also gradually rotate around the circumference.
Lapping paste
First of all, you need a paste for grinding in the valves. This is the first thing to buy in a specialty store. During processing, the paste is applied to the edge of the valve. This composition plays the role of a kind of small skin. Thanks to the paste, you can easily grind the valve to the socket. There are several main varieties of such tools. All of them have certain differences that affect the cost of production.
Pasta classification
The paste for grinding in the valves is classified according to the degree of surface treatment: for initial processing - coarse, for final - fine-grained. The latter option is very popular, since such products are recommended by masters engaged in engine repair. Fine-grained paste allows you to quickly and correctly grind the valves. However, a lot depends not on the composition of the product, but on the condition of the chamfers and the parts themselves. In addition, grinding in the valves with their own hands is far from everyone. For self-processing, it is recommended to use the usual composition, the cost of which is 100 rubles per tube.
Do not buy the most expensive pasta. If there is a need for it, then you can purchase it in the process.
"Grandfather" cones
Lapping the valves with your own hands is a simple process, if you know how and what to do. Previously, there were cones for cylinder head repair. Such a valve lapping device was mainly used to restore the seats of parts. Some masters still use such a tool. Externally, the device is a nozzle for a socket made in the form of a valve seat. The cone is fixed in the drill. The device is small and resembles a kind of drill.
Are cones always needed
Is such a tool needed? To answer this question, you need to look at the saddles, pressed into the heads. If their integrity is not broken, you can start grinding. If they are damaged, such as burnout, then it is recommended to treat them with special cones. The technology in this case is quite simple. Initially, it is recommended to change the guides, and then grind in. In each case, an individual approach is required. You can buy a special device for grinding valves in almost any specialized store.
Or maybe put new valves?
New valves are not always required. Of course, if the details are slightly curved, then do not try to align them. The process will not produce results, and you will only spend time and energy. In this case, it is better to visit the store with spare parts for vehicles and purchase a new kit.
When replacing parts, special attention should be paid to their quality. The height of the valves in any case should be the same. Roughnesses and marks on the ends, rods and sealing working bevels are not allowed. We recommend polishing the parts to a shine before installing a new kit. This process should be carried out not only on the valve stems, but also on the black neck of the valve, and on a flat plate. Thanks to this treatment, the parts will become less overgrown with soot and heat up. When processing, sealing chamfers are not recommended. They should only be rubbed to the saddles.
Valve lapping machine
Many for grinding valves make special devices. This may require a rubber hose and a conventional drill. Lapping the valves with your own hands in this case is carried out according to the following scheme:
- A rubber hose is put on the drill. This may require a drill and a few clamps.
- Lapping paste is applied to the end of the hose.
- One of the engine valves is inserted into this hose. For reliable fixation, clamps can be used.
- The valve is inserted into the seat and lapping begins.
With this method, it is very important not to include the maximum speed on the drill. The process should proceed slowly and accurately. As for the revolutions, they should be from 400 to 500 per minute. As the speed increases, the seats and girdle of the valves become very hot. In the process of grinding, it is not recommended to make circular movements. Simulate the operation of the engine valve while moving forward and then backward.
It is worth considering that grinding the valves with a drill and a hose is a painstaking process that takes a lot of time.