The screws are particularly needed to fasten a device or to support a gasket. Among the advantages of the metal screws we find the robustness, conductivity, as well as heat and cold resistance guaranteed by this material. Because the head of the block is subject to particularly extreme conditions, the respective screws must be expansion screws. The material must be able to expand without breaking or having the consequences of wear before it is due. Therefore, steel or various alloys are used most often. What makes the head screw different from many others is its shape.
In order to expand when it comes into contact with heat, the screw has to create a space for itself, without the need for the cylinder, otherwise losses may occur. It has a regular head, designed to cover the insert completely. Its lower part, on the other hand, must always be covered by a gasket. Here is the short thread, which leads to the head. The rest of her body becomes thinner as it goes in the interior, which is why when the components are not heated, there is a free space between the screw and the blockhead. Thus, once heated, the body of the vine extends and covers the whole area without breaking when it is pressurized. When the engine is switched off, the screw returns to its initial shape and, therefore, becomes thin again. As you can see, the head screw must withstand drastic changes in temperature. Only in this way can the gasket work well and, therefore, the perfect regularity of the combustion process.
Whenever you decide to replace the block head, you must consult the operating manual. It is very important that the space needed to allow vine expansion is sufficient. Regardless of the brand you are interested in, you will find spare parts of excellent quality (eg oscillating support, rally, windscreen wiper, ignition coil, etc.) at a very affordable price.