Cylinder heads 5D49.78spch (D26.78spch). Cylinder heads 5D49.78spch are one of the most heavily loaded parts of a diesel engine. They are subject to mechanical and thermal stresses from gas pressure, temperature differences and assembly efforts. The high rigidity of the head in the bottom area, significant temperature differences in the radial and axial directions cause high temperature stresses in the bottom, while the stresses from gas pressure forces and assembly efforts are relatively small. Uneven rigidity of the bottom leads to the fact that compression deformation during diesel operation is concentrated in the most pliable part - in the intervalve bridges. As a result of the relaxation process during diesel operation, part of the elastic compression deformation turns into plastic deformation and tensile stresses appear in the intervalve bridges on the "cold" head. The value of these stresses depends on the temperature state of the bottom, the distribution of rigidity over its section, the material, the operating time of the cover and the deposition of scale and additives in the cooling cavity. The cylinder cover of the D49 diesel engine is made of high-strength cast iron. The "head" contains an injector and four valves, including: 2 exhaust and 2 inlet valves. Guide bushings are pressed into the cylinder cover to guide the valve spindles. To minimize oil leakage from the valve box cavity into the combustion chamber, a unique seal is provided, consisting of a scraper and fluoroplastic rings. Between the scraper and the fluoroplastic rings are adjusting rings. Air enters the cylinder cover 30 from the air channel in the cylinder block through spacers.
