They are driven by overhead intake and exhaust camshaft cams via cylindrical hydraulic tappets. The parameters of the engine valves are given in the table. 3.4. The minimum height of the cylindrical part of the valve disc must be at least 0.5 mm.
Table 3.4. engine valve parameters
Valve parameters | Engine Model | ||
М54В22 | М54В25 | М54В30 | |
intake valves | |||
Plate diameter, mm | 30,0 | 33,0 | 33,0 |
Landing diameter, mm | 29.4 | 32,4 | 32,4 |
Head diameter tolerance, mm | from 0.00 to -0.016 | ||
Rod diameter, mm nominal | 6,00 | ||
1st repair | 6,10 | ||
2nd repair | 6,20 | ||
approval isp. | -0.025 to -0.040 | ||
Gap between guide bushings and valve stems, mm* | 0.5 | ||
exhaust valves | |||
Plate diameter, mm | 27,00 | 30,5 | 30,5 |
Landing diameter, mm | 26,50 | 30,0 | 30,0 |
Head diameter tolerance, mm | from 0.00 to -0.016 | ||
Rod diameter, mm | |||
nominal | 6,00 | ||
1st repair | 6,10 | ||
2nd repair | 6,20 | ||
tolerance | -0.040 to -0.055 | ||
Gap between guide bushings and valve stems, mm* | 0,5 |
* The measurement procedure is shown in fig. 3.7.
One of the main indicators of engine wear depends on the state of the valve mechanism - the amount of compression in its cylinders, which is checked by a special device - a compression gauge installed in the spark plug hole. The rules for its installation and removal, measurements are given in the instructions for the device and are described below. Instrument reading for a new engine - 10-12 bar (kgf/cm2), at wear limit - 8.0 bar.
The difference in pressure between the cylinders of the same engine must not exceed 1.5 bar. If the difference is more than 1.5 bar or the pressure is less than 8.0 bar. this indicates an increased wear of the piston rings, cylinder mirrors, valves. Such an engine must be removed and repaired.
Valve springs
Valve springs are designed to provide a hermetically sealed valve seat. Each intake and exhaust valve has a spring that is identical for both the intake and exhaust valves. The spring is installed with the top of the cone towards the crackers.