NOTE: When repairing engines with leaky valves, it is not sufficient to remake or replace the valve seats and valves. Especially in engines with a long service life, the valve guides must be checked for wear.
NOTE: Valve seats should only be machined enough to achieve a flawless seating surface. Before machining, the maximum allowable machining allowance should be calculated. If the machining allowance is exceeded, the function of the hydraulic clearance control in the valve drive may be impaired (hydraulic compensators), which will entail the replacement of the cylinder head.
Calculate the maximum allowable machining allowance as follows:
- insert the valve into the guide and press it firmly against the seat;
NOTE: If the valve is replaced during repair, the new valve should be used for measurements.
- measure distance A between the end of the valve stem and the top edge of the cylinder head (pic. 2.216);
- Calculate the maximum allowable machining allowance based on the measured distance A and the minimum allowable dimension.
Minimum dimensions:
- Inlet valve - 43.4 mm
- Exhaust valve - 43.2 mm
Measured distance minus minimum dimension = maximum allowable machining allowance.
Example:
- Measured distance - 44.1 mm
- Minimum size - 43.4 mm
- Maximum allowable machining allowance 44.1-43.4=0.7 mm
Inlet valve seat processing
a - 35.7 mm
b - 1.6 mm
45°- Valve seat angle
NOTE: 30°milling of the valve seat is required due to inlet flow ratio.
Exhaust valve seat processing
a - 31.4 mm
b - 2.7 mm
45°- Valve seat angle
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