Weichai America Corp.
26
1.
Valve Recession:
Valve recession is the vertical distance between valve undersurface and cylinder cover
undersurface. Any difference between the measured and required values of valve recession
can reflect the degree of wear on the valve and valve seat. A depth micrometer can be used to
measure valve recession, as shown in Figure below:
Reference Table below for valve recession requirements. If valve recession exceeds the allowed range,
the cylinder cover must be replaced to ensure engine reliability. If valve recession doesn’t exceed
allowed range, disassemble the valve and check the sealing surface between the valve and valve seat
for wear and abnormal damage.
Table: Valve Recession Specifications
Required value of valve recession (mm)
Intake valve
1.00~1.45
Exhaust valve
1.00~1.45
2.
Clearance between valve rod and valve guide pipe:
Internal surface of valve guide pipe is the contacting surface between valve rod and valve guide pipe, if
clearance between valve rod and valve guide pipe exceeds allowed value due to abrasion, then the
guide effect will at state, which may affect reliability of the engine. The inner diameter of guide pipe
can be measured with an inside micrometer, as shown in Fig. 3-5. Outer diameter of valve rod can be
measured with an outside micrometer. Both allowed ranges for clearance between intake valve rod and
its guide pipe, exhaust valve rod and its guide pipe are 0.03~0.06mm. If clearance exceeds allowed
range, the cylinder cover must be replaced to ensure reliability of diesel engine.
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