Chpter IV Mechanical System
Great Wall Baoding Internal Combustion Engine
Manufacturing Company Limited
153
Fig. 4-3-14 Measuring the valve contact width
Fig 4-3-15 Removing the valve seat
Fig. 4-3-16 Calibrating the valve seat
3.5 Checking the valve contact width
(1) Check the valve contact surface for roughness or
unevenness. Ensure the valve contact surface is
smooth.
(2) Measure the valve contact width. See Fig. 4-3-14.
(3) Replace the valve seat if any valve of contact width
is above the limitation.
The valves of contact width
Valve
Standard
Limitation
Intake valve
1.7 mm
2.2 mm
Exhaust valve
2.0 mm
2.5 mm
4. Valve seat
4.1 Removing the valve seat
(1) Conduct arc-weld inside the valve seat.
(2) Cool the valve seat for several minutes. The valve
seat will contract by doing so and its removal will
become easier.
(3) Pry the valve seat with a screw driver to remove it.
Be careful lest the cylinder head be damaged.
(4) Carefully remove the accumulated carbon and other
foreign matters from the valve seat mounting hole in
cylinder head.
4.2 Calibrating the valve seat
(1) Remove the accumulated carbon on the valve seat
surface with a gasket scraper or a steel wire brush.
(2) Treat the valve seat with a valve seat cutter (blade
of 15°, 45° and 75°) to minimize the area with scratches
or other kinds of irregularities, in order to recover the
standard value of contact width.
The valve seat angle
45°
Valve guide
Sectional view of
cylinder head cover
View of exhaust
valve seat
View of intake
valve seat
