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Valve Construction

 Valve Construction

  • The valves in the cylinders of an aircraft engine are subjected to high temperatures, corrosion, and operating stresses; thus, the metal alloy in the valves must be able to resist all these factors.
  • Because intake valves operate at lower temperatures than exhaust valves, they can be made of chromic-nickel steel.
  •  Exhaust valves are usually made of nichrome, silchrome, or cobalt-chromium steel because these materials are much more heat resistant.
  • The valve head has a ground face that forms a seal against the ground valve seat in the cylinder head when the valve is closed.
  • The face of the valve is usually ground to an angle of either 30° or 45°.
  • In some engines, the intake-valve face is ground to an angle of 30°, and the exhaust-valve face is
  • ground to a 45° angle.
  • Valve faces are often made more durable by the application of a material called a satellite. About 116 inch of this alloy is welded to the valve face and ground to the correct angle.
  •  Satellite is resistant to high-temperature corrosion and also withstands the shock and wear associated
  • with valve operation. Some engine manufacturers use a nichrome facing on the valves. This serves the same purpose as the satellite material.
  • The valve stem acts as a pilot for the valve head and rides in the valve guide installed in the cylinder head for this purpose.
  • The valve stem is surface hardened to resist wear. The neck is the part that forms the junction between the head and the stem.
  • The tip of the valve is hardened to withstand the hammering of the valve rocker arm as it opens the valve.
  • A machined groove on the stem near the tip receives the split-ring stem keys.
  • These stem keys form a lock ring to hold the valve spring retaining washer in place.

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