The valve face contact surface should be concentric with the guide to ensure seating.

The valve face contact surface should be concentric with the guide to ensure seating.

• A. True
• B. False
• C. It should be perpendicular to the guide
• D. It should be parallel to the deck

Answer: (A)

Concentricity of the valve face contact surface with the valve guide axis is essential for proper seating. When the contact surface is coaxial with the guide, the valve seals evenly around the entire circumference, and the contact pressure is uniform as the valve closes. This prevents uneven wear, binding, and leakage and ensures the valve seats true against the seat. If the surface were not concentric, the valve could tilt as it closes, leading to an incomplete seal on one side and accelerated seat or guide wear. Being perpendicular to the guide or merely parallel to the deck do not guarantee that the seating surface remains aligned with the guide, so they don’t ensure a proper seal. That’s why this statement is true.

Concentricity of the valve face contact surface with the valve guide axis is essential for proper seating. When the contact surface is coaxial with the guide, the valve seals evenly around the entire circumference, and the contact pressure is uniform as the valve closes. This prevents uneven wear, binding, and leakage and ensures the valve seats true against the seat. If the surface were not concentric, the valve could tilt as it closes, leading to an incomplete seal on one side and accelerated seat or guide wear. Being perpendicular to the guide or merely parallel to the deck do not guarantee that the seating surface remains aligned with the guide, so they don’t ensure a proper seal. That’s why this statement is true.