LO 9-5 Identify and describe the purpose, construction, and operation of components used in the valve train

1.3. Valve Face Angles

Valve Face Angles

Valve faces are machined at an angle so that they may wedge themselves into the valve seat and improve sealing. Valve face angles are measured from the horizontal. A 45-degree angle is common and is better at centering the valve at closure while wedging the valve tighter against the valve seat. Some manufacturers use alternate angles. Flatter angles of 30 or 40 degrees can be used on diesel exhaust valve faces to provide for better heat transfer. The valve face and seat angle also shape the valve face-seat gas flow characteristics. For example, some exhaust and intake valve face angles are flatter, using between 20–40 degrees to permit better flow over the edge of the seat when it begins to open. This flatter angle also creates less wear, resulting in fewer overhead adjustments.