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

LO 9-05: Identify and describe the purpose, construction, and operation of components used in the valve train.

Valve Protrusion
When installing replacement valves or valves and seats, the technician must ensure that the correct amount of valve protrusion or intrusion exists Figure 37. The manufacturer’s specifications are compared with measurements made using a dial indicator and sled. A valve sunk too low into the head not only will have incorrect seat-to-face contact but also will prevent proper gas flow. This condition likely requires a replacement of the valve seat. A valve sitting too high in the seat could potentially contact the piston during the valve overlap period, causing catastrophic engine damage. If valve protrusion is excessive, the valve seat requires grinding to lower the valve seat contact and protrusion.

FIGURE 09-37: Measuring valve protrusion or intrusion is critical after replacing valves and seats. Too much protrusion will allow contact between the piston and the valve; too little will prevent proper gas flow.

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