A stem assembly for a valve including a shaft having a longitudinal axis and a first end having a cross section less than a cross section of the shaft, and a protrusion near the first end extending away from the axis. In response to the first end and the protrusion being positionable inside a compartment of a valve plug having an opening in fluid communication with a fluid of a valve during operation of the valve, the first end and the protrusion being movable between a first position and a second position relative to the valve plug. In the first position, the first end blocking the opening for preventing fluid flow therethrough, and in the second position, the first end being movable away from the compartment opening for permitting fluid flow through the opening.