Cam apparatus for use with valves are disclosed. An example apparatus includes a cam having a cam surface to engage a valve stem, a first portion of the cam surface to engage the valve stem in a closed position, a second portion of the cam surface to engage the valve stem in an open position, and a third portion of the cam surface adjacent the first portion and defining a curved profile. The third portion is to engage the valve stem when the cam is rotated to a first intermediate position between the closed position and the open position. The example apparatus also includes a fourth portion of the cam surface between the second portion and the third portion and defining a linear profile. The fourth portion is to engage the valve stem surface as the cam rotates between the first intermediate position and the open position.