Abstract: An unloading valve for hopper cars used for transporting dry fluent material such as carbon black. An unloading pipe extends outwardly from the bottom of the hopper, and a closure removably attaches at the end of the pipe. The closure includes a plug extending within the pipe and presenting a surface that confronts the dry fluent material adjacent the inner end of the pipe. This surface has an angle selected to cause fluent material loaded into the hopper to become packed at the inner end of the pipe during loading and subsequent shipment of the hopper car. When the closure is removed for attaching an unloading conduit to the pipe, the packed material at the inner end of the pipe prevents any of that material from leaking out the pipe before the unloading conduit can be connected.