Abstract: A valve assembly for use in a dual compression/dual expansion engine having an internal housing operating within an external housing, the valve assembly having a valve element operating in a valve guide secured to the internal housing with a valve spring provided to ensure proper closure of the valve element, and a valve train subassembly extending coaxially about the valve spring, the valve train subassembly operating slidingly in the external housing of engine in response to a valve actuation means, such that the valve element and the valve train subassembly operate independently when the valve actuation means is not actuating the valve element.