A three-dimensional engineered fiber preform having a unitary, integral and seamless structure and rigid composite structure made therefrom for use as a mechanical component, particularly for use as a valve, and method for making the preform. The integral design and structure of the preform is formed by a combination of interlacing and non-interlacing fiber systems that permits variable cross-sectional area and dimensions from a first end to a second end along an axis, or from a stem end to a head end of a valve. A particular embodiment of the invention is an integral design of a carbon—carbon composite valve structure for engines of internal combustion, formed by set of straight and interlacing continuous reinforcing yarns with the help of the device with the combined mechanical scheme, allowing to produce various types of axis-symmetric braiding architectures, including, but not limited to cylindrical, conical, and radial yarn placement to make an integral valve with continuously variable reinforcement architecture at various zones of the said valve.