A valve support for use with a valve in a combustion driven fastener hand tool, the valve being formed by a flexible disc affixed to a central shaft having a circumferential edge resting against an anular valve seat affixed to a wall of a combustion chamber with the valve in a closed position is disclosed. The valve support comprises a plate affixed to the central shaft and against the flexible disc, the plate having one or more ports therethrough. In a closed position, the flexible disc has a circumferential edge resting against an anular valve seat affixed to a wall of a combustion chamber but also a central portion of the flexible disc is proximate or contacting a central portion of the support plate on the same side of the disc as the annular valve seat. Various port configuration are possible.