Abstract: A concentric valve includes a first cylindrical housing and a concentric second cylindrical housing, with the second cylindrical housing defining an internal combustion intake valve mounted within an associated overhead valve assembly. An exhaust valve is mounted concentrically of the second housing, wherein the first housing directs intake flow through the intake valve and the exhaust valve directing flow coaxially of the first and second cylindrical housing through an annular array of windows in the first cylindrical housing to direct exhaust flow exteriorly thereof.