A regenerative heat exchanger includes a pair of heat exchangers, an inlet valve assembly and an outlet valve assembly. Each valve assembly includes two corresponding pairs of valve ports and two poppet discs each being movable between said corresponding pairs of valve ports. The poppet discs have rods extending to distal ends. Distal ends extending from the inlet valve assembly are pivotably interconnected to distal ends from the outlet valve assembly and pivotably interconnected to a crank of an eccentric mechanical drive to operate one of the inlet poppet discs and one of the outlet poppet discs in tandem.