A valve for regulating speed of operation of a door closer, includes an elongated hollow tubular body having a closed first end with driving provisions thereon, an open second end, and an orifice in its sidewall adjacent its closed first end; an endplug for a cylinder bore of the door closer, the endplug having an axial port in which the closed first end of the tubular body is rotatably supported and which provides a fluid tight seal about the outer surface of the tubular body; an annular valve seat adjacent the endplug, the seat being fixed against rotation, and having an open portion and a closed portion which provide varying degrees of occlusion of the orifice when the tubular body is rotated; and a seal plate check valve captured against a piston head and occluding an opening therein during closing, the plate also providing a seal about the outer surface of the tubular body near the open second end thereof.