Abstract: A ball check valve for use in a hydraulic chain tensioner. The ball check valve contains a check ball, a ball seat having a passage for the flow of hydraulic fluid, a coil spring to urge the check ball toward the ball seat and a retainer to house these components. The retainer has at least two peripheral walls along its longitudinal axis, each of which is either substantially planar or slightly convex so that the check ball contacts a single point on each peripheral wall as it travels between full compression of the coil spring and secure abutment with the ball seat. The gaps or openings between the peripheral walls minimize turbulence in the flow of hydraulic fluid.