Abstract: A portable apparatus for mixing and dispensing interactive liquid components (such as epoxy resins and catalysts) which utilizes reciprocable positive displacement pumps which are mechanically connected for simultaneous pumping and filling movement, there being a common single acting selectively adjustable drive for effecting only output pumping movement at preselected output pressure, and the pressure exerted by the liquid components themselves are required to hydraulically effect the filling movement, with the amount of hydraulic filling pressure which can be exerted by one of the component liquids being specifically regulated to be less than that required to effect filling movement. This insures maintenance of precise ratio mixing since the filling movement requires exertion of hydraulic filling pressure by both of the component liquids thus assuring precision ratio pump filling at all parts of the filling cycle independent of varying temperature dependent viscosity of the liquids.