The present invention is a multiple-level stack mold for balancing the injection of molten plastic from an injection molding machine to a plurality of cavities, at least one cavity on each level of the multiple-level stack mold, for producing plastic parts facing in the same direction. Cavity plates are assembled in the multiple-level stack mold all facing in a first direction, and either core plates or plates having inserts thereon are assembled in the multiple-level stack mold all facing in a second direction. The clamping mechanism simultaneously moves the cavity plates and the core plates into engagement. Molten plastic is then evenly and simultaneously injected and distributed through a plurality of channels and passages, such that the flow of molten plastic is balanced throughout the system. Thereafter, the cavity plates and the core plates are simultaneously separated, thereby allowing removal of the resulting plastic parts, which are all facing in the same direction.