An edge-gated injection molding apparatus is disclosed having an injection manifold assembly for distributing a melt stream of moldable material to a plurality of mold cavities aligned on opposing sides of the injection manifold assembly. The injection manifold assembly includes a plurality of melt outlets with each melt outlet being in fluid communication with a respective mold cavity, and a plurality of biasing components disposed along a centerline of the injection manifold assembly. A nozzle seal is disposed between each injection manifold assembly melt outlet and its corresponding mold cavity, with an upstream end of the nozzle seal being slidably disposed against its respective melt outlet. Each biasing component is disposed between a pair of melt outlets and corresponding nozzle seals for biasing the melt outlets and nozzle seals outward from the centerline of the injection manifold assembly toward their respective mold cavities and applying a preload thereto.