A filter assembly having a filter head having inlet and outlet ports and a top cap having a substantially curved, non-planar flange portion, the non-planar flange sealingly received within the filter head such that the filter head is divided into inlet and outlet partitions. In some embodiments, the flange portion has a generally s-shaped cross-sectional profile. The flange portion incorporating a modified venturi for improved flow of both inlet and outlet streams through the filter assembly.