This study continues our ongoing investigation of magnetohydrodynamic (MHD) flows in poloidal ducts of the Dual-Coolant Lead-Lithium (DCLL) blanket with an insulating flow channel insert (FCI). We report our first 3D modeling results for an approximately ideally non-conducting FCI. The FCI and duct geometry match those of an experiment performed recently in Southwestern Institute of Physics (SWIP), China. The experimental FCI is made of epoxy and has a pressure equalization slot (PES) in one wall, which is perpendicular to the applied magnetic field. Previous 2D modeling efforts based on the fully developed flow model have demonstrated a significant difference with the experimental results in the MHD pressure drop, indicating 3D effects may be significant. The new 3D results, obtained with an unstructured, parallel MHD solver HIMAG, are in fair agreement with the experimental data. These results confirm a substantial reduction in MHD pressure drop by the FCI, but not as significant as would be expected under fully developed flow conditions.