In the manufacture of complex thick composite structures, isothermal process modeling simulation tools analyzing the three-dimensional flow of resin impregnating the thick fiber preform are instrumental in initial process optimizations. We present a new implicit formulation based on accurately taking into account the transient nature of the time-dependent conservation of resin mass and employing the pure finite element method to implicitly solve for the pressure field and to track the flow front progression of the resin inside the mold cavity. Our emphasis is on thick composites. Our previous efforts involved two-dimensional thin sections  and the implicit type approach. The present method is an extension of that effort to three-dimensional thick composites. The numerical developments involving the present implicit methodology and tracking of the resin progression flow fronts provide an improved and physically accurate representation of the physical problem. They do not involve the time step restrictions based on the Courant condition as in the traditional explicit finite element-control volume (FE-CV) associated formulation discussed in Part 1 in this issue. Instead, we treat the transient process as a series of quasi-steady-state processes. For illustrative purposes, the present developments are first validated with simple geometries, then extended to practical applications for isothermal conditions, and finally, contrasted to part 1 in this issue of this study.