Defects in investment casting will inevitably reduce the lifetime, degrade the quality of the casting, and increase the manufacturing costs. In this paper, the potential for shrinkage porosity was numerically determined and a retained melt modulus (RMM) model was implemented to analyze highly probable regions. The proposed casting schemes of gating designs are compared by the quality of casting (shrinkage porosity) and practical feasibility in terms of small hole drilling machinability. The purpose of this study was to determine the feasible plan with the lowest PES (percentage of elements with shrinkage porosity) while promoting near-net shape casting with minimum machining cost and increasing material usage. Virtual thermo-dynamical sensors (VTDSs) were adopted in the simulations to indicate the impacts of different pattern assembly gating systems on the cooling gradient and direction of solidification. VTDSs were used in simulating and virtually monitoring the casting systems, with the aim of characterizing the rates and directions of solidification in various regions of the cast. The best-case scenario of investment casting conditions was chosen to fabricate valve housing in an investment casting foundry. The experimental results of the X-ray image differentiated nearly none of the pernicious defects that typically occurred with the proposed casting, confirming the efficacy of the proposed scheme accordingly.