Lightweight design concepts demand a constant pursuit of materials with excellent mechanical casting properties associated with economical manufacturing processes. It is of great importance to influence and predict local microstructure and its properties, especially in topology optimization. The main focus of this work is the possibility to influence local properties selectively with 3D printed cores. A trial casting with internal core and different wall thicknesses was constructed, simulated, calculated by casting technique and poured. The use of 3D-printed cores and targeted cooling measures locally influenced microstructures. With simple compressed air cooling, an increase in strength of more than 70% in the cast state was achieved, without additional heat treatment. By exact control of the local cooling, high strengths in combination with good tension properties can be combined in one component and high heat treatment costs can be avoided. Using recorded cooling curves, the boundary conditions in the simulation were adapted and more accurate predictions of the expected local properties were made. The knowledge gained in the experiments forms the basis for the design and topology optimization of real components, using local cooling rates and microsructure properties of cast iron materials.