This dissertation studies the processing-microstructure-mechanical property relationships in the high pressure die cast A383 alloy. The high pressure die casting process has been widely used in automotive industry due to the rapid cooling rate and short cycle time. Much attention has been paid to the high pressure die casing aluminum (Al) alloys (A380, A319), however, there is still limited research concerning about the microstructures and mechanical properties of the high pressure die cast A383 Al alloy. In the proposed dissertation, the microstructures and mechanical properties of high pressure die cast A383 alloys will be systematically investigated as a function of casting conditions. First of all, the types, composition and distribution of Fe-rich intermetallics in high pressure die cast A383 alloy will be investigated by quantitative energy dispersive x-ray spectroscopy (EDS) and electron backscatter diffraction (EBSD) methods. Secondly, the relationship between cast microstructures and mechanical properties under a range of casting compositions and conditions will be studied. Thirdly, the distribution of nanostructures (twins, nano-clusters and aging precipitates) will be examined. Finally, the residual strains in the high pressure die cast A383 engine block will be studied by neutron diffraction techniques.