Some aluminium alloys can be strengthened through ageing process and alloying. The alloying elements will stimulate the formation of precipitates that finely and uniformly distributed. This paper discusses the effect of alloying with Sn on the properties of 319 cast alloys (Al-6Si-2.8Cu), to be used for automotive parts. Observation on the microstructure of the materials was conducted by using light microscopy and SEM (scanning electron microscope) equipped with EDS (energy dispersive spectroscopy). Research results show that minor addition of Sn up to 0.1 wt. %, increased the peak hardness of the alloys. This is due to enhanced formation of interdendritic structures. However, addition of more Sn seems to give rise to detrimental effects on mechanical properties. Alloys cast in metal mould possess better mechanical properties than those in resin-coated sand mould.