Cast aluminium alloy 354 has found widespread application in the automotive industry for its excellent mechanical properties and good castability. The stringent emission norms and demands for improved fuel economy have pushed automobile technology to new frontiers. This has led to efforts to reduce weight while maintaining higher vehicle performance. Cast aluminium alloy 354 is a material that performs with reasonable effectiveness in the high stress automobile environment. The present study looks at the use of strain energy density W and the quality index Qo to determine the effect of process parameters like aging temperature and modification on the quality of the alloy 354 and also to monitor the effect of interrupted heat treatments T6I4 and T6I6 on the quality of the material. The strain energy density W calculated for the interrupted heat treatments on alloy 354 show a broad inverse relation with yield strength Rp. An improvement in the yield strength and the strain energy density of the alloy is observed when the alloy is subjected to modification. At artificial aging temperatures lower than the artificial aging temperature adopted in standard aging treatment an improvement in the Qo and W quality of the alloy 354 have been observed.