Microstructure evolution and loss in mechanical properties due to ageing, in cast aluminium alloys used by different manufacturers for cylinder-heads with various initial heat treatments and amount of copper was studied. Two have been chosen as references, namely AS7U3G T5 (ASTM319) and AS7G03 T7 (ASTM356). They were subjected to different heat treatments, from the as-received state to saturated ageing state and studied in fatigue, with hardness evolution and by TEM image analysis. After numerical identification, a link was established between microsructural evolutions and phenomenogical modelling. Ultimately, the objective of this approach is to build a descriptive model for life prediction and behaviour of the cylinder head as a fonction of the chemical composition and heat treatments.