Purple Power
I don't know if you have access to a cleaner called Purple Power or not, but it works well, especially for aluminum. I cleaned up my engine compartment with Purple Power and it looks brand new. It actually etches the surface of aluminum so you have a fresh new surface on the aluminum. DO NOT use it on polished aluminum surfaces, however, as it will turn the polished aluminum into a dull finish.
I also use it on the Edelbrock aluminum intake of my Camaro to keep it nice and clean looking.