Its got probably 330 horses right now with aluminum heads what do you think it be approx.The material is not what establishes the performance. It is the shape, design, and volume of air flow through the ports. Editorial: If this persuit is all about the hobby--- have fun. Don\'t expect to make your money back on this car if you ever sell it though. In fact such modifications may reduce resale value. Editorial ended. Aluminum is easier to machine than cast iron and this is the biggest reason you find some high-performance heads in aluminum. A completely special designed part can be more easily machined, even from solid aluminum billet. Cast iron usually requires compromise in terms of being able to actually cast the raw part itself with roughed out shape in the sand mold. Even then if aluminum is sand-cast it is still easier to machine and clean up-- especially for low volume production. So you see many high-perf heads are aluminum. Its not the aluminum that does the job--- it is the design itself. Aluminum has better thermal conductivity for cooling, but that is not always an advantage when matching up to a cast iron block. It is a side consideration-- the shape of the combustion chamber and valve position and ports is what gets it done. Some engine makes have very good cast-iron performance heads that are factory proven and usually less trouble (like leaking head gaskets and all) than similar aluminum heads. Depending upon the make of engine you are working with, there are books, parts lists, and so on for various build-ups for performance. They list part numbers, advantages and disadvantages and so forth. Do a search on-line and it will be worth it to have the reference in hand. Summit Racing might be one place to start. If you have a particular part in mind, you can find the original specs from the manufacturer with some guidance to compare to their other parts and what are the advantages-disadvantages.everything being equal, aluminum heads will only make your engine lighter, not increase any horsepower. It\'s possible to buy aluminum heads that Will increase your horsepower, however the aluminum itself does nothing more than lower your weight. A lighter car moves easier.Head material does NOTHING. It is the DESIGN of the heads that is important. WHAT kind of car is this??Aluminum heads can crack easier depending upon WHO makes the heads and for what application. Expect NO real improvement. There are OTHER considerations, like intake system. cam shoice, compression ratio, and other factor5s. GOOD LUCK!!depends on the heads, what mods have been done to themid need a lot more details than you have furnished here to answer your question accurately.....Other related question