THe reason i did it was for prototyping. i didn't want to spend money on something that wasn't going to work and had to be modded lots of times. once the design is finalized i would definitely make them out of aluminum. right now i'm currently working on a manifold to mount an eaton m90 or m112 with intercooler to a small block mopar. will it work? i don't know. is it worth doing all the cad work? nope. this is something i can mock up in my garage late at night and make changes as i go. not to mention steel is cheaper than aluminum. the flanges i machined on my cnc. i made a fixture plate to make big block and small block flanges and can do one set at a time. i figure i can make them out of steel or aluminum or titanium if i chose later. right now the runners are made out of exhaust tubing so the interface to the manifold is plenum is round and then it goes rectangular at the flange end. the plenum is made from 18 gauge steel that i can cut with my harbor freight plasma torch and i can tig it together with my harbor freight tig welder. its more of a testiment to show what can be done in a garage on a budget. and yes even though i have cncs at my disposal my primary business is not automotive parts otherwise i'd be broke and out of business.

so for the little guy working out of his garage without the formula one budget i say use steel. for anyone else with the skills to work in aluminum good for you. i hope to acquire these skills when i get some time.