DLM printing a head is possible. Nascar is doing a lot of prototyping with this method. But it is not cost effective and I would never call it cheap. Figure 3 to 4x cost of castings, but no tooling costs. Dereck's approach is still most economical. In addition, I've never seen a machine capable of printing anything that long. EOS are the most common. The only way to do it right is to section a head and laser scan. Otherwise you will be guessing much of the internal passages. If you could produce an exact 3d model, the printing is easy IF you are working with someone who knows how to run the machine and is familiar with aluminum alloys, not a bunch of grad students. And dont forget you still have the challenge of adding all the machine surfaces to the correct datums after printing. Not an easy task, just ask Derek.