I plan to run the engine on air, but have not tried to run it yet. I only have a small air compressor, so have to take it to a friends, that has a big compressor.
Started building engines about 12 years ago. As I had no machining background, went to the local Junior College, took lathe, mill, and CNC classes. Bought a Craftsman 12" lathe, drill/mill, and Taig CNC mill. Did all the small parts at home, as they had open lab at the JC shop, were I could do the large parts. With the budget mess, they cut the class, so I got a Bridgeport mill, and Grizzly 12" lathe.
I have built over 40 casting kits, most of them hit miss type. Some years back, read in a magazine that with the kit makers getting old, and the foundry problems people were having, if you want a kit buy it NOW. At one point, had over 20 kits, in the garage, which a lot of, you can no longer buy. Down to one, un-started kit, that is why, I made the steam engine.