How long did it run? I'm not familiar with SUs, but on my Quadrajet there is a pretty big float area that can let an engine run for quite a while. The first time I started my engine, I just dumped some gas in the float before I put the carb all the way together, then put it on the engine, then started it. Not the safest or smartest idea but it ran for about a minute with a coupel revs. Or maybe you just figured out the new alternitave fuel idea, engines don't actually need fuel, they just like to have it around!