[rokndad]

My Dad used to fly for the Navy in the Phillipines in WW II and he told me when I was a teenager that those old radial piston-driven airplanes had water injectors for giving the engines a "little boost" and blowing out the carbon from the pistons and plugs.

I also recall seeing him use the hose with one of those "aqua guns" on the end, and using only the very smallest of misting inject it into the carb on our old V8 flathead when it was missing. Keeping the rpms up, because the water would make it want to stumble, the darn thing would smooth out after he did that. I think it had something to do with the fact that water doesn't compress in liquid state and a little bit of it introduced into the cylinders exploded in the combustion chamber thus blowing off the carbon. Just what I recall anyway, and wouldn't recommend anyone do it to engines today.