Mike, What is the temp that you run your engine at? My guess is some where close to what ever the boiling point of water is at the altitude you are running at.
Using the "latent heat of evaporization" means that what is cooling Mike's engine is the energy required to change the water that he sprays on his radiator into steam, which in the case of water is about 970 btu/lb. So if he is spraying two gallons of water, weights about 6.7 lb/ gallon then he is dissipating about 13,000 btus on his El Mo runs and 33,000 btu(s) at Bonneville, this combined with the the thermal inertia of the engine water and the radiator provides more than sufficient heat rejection. I think that IO (Interested Observer) at one time suggested this method. Obviously it works. This also works for the alcohol fueled engine as the latent heat of evaporization for methanol is 470 btu/lb and if you look at spraying 30 gallons through the engine then the reason that they can live with out water jackets begins to become obvious.
Rex