81 wagon - you are indeed correct in assuming that wetting the radiator will help cool it. the question is how much and is it worth it? Either way, it would be a fun experiment. You could for example use a few spray nozzles from an old windex containers and manifold them so they all make a wide, fine mist. Degrease the hell out the outside of your radiator, so all the water sticks to the rad. It's the evaporation from the surface that carries away the heat. If your water is pumped from an insulated cooler it will be of course much more effective than water at underhood temps of maybe 140F. But here's another idea... Turn off your wonderful A/C, roll down all the windows and turn your HEATER on full blast. During short bursts your passengers shouldn't get too uncomfortable and the heater ABSOLUTELY pulls extra heat out of the cooling system and exhausts it out of the car. I've done this with several vehicles over the years and it always helps a good deal.