My first 2 RVs were E350 class C (a 1979 23' Roll-a-Long, and a 1988 26' Jamboree) with the 460, although both of mine were carb, not FI. However, I live in SoCal, and cross the desert often in 100, 110, 120 degree heat. Both would get me across, but I had to really watch the temps. I realized that the heat coming off the pavement, at 120 degrees, and flowing through the radiator, was not very conducive to actually cooling the engine; I needed a way to actually cool the air before it hit the radiator. Believe it or not, I added a mist system.
I tapped into my fresh water system (after the water pump) and ran a small line (1/4" irrigation drip line) forward. I had a 1/4-turn valve in the line right where it passed the stepwell on the driver side, and mounted the valve so the the lever was accessible from the driver seat. The line then went forward to the grille, where I mounted 5 small mist nozzles (the type used for outdoor patios), spaced out around the front of the radiator just behind the grille.
On really hot grades, as I watched the needle slowly climb towards the "H" on the temp gauge, I would reach down and flip the valve. Almost immediately, the slow upward march of the needle would stop in it's tracks, and often even start dropping.
