Fan and Pump Calculations for Cooling Systems

That was rather vague, but we can get a start on it at least. For an IC engine, about 1/3 of the energy goes to mechanical output, 1/3 to the water cooling system, and 1/3 out the exhaust. Because of variations, we might assume 40% to the radiator. A reasonable ΔT for water through the radiator might be 10°C (18°F). Using your customary units, calculate how much water flow you need (at this assumed ΔT or other assumption) to equal 40% of the energy/time value of the fuel. Reasonable water pressure drop through the system would be around 10 psi (23.1 feet ≈ 7 m head). To be on the safe side, we might say 10 m (≈ 33 feet ≈ 14 psi) of head. (But this will depend on the radiator.) Combining this head and the required flow will give you the pump selection.

For air flow, a similar calculation is made. The specific heat of air is 0.24, and in a warm engine room it weighs about 0.075 lb/ft³. With this information you can determine the required air flow. Depending once again on the radiator, and any air ducting involved, determine the static pressure at which the fan must operate. Then select a fan (and its rpm) that meets the combined air flow and pressure requirements.

That's pretty abstract, but without data, c'est la vie. Good luck! [By the way, it should be "system", not "sysrerm"--Editor Crankshaft]