Actually, I am running a huge aluminum radiator with a 16" 3000cfm electric fan and my car still gets hot during the summer months. When it is really hot out, the temp creeps higher than I feel comfortable with. When the clutch was disengaged on the old fan, I couldnt feel any drag at all when driving it. Only when it was engaged would I feel anything at all. I will most likely be going back to that set up for next summer. I'm sure if I had no clutch at all and it was always on it would feel a lot more sluggish though.
You shouldn't be having an overheating problem with an aluminum radiator. There has to be something else causing it. I have a 72 service manual for my Cuda. It lists possible causes of overheating: blocked radiator air passages, incorrect timing, low engine oil, incorrect valve timing, bad temp gauge, restricted overflow tube, faulty rad cap, frozen heat control valve, dragging brakes, excessive engine idle, frozen coolant, faulty fan drive, faulty temp sending unit, faulty vacuum bypass valve, overfilling, insufficient corrosion inhibiter, blown head gasket, broken or shifted lower hose spring, low coolant level, collapsed rad hose, fan belt lose, glazed, or oily, air leak through bottom hose, bad thermostat, water pump impeller broken or lose, restricted rad water passages or restricted engine water jacket.
