I miscalculated the distance in front of my 350 and mounted an electric fan on the back of an aluminum rad because I thought the engine mounted fan was too far from the rad to be efficient. Duh! Now I have the electric fan in place AND there is enough clearance that the engine mounted one ALSO fits! I have both in place now and my question is - should this setup work OK without any kind of shroud?
I do not know for sure. Maybe mount another fan in front of the radiator. The people with experience with this will be here soon.
I'd think about removing the electric fan. Put a fan spacer on mechanical fan to get it near the radiator. If it doesn't overheat in the summer while idling at traffic lights, then no shroud would be needed.
The electric fan is just blocking the mechanical fan, I’d remove it. Get the mechanical fan the right distance from the radiator and go. A shroud always improves the cooling if done properly. What kind of car/installation?
With a good shroud, you can have the mechanical fan back a little from the radiator with minimal negative effect.
Oh boy, a buddy of mine back in the Bay has a '50 Plymouth with a SBC in it that likes to run warm. At one point it had a mechanical fan and an electric one inside the shroud. Still ran hot. If you don't have this problem then I would choose one or the other. I was never able to help him get it sorted out, with all of the timing adjustments, A/F adjustments and trimming the fender wells back to get the heat out, it fought everything we threw at it. Once the hood was ventilated it became bearable, but never right. It was a frustrating experience that spanned months.
As he has them, the air flow will be limited by the fan that is least efficient. The weaker fan will become an obstruction to the stronger one. The only way it would work is if the two fans worked "side-by-side" instead of in line. Think "in parallel" instead of "in series".
I would remove the electric fan and just run the mechanical one. But I would definitely use a shroud. That will allow the fan to pull heat from the radiator more efficiently. As the air flows through the radiator, the shroud will act like a funnel for the fan to pull the hot air out.
As stated, mechanical fan with a spacer. Build your shroud deep enough to cover 1/2 to 2/3 of the fan blade.
You could have the fan in the back seat, as long as you have a proper shroud/ducting making sure that as much as possible of the air moved by the fan is sucked through the radiator. It's when someone puts the fan some distance away from the radiator without anything forcing the air to move through the radiator it all fails. Mother nature is just like me quite lazy: if it's easier to suck air in from the sides between the fan and radiator than pulling it through the radiator, that's what will happen.
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