I've got a 91 F-250 302, is the fan shroud really necessary for cooling or is it a safety thing to keep fingers out of the fan?

 

It is necessary for proper air flow.

 

Yes, it keeps your fingers out, but it also directs the flow of air. Removing it will increase coolant temps during the warmer weather, and you'll risk overheating.

 

Unless you install an electric fan. No shroud needed. No power robbing fan clutch driven off a belt either. I've got a 14 inch electric fan w / a dual core all aluminum radiator. This cooling setup eliminates a lot of stock problems in the cooling area.

 

Fan shroud increases the cooling efficiency of your radiator, by more direct channeling of air through it.
Leave it on.

 

How come the 4.9L inline 6's have no shroud from the factory?

All they have is a cover on top of the fan to keep you fingers out of there. They have nothing going all around the fan?

 

The shroud increases cooling at low speeds. An electric fan is better than a fixed fan but the hydraulic fan clutch works pretty well. The biggest attraction of the electric fan is to help out at low speeds and it helps A/C performance. A fan big enough will put a pretty good load on the electrical system. In the past I have used single, duals, and an electric aux to supplement for towing. If an electric fan is going to be your only source of cooling I would go with duals. BTW all my fans came from the JY .
regards
rikard

 

Actually, a lot of car magazines have dyno tested new and old vehicles with mechanical fans then compared results with electric fans, and found that the older, hydraulic clutch mechanical fan leaves more horsepower to apply to rear wheels than an electric fan.

Part of the reason is converting from mechanical energy to electricity (alternator) is not all that efficient and converting from electricity back to mechanical energy (fan motor) is also not efficient.

The advantage of a mechanical fan is that it's simple and rarely breaks. Once in a while you might have to replace the fan clutch and that's four bolts and you're done in an hour. Since the fan clutch is a variable-clutch, fan speed increases with temperature.

The advantages of an electric fan (in my opinion) is more about packaging. If you measure the length of a mechanical fan, stem, clutch, and water pump snout that's a pretty long distance. Electrical fans are typically much more shallow and can be jammed in tight places (useful when swapping big engines into tiny engine bays). Some fans are also pusher fans, and take up no engine compartment space - they sit between the radiator and the grille.

And, from a CFM perspective, while a lot of newer electric fans have impressive numbers, the old style mechanical fan in a tight-fitting shroud typically has a 20-35% higher CFM rating.

Don't automatically assume an electric fan gives you back horsepower, because in most cases, it doesn't. But, it does solve a lot of packaging problems for sure.

 

I looked at dual fans and with a dual core all aluminum radiator i figured that it would be plenty good enough.