Why all the hype about the elctric fans then!!!
You can not expect to get full coverage with electric fans. They use two 12" fans which are not as efficient as one 18" mechanical fan. Without a shroud covering the tip of the fan blade (mechanical or electric) you reduce the effective area of the blade by a third; as the air on that portion of the blade just slides off the end of the blade without a shroud to stop it.
Compute the area of two 12" circles (226.19 square inches) and compare that with one circle of 18" diameter (A=π r^2) circle of 254.47 square inches. Now consider that the majority of the air is moved by the portion of the blade furthest from the central hub (radial velocity increases with the square of the radius) which tells you that a blade 33% longer will move more air because of its increased area and the tip speed of the blade.
The biggest factor involved in moving the air through the radiator, and the reason the electric blades are so small is because it has a wimpy 1/6th of a horse power motor. Compare that with the power of a SBC. Which do you think could turn a bigger blade better?
The "reason" every one goes to the electric fans is because they are new! Trendy, Fashionable, (Iím just waiting for the introduction of a designer label electric fan with a spiffy exclusive icon). Oh yeah, that and all modern cars (not muscle cars from the sixties) have a lower hood line for better aerodynamics (dictated not by stylist but by the EPA for mileage reasons). If you stuck an 18" diameter fan centered on the water pump in a new (well this assumed they still had front wheel drive) it would slice through the hood. And as mentioned new cars are mostly sidewinders with the motor put in wrong, and driving the wrong end of the car. So a fan stuck on the end of the motor would miss the radiator by a few yards (or should I say meters?).
There is no reason any one can give me to put an electric fan on an early model Camaro, or third generation (1968-í74 Nova); same for a 1957 to 1996 Chevrolet (B-bodies). Some SUVís are saddled with electric fans, only because GM likes to have one part fit all, and since they donít make mechanical fans any more your Caddy (former Suburban when it cost half as much) is stuck with it also.