I am going to agree with Jerry, he says factory designers weren't dummies. The used the best technology available at the time. Just like today's factory designers are not dummies. Just about every car on the road today uses an electric fan. Even the ones with a north south engine. Why because it is more efferent at the job.The guy that says a fan on a power stroke is pulling 25HP is either not a cooling fan engineer or forgot to move a decimal place. If he is including the water pump the number is probably still not correct but closer.
Electric fans are more efficient because they can be driven at the ideal speed for the fan blade shape. A mechanical fan operates over a large rev range. Also on the open highway you often don't need a fan, there is a lot of air being forced over the radiator to cool. At low speed or stopped the engine is at or near idle an a mechanical fan is not pushing much air when it is needed most.
What I did on a recent car (Jaguar XJ6) was measure the radiator and go to the local wrecker (not sure what you guy's call them maybe auto dismantler). I found the radiator of a local built late model ar called a Ford Falcon in Australia was almost identical size and these have a 4 liter engine. For a very small sum of money I walked out with an electric fan that was designed by one of those clever factory engineer types that did a brilliant job of keeping a 4.2 liter Jaguar engine cool in stop start traffic in an Australian summer and freed up a couple of horsepower.
Also something to consider when it comes to puller and pusher fans, apart from aircon condenser fans I don't think I have ever seen a pusher fan on a factory designed car. Refer to the first sentence and make your own judgment.
Steve
