How to choose an electric fan to keep your radiator cool

Electric fans offer benefits over traditional belt-driven fans

One of the more-important facets when restoring or upgrading a collector classic car is the cooling system and the role the fan plays in keeping everything running at proper temperatures.

It’s certainly not the sexiest part of the engine, but fans are key to keeping air moving through the radiator and other parts to avoid overheating. Some engines come with belt-driven fans, which move more air at higher rpm but take up more space, sap overall horsepower and can accidentally hit the radiator or shroud in some vehicles, while decreasing the life of the water pump in others. They also don’t move a lot of air at idle.

Although moving less air at higher rpm, electric fans offer a good deal of benefits. They’re slimmer, don’t steal horsepower and can help keep things cooler while the engine idles.

But selecting the correct fan can be problematic as there are numerous options in styles and models.

The first decision is whether you need a pusher fan or a puller fan. The pusher fan mounts on the front of the vehicle and blows air through the radiator core toward the engine. It’s not a bad option, but it can restrict airflow, which is why experts at Holley recommended using a puller fan whenever possible – basically, if you have room under the hood for a puller fan, go that route.

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“A puller fan … sits right behind the radiator,” host Ray Frescas says in the video above. “It pulls air through and has less impact on airflow at high speeds than a pusher fan since it sits behind the radiator. Puller fans provide more cooling capacity than pusher fans.”

The second factor when picking an electric fan is the diameter. You want one that covers as much of the radiator core as possible. Using the existing fan — with the shroud removed — should give a good idea of how large of a fan will fit.

Single- and dual electric-fan setups are available. The single should be adequate for most drivers, but those with bigger engines or a good deal of added horsepower, a dual fan should be considered.

There are two blade types: curved and straight. The curved blades don’t move as much air but offer quieter driving. The straight blades move more air but they are louder. If installing one into a high-performance engine, the straight blade is the way to go.

CFM — cubic feet per minute — is the rating given to every fan, signifying how much air a fan moves.  Bigger engines with more horsepower should use fans with the highest CFM rating possible. But aside from engines with extensive modifications, there’s a set of guidelines:

  • • 1,250 CFM for a 4-cylinder
  • • 2,000 CFM for a 6-cyliner
  • • 2,500 CFM for an 8-cylinder
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Another factor that can affect the amount of airflow an electric fan is capable of moving is the current it draws. This one is simple: The higher the current draw, the more airflow it has.

When wiring an electric fan, use a relay kit. These include sending units that lets you select the temperature at which the fan should start working.

No matter which fan you go with, use a shroud. Fans are basically useless without them as they direct the airflow through the radiator core.

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