A mechanical fan can draw as much as 20 horsepower at 6,500 rpm. That’s power that would otherwise go to the rear wheels, and a reason you may want to consider moving to an electric fan. Modern designs use ultra-efficient fan blades and powerful electric motors and do a better job of moving air through the radiator than older designs that often struggled to keep a race engine in the proper temperature operating range.

And other than the draw on the alternator (if you run one) an electric radiator fan causes no horsepower penalty. If you run short features you may even be able to get by running an electric radiator fan completely off your battery and not running an alternator at all. You may even be able to completely turn it off when racing under green-flag conditions if you’re moving enough air through the radiator to keep it cool on its own.

Don’t Restrict the Coolant

An old racing myth is that in order to maximize cooling efficiency you have to restrict the speed of coolant flow through the system. The thinking was that if the water travelled more slowly through the engine it would have time to pull away more heat. But that thinking won’t work for a few reasons.

First, restricting water flow through the cooling system causes the water pump to work harder than necessary. This not only can be a horsepower drain on your engine, but requiring the water pump to try to push water through a restriction can lead to cavitation. Cavitation hurts the system’s ability to cool the engine because it creates air bubbles in the coolant. And air not only doesn’t move heat as efficiently as water, but it can also get trapped in the water jackets and create steam pockets that lead to detonation.

Second, once the water gets past the restrictor, it moves more slowly through the radiator’s cooling tubes. Slow moving water moves smoothly through the tubes with little tumbling. It’s called “laminar flow” and when you have this condition the water that’s in contact with the cooling tubes is cooled while the water that’s in the center of the tube is insulated and isn’t able to shed its heat into the radiator and eventually the atmosphere.

But engine coolant that rushes quickly through the cooling tubes becomes turbulent. Instead of flowing smoothly, it tumbles through the cooling tubes so that it all comes into contact with the walls of the tubing. Turbulent flow promotes more homogenous cooling which makes for a more efficient radiator.

Servicing Your Radiator

Once you’ve selected the perfect radiator size and style for your racing application, you’ll also need to maintain it to make sure it’s performing just as efficiently at the end of the season as when you first installed it.

One of the most important things is to make sure you have absolutely no air trapped in the cooling system. Air trapped in the water jackets of either the block or cylinder heads, as we’ve already mentioned, causes high-pressure pockets of heat that the coolant can’t reach and causes all sorts of problems. Also, if air bubbles are pushed through the radiator’s cooling tubes it can cause them to swell or crack. And even if the tubes don’t crack, the expansion from swelling can smash the cooling fins together. This can be a difficult mystery to solve. You have a radiator that doesn’t leak or show signs of damage but isn’t cooling as well as it used to.

To keep this from happening, you should occasionally vent your cooling system. When routing your plumbing, make sure that the water neck on top of the intake is the highest point in the system. With the engine running, and before the coolant gets too hot, you can crack the line joining the water neck to vent the system until only water comes out. This helps eliminate any air that may have gotten into the cooling system.

Another option is to use a surge tank. Instead of filling the cooling system through the radiator cap, you can fill it through a surge tank that connects to the radiator through a length of flexible hose. The surge tank is mounted in the car so that it is the highest point in the entire cooling system, including the radiator, all hoses and cylinder heads. Water or coolant stays in the surge tank and is drawn into the system as necessary, and any air trapped in the system will find its way to the surge tank because the air will always seek out the highest point in the system.

As you race, getting trash built up in the radiator is inevitable. On dirt it’s usually mud, while on asphalt it’s bits of rubber and oil dry, but no matter what it is, debris caught between the fins blocks air from moving through the radiator core and should be removed.

Resist the temptation to blast it out when you’re cleaning the car with a pressure washer. This will normally only serve to push the debris in further, while a high-pressure stream of water can bend and damage the cooling fins on its own.

The best method for cleaning your radiator requires removing it from the car. Cap the openings to make sure no debris can enter either the headers or the tubing and run gently flowing water from a hose through the radiator from the back to the front. The idea is to push the debris back out the way it came. You may also need to periodically soak the entire radiator in soapy water to help loosen the more stubborn pieces of trash and debris.

Resist the urge to use any solvents. It may work the first time to get out pieces of tire rubber, but any solvent residue that remains will attack the next piece of tire rubber that lodges itself in the cooling fins. But instead of helping get it out, the solvent will only cause the rubber to swell and lodge itself even more securely in your radiator.

Cooling Boosters

Many class rulebooks allow only water in the cooling system—because antifreeze leaking on a racetrack is notoriously difficult to clean up—but if your class doesn’t have this rule you may want to consider a chemical additive that can potentially help increase the efficiency of your cooling system.

AMSOIL has long been an innovator in the racing industry when it comes to lubricants. And now it has introduced a new product called Coolant Boost that’s designed to both reduce corrosion (which can clog your radiator) and enhance the heat transfer capabilities of the water in your cooling system.

Coolant Boost contains chemicals that are safe for both your radiator and engine but also reduce the surface tension of the water allowing better contact with the metal surfaces inside the water jacket of the race engine and also the cooling tubes in the radiator. The idea is that the coolant is now better able to both draw heat away from the engine and to move it into the aluminum of the radiator.

While there are several different brands of coolant additives on the market, AMSOIL says it’s Coolant Boost additive is unique because it uses three different substances to reduce the water’s surface tension. The reason is each works best in a different temperature range, so the additive enhanced coolant works best at practically any engine operating temperature.

Leavitt Racing Components
174 Gasoline Alley
NC  28117
169-2 Gasoline Alley
NC  28117