These are the cooling tubes...
These are the cooling tubes that hold the water that flows through the radiator. Different designs stack more or less tubes in the core depending on the cooling demands. Cooling tubes can also be different thicknesses.
Robertson at Fluidyne agrees and says it can even reduce a radiator's ability to cool the water. Slow-moving water, he says, allows laminar flow through the radiator tubes. Laminar flow means the water travels in a nice, straight line. The coolant flowing against the sides of the tubes stays there and gets nice and cool, which is good. But the coolant travelling in the center of the tube also stays there. Because it has no contact with the aluminum tubing, it does not have the same opportunity to radiate off as much heat and does not receive adequate cooling.
Engine coolant that rushes quickly through the radiator tubes, however, becomes turbulent. Instead of flowing smoothly, it moves more haphazardly through the tube, which promotes more homogenous cooling.
Care and Feeding
Once you have laid out your cooling system, it's important to take care of it properly to make sure it doesn't lose cooling capacity over time. Chet Blanton of C&R Racing points out that making sure you have absolutely no air in your cooling system is one of the most important things you can do to ensure its continued effectiveness. Air in the engine block-or especially the cylinder heads-causes hot pockets that the coolant cannot reach and promotes all kinds of bad karma. Also, if air pockets are pushed through the radiator's narrow cooling tubes, it can cause the tubes to swell and crack. Even if they don't crack, Blanton says the expansion can cause the cooling fins to be smashed together. Now you have a mystery on your hands. You have a radiator that used to work properly and it isn't leaking, but now for some reason it isn't adequately cooling the engine. It's a problem that can be difficult to diagnose.
One of the best ways to make sure air stays out of the cooling system is to run a surge tank. Instead of filling the cooling system through a neck in the top of the radiator, it is filled through a surge tank that connects to the radiator. The tank is mounted 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 in the system will find its way to the surge tank because it is constantly trying to find the highest point in the circuit.
Also, as you race-either on asphalt or dirt-the fins in the radiator will eventually become clogged with dirt, rubber, or other racing debris. Resist the temptation to blow all this junk out with the pressure washer when you're washing off the race car. A high-pressure stream of water can bend or otherwise damage the cooling fins. Robertson recommends only gently-flowing water to flush out the loose particles and periodically soaking the entire radiator in soapy water to remove anymore determined pieces of trash. He also strongly discourages the use of solvents. It may work the first time to get rid of pieces of tire rubber, but the residue of that solvent will remain and attack the next piece of rubber that becomes lodged in the cooling fins. This time, however, that will only be enough to cause the rubber to soften and swell, which will only make it that much harder to remove the next time around.
Cooling Better with Water Wetter
If your existing cooling system is struggling to keep your race engine at a manageable temperature, you may want to consider helping it out with Red Line Oil's Water Wetter product. Water Wetter is a coolant additive that is supposed to improve water's ability to absorb heat from the engine.