"As far as water speed in the cooling system, the engine requires more than the radiator," Stewart says. "A few years ago the radiators required as much water speed as the engine. Today's radiators are more efficient, requiring only about 25 percent of the flow as before. However, engine water flow requirements have remained about the same. Stock water pumps do okay, but a good aftermarket pump will have a little more volume and have better longevity."
Looking at the end of the...
Looking at the end of the radiator with the end tank off, one can seethe tubes. Most OE radiators and some aftermarket models use four tubes.Some racing radiators, such as C&R Racing's, use two wide tubes. Theillustration shows how there is more water/tube/fin contact with widertubes. This means better heat transfer.
When asked about stock pump cavitation at high speeds, Howard says, "Stock pumps tend to cavitate when used with no pressure in the system--in other words, with the cap off. With a 24 to 26-pound radiator cap, my testing on the water pump dyno shows this doesn't happen. Use a restrictor in the water outlet from the engine to help stop steam pockets from forming in the heads.
"Always use a good fan shroud. The shroud should be long and the water pump short. This gives the air time to straighten out and pull from the corners of the radiator. The fan should have at least three fourths of the blade into the shroud, but it won't hurt much if it is further in.
Fin count of a radiator is...
Fin count of a radiator is measured in fins per inch. More fins attachedto the tube allows better heat transfer to the fins. This in turnexposes more fin area to the air. A low fin count plugs up about as easyas a high fin count. Use a high fin-count radiator and protect it fromtrash.
"Speaking of engine-driven fans, a metal flex fan should not be used. The blades don't completely flatten out at speed but they assume an 'S' shape. At this point, they pull little air and still soak up horsepower. In our testing on a cooling system dyno with the 17" six-blade stock car fan and the 19" four-blade tractor fan, both moved about the same amount of air. Surprisingly, the six-blade fan used slightly less power."
I went to Charlie Fewell of All Star Motorsports to ask about the use of electric fans in race cars.
"An electric fan is not a magic bullet that will save horsepower," Fewell says. "When using an electric fan on a race car, it must be of a size that will move the required amount of air. This fan will require a certain amount of power to move the air. To get this power, an alternator is required. The alternator takes power from the engine and after frictional losses in belts and bearings, it then turns this power into electricity. The electricity then powers the fan. The bottom line is, 'there ain't no free lunch.' You can move power around, but the same power is required to do a job no matter where it comes from.