Each week Winston Cup crews pull out $4 rolls of duct tape and make major changes to the performance of a $200,000 race car.

Crewmen use the tape to cover portions of the grilles on the cars, but what exactly happens when a crewman uses this sticky technique? Stock Car Racing turned to Larry Carter, crew chief for the No. 66 Ford of driver Todd Bodine, for the answer.

Generally, teams use one method of taping a grille for qualifying and another method for the actual race. The more tape that's used, the better the car is aerodynamically and the more downforce generated.

Before making a qualifying run, teams tape practically the entire grille, with some teams leaving a tiny opening to allow airflow to the engine. "Especially places where you get two laps to qualify, we try to be a little bit on the safe side," Carter says. "If something happens on the first lap, we don't want the motor to get too hot. That way we can run a second lap if we were to mess up on the first one."

On race day, grille tape takes on an entirely different life. The trick, Carter says, is to find the right balance between leaving enough open grille space for adequate airflow to the engine and having enough tape to achieve the right amount of downforce to make the car handle properly.

Carter says that before an event, the No. 66 Kmart crew applies tape in overlapping increments of 11/44 to 11/42 inch. Other teams may have different methods of taping grilles. Nonetheless, all teams have the same concerns when using tape. Too much tape on the grille, for example, can overheat the engine or, on short tracks, the brakes can become overheated. So preparations are made prior to a race to enable crewmen to pull tape off during the event if the car is running too hot.

"We really don't worry about that until Sunday morning," Carter says. "Then we'll put on some tabs or some zip ties with loops in them, just something so that if we get going and need a little more engine cooling during the race we can pull off a piece of the tape."

However, teams have to use caution to avoid taking off too much tape. "These engines have a temperature range they like to operate in," Carter says. "It's not as critical on the open motors, but on the (restrictor) plate motors we run at Talladega and Daytona if you get too much tape off and that engine gets too cool, it will really affect the way it runs. It won't run good at all. Or if you don't have enough opening and the motor gets too hot at Daytona or Talladega, it really hurts the performance.

"It's more (sensitive) on a restrictor plate situation than on an open motor. But on an open motor, if you've got too much air coming in and you're running cool, then you're obviously giving away some downforce we need on these downforce tracks."

Several factors-air temperature on race day, how closely the cars are running together on the track, even wind tunnel testing-contribute to the decision on how much tape to use initially.

"It's just based on experience, then we'll adjust from there," Carter says. "We'll check and see what the temperatures are during Happy Hour (the final practice before the race). If we feel like we need to change it, we will. Then on Sunday morning we try to make another educated guess on where we feel like we need to be and that's how we start."