Once Stewart decides what the track will take, two variables are set. One is the amount of weight added or subtracted to the primary "fingers" which are six little arms that apply pressure to the clutch at the initial launch. This is calculated via per-finger gram weight measured by half-nuts; to take three grams off (which is the weight of one half-nut) means that you will remove a total of 18 grams from the clutch. A fair total average would be approximately 90 grams total, or 15 grams per arm, with half-nuts added or removed, based on conditions.
Meanwhile, a group of pneumatic timers that will be activated by a micro-switch under the accelerator are set as well. These timers are attached to the clutch housing via pressure-fed air lines, allowing the throw-out bearing to transfer more and more horsepower to the output shaft and rear wheels by closing an air gap between the clutch discs. Secondary fingers handle this using the applied air pressure. In the case where a track is really hot or slippery, the clutch may be slipping to some extent during the entire run.
This technology has allowed drag racers to go from 0 to 320 mph through the rear tires in a quarter-mile; without the clutch slippage, the car would instantly spin the tires right off of the starting line. As the car progresses down the racetrack, more power is applied to the rear wheels via downforce and speed. John uses a metering block with a group of five air jets (like Holley carb jets), one for each line, that controls the amount of pressure that will go to the clutch during the run, while the timers are set so that they are actuated in microsecond increments. So as the car leaves the line, timer 1 will come in at .62 seconds, timer 2 at 1.48, timer 3 at 2.12, and so on, until the car is applying all 5,000-plus horsepower to the racing surface. Tire heat and growth is also critical to making this happen.
The team will normally attempt to go out on their first run with less clutch than they might need, in hopes of establishing a solid baseline. Since this lap is normally during the heat of the day, that first lap will give them a potential setup for the better, cooler evening air. Stewart said he doesn't make serious adjustments in the staging lanes unless the weather changes considerably; both he and Larsen both agree it is easily possible to "out think" yourself in one of these things.
THE TEAM: The Heroes
Nothing is simple about fuel racing, and Stewart and Larsen spend so much time analyzing data, they really can't be hands-on mechanically, even if they want to. So, a group of guys spin the wrenches between rounds, making sure the car is ready to go for the next run. While Dean is busy talking with the fans and sponsors or playing with his son Don II, Lance and John are in the truck determining air/fuel ratios and clutch settings, and patriarch Don is mixing fuel and performing other tasks while seven guys are thrashing on the equipment.
THE FUEL FRONTIER
Racing nitro isnt for everyone. If you want to stay at home most of the time and avoid crowds and hot, dirty work, or avoid the agony of working all weekend to see your efforts go up in a instant puff of smoke (or worse, a ball of fire), you're probably not fuel-racing material. On the other hand, as Skuza said, nitro is like a chemical addiction: the smell of it burning, the cackling sound of the horsepower with its licks of flame, and the incredible speed and danger of explosion. Many former racers admit that they never go back to the track once they quit. The fact that every machine on nitro at major meets derives its heritage from Mopar engineering makes it all the sweeter for Chrysler fans.
"NHRA Winston Drag Racing is the only form of motorsports that is completely 'maxed out'," said Skuza in conclusion. "We're not worried about conserving tires or anything for that matter. We take the most modern technology and apply it to go as quick and as fast as we can...whatever it takes at any cost. Is that American or what?"