By Bob Gates

Even though it’s been nearly 45 years since carburetors were last used on an Indy- car engine — the 1963 Fords of Jim Clark and Dan Gurney had them — Carburetion Day remains one of those traditional, cherished events so unique to Indianapolis Motor Speedway.
It’s just been in the last few years that the Speedway has officially called this popular event what the fans and media have known it as for years, Carb Day. A shortened, catchy version of what had been known previously as carburetion test day. Regardless of the name, however, in the past 10 years Carb Day has eclipsed all events at Indy, with the exception of the race, as a Month of May happening in terms of attendance, anticipation and excitement.
It’s for good reason.
The jam-packed day begins with a two-hour practice session for the 33 cars and drivers that have qualified for the race. That often hectic, sometimes drama-filled session is followed by the very popular Miller Lite Pit Stop Competition, and, since 2004, the Freedom 100 for the Indy Pro Series.
Sprinkled in with the racing are demonstration laps by historic and replica Indy cars, music, autograph sessions and a host of other fan-oriented activities. And, at  $10, it is one of the best deals in all of sports.
It is quite an evolution for a day that was originally intended to simply give competitors one last practice before the big event. The day has been part of the activity since the first race in 1911. That day often varied. Sometimes a practice session was held as late as the day before the race. Most often, though, it took place two or three days before.
Then in 1974, when the race was permanently moved to the last Sunday in May, Carb Day became a fixture on the Thursday before the race. That is until it was moved to the Friday prior to race day in 2005. 
Having the two-day gap between Carb Day and the race is important because it gives crews a chance to find problems and still have time to make repairs before the 500.
Through the years, Carb Day practice has indeed saved the race for many teams. Often a weak engine, a failing rear end or a fractured component was discovered that would have caused the car to fall out in the early laps of the race. 
In 1954, the Howard Keck team struggled with Bill Vukovich’s car all month. They thought they had the problem resolved, but in only a few laps on Carb Day, they discovered they had not. The practice did allow them to uncover the cause, however. They fixed it by the race, and Vuky drove to his second-consecutive 500 triumph. 
In 1969, Mario Andretti qualified his old, backup Hawk after he crashed his new, high-tech Lotus in practice. Clint Brawner, his mechanic, knew overheating with the Ford engine would be a problem and hung an external cooler on the car. USAC, though, insisted that it changed the configuration of the car after it had qualified, and officials wouldn’t allow it.
The device was removed, and the team used Carb Day practice to establish particular rpm parameters that would allow the engine to be competitive but survive. On race day Andretti won his first and only Indianapolis 500.
Sometimes Carb Day practice rather than aiding in uncovering problems creates them. In 1975, with only two minutes of practice remaining, Pancho Carter lost control of his Eagle Offy in turn one. The car slid hundreds of feet, clipped a fire truck and leaped a four-foot-deep drainage ditch.
Carter’s back was injured, but the car was in worse shape. The tub was nearly destroyed, and the rules didn’t allow it to be replaced with a new one. The original had to be repaired or Carter was out of the race. The remains of the car were transported to Steve Stapp’s nearby shop, and an around-the-clock repair effort was made by legendary fabricator Don “The Prince of Darkness” Brown. As a result, Carter finished fourth in the 500.
In 1986, an even more dramatic Carb Day accident occurred. This one involved four of the starters and drastically altered the starting field. A rear brake rotor exploded on Dennis Firestone’s car, blowing the tire and sending him directly into the path of Roberto Moreno. Moreno, in turn, slid into the pit entrance, where he clipped a slow-moving George Snider, and then slammed into the parked car of Josele Garza.
The drivers were unscathed, but a spectator and two crewmen were injured. The cars were a mess.
Snider’s and Moreno’s cars were damaged severely enough that they were forced to backup cars. Firestone’s car caught the brunt of the damage. It was sheared in half behind the seat and was beyond repair. Without a backup, Firestone was forced to miss the 500. Alternate qualifier Dick Simon took his place. Garza’s wrecked car was repaired after a banzai effort that lasted until race morning. 
Mario Andretti seemed to have actually benefited from the accident, as he moved from 33rd to 30th position. He had destroyed his car in a crash earlier in the month and was forced to the last row in his backup car. The Andretti fortunes being what they are at Indianapolis, however, the short change of luck was just that. On race day Mario ran only 19 laps and finished 32nd.
Other than running their cars, crews spend a lot of time on other facets of race prep on Carb Day. Pit-lane pit-stop practice is allowed for the last time on Carb Day, and a variety of race-encountered emergency scenarios are developed and practiced at that time — everything from the quick change of a rear-wing wicker bill to the switching of an entire nosepiece or side pod. All the mundane bits and pieces of pit equipment are checked and tested as well. At Indianapolis there’s sometimes even drama in the mundane. 
Driver or fan, people watching is certainly one of the main attractions of Carb Day. And people in various stages of unusual dress — and undress — add to the viewing amusement. Rock music fills the air. Kid Rock is to perform this year, permeating the Old Speedway with a carnival-like atmosphere as the month-long party that is Indianapolis begins a festive three-day wind-down.
Purists might argue that what’s happening on Carb Day is no longer just about racing. Maybe not. But, in today’s competition for the fan’s dollar, racing has to be an event. American open-wheel racing in particular needs more events.
And there are few happenings in all of sports like Carb Day at the Indianapolis Motor Speedway.