C5 Twenty Five

Also from Issue 48

  • C6.R replica
  • 1966 restomod
  • Marcos TSO-GT2
  • Market Report: C1/C2
  • 800-bhp Supercharged C6
  • 1968 big-block convertible
  • Ex-Lou D’Amico C2 racer
  • How-To: Steering box rebuild
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Conveniently, Aaron Pfadt is no stranger to planning. The Salt Lake City engineer moved to Utah from Detroit a little over half a decade ago with his wife, Robbin. Aiming to start a small business, the couple gutsily left behind two solid jobs and almost everyone they knew. The result of their efforts is Pfadt Race Engineering, a company that specializes in suspension and race components for C4, C5 and C6 Corvettes.

Pfadt campaigns a C5 in the National Auto Sport Association’s (NASA) Super Touring 1 road-race class. It’s that car that he has brought to Thunderhill, complete with a well-organized crew composed of friends and employees. From the start, the prognosis looked good: Pfadt had raced in the 25 once before, in a Corvette-powered Porsche 944, and he did fairly well. He also won his class at NASA’s national championships in September. Going for a win at the 25-hour in a C5, a familiar car with the speed required to run up front, seemed like a logical next step.

Ninety minutes after Pfadt gives the order for Goldrich to press on regardless, another problem rears its head. This time, it’s the fuel system. “I paged through the digital dash,” Goldrich says after climbing out of the car, “and [the engine] was running really lean when the throttle was fully open.”

In the back of the Pfadt pit, someone lets out a groan. Positive thinking has ruled the day so far, but various problems have plagued the team since the first practice lap. Shortly after the car arrived at the track, input-shaft noises led to a late-night driveshaft removal. A wheel supplier shipped two rear alloys with the wrong offset, a mistake that resulted in a pair of shaved brake calipers and a lot of boiled brake fluid. Both fuel tanks were removed and inspected in order to try and trace an early fuel-starvation issue. Topping things off, the Corvette overshot Thunderhill’s noise regulations by a couple of decibels, and the solution required a time-consuming rearrangement of exhaust plumbing. All of this took place before the green flag dropped.

Three hours into the race, Pfadt holds court in the team’s support tent: At the risk of losing laps, the car is coming in. With just over 22 hours to go, both fuel tanks are coming out again, the in-tank fuel strainers are going to be removed and a second fuel filter is going to be plumbed in. While the car is off the track, Popp and one of the team’s mechanics will repair the leaking steering rack. The hope is that restoring some of the Corvette’s lost speed and making it easier to drive will be worth the downtime.

It’s been said that the Thunderhill 25 is NASA’s equivalent of the American melting pot, a race as diverse as it is large, and that statement isn’t far off: The starting grid for the 2008 25-hour was composed of 63 cars, no two of which were identically prepared. Because NASA prides itself on a run-what-you-brung approach to competition, disparity between entries is common. Professional race teams armed with 500-horsepower Daytona Prototypes, enclosed transporters and catering crews share the paddock with ramen-noodle budget racers fielding 100-bhp Volkswagen Golfs. Predictably, lap speeds vary greatly: Cars at the front of the pack often average 100 mph or more on Thunderhill’s 3.0-mile, 15-turn course, while the bottom end of the grid usually hovers around 75 mph.

Although the Pfadt team is just an amateur effort, its silver machine is one of the faster cars in the field. Even with fueling problems limiting his engine’s output, Aaron Pfadt was able to qualify with a 1:58.9 lap time, placing the car fifth on the grid. Pfadt is a talented driver, but a good part of his car’s speed comes from his engineering skill. He has something of a reputation as a suspension guru, and it’s not unfounded: At NASA’s 2008 National Championships, two of the three cars on the ST-1 podium wore Pfadt components.

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