Restrictor-plate gamesmanship: Here’s how teams gained more speed

Photo by Jared C. Tilton/Getty Images for NASCAR
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DAYTONA BEACH, Fla. – Eyes dart and scan the surroundings. Satisfied we are alone, a grin emerges. Still, because of the sensitivity of the subject, the person speaks in a hushed tone. One does not loudly boast about outsmarting NASCAR inspectors.

But they do boast.

“Oh hell, I’ve got all kinds of stories.”

While NASCAR discourages rule breaking with more severe penalties — including the recent announcement that officials will disqualify any car that fails inspection after a race — the sport’s history and part of its charm stems from those who broke the rules.

This weekend’s Daytona 500 marks the final race with restrictor plates. Tapered spacers will control horsepower moving forward. And so closes a chapter of ingenuity by teams to find extra horsepower. The storytellers prefer to remain anonymous but are willing to share with NBC Sports their cat-and-mouse tales through the years with officials.

One person recalls a time in the 1990s in what was then called the Busch Series. This was back when nearly 10 cars would fail to qualify for the season-opening race. This particular team was in danger of failing to qualify.

The team’s luck changed when a garage veteran offered a tip on how to make more horsepower: Slip a couple of acrylic washer rings between the restrictor plate and the carburetor. That gap allowed more air to flow into the engine and create more horsepower.

“We got them in and our car qualified in the top 10 and we’re scared to death,” this person said. “We’re going to end up being checked (by NASCAR).

“We were hoping to be under the radar, come in around 20th or 25th and just be in the race and we’re being held and I’m like ‘Holy crap.’ ”

They were eventually waved by and didn’t have to go through inspection after qualifying. As they headed back to the garage, the driver told the crew member: “Make sure you get them out of there!”

They did. The team didn’t use the rings in the race because the draft was enough of an equalizer.

“Never did anything like that ever again,” the person said. “I’ve never shared that with anybody.”

The need for such creativity came after Bobby Allison’s car destroyed a section of fencing in the May 1987 race at Talladega Superspeedway. NASCAR sought to slow the cars to keep them from exceeding 200 mph and getting airborne. That led to the use of restrictor plates. They also were used for a time in what is now the Xfinity Series.

With an inspection process less stringent years ago than it is now, teams found ways to harness more horsepower despite the restrictor plates.

Sometimes it was quite elementary. One person recalled asking inspectors for permission to tighten a nut after the restrictor plate had been inspected.

“You would have a mark on the stud and you knew that (the mark) had to be at 12 o’clock and you would leave (the nut) at 10 o’clock,” they said. “You would turn it and it would leak air. It was like a tunnel (of air).”

Anything to get air into the engine.

“They were all talking about air leaks … like somehow leaving the carburetor loose or get back in there and loosening nuts because if you could raise the carburetor up, then you sucked air underneath it,” another person said.

Someone else talked of making the plates slide along the carburetor.

“As you cranked (the engine), the vacuum would pull it and it would give eight or nine horsepower,” the person said of the widened avenue of air to the engine. “Enough to haul ass.”

Another person talked about having a bit of sandpaper on a fingertip and rubbing the finger around the inside of each four rings to smooth them and allow more air to seep through the restrictor plate into the engine.

And another noted how they would “offset the center of the baseplate to the restrictor plate so it wasn’t lined up anymore and that created more airflow. You misaligned it by creating a special baseplate on the carburetor. There was no rule against it. … It was worth about seven horsepower. It was a really big advantage.

“Finally people figured out what you were doing, and they came up with a rule.”

As so often happened, rules were added and the game of getting additional air through the restrictor plate became more challenging through the years.

Still, what was done, makes for some entertaining stories.

“There are so many great stories.”