Restrictor Plate vs Tapered Spacer: What NASCAR Uses Now
Welcome to the Happy Hour Racing Wednesday Tech Breakdown - where we take one confusing part of NASCAR and make it make sense. No engineering degree required.
The Short Version
A restrictor plate was a thin metal disc with four holes that choked the engine down at Daytona and Talladega so the cars could not go fast enough to fly. NASCAR ran plates there for 32 years and then retired them after the 2019 Daytona 500. What replaced them is a tapered spacer, which does the same job with better airflow. That spacer is still on the engine today, at every single track, and swapping it is how NASCAR sets the horsepower number you hear about all season.
Why NASCAR Choked the Engines Down
On May 3, 1987, Bobby Allison blew a tire in the tri-oval at Talladega at around 200 mph. His Buick spun, got airborne, and went tail-first into the catch fence. The crash tore down close to 100 feet of fencing and debris injured several spectators. The car never made it into the grandstand, but it came far too close.
NASCAR's answer, starting in 1988, was to stop the cars from ever getting to those speeds at the two biggest tracks. Not with a speed limit, and not by making the tracks smaller. By starving the engine of air.
What a Restrictor Plate Actually Was
Here is the part that surprises people: the plate was about as low-tech as a part can get. It was a stamped aluminum disc roughly an eighth of an inch thick with four holes punched in it. It bolted in where the carburetor met the engine, and later, after NASCAR went to fuel injection in 2012, underneath the throttle body.
An engine is really just an air pump. The more air you feed it, the more fuel it can burn and the harder it pushes. Cap the air and you cap the power, no matter what the crew does with the rest of the motor. At most tracks in the plate era a Cup engine made about 750 horsepower. With the plate bolted on at Daytona and Talladega, that dropped into the 400s, somewhere around 410 to 450 depending on the year.
That is why superspeedway racing looks the way it does. When nobody has enough power to drive away, everybody runs nose to tail in a giant pack and passing becomes a group project. We broke that part down in our drafting and "Big One" breakdown.
Restrictor Plate vs Tapered Spacer: The Real Difference
A tapered spacer is a chunk of machined aluminum about an inch thick with four holes bored through it. The holes are not straight-sided. They taper inward at a 7 degree angle, which is about the steepest angle you can use before moving air peels away from the wall and starts churning.
That is the whole trick. A plate is a hole in a wall, so the air has to make a hard turn and then tumbles into the engine. A spacer is a funnel, so the air stays smooth all the way through. Same amount of restriction, much better behaved. The spacer also feeds the cylinders more evenly, and it is machined rather than stamped, so a tiny nick in the metal does not hand one team free horsepower.
NASCAR was already running tapered spacers everywhere else. The 2019 Daytona 500 was the last plate race in Cup history. After it, the superspeedways got a very small spacer, 0.922 of an inch, which put the cars around 550 horsepower. The plate era ran from 1988 to 2019, 32 seasons.
The Spacer Is Now NASCAR's Volume Knob
Here is the part worth knowing as a fan. Every Cup car runs a tapered spacer at every track, superspeedway or not. All of the horsepower numbers you hear argued about on the broadcast come down to which spacer NASCAR bolts on that weekend.
For 2026 the number went up at every track shorter than 1.5 miles plus every road course, from 670 to 750 horsepower, using a bigger spacer. That list covers Bristol, Martinsville, Richmond, Phoenix, Darlington, Dover, Iowa, Nashville, North Wilkesboro, Bowman Gray, New Hampshire, World Wide Technology Raceway, Sonoma, Watkins Glen, COTA, the Charlotte Roval and the San Diego street course. We covered what that does to the driving in our 750-horsepower breakdown. The intermediates and Michigan stayed at 670.
What Changed at Daytona in August 2026
The superspeedways are where this stays interesting. Since the Next Gen car arrived in 2022, Daytona, Talladega and Atlanta have run 510 horsepower with a 7-inch rear spoiler. For the summer Daytona race, NASCAR cut both: the spoiler down to 4 inches, the same as the intermediate tracks, and the power down to 465 to match the lost downforce. Less drag, less of a tow, and in theory more chances for a driver to pull off a pass on his own instead of riding around saving fuel.
NASCAR has announced that the rear spoiler for Daytona in August will be shortened to four inches (same as intermediate tracks), and horsepower will be reduced from 510 to 465 to adjust for the reduced downforce
— Steven Taranto (@STaranto92) July 15, 2026
The goal of these changes is to reduce drag and allow drivers to… https://t.co/IRnQat2qwA
Ryan Preece won that race on August 29. The drivers did not agree on whether the package worked. Daniel Suarez, who finished second, said "I think you can make runs actually by yourself. You couldn't do that before, so I personally thought it was a positive." Michael McDowell, fourth, said "I thought it raced pretty well. It seemed pretty racy." Christopher Bell, who finished 17th, went the other way: "It wasn't different at all, and it was worse." Brad Keselowski said he could not tell the rules had changed at all.
NASCAR called it a one-race look for now. Whether it shows up again at Talladega or next February is still open.
The Bottom Line
No, NASCAR does not use restrictor plates anymore, and has not since February 2019. The part doing that job today is a tapered spacer, a one-inch block of aluminum with four cone-shaped holes that sits on top of the engine on every car at every track. It is the reason a Cup car makes 750 horsepower at Martinsville and 465 at Daytona in August. Next time the broadcast throws a horsepower number on the screen, you will know exactly which part put it there.
Superspeedway racing is its own sport, and the gear should say so. Grab the 2026 Daytona 500 trophy car tee or the 2026 Daytona 500 patriotic event hat. If Talladega is more your speed, there is the Chase Briscoe Talladega win shirt. And if you liked what the drivers who liked the new package had to say, rep Daniel Suarez or Michael McDowell. New tech breakdowns drop every Wednesday.
