How NASCAR Engines Work

The original NASCAR races were run on dirt tracks in regular street cars. Today, almost every piece of a NASCAR race car is handmade.
The original NASCAR races were run on dirt tracks in regular street cars. Today, almost every piece of a NASCAR race car is handmade.

­From the front air splitter to the r­ear deck-lid wing, a ­stock car sports scores of engineering achievements. Ironically, one of the most engineered parts of the car lies hidden from the view of most racing fans. We're talking, of course, about the engine.

Aside from assembling a great crew, one of the most important elements of winning NASCAR races is the ability to build -- or buy -- a monstrously (and reliably) powerful engine. While aerodynamic tweaks and suspension settings can give race teams an edge, just about everyone in NASCAR agrees that the engine is the heart of a race car.


­In NASCAR's Sprint Cup Series, those engines are rated at nearly 800 horsepower. Since NASCAR completed its transition to the Car of Tomorrow body style in 2008, engine power has actually increased to about 850 hp. These engines are so powerful that NASCAR forces member teams to restrict horsepower on certain race tracks, fearing that a 200-plus mph crash might send debris hurtling into the grandstands.

But what makes NASCAR engines so special, anyway? Can you simply stuff one beneath the hood of your Monte Carlo and proclaim yourself King of The Road?

This article will take a look at the engines of NASCAR and the vast amounts of effort and money that go into building them. NASCAR engines are expensive. Owners often spend $50,000 or more for a single engine just to be competitive. Spread that out among a fleet of more than a dozen cars, as most successful teams have, and the money adds up pretty quickly.

For their investment, these teams get a finely tuned and engineered piece of equipment that incorporates the most exotic and expensive metal alloys available. These teams may also have one or more engineering PhDs tinkering with the engine to extract every last drop of potential power from it. As you may have already guessed, careful design and extensive testing come standard when creating something as critically important to a stock car as its engine.

­By now, you may be wondering, "If everyone else's engines can only muster 800 or 850 horsepower, why wouldn't a team just build one with 900 or even 1,000 horsepower? We'll cover that next.

NASCAR Engine Rules

In NASCAR, technology is similar to an arms race. That is, teams are constantly looking for innovations that will make their cars faster and better than the rest of the field. However, if any one team finds too big of an advantage and starts winning too easily, that makes racing predictable and boring to the fans. Bored fans mean empty grandstand seats, which means less revenue.

Understandably, NASCAR goes to some pretty extreme lengths to ensure a level playing field. At the end of a race, you might see the driver spraying champagne on teammates and perhaps giving a quick on-camera interview. However, the day is far from over for the exhausted winning team. NASCAR officials then roll the winning car away and conduct a teardown, or dismantling, of the vehicle. This can include a complete disassembly of the engine, suspension system or anything else that the officials choose to inspect. They're looking for any irregularity, such as forbidden parts or measurements, which might unfairly enhance performance.


­Teams can and do take certain liberties with engine design, but a few NASCAR rules are quite rigid. The engine, for example, must be a carbureted V-8 with an iron block. NASCAR places strict limits, for instance, on how engine cylinders are bored -- that is, how they're made larger by removing material. NASCAR also requires teams to use blocks, cylinders and intake manifolds made from castings of approved manufacturers. The mandatory Car of Tomorrow design, mentioned earlier, standardizes engines even further.

These rules are clearly spelled out in NASCAR guidelines, yet there are often disputes between teams and officials about their interpretation of these rules. Teams can become quite inventive in finding ways to bypass the limitations imposed by a rule, only to have NASCAR become more specific and stringent with its language to eliminate the advantage [source: Martin]. This is one reason why stock cars are so uniform in dimension. The bodies have similar shapes and aerodynamic properties because they must conform to certain templates, or patterns mandated by NASCAR to ensure a consistent car size and shape. NASCAR maintains an equally explicit list of interior features that cars must have for both safety and to promote a reasonably level playing field.

­Now that we've got some of those pesky rules out of the way, we can look at some of the technologies that make NASCAR engines such powerful beasts.

What Makes NASCAR Engines Different

This engine is so pretty, NASCAR had to show it off.
Robert Laberge/Getty Images

­You may have heard racing people speak of "blowing an engine." That's just a bit of racing jargon referring to a critical component damaged enough to make an engine useless for the rest of a race. Blowing an engine can be something repairable and replaceable, such as breaking a connecting rod or damaging a piston. It can also be something catastrophic like cracking the engine block or melting part of the block. That begs the question: Just how do you break something made out of cast iron, reinforced steel and exotic metal alloys?

The answer is actually quite simple: Subject the engine to lots of heat and pressure. During the course of a race, which may last hundreds of miles, engines are subjected to multiple cycles of extreme heat and pressure. Certain racetracks, like the tri-oval-shaped Pocono Raceway in Long Pond, Pa., concern teams due to their layout and propensity for engine failure. The Pocono track requires a great deal of severe decelerating, then accelerating in the turns. This rapid transition of performance requirements produces engine fatigue [source: Martin].­


The temperature inside a NASCAR V-8 engine can reach 2000 degrees Fahrenheit and the pressure can reach 1500 psi, or more than 100 times the normal air pressure we feel around us every day. NASCAR engine parts are heavily reinforced to protect against these extreme conditions. In other words, they're bigger, stronger and thicker than their counterparts would be on a less powerful car. In fact, practically any moving engine part you can think of, from crankshaft to valves to valve springs to pistons, feature some reinforcement.

Some parts exposed to the worst of an engine's extreme heat use special metals to keep them from melting and fusing with another part of the engine. This is why valves are made out of titanium, for example. Titanium has the highest strength-to-weight ratio of any metal, is highly resistant to heat and corrosion and is considerably more expensive than more conventional metals and alloys. The engine blocks themselves are made out of cast graphite iron. Because of graphite's molecular structure, adding it to iron makes the resulting alloy stronger and more resistant to heat [source: Leslie-Pelecky].

While some teams build and maintain their engines in-house, others defray expenses by leasing their engines from someone else. One of the most well-known providers of leased engines is Hendrick Motorsports, which builds more than 700 engines per year for Hendrick race teams and outside clients.

Over the years, NASCAR engines have been highly refined to squeeze the most performance out of what many consider to be old-school engine technology. Nonetheless, the most recent cutting-edge advances in NASCAR have come in non-engine areas, such as aerodynamics and safety.

­With NASCAR teams constantly pushing the boundaries of racing know-how, cars have progressively become faster and more powerful. In fact, they got so fast that NASCAR officials worried for the safety of drivers and fans.

Restrictor Plates

A crew member prepares an engine for a NASCAR race.
A crew member prepares an engine for a NASCAR race.
Rusty Jarrett/Getty Images Sport

­Speeds can get pretty high in NASCAR. In 1987, driver Bill Elliott turned in an astounding qualifying lap speed of 212 mph at Talladega Superspeedway. During the actual race, Bobby Allison's vehicle suffered a sliced tire and went airborne into a retaining fence, narrowly averting catastrophic injury to the driver and hundreds of fans behind the fence. As a result, NASCAR brass decided to slow down the cars for safety's sake by introducing restrictor plates.

At Talladega and other fast NASCAR tracks, teams must use carburetor restrictor plates to decrease their engine's output. A restrictor plate is simply an aluminum plate with four holes in it to restrict the amount of air and fuel that can go into the engine.


The fuel and air mixture goes through the four small holes before it can enter the four larger holes of the carburetor and into the engine. Think of the overall effect as the difference between drinking a soft drink from a normal straw versus drinking it from a coffee stir straw.

NASCAR has a controlled process to select restrictor plates to prevent cheating: A team member gets to reach over a barrier to select a plate at random. An official raises the plate aloft for spectators, then inserts the plate on a pole to measure the hole diameter -- the holes are each about the size of a quarter, give or take a few fractions of an inch. After that, the official installs the plate on the team's engine before securing it with a NASCAR seal to prevent tampering [Source: ­Martin].

A restrictor plate can reduce horsepower by as much as half, from about 800 hp normally, down to 400 hp with the plate installed [source:]. Incidentally, many drivers have complained that the bunched-up style of competition known as "restrictor plate racing" actually causes more accidents. When one driver loses control, the cars' proximity can spark a chain reaction of crashes that drivers and fans have come to call "The Big One" [source: Busch].

­When it comes to building stronger and faster engines, NASCAR is among the major leagues. Like any high-level sport, becoming one of the best takes talent, hard work and experience.

Building Engines for NASCAR

Roush Racing crew chief Doug Richert explains engine design and performance to members of the North Carolina National Guard.
Roush Racing crew chief Doug Richert explains engine design and performance to members of the North Carolina National Guard. NASCAR engine builders are widely considered to be among the world's best.
Robert Nickelsberg/Getty Images News

­If you really want an idea of how much skill it takes to build a NASCAR engine, simply check out the MAHLE Engine Builder Showdown (formerly the MAHLE Clevite Engine Builder Showdown). In this televised contest, two-person teams of professional builders face off to see who can put together a running, 357-cubic inch, Ford Sprint Cup engine in the fastest time.

In 2008, the event took place at the NASCAR Technical Institute in Mooresville, N.C., one of the places that specialize in training technicians for the unique expertise required in NASCAR. The contest was broadcast on the SPEED Channel show "Two Guys Garage." The winners, Dennis Borem and Darrel Hoffman of Pro Motor Engines, built their engine in an astounding 15 minutes and 59 seconds, beating their own record from the previous year by nearly thirty seconds [source: MAHLE Clevite].


In addition to understanding the mechanical engineering principles of how engines work, you'll need to learn advanced diagnostic techniques. This may entail hooking up the engine to computerized measuring tools designed to maximize performance. One of the best-known engine diagnostic tools is an engine dynamometer, or engine dyno. This tool gives computerized screen readouts of torque, revolutions per minute (rpm) and horsepower, as well as other critical engine information.

Many team and independent engine-building programs have people with doctoral degrees on staff. They might study such specialized topics as fuel atomization and the properties of combustion "flame kernels," among other things. Some high-end engine builders come from careers working with major automakers. Of course, they all share the expertise necessary to thrive in the fast-paced world of NASCAR.

To find out more about NASCAR engines and other NASCAR-related topics, take a look at the links that follow.

Lots More Information

Related HowStuffWorks Articles

­More Great Links

  • Busch, Kyle. "Restrictor Plate Blues Strike Again." USA Today. Oct. 4, 2005. (Accessed Dec. 4, 2008)
  • "Evolution of a Stock Car - Part III." February 26, 2002. (Accessed Dec. 1, 2008)
  • Gillies, Mark. "In The Hot Seat - Sport (Drivers aren't huge fans of the Car of Tomorrow)." Car and November, 2008. (Accessed Dec. 4, 2008)
  • Leslie-Pelecky, Diandra. "The Physics of NASCAR." Dutton, New York. 2008.
  • Mahle Clevite Inc. "2008 MAHLE Engine Builder Showdown to Premiere on SPEED Channel's 'Two Guys Garage.'" Sept. 26, 2008. (Accessed Dec. 3, 2008)
  • Martin, Mark and Tuschak, Beth. "NASCAR for Dummies." John Wiley and Sons. 2005.
  • "Saving Fuel Top of Mind at the Track, On The Highway." Nov. 20, 2008. (Accessed Nov. 31, 2008)­
  • "Up to Speed On - Restrictor Plates." (Accessed Dec. 1, 2008)
  • Packman, Tim. "Financing a Top-Tier NASCAR Team." Popular Mechanics. July 2005. (Accessed Nov. 11, 2008)