A stock car, in the original sense of the term, described an automobile that has not been modified from its original factory configuration. Later the term stock car came to mean any production-based automobile used in racing. This term is used to differentiate such a car from a race car, a special, custom-built car designed only for racing purposes.
The actual degree to which the cars conform to standard model specs has changed over the years. Today most American stock cars may superficially resemble standard American family sedans, but are in fact purpose-built racing machines built to a strict set of regulations governing the car design ensuring that the chassis, suspension, engine, etc. are architecturally identical on all vehicles. These regulations ensure that stock cars are in many ways technologically similar to standard cars on the road.
Your Taurus, Monte Carlo, and Grand Prix will never race in a Winston Cup race. There was a day when a racer could literally go to a dealership and buy a race-ready car. That was a time when stock-car racing was much closer to stock than it is today. As race cars have evolved, they have, by necessity, become less of a stock car and more of an aerodynamic safety cage (just ask Richard Petty).
The original races were run on dirt tracks that got rutted and bumpy. The unmodified cars were not tough enough for this type of abuse, so NASCAR began allowing modifications to the stock cars to increase their durability.
Over the years, more and more modifications were made, sometimes to increase safety and sometimes to improve competition. NASCAR strictly controls all of these modifications. Cars are checked for compliance with these rules at every race. Many features in today’s racing platforms have been designed specifically for high-speed safety, and they would be hard to incorporate in a street car.
Roof flaps are one such example. Roof flaps are designed to keep a car from flying, and it would be unlikely that this high-speed feature would have any function on a passenger vehicle. Another example is the rollcage. The ‘cage does its job in a race car, but it would be a gross overkill in a consumer model–think of the loss of passenger space.
The point is that we all look to racing for drivers competition and brand-name supremacy. However, to believe that what we see on the track bears much resemblance to what we drive to the grocery store would be wrong. Today’s race cars have brand names on the front bumper and authentic looking headlight decals on the nose piece that tend to make the race cars resemble a specific production car. They also have a hood-to-rear-deck profile that resembles a car you may own.
Yet, the comparisons between the two pretty much end there. Today, NASCAR race cars have very little in common with street cars. Almost every detail of a NASCAR car is handmade. The bodies are built from flat sheet metal, the engines are assembled from a bare block and the frame is constructed from steel tubing.
So here we are with today’s high-tech race car that has proven to be worthy in both speed and safety, but it’s still called a stock car. The truth is that a Winston Cup car only has a few things in common with a consumer version of the same name. With that thought in mind, Circle Track looked at a Winston Cup stock car to see what is actually stock about it.
By NASCAR rules, the block and cylinder heads are required to be of original equipment manufacture. So both the block and heads come from Dodge, Ford or GM. The rearends used in the cars are still stock-production type. For those who are unaware, Chevrolet, Pontiac, and Ford all run a 9-inch Ford setup. Ratios of the gears, of course, vary as needed at a given track.
To run a car in Winston Cup competition, the car is required to be available to the public as a consumer production model. Both the Pontiac Grand Prix and Chevrolet Monte Carlo have counterparts available to the public. The Ford Taurus is also available to the public but in a four-door model only. The fact that the Taurus comes as a four-door is an important point to note because of the other requirement of a car type. The general profile of a production model is theoretically intended to be maintained in a race-car profile. The specific guideline is that the hood, roof, and rear-deck surfaces should resemble the consumer unit.
In the case of the GM passenger car, the profile is roughly equivalent to the race car, but because the street Taurus comes only as a four-door, some allowances were necessary to make a race version of it. This happened when the Thunderbird was phased out, and the Taurus became the car Ford put forward. The big difference is that the production four-door has a roof that is taller than the race version.
For the most part, examples cited here are the main features that are still regarded as stock in a Winston Cup car. It’s important to note that for a race car, not being stock is a drivers thing. Stock cars are not and never will be vehicles that were meant to be in circle-track competition. It’s safe to say that this is an axiom that applies to any racing done on any circle track. The bottom line is that you can go out and pull for your favorite brand name, but when you look at a race car up close, don’t expect it to be much of a stock stock car.
Race cars are Spartan inside, without creature comforts such as upholstery, glove compartments or cup holders. Like Dick Trickle, three-time Winston Cup champion David Pearson (1966, 68-69) had a cigarette lighter on the dash of his car. Pearson liked to smoke during caution flags. Up until the late 1970s, race cars had real doors that were welded shut. That changed after cars were downsized in the early 1980s. Today, the body shape may look like there’s a door there, but it’s a complete, seamless skin.
The stock car’s V8 engine is nearly unchanged since the days of the Model A, with no electronics allowed. The passenger car has a 3800 V6 supercharged engine with fuel injection. Race car engines are normally aspirated. They’re also rebuilt after running just a few hundred miles. The engine parts are specialized – made to withstand high rpms (7,800) and lots of horsepower (750). A racing engine costs $35,000 to $40,000, and almost every team builds its own.
The engine in the NASCAR race car is probably the most crucial component. It has to make huge amounts of power for hours on end, without any failures. You might think these engines have nothing in common with the engine in your car. These engines actually share many features with street-car engines. The actual engine blocks and heads are not made from the original tooling. They are custom-made race-engine blocks, but they do have some things in common with the original engines. They have the same cylinder bore centerlines, the same number of cylinders and they start out at the same size (they get a little bigger during the building process). Like the original engines, the valves are driven by pushrods.
The engines in today’s NASCAR race cars produce upward of 750 horsepower, and they do it without turbochargers, superchargers or particularly exotic components. How do they make all that power? The engine is large — 358 cubic inches (5.87 L). Not many street-cars have engines this big, and the ones that do usually generate well over 300 hp. NASCAR engines have extremely radical cam profiles that open the intake valves much earlier and keep them open longer than in streetcar engines. This allows more air to be packed into the cylinders, especially at high speeds.
The intake and exhaust are tuned and tested to provide a boost at certain engine speeds. They are also designed to have very low restriction — that is, to provide little resistance to the gases flowing down the pipe. There are no mufflers or catalytic converters to slow the exhaust down, either. They have carburetors that can let in huge volumes of air and fuel — there are no fuel injectors on these engines. They have high-intensity, programmable ignition systems that allow the spark timing to be customized to provide the most possible power. All of the subsystems, like coolant pumps, oil pumps, steering pumps and alternators, are designed to run at sustained high speeds and temperatures.
When these engines are machined and assembled, very tight tolerances are used (parts are made more accurately) so that everything fits perfectly. When an engine (or any part, for that matter) is designed, the intended dimension. Making the allowable error small — tightening the tolerances — helps the engine achieve its maximum potential power and also helps reduce wear. If parts are too big or too small, power can be lost due to extra friction or to pressure leakage through bigger than necessary gaps.
Several tests and inspections are run on the engine after it is assembled: Run on the dynamometer (which measures engine power output) for 30 minutes to break it in. The engine is then inspected. The filters are checked for excess metal shavings to make sure no abnormal wear has taken place. If it passes that test, it goes back on the dynamometer for another two hours. During this test, the ignition timing is dialed in to maximize power, and the engine is cycled through various speed and power ranges. After this test, the engine is inspected thoroughly. The valve train is pulled and the camshaft and valve lifters are inspected. The insides of the cylinders are examined for abnormal wear. The cylinders are pressurized and the rate of leakdown is measured to see how well the pistons and seals hold the pressure. All of the lines and hoses are checked. Only after all of these tests and inspections are finished is the engine ready to go to the races. Insuring the reliability of the engine is critical — almost any engine failure during a race eliminates the chance of winning.
Passenger cars have fuel overflow tubes, too, but they’re under the car. Race cars don’t have fuel gauges, so when the gas tank is full, the excess spills out. A crew member catches the overflow in a can, then measures that amount so the crew knows exactly how much is in the car and can precisely calculate gas mileage. A race car’s gas tank holds 22 gallons. The gas comes from a central tank to ensure teams don’t add additives. The gas cans used to refill cars hold 11 gallons each and weigh about 70 pounds when full. Racing gas is leaded, 104 octane. Development of an unleaded racing fuel is a year or two away.
Upon closer inspection, those headlights on stock cars aren’t headlights at all. They’re decals. The decals, added in recent years, are backed by the automakers eager to accentuate the resemblance between race cars and passenger cars. When NASCAR holds races at night, drivers can see because the tracks are so well lit. The hole near back windshield is not an air vent; it’s a spot to slip a tool in to make adjustments that affect the way the car handles. One hole is to make adjustments to the springs. A second hole lets you slip a tool in to adjust the track bar. The track bar affects the rear suspension.
Spoilers have been a feature on race cars for decades, but the size, shape and angle have varied over time. As speeds have grown, so has spoiler size. At all tracks except Daytona and Talladega, they’re used to create downforce and improve traction. At those two giant superspeedways, where carburetor restrictor plates are required to slow the cars, traction isn’t a problem, so the spoilers are used to create drag and further slow speeds. The size and shape vary slightly by car make because they must conform to the shape of the trunk.
One of the most effective safety innovations of recent years, the roof flaps basically serve as an air brake – similar to the flaps that pop up on the wings of an airplane when it lands. The roof flaps deploy when the car spins backward, and the force of the air pushes them up. That creates downforce, which helps keep a car that is spinning out of control at 180 or 200 mph from flying up in the air like a kite.
Windshield glass is not glass, but a type of plastic known as Lexan. Similar to windows in an airplane, it’s lighter and tougher to break than glass. For added support, there is a roll bar on each side of the windshield. An extra bar of reinforcement has been mandated for the center of the windshield since Dale Earnhardt’s violent crash at Talladega, Ala., in 1996 to keep large pieces of debris from flying into the car.
From an engineering standpoint, tires are the single biggest difference between a passenger car and a race car. Like the tires on your car, NASCAR tires are radial tires, but that is about the only similarity. The tires on a NASCAR race car have some very special requirements. You notice the width first – roughly a foot, as opposed to five or six inches for a regular car – and the fact that they are treadless. Both the wider footprint and lack of grooves help provide more traction and grip.
On a dry track, tires can generate more traction if more of their sticky rubber is in contact with the ground. Putting a tread pattern on the tire helps in wet weather, but in dry weather it is better to have the whole tire touching the ground. That’s why NASCAR races stop whenever the track is wet.
NASCAR’s top series uses only Goodyear racing tires, which cost about $350 apiece and are worn out after 75 to 100 miles, although track surface and driver skill affect tire wear. They don’t weigh as much as you’d think because of their thin construction. Because the car always turns left, the right-side tires bear more strain and are softer.
Most of the teams remove the air from the tires and replace it with nitrogen. Compressed nitrogen contains less moisture than compressed air. When the tire heats up, moisture in the tire vaporizes and expands, causing the pressure inside the tire to increase. Even small changes in tire pressure can noticeably affect the handling of the car. By using nitrogen instead of air, the teams have more control over how much the pressure will increase when the tires heat up.
The Car of Tomorrow, sometimes called CoT or “Car of Today”, is the car style for the NASCAR Sprint Cup Series. Larger and boxier than the design it replaced, the Car of Tomorrow is safer, costs less to maintain, and was intended to make for closer competition. The car was introduced in the 2007 Cup season at the Food City 500 on March 25 and ran a partial schedule of 16 races. The plan was to require all teams to use the new car in 2009, but NASCAR officials moved the date up to the 2008 season as a cost-saving measure. NASCAR Sprint cup series now requires fuel injection. Fuel injection replaced the carburetor as the fuel distributor in the Car of the Tomorrow starting in 2012. For 2013, NASCAR is allowing manufacturers to design a brand-new body style for the CoT chassis that will resemble a given production car even more.
The change is purely cosmetic, as the chassis and mechanics of the car will remain the same. The new Ford Mondeo Mk.5 will replace the current Mazda-based Fusion, and the Chevrolet SS will replace the Chevrolet Impala. The splitter is a piece of fiber-reinforced plastic used on the bottom front of the car to produce downforce, replacing the valance. The car’s exhaust exits on the right side, which diverts heat from the driver. The fuel cell is stronger, and has a smaller capacity 17.75 US gallons, down from 22 US gallons, which as of 2007 has become standard in all cars.
The car is less dependent on aerodynamics. It had a detached wing, which has not been used since the Dodge Charger Daytona and Plymouth Superbird in 1970. The windshield is more upright, which increases drag. The radiator air intake is below the front bumper of the car, which reduces overheating caused by clogged grilles. The front bumper is more box-like, which catches more air and slows the car. The front airdam is gapped, as opposed to being a flush piece on the older cars.
All cars are required to fit the same set of templates, using a device that has been named “the claw” that is designed to fit over the new cars. NASCAR’s old rules had a different set of templates for each manufacturer (Ford, Chevy, Dodge, and Toyota). NASCAR has frequently adjusted the rules to ensure that different car manufacturers have relatively equal cars. On Friday, January 15, 2010, Sprint Cup Series director John Darby informed teams that NASCAR would transition back to the spoiler, and get rid of the rear wing because it is contributing to flips.