NASCAR, the highest governing body and top level division for stock car racing in the United States, has used a range of different types of engine configurations and displacements since its inaugural season in 1949. The engines are currently used in the Cup Series, O'Reilly Series, Craftsman Truck Series, and the Whelen Modified Tour.
Overview
The 1949 Oldsmobile Rocket V-8, with a displacement of , is widely recognized as the first postwar modern overhead valve (OHV) engine to become available to the public.Automotive History Online "Oldsmobile advances" Retrieved May 13, 2009. The Oldsmobile was an immediate success in 1949 and 1950, and all the automobile manufacturers could not help noticing the higher sales of the Oldsmobile 88 to the buying public. The motto of the day became "win on Sunday, sell on Monday."
At the time, it typically took three years for a new engine design to end up in production and be available for NASCAR racing. Most cars sold to the public did not have a wide variety of engine choices, and the majority of the buying public at the time was not interested in the large displacement special edition engine options that would soon become popular. However, the end of the Korean War in 1953 started an economic boom, and then car buyers immediately began demanding more powerful engines.
During the early days of stock car racing, more horsepower ultimately meant more wins. The sleek and aerodynamic Hudson Hornet managed to win in 1951, 1952, and 1953, using a flat-head inline six-cylinder engine.
In 1955, Chrysler produced the C-300 with its Chrysler FirePower engine OHV engine, which easily won in 1955 and 1956.
In 1957, Chevrolet sold enough of their new fuel injected engines to the public in order to make them available for racing (and Ford began selling superchargers as an option), but Bill France immediately banned fuel injection and superchargers from NASCAR before they could race. However, even without official factory support or the use of fuel injection, Buck Baker won in 1957 driving a small-block V-8 Chevrolet Bel Air.
In 1961, Ford introduced the "FE" (Ford-Edsel) 390 in a low drag Galaxie "Starliner", but 1960 and '61 championships were won by drivers in 409-powered Chevrolet Impalas.
Pontiac introduced their "Super Duty" 421 in Catalinas that made use of many aluminum body parts to save weight, and the Pontiacs easily won in 1962.
It became apparent that manufacturers were willing to produce increasingly larger engines to remain competitive (Ford had developed a 483 they hoped to race). For the 1963 season NASCAR engines were restricted to using a maximum displacement of , and using only two valves per cylinder.
Then, in 1964 the new Chrysler 426 Hemi engine so dominated the series in a Plymouth Belvedere "Sport Fury", the homologation rules were changed so that 1,000 of any engine and car had to be sold to the public to qualify as a stock part, instead of just 500. This made the 426 Hemi unavailable for the 1965 season.
In 1965 Ford adapted two single-overhead-cams to their FE 427 V8 to allow it to run at a higher RPM (called the Ford 427 Cammer). Ford started to sell "cammers" to the public to homologate it (mostly to dealer-sponsored privateer drag racers), but NASCAR changed the rules to specify that all NASCAR engines must use a single cam-in-block. But even without the cammer, the Ford FE 427 won in 1965. This engine powered the early-to-mid-1960s Ford Galaxie, and produced @ 7000 rpm, and at 3800 rpm, using a standard single four-barrel carburetor, and over using a double four-barrel carburetor.
In the 1980s, NASCAR Xfinity Series competitors began looking at alternatives from the 5-litre based ( engines, as in short track racing there was a push for six-cylinder engines to save on costs, with some series allowing weight breaks. One popular idea was to use six-cylinder engines; instead of Cup Series' V-8s.
In 1989, NASCAR changed rules requiring cars to use current body styles, similar to the Cup cars. However, the cars still used V6 engines. The cars gradually became similar to Cup cars.
1994 was the final year that V6 engines were used in the Busch Series, as many short track series had abandoned six-cylinder engines.
In 1995, changes were made. The series switched to V-8 power, with a compression ratio of 9:1 (as opposed to 14:1 for Cup at the time). The introduction of V-8s, made the two series' cars increasingly similar.
The cars are currently powered by EFI V8 engines, since 2012, after 62 years using carburetion as engine fuel feed with compacted graphite iron blocks and pushrod valvetrains actuating two-valves per cylinder, and are limited to a 358 cubic inch (5.9-liter) displacement. The 2011 Sprint Cup season was the last complete Cup season with carbureted engines; at the end of the 2011 season, NASCAR announced that it would change to an electronic fuel injection system for the 2012 racing season. NXS cars do, however, continue to use carburetors. However, modern technology has allowed power outputs near in unrestricted form while retaining the conventional basic engine design. In fact, before NASCAR instituted the gear rule, Cup engines were capable of operating more than 10,000 rpm, and producing near .USAToday"Debut of new rules could offer glimpse at road ahead" Retrieved August 25, 2008. A NASCAR Cup Series engine with the maximum bore of and stroke of at 9,000 rpm has a mean piston speed of 80.44 fps (24.75 m/s). Contemporary Cup engines run 9,800 rpm, 87.59 fps (26.95 m/s), at the road course events, on Pocono Raceway's long front stretch, and at Martinsville Speedway (a .526-mile short-track). At the backbone 1.5- to 2.0-mile tri-oval tracks of NASCAR, the engines produce over 850 hp running 9,200-9,400 rpm for 500 miles, 600 mi for the Coca-Cola 600 Charlotte race. The current NASCAR Cup engines curb weight is roughly at .
For the 2015 NASCAR Cup Series, power output of the competing cars ranged from 750 to 800 hp (560 to 600 kW).
The engines used in the final iteration of the Generation 6 cars were limited to on tracks 1 mile or below; on tracks greater than one mile (2019–21)
Modern contemporary NASCAR engines are capable of producing well over 2 hp/cu. in. (up to 2.5 hp/cu. in.).
Currently, Next Gen NASCAR engines are rated at for road courses, short tracks, and intermediate ovals less than 1.5 miles, intermediate ovals 1.5 miles or bigger, and for restrictor plate racing.
NASCAR will test a hybrid powertrain at the 2023 24 Heures du Mans in the Next Gen car with a smaller engine, per request of the Automobile Club de l'Ouest with a potential of a formula change in 2024.
NASCAR Whelen Modified Tour NASCAR Whelen Modified Tour series stock cars are powered by small-block V-8 engines, usually of of displacement, although larger or smaller engines can be used. Engine components are largely similar to those used in the Cup Series, but Whelen Modified Tour engines use a small four-barrel carburetor (rated at per minute, about half the airflow of previous modified carburetors), which limits their output to . On large tracks such as New Hampshire Motor Speedway, the engines must have a restrictor plate between the carburetor and intake manifold, reducing engine power and car speed for safety reasons.
Restrictor Plates
As a safety measure to reduce speeds at the two high-banked superspeedways (Daytona and Talladega), restrictor plates are used. There are some tracks, however, where restrictor plates are not mandated and therefore see faster speeds—specifically Atlanta Motor Speedway and Texas Motor Speedway. While Atlanta is generally considered the fastest track, restrictor plates are not mandated there. In 2004 and 2005, higher qualifying speeds were posted at Texas, earning it the title of the circuit's fastest track. Unrestricted, Sprint Cup cars produce over 750 horsepower (560 kW) and can run at speeds in excess of 200 mph. Rusty Wallace completed a 2004 test for NASCAR at Talladega in which he used an unrestricted motor to complete average lap speeds of and top speeds near . The 2010 width is 63/64-inch. This is the largest carburetor restrictor plate opening since the one-inch mandate in 1988, the first year the horsepower-reducing plates were used in the Cup Series at Daytona.NASCAR.com Report on Rusty Wallace at Talladega
Unfortunately, the restrictor plates have an unintended effect on the race. Because of the reduced horsepower of the cars, the cars form large packs. During a race, it is not uncommon to see thirty or more lead changes during a race. This also is the source of the Big One. When a driver crashes, usually, they take that pack with them. During the 2010 Coke Zero 400, 21 of the 43 cars crashed. This is a safety concern that has puzzled NASCAR. However, an unexpected consequence of the introduction of the Car of Tomorrow and re-paving of Daytona and Talladega track surfaces has been the separation of the pack into two-car pairs.
Since the 2012 season, NASCAR Cup cars now have fuel injection instead of carburetors, but restrictor plates are still being used.
Beginning in 1971, NASCAR rewrote the rules to effectively force the Ford and Chrysler specialty cars out of the competition by limiting them to 305c.i. (5.0L). The cars affected by this rule include the Ford Talladega, Mercury Spoiler II, Dodge Charger 500, Dodge Charger Daytona and the Plymouth Superbird. This rule was so effective in limiting performance that only one car that season ever attempted to run in this configuration.
In 1971, NASCAR handicapped the larger engines with a restrictor plate. By 1972, NASCAR phased in a rule to lower the maximum engine displacement from 429 cubic inches (7.0 liters) to its present 358 cubic inches (5.8 liters). The transition was not complete until 1974 and coincided with American manufacturers ending factory support of racing and the 1973 oil crisis.
After a series of flips and dangerous crashes in the 1980s, NASCAR began requiring all cars to run a restrictor plate at Daytona and Talladega. The restrictor plate limits air into the engine, reducing horsepower and speed at these tracks from 230-240 mph to 195-200 mph. At these races, in addition to the restrictor plate, there are a variety of other technical rules and regulations to keep the cars stable and on the track. In addition to these technical rules, restrictor-plate races and road courses are the only races where NASCAR enforces track limits. At the high-speed superspeedways, track limits are marked by a double yellow line separating the apron from the racing surface. Exceeding track limits to advance one's position is subject to a drive-through penalty, or if the foul occurs on the last lap that car will be relegated to the last car on the lead lap in official race results. The superspeedway track limits (often referred as the "yellow line rule") have been part of considerable criticism and controversies, such as when Regan Smith was stripped of second-place finish at the 2008 AMP Energy 500 following a last-lap pass attempt that went below the line and controversies surrounding the finish of the 2020 YellaWood 500, with former drivers turned television coverage pundits Dale Jarrett and Dale Earnhardt Jr. (the latter being involved in a track limits controversy at the 2003 Aaron's 499) calling for the repeal of the rule. If track limits are violated on road courses (such as not making a chicane, enforced at Watkins Glen, Daytona, and Charlotte road courses), drivers must stop at an assigned point of the circuit or face a drive-through penalty.