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Building Drag Racing Engines and Modification Work

Regardless of what type of engine work your shop currently does, chances are you have worked on at least one engine that found its way to the drag strip

By Jim Walbolt

Page 1 of 2

Although drag strips are far outnumbered by oval tracks in the United States - approximately 1,043 oval tracks to just 295 drag strips - the number of competitors in drag racing nearly equals those in the circle track ranks. The NHRA alone has more than 35,000 licensed members. One reason might be that virtually any vehicle can be driven in a drag race, and with the competition rules that include handicapping, any vehicle can be competitive with any other.

Drag racing engines can run from the 7,000-plus hp nitromethane burning Top Fuel dragsters, to the 5 horsepower junior dragsters that resemble the Top Fuel dragsters, albeit, at 1/2-scale. In between, there are literally hundreds of chassis and engine combinations from your everyday go-to-work car, to a purpose built "weekend warrior."

Regardless of what type of engine work your shop currently does, chances are you have worked on at least one engine that found its way to the drag strip. The sport compact and import racing markets are growing daily; but we aren't going to focus on that area of drag racing as it's been covered extensively in recent issues of Engine Builder.

Although there are many organizations that sanction drag racing in the United States, the two main organizations are the National Hot Rod Association (NHRA) and the International Hot Rod Association (IHRA). Nearly all other groups take their cues from these two sanctioning bodies, and while other groups may have their own competition rules, nearly all abide by either NHRA's or IHRA's safety rules. Of course, if you're going to build an engine for a particular organization and class, you need to be familiar with their rules. In some classes, internal engine modifications may be unlimited, while in others those modifications may be strictly limited. NHRA and IHRA, for instance, list approved replacement parts for most of their "Sportsmen" classes.

For simplicity sake, we'll use the NHRA's classes as we discuss different engines and classes. These class listings and descriptions are courtesy of NHRA. IHRA is set up similarly. Top Fuel, Funny Car and Pro Stock are just three of the more than 200 classes of vehicles featured in NHRA competition. Those classes are grouped into 12 categories, or eliminators, each strictly governed by NHRA rule makers. Class eligibility is based on various requirements and specifications, including type of vehicle, engine size, vehicle weight, allowable modifications and aerodynamics.

The four Professional categories are Top Fuel, Funny Car, Pro Stock, and Pro Stock Motorcycle. They, along with Top Alcohol Dragster and Top Alcohol Funny Car and the three "Super" classes - Super Comp, Super Gas and Super Street - feature a single class of vehicle in heads-up competition. The remaining categories - Comp, Super Stock and Stock - are made up of a variety of classes and use a handicap starting system to equalize competition.

Top Fuel
Top Fuel dragsters are the fastest-accelerating vehicles in the world. The 25-foot landlocked missiles can cover the quarter-mile in 4.4 seconds at speeds in excess of 330 mph. The engine of choice for most teams is an aluminum version of the famed 426 Chrysler Hemi. These supercharged, fuel-injected, nitromethane-burning engines produce an estimated 8,000 hp.

Funny Car
With aerodynamically enhanced carbon-fiber bodies that loosely resemble the production cars on which they are based, these supercharged, fuel-injected, nitromethane-burning machines travel the quarter-mile in 4.7 seconds at more than 325 mph. Most teams use an aluminum version of the 426 Chrysler Hemi engine that produces an estimated 8,000 hp.

Pro Stock
Pro Stock cars look a lot like streetcars, but looks can be deceiving. Extensive modifications to the cylinder heads, manifold, chassis, and suspension thrust them to 6.7-second elapsed times at more than 200 mph. The most popular engine choices for these carbureted, gas-burning vehicles are the GM big-block wedge, the Mopar Hemi, and the Ford wedge.

Pro Stock Bike
Producing more than 300 hp, these highly modified motorcycles can cover the quarter-mile in less than 7.1 seconds at more than 190 mph. The chromoly steel chassis is cloaked in a lightweight, aerodynamically enhanced replica of the original motorcycle body, and the carbureted gasoline engine may be a Harley V-twin - two-valve or four-valve.

Top Alcohol Dragster
Top Alcohol Dragsters bear a striking resemblance to Top Fuelers, but most burn methanol. Nonsupercharged nitro-burning entries are also permitted. These vehicles can cover the quarter-mile in less than 5.3 seconds at speeds faster than 260 mph. They are the quickest class in the regional Lucas Oil Drag Racing Series.

' Top Alcohol Funny Car
Top Alcohol Funny Cars look like their fuel-burning counterparts, but instead of nitromethane, they burn methanol. The performance marks of the cars are in the mid-five-second range at better than 260 mph. This class shares the spotlight with Top Alcohol Dragster in the regional Lucas Oil Drag Racing Series.

Competition Eliminator
Comp, which boasts 80 classes, showcases a variety of gas-burning dragsters, altereds, street roadsters, coupes, sedans, and trucks powered by engines ranging from tiny four-cylinder screamers to powerful V8s. Some are supercharged, others turbocharged, but most are carbureted. A handicap starting system equalizes competition.

Super Stock
Super Stock features an array of stock-appearing foreign and domestic factory automobiles and sports cars with limited modifications. Eighty-three classes of cars and trucks, from late-model sedans and passenger vehicles to vintage muscle cars from the 1960s and 1970s, are showcased. A handicap starting system equalizes competition, and breakout rules apply.

Stock Eliminator
Stock encompasses a variety of foreign and domestic production vehicles. Everything from late-model passenger cars and trucks to the popular vehicles of the 1960s and 1970s can participate in any one of Stock's 102 classes. Few modifications or alterations are allowed. As in Super Stock, a handicap starting system is used, and breakout rules are enforced.

Super Comp
Super Comp features one class of vehicle and is the quickest of the three Super classes. Made up mostly of gas-burning dragsters, though full-bodied production vehicles and roadsters are eligible, Super Comp features heads-up competition on an 8.90-second index. Engine modification is virtually unlimited.

Super Gas
Super Gas features mostly full-bodied production vehicles with full fenders, hoods, grilles, tops, windshields, and functional doors. Left-hand-steering street roadsters are allowed, but dragsters are not. The class is governed by the same rules as Super Comp; only the index is different. A heads-up start is used, but racers may not run quicker than the 9.90-second index.

Super Street
Super Street, designed as an entry-level category. It is reserved for full-bodied production vehicles, including sports cars, vans, and trucks with full fenders, hoods, grilles, tops, windshields, and functional doors. Racers compete on a 10.90-second index.

Sport Compact
Sport Compact cars are exotic four- and six-cylinder machines fed by turbochargers and nitrous oxide. Racecars in the fastest classes can cover the quarter-mile in as few as six seconds at more than 200 mph, but NHRA also offers novice and intermediate categories for every level of enthusiast. Many people think Sport Compact racing is only for imports such as Hondas and Toyotas, but there's room for the Detroit makes in this extremely popular scene.

Jr. Dragster
A half-scale version of a Top Fuel dragster designed to be driven by kids ages 8-17 in the NHRA Jr. Drag Racing League. Using a five-horsepower, single-cylinder engine, a Jr. Dragster can go as fast as 80 mph in as little as 7.90 seconds on the eighth-mile.

E.T. Brackets
Just about any vehicle, from a dragster to a muscle car to a grocery-getter, can compete in E.T. bracket racing at NHRA's 140 member tracks in the United States, Canada, Mexico, and Puerto Rico. Believe it or not, even snowmobiles are welcome.