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Sportsman Drag Racing Engine Rules

Start flipping through the TV channels anytime of the day or night and there’s a good chance you’ll find a drag race. It may be any one of several different game shows, it may be active competition or it may be a reality series about competition.

By Doug Kaufman

Drag racing – lining up next to the other guy and seeing who’s got the best stuff – remains an incredibly popular sport, for both spectators and participants. Although multi-lap circle track and road racing competition may have received the lion’s share of media attention over the past several years, mashing the throttle and driving to the finish line is good business.

According to some recent (admittedly unscientific) polls on our website, our readers are excited about the upcoming drag racing season. When asked “Which racing series are you most looking forward to in 2011?” nearly half of the respondents said NHRA racing, more than twice the next highest number.

According to some recent information from various motorsports industry groups, there are well over 150,000 active drag racers in the United States. And from the response the Engine Builder staff saw at the recent International Motorsports Industry Show in Indianapolis, IN, and Performance Racing Industry Trade Show in Orlando, FL, they have all decided “economy-shmonomy” – it’s time to go racing again.

Drag racing engines run the gamut from 5-hp junior dragsters to nearly 10,000-hp nitro burning Top Fuel cars. In between, there are hundreds of engine combinations that find their way under a hood, onto the street or strip – often starting in your shop first.

Sportsman and bracket racing offer a great deal of potential to engine builders, say industry experts. Sportsman racers are slugging it out at little strips on Saturday nights, getting ready for their real jobs during the week then doing it all again next week, so they depend on YOUR expertise to maximize their investment. A durable, consistent engine will go a lot further than one that makes a lot of power but can’t stand up to repeat runs.

Racing Classes
“There are many organizations that sanction drag racing in the United States, but the two main organizations are the National Hot Rod Association (NHRA) and the International Hot Rod Association (IHRA),” says Engine Builder contributor Jim Walbolt. “While other groups may have their own competition rules, nearly all abide by either NHRA’s or IHRA’s safety rules.”

There are more than 200 classes of vehicles featured in NHRA competition (IHRA has similar categories). 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.

We’ll leave the Pro classes out of this discussion (but we won’t abandon it entirely – we hope to feature Pro engine builders in print and online at enginebuildermag.com in 2011) and give a brief explanation of some of the Sportsman classes and some further explanation of some engine-specific rules.

Competition Eliminator
Comp, which boasts nearly 100 classes, showcases a variety of gas-burning dragsters, altereds, street roadsters, coupes, sedans, and trucks powered by engines ranging from turbocharged inline four cylinders to high winding small block Chevy V8s to 700-cid gas carbureted gas burning “mountain motors.” 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. More than 80 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 100 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, grills, 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, grills, tops, windshields, and functional doors. Racers compete on a 10.90-second index.

Here are some specific rules from NHRA as they relate to the Stock and Super Stock classes:

Stock Cylinder Heads
Must be correct casting number for year and horsepower claimed, per NHRA Technical Bulletins or NHRA accepted. Porting, polishing, welding, epoxying and acid-porting prohibited. Combustion-chamber modifications prohibited. Cylinder heads are additionally restricted in that they must retain original-size valves at original angles +/- 1 degree and must be able to hold original cylinder-head volume per NHRA Specifications.

Runner volumes may not exceed the current Super Stock cylinder-head volumes as listed on www.NHRA.com. Regardless of the poured volume measurement, any modifications to intake or exhaust runners prohibited. Any evidence of modifications from the original castings will be grounds for disqualifications as determined by NHRA in NHRA’s sole and absolute discretion.

Any aftermarket steel valve permitted, must retain stock head and stem diameters. Only engines OEM-equipped with sodium-filled valves may use sodium-filled replacement valves. Titanium is prohibited. Hardened keepers are permitted. Lash caps are prohibited. Valve-diameter tolerance: +.005˝ or -.015˝ from NHRA Specs.

The following are prohibited: spark-plug adapters; cylinder-head studs; any grinding in ports or combustion chambers; removal of any flashings; sandblasting or any other modification to cylinder heads; any film coating of intake and exhaust runners; any film coating of combustion chamber.

Runners and combustion chamber must retain OEM appearance. Final acceptance is determined by NHRA at their discretion.

Intake side of head may not be cut into any part of the valve cover bolt holes. Heat riser passage may be blocked from intake manifold side of cylinder head. Blocking passage down in valve pocket prohibited.

The following are permitted: polylocks, jam nuts, screw-in larger-diameter rocker studs or pinned studs, bronzewall valve guides. Valve spring umbrellas optional. Cylinder head may have all of the seats replaced. Any valve job permitted, O-ringing prohibited. Exhaust plates prohibited.
 
Engine
Must be same year and make as the vehicle, aftermarket NHRA-accepted cylinder blocks are permitted. Equipment other than original factory-installed is prohibited. Any special equipment export kit (superchargers, dealer-installed options, etc.) automatically disqualifies the car.

Engine must remain in stock location — height, setback, etc. Cylinder bores must not exceed .075˝ over stock. Bores are measured at the top of the cylinder where ring wear is not evident. Crossbreeding parts is prohibited.

Normal balance job (i.e., one piston/rod assembly untouched) permitted. Otherwise lightening of component parts is prohibited. All carburetors, manifolds, heads, etc. must be tightened to prevent any air or fuel leaks. Vacuum lines must be securely connected or blocked off.

Stroke tolerance is +/- .015˝. Stock OEM crankshaft is mandatory. Lightening of the crankshaft other than normal balance job is prohibited.

Cylinder blocks may be sleeved. Aftermarket SFI Spec 18.1 harmonic balancer mandatory in AA/S through G/S and AA/SA through G/SA.

Super Stock Cylinder Heads
Must be correct casting number for year and horsepower claimed, per NHRA Technical Bulletins or NHRA-accepted. Cylinder head casting must also be on NHRA runner volume list as published in National Dragster and on NHRA.com.
Porting, polishing, welding, epoxying, and acid-porting is permitted. Grinding and polishing in combustion chamber permitted. Welding and/or applying epoxy in combustion chamber prohibited. Spark-plug hole must maintain the stock location, size, and angle as machined by the OEM; spark-plug adapters prohibited.

Valve-guide centerlines must maintain the stock lateral and front-to-back location as machined by the OEM. Valves must maintain stock angle; valvestem angle must remain stock, +/- 1 degree. Cylinder head must be able to hold combustion chamber, intake and exhaust runner volumes per NHRA Specifications. Any aftermarket steel valve permitted; must maintain stock head and stem size; titanium valves prohibited. (OEM sodium-filled valve may be replaced with titanium, provided weight is equal to or greater than original.) Valve diameter permitted to be +.005˝ or -.015˝ from published NHRA Technical Bulletins.

External modifications prohibited. Welding or epoxying permitted on external portion of runners for repair only, maximum 2 runners per head. Heat riser passages may be blocked off from intake-manifold side of cylinder head or in exhaust port. The following are permitted: polylocks, jam nuts, screw-in or pinned studs. Any valve job accepted. Exhaust plate permitted between header and cylinder head, maximum 1/2˝; may not protrude into exhaust port. Cylinder head may have all seats replaced.

Engine
Must be same year and make for car used, aftermarket NHRA-accepted cylinder blocks permitted. Equipment other than original factory-installed prohibited. Any special-equipment export kit (superchargers, dealer-installed options, etc.) automatically disqualifies car.  

Engine must remain in stock location, cylinder bores must not exceed .075˝ over stock. Bores are measured at top of cylinder where ring wear is not evident. Crossbreeding parts prohibited. Normal balance job permitted. Otherwise lightening of component parts prohibited.

Carburetors, manifolds, heads, etc., must be tightened to prevent air or fuel leaks. Vacuum lines must be securely connected or blocked off. Stroke tolerance is +/- .015˝. Stock OEM or NHRA accepted aftermarket crankshaft mandatory.

Aftermarket crank must retain OEM configuration; i.e., billets, knife edging, etc., prohibited. Lightening of crankshaft other than normal balance job prohibited. Cylinder blocks may be sleeved. Aftermarket SFI Spec 18.1 harmonic balancer mandatory. Timing-belt covers optional.

Walbolt reminds us that if you’re interested in working with sanctioning bodies OTHER than these, you’ll 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.

Other racing bodies include the National Mustang Racers Association (NMRA), the largest Ford focused drag racing group in the United States. It recognizes 14 different classes, and has rules specific to each.

The National Muscle Car Association is another drag racing organization that recognizes 1950 and newer American production cars and trucks. NMCA recognizes multiple classes including the Pro Stock class.

The NMCA Pro Stock Class is a naturally aspirated class designed for 1950 and newer American production cars and trucks that are equipped with stock-type chassis and 10.6˝ wide tires. Pro Stock entries can use small block and big block engines up to and including a maximum of 525 cid (depending on combination). Pro Stock permits a variety of race-proven modifications and performance enhancements on stock bodied, stock appearing vehicles.

Winning in Sportsman drag racing doesn’t always mean coming in first – consistency and reliability are demanded. Knowing the rules is a plus.