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Sportsman Drag Racing Engine Rules

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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.

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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.

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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.

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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.

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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.

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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.

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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.

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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.

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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.

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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.

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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.

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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.

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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.

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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.  

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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.

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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.

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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.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
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