How to Build a Mustang Race Car for NASA American Iron and SCCA Super Touring

Fourth Generation Mustangs (SN-95):

NASA and SCCA Rules for the Ford Mustang

For a Mustang race car to be eligible for American Iron or Super Touring Over classes, it must have: 1) a unit body construction (no tube frame), 2) minimum 100 inch wheelbase, 3) front engine/RWD layout, 4) a solid axle or "approved" independent rear suspension, 5) stock bodywork including front clip, floorpan, and subframes. Limited production factory approved Mustangs such as the SVT Cobra R, FR500, Shelby, Roush, Saleen and Hennessey are acceptable, but these tend to be very expensive cars to start with.

A piece of advice here: It always costs twice as much to build a car from scratch as it does to start with an existing race car that has the major work such as cage and suspension upgrades already installed. It's much easier and less costly to incrementally improve and existing Mustang American Iron or STO race car than it is to build one from scratch from a street car.

When deciding on a car and motor package, it's critical to conform to NASA's rules for power-to-weight and torque-to-weight ratios. The minimum weight for a V8 powered AI car is 2700 pounds with driver. The “American Iron” (AI) class has a strict 9.5:1 (9.5 pounds of vehicle weight per each horsepower) power to weight ratio maximum and 9:1 (9 pounds of vehicle weight per each foot-pound) torque to weight ratio maximum as measured at the rear wheels. The SCCA Super Touring Over (STO) rules have similar limitations. These classes are about fair competition and reasonable cost as opposed to maximum horsepower.

See NASA's American Iron rules here: http://www.nasaproracing.com/rules/american_iron_rules.pdf

See SCCA's Super Touring Over rules Section 9.1.4 here: http://www.calclub.com/html/html2/archives/2012/2012-GCR.pdf

If you want to go beyond these limited rules you can race in NASA's American Iron Extreme (AIX) or SCCA's Super Producton Over (SPO) which are basically unlimited classes.

Once you have your Mustang, it's time to strip the interior and build the cage.

In AI and STO the stock dashboard or equivalent must be retained. The remainder of the interior should be fully stripped and painted, with the exception of the wiring harness. On 4th generation 1994-2004 Mustangs it is possible replace the wiring harness and all unnecessary electrical switches and gadgets. On the later 5th generation 2005-2013 cars it is STRONGLY ADVISED not to remove the wiring harness or any computers because this can cause severe electrical issues. Just tuck the wires and switches into bundles and zip tie them out of the way. Contact Ford Racing as they may be able to provide detailed instructions to transform the electricals of a street Mustang to meet racing standards.

Once all the interior and door panel pieces are removed, cut out the door interior metal skins and stock impact bars. The doors will be filled with NASCAR-style door bars extending outward into the empty door space (See NASA CCR Section 15.6.12). Make sure you round off any sharp edges, and wrap them with vinyl edging material.

Next, remove all the sound deadening material, glue and gunk. It helps to heat it with a torch and use a paint scraper. The glue can be removed with acetone or paint remover. CAUTION! Do this outside or in a well-ventilated area!

NASA and SCCA rules require a full cage that meets the respective rules. Use a minimum of 1.75 x 0.120 inch drawn over mandrel (DOM) mild steel tubing, professionally TIG welded. Most AI and STO race Mustangs have 6 point cages with 2 additional bars running forward to the front shock towers. You can tie in the cage to the A and B pillars. NASA rules allow the cage to penetrate forward through the firewall and backward through the rear seat panel to tie in the shock towers and suspension pickup points. A good cage will always have a cross bar behind the dash. For greater safety, it's good to have another cross bar at foot level to prevent engine penetration into the driver compartment.

The cage mounting points must be reinforced with broad metal foot plates to prevent the tubing from punching through the unit body sheet metal. All cage points should be triangulated, especially in the upper corners of the A and B pillars. The main roll hoop should have an X-shaped cross bar. The cage should be overbuilt wherever it makes sense, as the extra tubing will protect the driver, stiffen the chassis, and allow for increased power under NASA's power-to-weight ratio. Do not skimp here!

Below are several photos of well-built cages in American Iron and STO Mustangs.

The difference in handling between a fast American Iron or Super Touring Over Ford Mustang race car and a standard Mustang street car is massive. It all comes down to the sophisticated suspension package that plants the car in turns, under braking and under hard acceleration. Both NASA American Iron and SCCA Super Touring Over rules require the tires to fit under the stock fender wells and NASA has a maximum track width for 2005 and up Mustangs of 74.5 inches with the spec Toyo RA-1 tires. Minimum ride height at the lowest point of the rocker panel is 5 inches, measured with the driver and fuel in the car.

1994-2004 Mustang race cars require a virtually complete chassis and suspension transformation to get the most out of the car. Although the SN-95 chassis itself is fairly stiff, the combination of poor suspension geometry and flex in the joints prevent these Mustangs from getting around the track quickly.

Here is a great view of the front suspension of an American Iron SN-95 chassis Mustang in action on the race track:

The suspension and chassis modifications you will need on your 1994-2004 Mustang race car to be competitive include:

This video shows how Chris Cobetto and Performance Autosport built a NASA National Championship winning Saleen Mustang GT from a brand new 2011 car off the lot:



The all-out suspension and chassis modifications needed for winning in your 2005-2013 Mustang AI include:

Both NASA American Iron and SCCA Super Touring Over rules allow motor upgrades to give your Mustang race car the increased horsepower and torque needed to win.

NASA American Iron Rules limit your Mustang to 9.5:1 (9.5 pounds of vehicle weight per hp) power-to-weight ratio and 9:1 (9 pounds of vehicle weight per foot-pound) torque-to-weight ratio. Both are measured at the rear wheels. NASA requires an official dyno sheet from an approved dyno shop to accrue AI series points. Nitrous Oxide, turbochargers and superchargers are prohibited. Engine blocks must be OEM or OEM-equivalent (i.e. Ford Motorsport crate motor). The stock synchro transmission must be used. Other than this, NASA has no further limitations on motor and transmission. Just meet the power-to-weight and torque-to-weight ratios and you're good.

SCCA Super Touring Over Rules also have a maximum power-to-weight ratio limit. This is decided by specific model, year and performance package and is listed in section 9.1.4 of the SCCA General Competion Rules (GCR-471 for 2012).

Engine and transmission modifications allowed in SCCA Super Touring Over are given below. These are equally applicable to NASA American Iron, even though NASA doesn't specify this level of detail. What you're looking for is an optimum power-to-weight ratio in both classes, rather than outright horsepower. Spending huge amounts of money on an ultra-powerful motor will just get weight added to the car to slow it down (and NASA has a 300 lb ballast limit, effectively making 800 hp motors illegal). The fast guys build solid and reliable motors, try to minimize the weight of the car so ballast can be used in different places, and spend their money on suspension and braking performance.

4.6L Modular aluminum block DOHC 4-valve V8 from 1999 and 2001 Mustang Cobra. It puts out 320 hp and works with 4:10:1 gearing since max hp is achieved at higher RPMs.

4.6L Modular iron block SOHC 2-valve V8 from 1998-2001 Mustang, GT and Cobra. This motor puts out 215-260 hp depending on the model and uses either the Teksid block (1998-2000) or WAP block (2001). Max power output is higher in the RPM range than the pushrod Windsor, so a 4:10:1 rear end works well.

Teksid Block from the SOHC 4.6L Modular V8.

Windsor Aluminum Plant (WAP) Block from the SOHC 4.6L Modular V8. Slightly weaker than the Teksid blocks, but sufficiently strong for AI and STO.

2005-2009 Mustang GT 4.6L aluminum block SOHC 3-valve Modular V8 motor with variable timing cam (300 hp). This is a competitive motor with some minor modifications, especially on tracks that reward handling over horsepower, since it allows a lighter car versus the more powerful BOSS 302 motor.

Ford Racing BOSS 302 5.0L Coyote 4-valve V8 Crate Motor. You can buy and install this NASA American Iron national championship winning motor straight from Ford Racing. It is the perfect AI or STO engine for 5th Generation Mustangs straight out of the box.

NASA American Iron and SCCA Super Touring Over allow limited body and aero modifications to your Mustang which increase downforce, help tune the handling, and reduce drag at high speeds. You can spend a lot of money here, so keep in mind that any money spent must result in higher performance within the power-to-weight ratio limitations of AI and STO.

Body panels:

Replacing the hood, rear deck, front fenders and rear fenders with fiberglass or carbon fiber is allowed. Fenders must be the same dimensions and shape as stock parts, and must entirely cover the tread portion of the tire when observed from above. Fender flares are not allowed. If you have a lower output motor, saving weight by replacing metal body panels with carbon fiber should be weighed against investing more in your motor package. If you have a powerful motor already, then you can probably stick with the stock metal bodywork.

Front fascia/splitter:

NASA AI rules: Splitter cannot extend frontward or sideways more than 5.0 inches beyond the outline of the nose of the car as viewed from above, and must end at the front axle centerline.

SCCA STO rules: Splitter cannot extend more than 2.0 inches beyond the outline of the nose of the car as viewed from above, cannot extend more than 2.0 inches horizontally outside the bodywork, and cannot be wider than the outside of the wheels when pointed forward.

4th generation Mustang nose with deep splitter and 4 hangers.

Mustang Cobra style nose with additional splitter.

Ford Racing kit 5th generation splitter with dual adjustable hangers.

Splitter on Chris Cobetto's NASA AI National Championship Mustang GT.

NASA AI rules: Adjustable with 2 pillars, cannot extend more than 1.5 inches beyond the rear bumper, and maximum width 72 inches.

SCCA STO rules: Adjustable, cannot extend past the rear bumper or be higher than the roof of the car, maximum width 72 inches or the maximum width of the car (whichever is less), maximum chord 12 inches including wicker, maximum end plate size 144 square inches.

Rear wing on NASA AI Mustang with "wrap around" mounts.

Wing that meets SCCA STO "top of roof" height limit.

G-Stream adjustable rear wing.

Ford Racing rear wing.

Hood and rear deck pins: Minimum of 2 pins are required.

Brake cooling: Using air dam holes or openings for the lights to duct air to the brakes is allowed. Water spray into the ducts is allowed, but not directly on the disk.

Lightening the body shell: Acid dipping body panels to lighten them is illegal. You can remove extra unused brackets. Be VERY careful about cutting or bending sheetmetal -- read the regulations very closely!

Window materials: Stock glass, Lexan or polycarbonate windshield, rear glass and side windows are allowed. If Lexan, center inside bracing to support the windshield is required.

Ballast: See the SCCA rulebook on how to design and mount ballast.

NASA AI rules: Ballast must be securely fastened per CCR 15.20 (i.e. - at least one grade five 3/8 diameter bolt per 10 lbs of ballast) and approved by NASA tech and safety officials. Any ballast mounted inside the vehicle may not be taller than three inches or stacked higher than three inches. No more than 300 pounds of ballast is allowed.

SCCA STO rules: See the SCCA rulebook on ballast.

Other: Headlights and fog lights can be removed. At least one windshield wiper is required. Stock dash or equivalent is required.

The following safety equipment is required to race your NASA American Iron or SCCA Super Touring Over Mustang:

Here are a few videos of AI and STO Mustangs on track:

Addison Lee at Infineon in his 4th Generation American Iron Mustang

2011 World Challenge Mosport Race Onboard the Mustang GT of Eric Foss (SCCA Super Touring Over rules are nearly the same as World Challenge)

Jeff Wood at Putnam Park in his 2007 American Iron Mustang GT

Chris Cobetto at VIR at March 2011 NASA American Iron race - watch him use ALL the track!

Here are some additional links to Mustang race car projects that can help out:

1995 Mustang GT race car project

2012 RTR Mustang race car project

2002 Mustang race car project

Chris Cobetto's Mustang GT 2011 NASA AI championship car project Part 1

Chris Cobetto's Mustang GT 2011 NASA AI championship car project Part 2

Chris Cobetto's Mustang GT 2011 NASA AI championship car project Part 3

Speedlab's blog posts about Chris Cobetto's Mustang GT 2011 NASA AI championship car build Part 1

Speedlab's blog posts about Chris Cobetto's Mustang GT 2011 NASA AI championship car build Part 2

2003 American Irong Mustang build article

RPM Racing detailed blog about upgrading a 5th generation Mustang's suspension for racing

Good article on 4.6L Modular V8 Mustang 4th generation motors and their upgrades