Spec Mustang: A Step Away From The Momentum Car

I’ve noticed some of my peers have a tendency to give a clinical driving experience a better rating than what’s simply fun. Why they seem to prefer bags of grip and accuracy over unmitigated playfulness is beyond me. Maybe these people are just repressed. Whatever the reason, they would be wise to get in touch with a more primal side of themselves by sampling a Spec Mustang. This relatively new race car, based upon the 2005-2009 Ford Mustang, makes a compelling case for hooliganism over precision and refinement.

“It’s a dramatic car,” Roger Eagleton puts it. “It’s something that forces you to really hustle it if you want to find those last tenths.” Simple, straightforward, reasonably priced, playful, a glutton for punishment, and torquey. With enough grip, but not so much to turn it into a momentum car, the Spec Mustang offers the aspiring driver a completely new experience after they’ve enjoyed most of what momentum cars like a Spec Miata, Spec Boxster, or even a Spec E46 can offer.

Eagleton’s qualified to discuss the differences between the aforementioned cars. After moving out of karts, he started sampling most of the available momentum cars out there, trying a new vehicle every season the following six years. First, he became a Spec E30 champion, then he drove a Miata at the 25 Hours of Thunderhill. Following that, he moved into an E90 BMW for a season in the U.S. Touring Car Championship, and then, hungry for a new challenge, tried his hand at Spec Mustang.

Eagleton looking sagely before a race start.

With four years spent in the seat of his pony car, it’s clear he’s happy where he is. The power, the costs, and the growing size and number of classes it’s eligible for all keep him challenged and satisfied — as does the way it rewards a naturally aggressive driver. “To get the last few tenths from this car, you’ve got to wrestle with it. Although, even if you’re driving it below the limit, the torque and V8 rumble make it a thrilling car.”

The Spec Mustang has a lot going for it. Few cars under $30,000 can lap Sonoma Raceway in the 1:47 range. Its parts are widely available, it’s been refined to an extent but limited heavily by the rules, and despite the variety of machinery out there, effective regulations have kept the playing field quite even. Most importantly, it has just a little more power than it has grip, and that changes the driving experience entirely.

Playfulness Over Poise

“The Spec Mustang operates in that happy medium between momentum car and muscle car,” Eagleton declares. What that means in more technical talk is, when driven properly, the Spec Mustang moves through corners with more slip angle than most of its rivals. At the ragged edge, the driver must manage wheelspin. When there’s 325 lb-ft of torque available from low revs, it takes a careful right foot.

One drives the Spec Mustang with more slip angle than other comparable cars.

“Most people end up looping it in their first lap or two,” he laughs. Moving from a Spec Miata, Boxster, or even E46 and the way they allow a driver to mat the right pedal post-apex doesn’t always apply when a V8 is providing the punch. However, the big Ford’s chassis is surprisingly sharp — it really belies its 3,400 pounds — and still operates well within its range of abilities when driven with more slip angle than a Spec E46 would reward.

If the Spec E46 — perhaps the most popular and capable momentum car following the Spec Miata — had quite the poke that the pony car has, it might be a different matter. But as the Spec E46 currently stands, it is slightly underpowered for the traction and poise it possesses.

The BMW is a capable, accurate, refined, and confidence-inspiring car. Perhaps too surefooted for its own good, as the balance between power and grip doesn’t necessarily make for the most exhilarating driving experience. It rewards accuracy and patience, but if it cannot be steered with the throttle, it runs the risk of becoming too competent; too clinical.

The Mustang is driven a little differently. When Mustang shifts its load forward, it’s quite easy to adjust the attitude of the car mid-corner. Thanks to stellar Stoptech Trophy brakes, it remains settled when shifting from peak braking pressure through the trailbraking phase, and easy modulation helps it to zero-steer in a manageable fashion. If a driver isn’t comfortable with a car dancing underneath them, this amount of rotation may come as a shock, but this is the sort of aggressive style which the Mustang rewards.

“The handling characteristics are not that different from a Miata’s,” Eagleton adds.

If we can imagine a car that works best when it’s free to rotate through the pedal on the right, we can start to picture how the Spec Mustang prefers to corner. This isn’t only for drivers of Eagleton’s caliber. The reason this is manageable in the hands of casual hobbyists is because CorteX Racing worked their magic with the suspension setup. 

The CorteX Racing coilovers are tailored to the Spec Mustangs weight. Their springs rates come available in either 600 lb/in front and 450 lb/in rear or 500 lb/in front and 400 lb/in rear. Along with that, the kit includes: 

  • Adjustable Watts link system
  • Rear lower control arm system with angle correction brackets and spacers. These optimize the suspension geometry at lowered ride heights.
  • Bumpsteer adjustment kit

These items help make a car that’s quite friendly, even when driven with a good amount of slip angle. Having a square setup makes it more easily pitched into oversteer, and lacking a rear sway bar, as per the rules, softens the Spec Mustang’s rear to make it easier to lean on. “The car was strong from its first days, but the CorteX kit and the upgraded cage brought us the refinement and adjustment we were after,” says David Ray, Hooked on Driving founder and Spec Mustang pioneer. 

The Appeal of the Modular Motor

There’s a lot to love about the powerplant in the Spec Mustang. The modular 4.6-liter may not seem like anything special at first glance, but as far as engines in this category of racing cars go, it’s fairly powerful. Aided by a set of Borla longtube headers, a Ford Performance intake, and a tune for 100 octane race fuel, most engines will produce around 315 horsepower and 325 lb-ft of torque at the rear wheels. Thankfully, the 4.6 is reasonably inexpensive to purchase and relatively cheap to run. Running the mandated factory clutch, flywheel, and limited-slip differential keep the costs relatively low.


Cost of consumables is one issue with this car. Being a reasonably heavy vehicle, it does place some strain on its tires. If the tire bill is higher than other Spec racers, the upside is the amount of seat time possible any given weekend is pretty high.

“Most Spec Mustang weekends coincide with American Sedan races under SCCA — another class this car is eligible for. On most of these busy weekends, the Stoptech brakes run without fade. The tires do fade by the end, however,” Ray tells us. The Hoosier R7s will work well for about four races, which happens to be the number of races Ray and Eagleton are able to participate in most weekends.

One point to add on tire wear: provided the driver treats the throttle pedal with some care, the Mustang is well-balanced and tends to wear all four tires pretty evenly. Pads for the Stoptech Trophy brake kits last 3 to 4 race weekends, and while the Spec Mustang’s one nanny system, ABS, can accelerate pad wear, it also prevents an overly eager driver from flat-spotting a set of cold tires in the rush to generate some temperature during a chilly practice session.

Stoptech Trophy brakes look the business inside a nicely matched set of Apex EC-7 wheels.

Fortunately, there’s a good chance that a friendly, fun, cost-effective solution is coming. Eagleton’s hinted at a new tire on the horizon that ought to reduce the consumables bill, but he’s still cagey about the specifics. At the cost of a couple seconds per lap, this new rubber should halve the current tire bill.

A Versatile Package

The layout does work for other categories as well. In addition to Lucky Dog Racing League and Trans-Am’s GT class, the Spec Mustang can run towards the sharper end of the pack in NASA’s American Iron. With growing fields at race weekends and more than ten cars showing up most Spec Mustang weekends, the class offers strong racing at the front and the back of the grid. Fierce competition and a wide variety of opportunities to race makes Spec Mustang the right platform for teaching a driver how to manage a powerful car in little time. 

Occupying a rung relatively low on the racing ladder, Spec Mustang must offer its user ample seat time at a reasonable cost.

If one can look past the tire and fuel bill, Spec Mustang doesn’t seem like such a pricey proposition. A junkyard engine can be had for roughly $3,000, new engine from Ford costs about twice that, and body parts are ubiquitous. “If you tap a wall, you can grab a fender from a V6 Mustang at most junkyards,” Eagleton reassures us. 

In 2019, DIG Motorsports decided to take one of its Spec Mustangs and run the 25 Hours of Thunderhill, where it was not fitted with any modifications to handle the extended abuse. Admittedly, the accessible torque kept the engine humming a little lower in the rev range than some, but that junkyard 4.6 still lasted the full race. With only a full fluid flush, this essentially stock engine ran without a single hiccup and performed well enough to put them in a very competitive position. 

So competitive, in fact, that they nearly won. With consistent lap times around the 2:00 range, they finished second in the E0 class — within striking distance of the winning team. Considering the wide range of machinery present and the cost of its competitors, that podium is worth a tip of the hat.

The DIG Motorsports team after this second-place finish in the rain-soaked 25 Hours of Thunderhill. Photo credit: Borders Racing

Being laps in an endurance racing situation, those times were done with some in reserve. In a sprint setting, the Spec Mustang can lap Thunderhill (East) in 1:58, Sonoma Raceway in 1:47, and Laguna Seca in 1:37. Those are remarkably quick times — roughly 3 seconds faster than what a Spec E46 can muster at those circuits. “Unless they’re moving into a GT4 or GT3 car, this car might offer the best combination of power and grip most drivers will be able to access,” Eagleton declares.

However, even a quicker car might not provide the unadulterated thrills which the analog Mustang can. “After getting two races in the IMSA GT4 Mercedes, still the quickest car I’ve been in, I wasn’t convinced it was the best car I’d driven. With all the systems active in that car, it just wasn’t as involving,” he elaborates.

It’s a car that can wear many hats, and this versatile platform brings thrilling power and enough playfulness to silence any naysayer. Those looking for more than the scrub minimization and the underdog thrills of racing a momentum car ought to inspect this burgeoning class — it’s more likely to put a smile on their face than most in the price range.



About the author

Tommy Parry

Tommy Parry has been racing and writing about racing cars for the past seven years. As an automotive enthusiast from a young age, he worked jobs revolving around cars throughout high school, and tried his hand on the race track on his 20th birthday. After winning his first outdoor kart race, Tommy began working as an apprentice mechanic to amateur racers in the Bay Area to sharpen his mechanical understanding. He has worked as a track day instructor and automotive writer since 2012, and continues to race karts, formula cars, sedans, and rally cars in the San Francisco region.
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