In the Mustang performance world, engine swaps are all the rage. The modern Coyote swap is a go-to solution for big horsepower builds. It’s reliable, it’s efficient, and it’s almost expected. However, Dan Mulvihill didn’t take the popular path. Instead, his 2008 Mustang GT/CS proves the potential of the under-appreciated Three-Valve 4.6-liter engine under its hood with reliable four-digit output.

I stuck with the Three-Valve engine because I believed I could achieve my power goals even though most others were doing a Coyote swap… — Dan Mulvihill

“Most people don’t notice the car, which is the intent of the build,” Mulvihill said. “If a knowledgeable person inspects the car at a meet, that usually leads to an appreciation for the amount of work that went into the build and the uniqueness of the build. Most people who see the car up close comment on the immaculate condition of the car, though.”

It might seem California cool on the outside, but it hides over 1,000 horsepower beneath a stock-appearing visage. (Photo Credit: Dan Mulvihill)

Much like his unusual combination, Mulvihill didn’t take a direct path to buying this California Special project. He originally intended to pursue a Brand X path, but the retro style and Modular horsepower won him over.

“Growing up, my friends and I loved Chevy and Pontiac. During that time, I owned a 1967 GTO and a 1969 Firebird,” Mulvihill said. “My favorite car, however, was the 1969 Camaro. As an adult, many years later, I planned to buy the 2009 Camaro because I hoped that it would look similar to the 1969 Camaro. I bought the Mustang in the interim, started fixing it up, and never looked back.”

No Coyote, no problem. Instead, an MPR-fortified Aluminator Three-Valve with ported heads, Diamond pistons, Manley I-beam rods, and twin Precision snails rewrites the rules. Four-digit rear-wheel horsepower with modular DNA intact turns this engine bay into a conversation starter when onlookers find out just how much power it produces.

Strong Start

The combination began with a rear-mount turbo kit upgrade and a nitrous kit, the latter of which was facilitated by the trade of a cat-back exhaust that had become unnecessary with the turbo kit. The result was a fun, 530-horsepower combination he enjoyed for years. Eventually, he sold the stock engine, added a Ford Performance Aluminator crate engine, and stepped up the boost, resulting in a sporting 730 horsepower at the wheels.

“After a few years of constantly tweaking the boost level up, I over-boosted it by more than 10 psi and threw a couple of rods through the block,” Mulvihill confessed. “With the ever-increasing desire for more horsepower, I decided to rebuild the motor with the best parts available and to upgrade to a custom front-mount twin turbo…”

From behind, it could pass for a cruiser, but those Weldcraft-widened wheels wrapped in Nitto drag radials hint that this GT/CS is packing far more than style. When the boost hits, that 9-second slip proves the rear view is the only one most people will ever see.

On the dyno, the car delivered 1,027 rear-wheel horsepower and 844 lb-ft of torque on E85 — and that’s with the nitrous switched off. Add in a 150-shot from the Wilson Pro-Flow wet nitrous system, and the GT/CS has far more firepower than most street cars will ever dream of. And, while it looks like an unassuming street machine, Mulvihill’s S197 delivered on the drag strip in full street trim as well, with a personal best of 9.7 seconds at 148 mph in the quarter mile. There was no weight reduction, no slicks, no open headers, just a legit, streetable Mustang running deep into the nines.

That’s where the build got serious. While Three-Valves are recalled as a transitional phase in the Mustang lineage, this combination proves they are far more than an afterthought.

“…Ever-increasing power goals and a failure led to the fully built engine. The first build of the engine had a Cobra crank, pistons with lateral nitrous ports to energize ring sealing; ceramic top coat, and moly skirt coating on the pistons; H-beam rods; Inconel extreme-duty exhaust valves; ported and polished heads; and a billet oil pump,” Mulvihill explained. “After throwing a couple of rods with the overboost, the engine was then rebuilt with I-beam rods.”

Muscular Modular

To keep a 4.6-liter Modular alive at these levels, a stout foundation is required. That’s where MPR Racing Engines of Boynton Beach, Florida, got the nod. They assembled the long block, starting with an Aluminator block stuffed with Diamond forged pistons featuring ceramic tops, moly skirts, and lateral nitrous ports. A set of Manley I-beam rods and an eight-bolt Cobra crank ensure strength at high power. Bullet Racing cams bring the Three-Valve heads to life, while Kris Starnes Racing ported and polished those factory castings for maximum airflow.

Supporting hardware includes ARP fasteners throughout, a billet oil pump, and an ATI Performance harmonic balancer. On the top end, Ford Performance Parts components dominate, as the Blue Oval performance arm’s valve covers, intake manifold, and a twin 62mm throttle body all contribute to a factory-meets-fast aesthetic. The compression ratio sits at 9.2:1, which is ideal for big boost and E85.

That steady flow of corn comes courtesy of a Fore Innovations triple-pump system, Injector Dynamics ID1300X injectors, and Fore fuel rails. Gearhead Fabrications in Jensen Beach converted the system to return-style and set it up to run on E85. Not only does that fuel cool the charge, but it supports the massive flow requirements of a twin-turbo Three-Valve with an occasional squeeze of nitrous.

Twice As Nice

Those two turbos are the hidden heroes of this combination, and Gearhead Fabrications crafted a twin setup that tucks Precision 6266 billet ball-bearing units behind the front bumper. Hot and cold side piping received ceramic and powder coating, respectively, while a Treadstone TRTT9 intercooler handles airflow at up to 1,950 CFM.

“Decided on twin turbos for the combination of faster spool time and good power level. Since the car was being built for highway use, local use, and occasional fun, I decided that twin turbos would provide the best combination of low-end power, maximum power, minimal lag, excellent throttle response, and good drivability,” Mulvihill said.

Controlled by a Turbosmart eBoost 40, the system can switch between 18 and 26 psi, with meth injection on standby to further rein in the inlet air temps. The MagnaFlow 3-inch Competition Series system lets the two turbos spool without restriction while delivering a performance personality. A Gearhead Fabrications calibration using HP Tuners hardware and software makes the combination play nice.

“Also, the custom twin-turbo setup would have exceptional quality, placement, and attention to detail. Turbo placement was of utmost importance due to the heavy South Florida rains,” he elaborated. “Having the turbos tucked behind the front bumper ensures no water ingestion if caught in the rain. Hidden turbos also supported my desire to build a car that was as stock-looking as possible, but fast enough to thoroughly enjoy the ride.”

Spool & Spray

As if the boost weren’t enough, Mulvihill also installed a Wilson Pro-Flow wet nitrous system himself. The setup runs through a Nitrous Outlet plate, with jetting adjustable between 75 and 200 horsepower. It’s toggled by an MSD digital window switch set between 3,000 and 7,800 rpm. With a 15-pound bottle, heater, purge, and remote opener, the nitrous system is as dialed in as the turbo setup.

All this power requires a drivetrain that won’t fold under pressure. Dan’s GT/CS runs a fully built 4R70W automatic transmission with a scattershield, 3,200-rpm stall, and both overdrive and reverse lockouts. A Bauman Quick 1 programmable controller puts the shift points where Mulvihill wants them, while a transbrake helps it charge off the line.

“The car was originally a manual, but I switched to the 4R70W because I wasn’t aware of any manual transmission that, at the time, could handle the planned power levels,” Mulvihill explained. “In addition, I had already corn-cobbed the splines on a twin-disc clutch (one of the two discs) and was concerned that the available clutches were not robust enough.”

Out back, the 8.8-inch rearend houses Ford Performance 3.27 gears, an Auburn Gear differential, and a Ford Performance axle girdle, all connected by a custom steel driveshaft.

Of course, putting four-digit power to the pavement takes more than just tires and gears.  Suspension and related upgrades included Steeda lower and adjustable upper control arms to harness the hook and a UPR tubular K-member to cut weight and stiffen the chassis. A line-lock and MSD two-step launch control rounded out the straight-line setup.

Still, something was missing. That’s where Tint Haus Customs in Davie, Florida, got the nod to fine-tune the suspension. They added Steeda Pro Action struts, installed a Steeda adjustable Panhard bar, and sharpened the steering response.

Street Star

Despite the performance hardware, the car retains much of its street-friendly demeanor. The Hurst Pistol Grip shifter, Auto Meter Cobalt gauges, add more functionality to the comfortable factory interior. Dan even kept the stock GT/CS wheels, albeit widened by Weldcraft — wrapped with Nitto street rubber in front and drag radials out — to maintain that sleeper vibe.

“The rear rims are widened about 1 inch to the inside so that the car looks stock from the side,” Mulvihill explained. “The bigger tires are easily noticeable from the back, though…”

Though this Mustang is capable of serious track times, it isn’t a gutted, trailer-bound drag car. Dan still enjoys hitting the Florida streets regularly in his four-digit ride.

Enhancing the S197’s traction are Steeda Pro Action struts and a UPR Products K-member up front, while Steeda control arms and an adjustable Steeda Panhard bar do their part out back. Add in line-lock, an MSD two-step, and sticky Nittos, and this street car cuts 1.4-second 60-foots without breaking a sweat.

“The car was built with the intent to keep it as stock-looking as possible, so most other drivers don’t notice the car until it starts accelerating. With mufflers and 3-inch exhaust, it’s louder than stock, but still quiet enough to comfortably drive it on the street. However, it roars to life when accelerating,” Mulvihill shared. “The car is a thrill to drive, but the driver has to be very careful of the driving conditions and the rate of acceleration when driving on the road. Wide-open throttle on the street with this power level requires wide-open spaces.”

That’s where this build stands out most. In a pack of modern engine swaps, Dan Mulvihill’s California Special proves that the forgotten Three-Valve still has some serious bite.

“I stuck with the Three-Valve engine because I believed I could achieve my power goals even though most others were doing a Coyote swap,” Mulvihill added. “In hindsight, I’m happy with the choice because of its uniqueness.”