Michael Galimi
May 29, 2014

The Three-Valve 4.6L mod motor seems to be forgotten in a world filled with '11-to-present 5.0L Mustangs, Fox-rod swaps using Coyote 5.0L and Four-Valve 4.6L powerplants, and the more budget-oriented Two-Valve mod motor engine swap.

It isn't like the Three-Valve variant of the 4.6L mod motor family isn't good—it came with 300 hp from the factory and was first offered in the retro-themed '05 Mustang GT model. The 24-valve engine enjoyed a production run through the '10 model year and has a nice following in the high- performance market. To the uninitiated, the Three-Valve might be overlooked, but true enthusiasts know its potential far exceeds the GT powerplants that came before it.

The Three-Valve could be the biggest secret in the Mustang world. It responds very well to modifications—particularly boost—and '05-'10 Mustang GT models are priced right. Used S197 models with the Three-Valve engine (in excellent condition) can be purchased for around $10,000-$15,000.

The near-stock 4.6L features two intake and one exhaust valve. Jim LaRocca’s ’06 Mustang GT features a custom tune, L&M throttle body, X-style mid-pipe, and after-cat exhaust system. It laid down 293 rwhp through a stick-shift transmission.

Case in point is Jim LaRocca, a second-generation Mustang gearhead, who picked up a clean '06 Mustang GT in that price range. The high school student spent last year working part-time as an apprentice at Krazy House Customs to learn how to work on high-performance vehicles and earn a few bucks to roll right back into his hot rod.

LaRocca spent the year doing all the small tasks like cleaning up and being the extra set of hands for Krazy House's technicians, but he picked up a lot of valuable tips and experiences along the way. His father, Jimmy LaRocca—legendary Mustang racer, lifetime Procharger spokesman, and former Mustang shop owner—taught the junior LaRocca the merits of a good power-shift and aggressive drag racing skills during the family outings at Old Bridge Township Raceway Park (Englishtown, New Jersey). Little by little, the car ran faster, and eventually the young driver knocked off a best of 12.97 at 105 mph.

The GT benefited from 3.73:1 rear gears, L&M throttle body, X-style mid-pipe, after-cat exhaust, and a set of Nitto 555R tires. But when you carry the surname of LaRocca, then a belt-driven compressor will eventually find its way onto your Mustang.

Given that the elder LaRocca has worked with ProCharger since the company's inception, it made sense for the kid to bolt one on his Mustang. The Three-Valve powerplant is near stock so the fine folks at Procharger recommended the P-1SC-1 supercharger system for that model.

Krazy House Customs' Brandon Carrabba ordered the tuner kit version so he could handle the tuning in-house. Another reason for the tuner kit was the custom MAF sensor placement—more on that in a bit. All Procharger systems for the modern Mustang come standard with an air-to-air intercooler and this particular tuner kit came with larger fuel injectors and an upgraded fuel pump. Carrabba handled the custom tuning using SCT software and an XCal3 to upload it into the factory ECU.

The P-1SC-1 head unit is more than enough to destroy any stock Three-Valve engine. Typically the upper limit for a supercharged factory long-block is in the 450 to 490 rwhp range on a DynoJet chassis dyno and around 420-450 rwhp on the more conservative Mustang Dyno brand. Those results usually are achieved with 10-12 psi of boost. Some enthusiasts have attained higher rwhp numbers in stock long-block combinations, but with limited success in the longevity department.

In this application, LaRocca is running the standard pulley that comes with the system, which is designed to produce up to 8 psi. That puts output far below the threshold of the untouched 4.6L engine. Of course, more boost is just a pulley change away, but the decision was made to increase power only after LaRocca is comfortable with the standard kit. The P-1SC-1 head unit achieves the moderate boost pressure thanks to a 3.90-inch blower pulley and a 7.65-inch crankshaft pulley. As a side note, the supercharger runs its own independent belt instead of being run inline with the accessories. The belt features an eight-rib width for better traction.


01. The first order of business was to lose the front fascia, and pull off the intact tract tubing and air-filter assembly.

02. The Procharger system uses a dedicated supercharger belt drive and the lower crank pulley uses three dowel pins to lock it on the stock balancer.

03. Procharger supplies a longer crank pulley bolt due to the additional blower pulley that is bolted on. The crank bolt is installed with 35 lb-ft of torque and then turned 90 degrees.

04. A bracket setup bolts on the driver’s side of the engine. Procharger built it to be durable thanks to thick mounting plates and a heavy-duty adjustable tensioner.

05. The P-1SC-1 needs to have a few accessories added to it before bolting it on the engine. The oil drain line is an added convenience that allows the supercharger oil to be changed without removing the supercharger head unit.

06. LaRocca bolts on the P-1SC-1 head unit, which is capable of producing upwards of 825 hp and flows 1,200 cfm.

07. Procharger recommends changing the supercharger oil every 6,000 miles, and the drain hose helps servicing the blower a lot of easier and quicker.

08. An eight-rib belt turns the supercharger and the blower pulley checks in at 3.90 inches. A swap to a smaller diameter pulley will increase the supercharger impeller speed for more boost.

09. Procharger supplies a new electric fan assembly with custom shroud. The same factory fan speed controller is used on the new setup. The extra pipes under the hood and supercharger placement makes the installation a tight but exact fit.


The installation is fairly straight forward, with the head unit bolting into a dedicated bracket system that is hung off the driver's side of the engine. The discharge piping is run down and into the front-mounted intercooler, the air exits the cooler, and then ultimately enters the throttle body thanks the massive aluminum pipes included in the system.

Procharger prescribes '03-'04 Cobra fuel injectors for its kit, which are rated at 39-lb/hr with 39 psi of fuel pressure. A second fuel pump and installation kit is included to help supply the hungry injectors with dead-dinosaur juice.

A major modification to the kit was the custom MAF sensor location. Krazy House Custom specifically installed the factory MAF sensor in one of the discharge pipes after the intercooler for smoother flow and a better MAF signal. Carrabba then sent the pipe—with the relocated MAF sensor—to PMAS for flow testing. The flow/voltage curve of MAF sensor and housing is vital for the ECU calibration.

Essentially the MAF sensor reads the mass of air that is flowing past it; the reading is measured in volts. The ECU is programmed to assign a certain airflow value to the voltage reading to determine how much fuel is needed to feed the engine.

PMAS flowed the supercharger pipe with the MAF sensor installed and created a transfer function. That information is used to add values in the MAF transfer function portion of the SCT software. Tuners will spend countless hours using a trial-and-error method to get the transfer function correct, whereas Carrabba has the exact flow curve and can skip that tedious process. He can program the ECU with an accurate voltage/airflow value, making the engine run smoother and cut down considerable tuning time.

LaRocca's near-stock GT produced a paltry 291 rwhp and 308 lb-ft of torque at the wheels sans blower. After the Procharger was installed and Carrabbi fiddled with the calibration, the Three-Valve made an impressive 405 rwhp and 384 lb-ft of torque on 7.5 psi. Those results were accomplished with a very conservative 15 degrees of ignition timing and an 11.2:1 air/fuel ratio.

“We wanted to start Jim with a mild tune so he can learn to drive the car,” Carrabba said. “Once he gets more time behind the wheel, then we can turn up the boost and put a little more timing in it.”

As the nasty New Jersey winter is coming to a close, the LaRocca family is itching to get on track so they can get the Three-Valve singing with the 7.5 psi of boost flowing.


10. A massive air-to-air intercooler is located in the front bumper area and is mounted using three sets of brackets.

11. Once the intercooler was bolted into place, it was time to add the charge piping. A bypass valve attaches to the pipe in the lower corner on the driver’s side, just outside of the engine compartment. A bypass valve relieves pressure in the system when the throttle blades close. This is done so air doesn’t “back up” into the centrifugal supercharger, which causes turbulence that’s capable of breaking the head unit.

12. LaRocca adjusts the charge piping as he works his way from the supercharger to the intercooler, out of the ’cooler, and into the throttle body. Rubber couplers and clamps are used to join the different sections of piping together.

13. Here is the custom MAF sensor location that Krazy Horse Customs built for this application. PMAS flowed the pipe and MAF sensor to create a flow/voltage chart for the MAF transfer functions in the SCT tuning. The specific placement of the MAF sensor produces a clean signal and reduces the time it will take for Brandon Carrabba of Krazy House Customs to tune.

14. The relocated MAF sensor requires extension of the factory harness. The Krazy House Custom guys stressed that you have to use quality wire and solder the wires.

15. The charge piping fits in perfectly, but the tight confines of the engine compartment required Procharger to include a new overflow tank, which now mounts on top of the radiator.

16. A Shelby GT500 pump is included in the kit, and Procharger supplies the required materials, such as a clamp, a fuel pump sock, and fuel line in order to add the second fuel pump. LaRocca pulled out the fuel pump by removing the back seat and accessing the drop-in fuel-pump setup.

17. Of course, the elder LaRocca was compelled to jump in and check over his son’s work to ensure it was all systems go. Once he gave the green light, it was game on for the Mustang GT to spin the chassis dyno rollers at Krazy House Customs.

18. The results of just 7.5 psi of boost—405 rwhp and 384 lb-ft of torque. Krazy House Customs utilizes a Mustang Dyno, which generally reads 10-15 percent lower than the more traditional DynoJet chassis dyno. Also included on this chart is the car’s best run in naturally aspirated trim, 291 rwhp and 308 lb-ft of torque.