Steve Baur
Former Editor, Modified Mustangs & Fords
July 7, 2010
Photos By: Kevin DiOssi

When we asked Diego Castro what he liked most about his Mustang, his answer was, "how easy it is to drive." One wouldn't think that a vehicle capable of running a 10.07 at 141 mph would be easy to drive, but that's what this Lake Worth, Florida, resident says of his twin-turbocharged, Four-Valve Mustang GT, which laid down the aforementioned numbers using nothing more than boost and a pair of 305/40/18 Nitto drag radial tires.

Diego's '00 GT started out as a Spring Feature Edition Mustang GT. The Spring Feature package was available for '00 and '01 GT models, and was equipped with black hood stripes, machined-face alloy wheels, hood and sidescoops, and black lettering that darkened the Mustang name in the rear bumper cover. Diego had several Mustangs before this one, but was turned off by the '94-'98 body style. That all changed with the New Edge design, and before long, he was behind the wheel of this Spring Feature Edition.

The usual bolt-ons followed, and then the power-improved GT received a real boost in the form of an ATI ProCharger P-1SC centrifugal supercharger. "I grew out of that and upgraded to a D-1SC and a Bullitt intake manifold," recalls Diego. With the propulsion system up to an acceptable level, he turned to modifying the car's exterior with a full Saleen makeover for his SN-95. A Kaenen hood was also added for more muscular appeal, and the GT now rolled on 18x9 front and 18x10 rear Saleen hoops.

Shortly thereafter, the '03 Cobra was introduced to the world and Diego's 450 rwhp machine just wasn't enough. "Next up was a built short-block, and while it was apart, I decided to do a Four-Valve conversion," says Diego. Since the ProCharger had served him well, this Spring Feature owner upgraded yet again to an F-1A head unit, and was quite satisfied with the 600-plus rear-wheel horsepower the Mustang was churning out. Belt alignment issues, however, prompted him to look for a different horsepower solution.

The answer came in the form of an HP Performance twin-turbo system, but Diego didn't stop at the power adder. The HP 57 turbochargers would soon pressurize ported heads with custom turbo camshafts, before mixing with the amplified fuel from the upgraded fuel system. A Lentech AOD automatic transmission was installed, and pushing through a non-lockup torque converter, the Modular mill produced 780 rwhp.

At the local track, Diego's Saleenized GT charged to 114 mph in the eighth-mile, but during a test-and-tune night, a valve seat fell out of one of the cylinder heads.

"Once again, the car went under the knife," says Diego, "but it was time for me to be a bit more hands-on with the engine build. I always wanted to learn, and fortunately for me, the guys at Power By The Hour (Lake Worth, Florida) were willing to hold my hand while I put it together."

Segundo Perez at Engine Rebuilders of West Palm Beach, Florida, machined the aluminum block, and then Jake Long and Jesse Guajardo helped Diego screw the overbored 283ci Teksid block together with CP pistons, and stock Cobra Manley connecting rods and crankshaft.

Diego opted to throttle back the build by using stock Four-Valve cylinder head castings and camshafts, and Engine Builders went through the heads to freshen them up. A stock '01 Cobra intake manifold went back on, along with an Accufab twin-bore throttle body and a Pro-Flow mass air meter. Ford GT supercar fuel pumps pressurize the 60-lb/hr injectors. Speaking of pressurizing, Diego upgraded the turbochargers to 60mm units, and HP's air-to-air intercooler keeps the 21 psi of boost reasonably cooler.

Power By Hour then built one of its 4R70W "1-2-1" transmissions that featured a Performance Automatic valvebody and a Baumanator transmission controller. An FTI torque converter with a 3,800-rpm stall speed pushes the horsepower to the 4R70W, and eventually back to the 3.31-geared 8.8 rear. Moser axles and an Eaton differential have been entrusted to deliver the ridiculous amount of power and torque to the pavement. QA1 shocks and struts join UPR front coil springs and Bullitt rear springs in controlling body movement, while a quartet of Steeda rear control arms limit the twist.

Inside the Mustang, little has changed other than the sound system installed by Ron Storms at World of Sound. Diego is also quick to thank Dennis "OMPC" Rowe for the countless hours spent in the garage, and his wife, Karen, who has put up with all of those late nights in the shop.

As far from stock as Diego's Spring Feature is, it's not quite finished just yet. "For 2010, I want to make some minor adjustments, switch it over to E85, and push the envelope a bit further-9s in street trim is the goal. Jake Long had been running a high-compression/E85 combination for a few years now and has had great success," notes Diego.

A recent mishap at the track resulted in a holed piston, and that turned into a bump in compression with some new flat-top pistons. Diego then converted the fuel system to run on the E85, and Long loaded up the custom tune using SCT software. Diego also switched to Nitto's new 315/40/18 NT05R drag radials, and with just 11psi of boost, the car has gone 10.49 at 141-only 10 more psi of boost to go.