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They're Both Fast

His Or Hers, Big Cubes Or Blower? It Really Doesn't Matter 'cause...

Bob Wallace Jul 2, 2003

No doubt about it, folks do things in a big way down in the Texas direction. That holds true in a great many ways, from the sizes of the ranches to the potency of the chili--and to the power output of the Corvettes. And in keeping with this outsize approach, we have Houston's David and Diane Morrow and their pair of wickedly fast C5s.

There are, without a doubt, other C5s residing in the vast reaches of the Lone Star State that make more power, run quicker and faster in the quarter-mile, or are better prepped for shows. But, we doubt that you'll find another husband and wife duo that each own a steroids-for-cars enhanced C5.

David, CEO of an electronics and hardware distribution firm, took the plunge first when he linked up with local GM Gen. III performance guru Jason Cohen and his gang of speed crazies at Motorsports Technologies, Inc ( Cohen and crew are building some of the wildest, highest horsepower, and fastest truly streetable LS1- and LS6-powered Corvettes and F-Bodies in the south and southwestern United States, and have an impeccable reputation, so David had few qualms about handing them the keys to his pristine black '00 automatic coupe.

After discussing the possibilities with Jason, David opted for MTI's 7.0L "Z07" package for LS1s and LS6s. MTI machines away the original steel cylinder sleeves then fits their own big-bore steel sleeves into the cavities, ready for a final honing. With custom forged aluminum pistons in a 4.100-inch bore and billet steel connecting rods working with a 4.000-inch stroke forged steel crankshaft, the fortified Gen. III measured out at 422 ci. (Editor's note: MTI has since slightly increased the bore to 4.125-inches, to yield a total of 427 cubes.) An MTI-spec, split-pattern high-lift cam controls the opening and closing of the plus-sized (2.080-inch intake and 1.60-inch exhaust) valves in MTI's own seriously reworked Stage III LS1 heads. This mega-size Gen. III small-block utilizes a stock LS6 intake manifold, ported stock throttle body, an MTI True Ram air inlet system, and OEM 2002 Z06 28 lb-hr injectors to supply copious quantities of outside air and high octane fuel. After the combustibles are, well, combusted, they're expelled through a set of ceramic-coated TIPS long-tube headers, Car Sound 3-inch in-and-out high-flow catalytic converters, and a stainless steel Corsa Pace Car cat-back system with Pro tips. Through the automatic, the big-cube Gen. III pushes out 472 rear wheel horsepower (rwhp) on MTI's Dynojet.

The rear-mounted C5 version of the 4L60-E automatic overdrive tranny is perfectly capable of handling all the abuse a reasonably close-to-stock LS1 can dish out. However, when you bump up the displacement by roughly 22 percent, and the horsepower by a substantially higher percentage, a stock 4L60-E's lifespan will be shortened considerably. Thus while the MTI crew was busily building the engine for David's coupe, the trans was at Century Transmission's Richmond, Texas, shop for a thorough upgrading. Before the 4L60-E was re-installed, it was treated to a Vigilante 2,400 stall speed torque converter, and the differential was swapped out for a six-speed C5's slightly steeper 3.42:1 cogs.

The "base" underpinnings on a C5 are better and more capable than the best upgraded suspensions on most other cars. Thus David and Jason pretty much left well enough alone, with the sole exceptions of a slight altitude adjustment (primarily for looks) and, considering the substantially enlarged LS1 under the hood, a much-needed brake upgrade to Baer's EradiSpeed front and rear brake rotors.

Before calling it quits, David made a few final and notable changes to the black coupe. He ditched the stock five-spoke alloys and factory-installed run-flats for a set of 17-inch Fikse FM/5forged modular wheels, 9.5-inches wide up front and 10.5-inchers at the back. The fronts are cloaked in 275/35ZR-17 Nitto Extremes while the rears got wrapped in 315/30ZR-17 Nitto drag radials--for street duty (a pair of Hoosier 10x28-16 slicks provide the sorely needed bite for passes at nearby Houston Raceway Park). Richey Custom Paint fitted, painted, and installed a Caravaggio rear spoiler and a Motor City carbon fiber hood. And should he ever get bored whilst sitting in HRP's staging lanes, David can always make use of his C5's audio (and video) upgrades that include a Pioneer DVD, Dolby 5.1 digital gear, Kenwood amps, and 10-inch Eclipse subwoofers.

After watching her husband have all the fun, Diane Morrow, a financial adviser, decided it she deserved some four-wheeled festivities and bought herself a Torch Red '02 convertible, with the standard automatic transmission and the optional 3.15:1 "Performance Axle" ratio gears, and promptly proceeded to go bonkers in her own unique way.

Once again, Jason Cohen and his merry band of ultra-performance pranksters at MTI were called upon to boost a C5's go-fast factor. But this time, instead of building another big-inch LS1, they left the bottom end alone. The focal point of the convertible's muscle enhancement program was a Magnuson Products Magna Charger (see "Of A Greater Magna-Tude" in the February issue for more details of this positive displacement supercharger system), highly polished, pullied to make 5.5 psi of boost. The crew aided and abetted the blower's task of force feeding the LS1 with a set of MTI Stage II cylinder heads, ram air, and a ported throttle body, then assisted its ability to exhale by installing another set of ceramic coated TPIS long tube headers, 3-inch Car Sound high-flow cats. The balance of the exhaust is from Corsa, including a "X" crossover pipe and Touring cat-backs with Pro tips. MTI also installed some apropos-for-Texas 42 lb-hr gushers, er, injectors and performed their own recalibration of the engine management system. Pushing the power through the automatic tranny, the blown and mildly tweaked LS1's rear wheel output was measured on MTI's chassis dyno at 410 hp.

Diane wasn't inclined to get quite as nuts with her Corvette as husband David had gotten. Thus the 4L60-E received only a mildly beefing up by Century Transmissions and the stock torque converter was retained, as were the 3.15:1 rear gears. She did, however, have the boys at MTI install a Ron Davis radiator, a Doug Rippie Motorsports external engine oil cooler, and a B & M auxiliary transmission cooler, all in the interests of longevity during the hot and humid Texas summers.

Because of its added height, a C5 Magna Charger requires a raised center hood. That was all the excuse Diane needed (as if she needed any excuse) to add some extra flash and pizzazz to the exterior of her red ragtop. Several companies are now offering custom domed C5 hoods for Magna Charger installations. Diane opted for one from RK Sport and had it prepped and painted by Richey, along with a Caravaggio rear spoiler, just like the one on David's coupe. Additional yet functional eye candy came in the form of 18x9.5 and 10.5 Weld EVO forged and chrome-plated Axis SL wheels, sheathed in 275/35 and 295/40-ZR18 Michelin Pilot Sport tires.

Last but not least, Diane turned her attention to the convertible's interior. A pair of AutoMeter gauges (boost and fuel pressure) was installed in a double pod cover on the left windshield pillar, while CK seat covers, a shift knob from Extreme, and a selection of faux burlwood trim and leather accents from Mid America Designs round out the dress-up.

His or hers, big cubes or blower. David has clocked a best of 11.12 at 126 mph, with a 60-foot time of 1.62 seconds, on the Hoosiers, at Houston Raceway Park. Diane's droptop ain't no slouch either. Mrs. Morrow has guided her rapid red ragtop to a best of 11.72 at 124 mph, with a 1.74 second 60-foot time, on the same set of Hoosiers, at HRP. No, it really doesn't matter. They both are quite fast.



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