First Drive: 757 Horsepower Callaway Corvette Z06 SC757

    Bradley IgerWriter, Photographer

    For sane, rational people, the C7 Corvette Z06 offers more than enough performance right out of the box. Chevrolet's current top-spec sports car rolls out of the Bowling Green assembly plant boasting 650 horsepower and 650 lb-ft of torque from its supercharged 6.2-liter LT4 V8, enough grunt go toe-to-toe with the most capable exotics from around the world, many of which costing multitudes more.

    Chevrolet pegs the Corvette Z06's straight-line performance at 3.2 seconds to get to 60 mph from a standstill when equipped with a manual gearbox (2.95 seconds with the automatic), and 11.2 seconds to complete the quarter mile (10.95 with the automatic). Actually achieving those numbers in the real world is a feat in and of itself, since all of that twist is all getting sent exclusively to rear wheels all too happy to go up in smoke if you're a bit overzealous on the throttle.

    For some, too much is never enough. For those who seek performance above and beyond the standard Z06, Callaway Cars offers a solution: the Callaway Corvette Z06 SC757. As the name suggests, the SC757 treatment takes the LT4's output above and beyond what the car delivers from the factory, dishing out a Hellcat-besting 757 horsepower and 777 lb-ft of torque.

    Does Callaway's tuning make a great sports car even better, or is this a case study in the law of diminishing returns? We grabbed the keys to this manual-gearbox-equipped example while Pete Callaway wasn't looking and embarked on a tire-melting discovery mission through the back roads around Los Angeles to find out purely in the name of science, of course.

    Beyond Bragging Rights

    It's easy to dismiss the SC757 as an exercise in excess. After all, adding 107 horsepower and 127 lb-ft to a car that already incinerates the rear tires should, by all logic, be a recipe for more of the same. But Callaway's modifications to the Z06 prove to be more substantive than sheer horsepower one-upmanship, and much of it has to do with how that additional grunt is generated.

    It's no secret that the C7 Z06 has struggled with heat management since its debut in 2015, particularly when being pushed hard on a racetrack. While the issue has several facets, a significant contributor to the problem was GM's decision to move to a smaller 1.7-liter supercharger for the LT4 versus the 2.3-liter unit they had used previously with the C6 Corvette ZR1's LS9 V8. Using a smaller blower meant that the LT4's supercharger would have to spin faster in order to generate a similar amount of boost, and that in turn creates more heat.

    Callaway's SC757 treatment ditches the stock 1.7-liter unit and swaps in the company's GenThree supercharger system. The package consists of a 2.3-liter TVS2300 roots-style blower with three discrete intercooler elements and a larger capacity coolant pump to keep air inlet temperatures down. It's paired with a new intake manifold with a runner configuration tweaked to increase mid-range torque. Exposing the supercharger housing through the hood isn't just for aesthetics, either it also allows for better air flow and heat transfer through the engine bay versus the stock hood, another aspect of the heat management equation that the standard Z06 has struggled with in the past.

    Aesthetically, Callaway opts for subtlety rather than bravado with the SC757 package. Aside from the hood extractor and the factory-style badging that adorns the rear fenders and rear fascia, there isn't much to tip off onlookers to the fact that Callaway has had a hand in enhancing the car's performance. It's a similar story inside the car as well, with a center console badge, sill plates, and a pair of embroidered floor mats serving as the Callaway identifiers. While the package may be visually low key, once we got this Callaway-tuned Z06 out on the road, the SC757 treatment proved to be far less subtle in practice.

    Behind The Wheel

    Callaway's testing shows that the Z06 SC757 is capable of sprinting to 60 mph in 2.8 seconds on its way to a quarter mile time of 10.5 seconds on stock rubber. This puts the SC757 Corvette roughly on par with a McLaren 675LT for straight-line pull a car which weighs less than 3000 pounds, has a dual-clutch transmission, and costs about $400,000.
    Like the Mclaren, or any car with this level of performance capability, pilots must be respectful with their use of the throttle at any remotely legal speed. Watching the traction control light come on as the speedometer rapidly approaches triple digits is simultaneously amusing and unnerving, but its intervention is surprisingly measured and unintrusive, much the same way it is with a stock Z06.

    And that theme is maintained throughout despite the additional power on tap, the SC757 behaves much like a factory-stock Z06 during normal driving. It's happy to lope along in traffic when required, and the throttle doesn't function like some sort of on-off switch (as is the case with some aftermarket performance packages).

    But find an open stretch of road, put it in second gear and drop the hammer, and the Callaway-tuned Z06 pulls like very few warrantied vehicles can. A few tenths may seem trivial in the grand scheme of things, especially when you're talking about a sports car that's as fast as a stock Z06 is. But trust us, the difference is noticeable, and under the right circumstances, the additional performance is indeed usable.

    Perhaps even more importantly, Callaway's efforts to address the Z06's heat management woes appear to have paid off extended spirited sessions on roads which saw a stock Z06's temperature climb unnervingly high seemed to have little effect on the SC757, though repeated lapping sessions on a road course would admittedly be a more conclusive test. Nevertheless, the system definitely shows promise in that regard, and Callaway is currently developing an optional heavy duty cooling system for would-be customers that plan to do serious track work. That package will add a reshaped front fascia and a higher capacity cooling system to the mix, among other tweaks.

    Speaking of additional options, this tester has a few. Callaway's sport exhaust system is a low restriction design that does away with the factory dual-mode system in favor of a non-active system that's tuned to eliminate cabin resonance while giving the SC757's bark a little more character. While it didn't sound dramatically different from the stock system in "loud" mode to us, we appreciated the improved sound at idle and low revs, and the lack of sudden jumps in volume that are all too common with the factory setup. Similarly, Callaway's short throw shifter feels like a tangible improvement over the stock unit as well, eliminating the rubbery feel and reducing the fear of missed shifts particularly from second to third.

    By The Numbers

    The SC757 package starts at $17,995 and can be applied to a factory-stock Corvette Z06 from the current or previous model year. Alternatively, the package can be optioned onto a new Corvette Z06 when the car is ordered through one of the Chevrolet dealerships in Callaway's network. It's also important to note that Callaway's package doesn't void the existing GM warranty, and Callaway provides an additional three-year, 36,000 mile warranty of their own, which can optionally be extended to five years and 60,000 miles.

    While there's an argument to be made that there're cheaper ways to make a Z06 faster, there's certainly something to be said for the notion of not being left holding the bag if those mods cause issues down the road, and GM's willingness to work directly with Callaway to provide coverage to their customers speaks volumes for engineering behind the SC757 package.

    Even if you're in the camp of folks who'd consider the LT4's output to be stout as is, Callaway's efforts to address the heat management issue are probably reason enough to give the SC757 treatment some consideration if the car is going to see any significant track time. After all, all the power in the world isn't worth much if you have limp back to the pits after a handful of laps. Think of the additional 100 horsepower as a nice bonus.