Aspiration Affirmation

This Nowicki Autosport Concept7 packs a 416-cube engine and no supercharger, thank you very much

March 23, 2017
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Cats versus dogs. Mary Ann versus Ginger. Black licorice versus that red stuff. We’ve all got our preferences, and for some nothing beats the visceral thrill of a positive-displacement supercharger and the sledgehammer application of power it offers at the very twitch of the throttle.

On the other side of the paddock is the natural-aspiration camp. For them, the more measured run-up in horsepower, delivered through a crisply tuned, deep-breathing combination drawing breath on its own terms, is the only way to go. In our experience there’s no middle ground. You’re either for forced induction or you’re not—just like your wife’s preference for Chip and Joanna over Tarek and Christina. Ask her, and she’ll tell you in no uncertain terms.

You can count David Woodbury as a card-carrying member of the Natural Aspiration Society. The Little Rock, Arkansas resident firmly eschewed the blower idea when it came to pumping up the output of his 2015 Stingray.

“Blowers are all well and good, but heat soak is a real issue, especially on the track, and there’s a front-end weight penalty that comes with them, too,” he says. “That’s not to say they’re not effective, but I prefer a naturally aspirated engine, even if it doesn’t make quite as much horsepower as you could achieve with a supercharger.”

Engine output these days is a subjective thing, with advances in tuning enabling some truly astounding power ratings in honest, drive-it-to-work Corvettes, especially with turbos and, yes, superchargers. That’s not to say naturally aspirated engines have been figuratively or literally sucking wind. The 640-horsepower/595-pound-foot dyno ratings for the Nowicki Autosport–built LT1 in Woodbury’s car nearly matches the 650-hp output of the C7 Z06’s supercharged LT4, and it eclipses that of the C6 ZR1’s vaunted LS9.

This eyebrow-raising achievement was made possible largely by replacing the original 3.62-inch-stroke crankshaft with a 4.125-inch Callies Dragonslayer unit, which pushed displacement from 376 cubic inches to 416. It was complemented with a special-grind Comp Cams camshaft—the specs of which are more closely guarded than Jay Leno’s denim-shirt collection—to make the most of the engine’s newfound air-pumping capability. (For customers who prefer to retain the LT1’s factory displacement, Nowicki offers a head-and-cam setup rated at still-formidable 612 hp and 531 lb-ft.)

There’s more to the formula. The stock heads were decked and ported, and the stock valve springs were swapped for PSI’s dual-coil springs. The lifters, meanwhile, were replaced with those from GM’s supercharged LSA engine. That last change effectively eliminated the engine’s ability to switch into cylinder deactivation mode, but given the vigor with which Woodbury drives the car, it wasn’t likely to enter it anyway. There’s also a physical “phase limiter” to prevent the factory variable valve-timing system from phasing the big cam right into the valves. Nowicki Autosport founder Jeff Nowicki also changed from the factory Dexos oil to Mobil 1 5W30, a tradition for his engines that dates back years to his endurance-racing days.

Also from Issue 113

  • 1969 "Quarter-Millionth" Convertible
  • Buyer's Guide: $20K
  • Original 1967 Convertible
  • DIY Corvette Museum
  • Father-Son C4 Driver
  • Racing: Behind the Scenes
  • 1955 LaSalle Show Cars
  • Inside Bowling Green Assembly
Buy Corvette magazine 113 cover
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