Four Score

Also from Issue 40

  • 2009 C6 ZR1 debut
  • 1965 big block at Goodwood Revival
  • Comparison Test: 2007 vs. 2008 Z06
  • 2009 Indy Pace Car
  • Saddle Tan Split-Window
  • Rare Aztec Gold 1998 coupe
  • Market Report: C4
  • CRC’s C1-look C5 convertible
  • Callaway B2K at Bloomington
  • How-To: C2 radiator support repair
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“The Aerovette had another problem, too: a difficult manual-transmission layout. The entire drivetrain became complicated by having to circulate the torque flow around the engine compartment a couple of times. (Mid-engined) is certainly doable, (but it’s not easy).”

Worse yet, the midship concept showed no real-world advantages in handling. The front-engined concept for the C4 was already promising near 50/50 weight distribution, so this key attraction of mid-engine cars was made moot. Also, said McLellan, "Our objective was…to give the car very high limits from a handling standpoint, (but also) to make those limits stable in the sense that the driver (didn’t) have to interact with the car in trained ways. In other words, the car isn’t going to spin out on him when he closes the throttle.

“Finally, there’s the crash-integrity issue—having that very large engine behind you when you have to deal with real-world collisions. To contain the engine behind the occupants be­comes not an impossible job, but an additional job. That task, of course, gets easier when you have a small, lightweight engine, like the (Fiat) Xl/9 or the Fiero.

“So to make a long story short, yes, the mid-engine would have given us a more extreme appearance change, but that’s about the only real advantage. (Since) Corvette buyers, accor­ding to our surveys, didn’t much care, there were just too many reasons why we felt better off going front-engine.”

SKELETON KEY

With that question out of the way, the real job of engineering the car could begin. Due to tradition, relatively low production, and a longstanding preference for plastic bodywork, it was already assumed the C4 would use body-on-frame construction, not the more common all-metal unibody. The frame that was created, however, had many characteristics in common with unibody structures, most notably its construction from separate stampings of fairly thin sheet steel welded together. Chevrolet dubbed the new layout a “uniframe.”

Ronald N. Burns, who worked under staff engineer Robert A. (Bob) Vogelei, explained the uniframe this way. “The basic concept real­ly came out of marrying the frame with what we called the birdcage, or upper structure, of the previous car. In Corvettes from 1963 through the 1982 model, the birdcage surrounded just the (cabin and was) perched on the frame rails on rubber body mounts. The ‘84 marries those two elements together in an integrated body/frame structure. There’s no more separation of frame rails and birdcage: Everything is welded up as one unit. What re­sults is a stiffer, better structure from the mass- and cost-efficiency standpoints.”

Another thing that made the new uniframe unlike past Corvette frames was a lack of a central crossmember under the passenger floor. This allowed the floorboards to be placed as near to the road surface as possible, lowering the car’s overall stance.

“Another important element” Burns went on, was “…the extensive use of high-strength, low-alloy [HSLA] steel. We worked closely with (GM Manufacturing Development), the GMAD tooling people, the Bowling Green tooling people, and our suppliers in perfecting techniques for welding the high-strength, low-alloy material to itself.”