It was to become a turning point, the pivotal moment, that critical juncture. Whichever expression you prefer for the decisive shift from the C4 to the C5, it wasn't the first time this sort of thing had occurred in Corvette history.

To mention just a few, we'd point to the first V-8–powered model in 1955, which replaced the anemic Blue Flame Six. Then there was the end of the straight-axle era, when the chassis was upgraded to include an independent rearend. The 427 big-block Vette was certainly a startling development. Ditto for the shift in body style from the hard-edged, midyear Sting Ray to the Coke-bottle Stingray shape. And perhaps one of the more ignominious events was when smog laws emasculated America's sports car. The list goes on and on.

Then there's the sea change that took Corvette into the modern era of C5 and C6 supercars. Not that the C4 was somehow wanting during its time. After all, its preliminary introduction in 1983 heralded the first all-new Corvette in two decades. Only 44 pre-production cars were built that year, but none of them was ever sold, and all but one was eventually destroyed, making it the "missing year" of Corvette production.

As Mike Yager, head of Mid America Motorworks, points out, most pre-production vehicles are crushed during testing or soon after, when they are no longer needed. Sadly, there are no engineering test platforms in existence from any prior Corvette generation.

Not so with the C5 prototypes, three of which Yager now owns. In 1988, GM began development of this radically reworked model with the CERV-4b. It appeared to be a C4 on the outside, but underneath were a number of mechanical upgrades being developed for the C5, such as the interior, exhaust, suspension, gas-tank filler, and rear convertible trunk entrance.

As these prototype designs morphed from CAD drawings into real-world test vehicles, 14 "Alpha Build" cars were assembled. The Alpha cars were a rough approximation (putting it charitably) of how the C5 Corvette would look. They were then followed by a Beta version, which improved on the rudimentary R&D phase, in part by perfecting both the hydroformed framerails and the all-new Gen III powerplant.

For those who like to see what those GM's wizards of engineering did behind the curtain, we prevailed on Yager for an exclusive shoot combining not only both the Alpha and Beta test beds, but also the last-ever C4 produced. This troika of collectibles, gleaned from Yager's extensive personal collection, provides a revealing look at how the C4 was transmogrified into a crudely camouflaged C5 prototype. Like grinding sausage or watching a bill making its way through the legislature, it ain't pretty, but the final result sure was.

While it might not be immediately obvious from these primeval prototypes, Chevrolet designers worked hard to improve on the C4's dated lines and aging chassis, the latter by reducing the number of parts needed by a whopping 1,500 items. This deletion was designed to tighten up the rattletrap dynamics of the C4 (for a firsthand confirmation, just ask our long-suffering editor about his personal car), while also streamlining production and maintenance. In addition, the frame was substantially stiffened by using the aforementioned hydroformed main-rails linked to a backbone configuration.

In contrast to stamped or welded parts, this manufacturing process basically consists of using high hydraulic pressure to press room-temperature metal into a specialized die. To hydroform aluminum into a Corvette framerail, a hollow tube of aluminum is placed inside a negative mold with the desired shape. Hydraulic pumps then inject fluid at very high pressure inside the aluminum, which causes it to expand until it matches the mold.

Hydroforming allows for production of complex shapes with concavities that would be difficult if not impossible with standard solid die stamping. It also optimizes the stiffness-to-weight ratio at a lower cost per unit. A stiffer frame, in turn, allows for softer suspension settings to enhance ride comfort, even as the handling is more stable. (The 8-inch-wider track of the C5 improved this aspect as well.)

As for body styling, the influences came from a number of places. In the past, the concept and design of the Corvette was largely conceived by legendary individuals such as Zora Arkus-Dutov, Bill Mitchell, and Pete Brock. Instead, the C5 stemmed from both market research and feedback from 1,600 or so Corvette owners (along with owners of similar sports cars). In the halls of GM, this "Voice of the Customer" had been previously a distant note. One thing designer John Cafaro heard loud and clear, though, was that prospective customers feared that America's favorite sports car might end up looking like a "furrin" concoction; e.g., a Ferrari or an Acura NSX.

That anxiety was not totally unfounded, as GM designers admitted to looking at cars like the Nissan 300ZX and Mazda RX-7 for styling cues and quality control. Even so, all this lucubrating by GM stylists and engineers over the lines and underpinnings eventually paid off, as the C5 was significantly superior to the C4 in every meaningful way.

That included a new, 345hp (later increased to 350 horses) LS1 small-block. This lighter, all-aluminum mill also represented a complete redesign, featuring a distributor-less ignition and a revamped firing order. Combined with a more slippery shape with a mere 0.29 coeffcient of drag, the new model would eventually achieve a surprising rating of 28 mpg on the highway. Of even greater interest, of course, was the enhanced performance.

To maximize this aspect, the C5 Alpha and Beta cars were subjected to a number of studies to evaluate aerodynamics, durability, driveability, and the like, providing essential data so Corvette engineers could further refine the design. Using that research, GM started building the first of a baker's dozen of test cars in the mid '90s.

These test mules were driven extensively, their higher-caliber firepower disguised with ersatz body panels, like modern-day Q-ships, to fool prying eyes and photographers as to the underlying reality.

So how did Yager come to own these intriguing slices of Corvette history? The Alpha and Beta Corvettes were obtained to join another research vehicle in the Yager stable that played a significant part in the creation of the C5. In 2009 Mike's sons, Michael and Blake Yager, purchased the CERV-4b at auction. After that, the Alpha and Beta versions, which had been in the GM Heritage Collection, were sold at a later Barrett-Jackson auction. The buyer, appreciating their historical significance, later contacted Yager and asked if he would like to have them safely installed in his collection at the hammer price. Aside from the attractive price, Yager jumped at the chance to round out his display of the engineering platforms of the C5 Corvette.

"They're an exceptional piece of Corvette history," he points out. "The C5 is such a special car. And there's only one left of each of these development cars. They're not prissy cars, but they drive and handle really well. They're testing tools, works in progress that show the engineering process."

Like a modern-day Indiana Jones, Yager uncovered intriguing details in these test beds, such as old decals indicating the age of certain components. "The dates of things were surprising, how early they started on the project. People don't realize how long it takes."

He also could spot some detours along the way, such as items for the dash and door panels that never made it into production, as the designers took a different direction. He even came across some jury-rigged stuff. "In the Beta car, the ignition switch looked like it came off a '53 pickup. Of course, the engineers just needed something to get the engine started."

Delineating the development process even further, Yager notes that there were five basic stages on the C5: CERV-4b, Alpha, Beta, pre-pilot (or pre-production), and pilot cars (which are actually available for purchase by consumers). He has a number of contacts at the factory who have helped him gain some insight into what goes into creating a new Corvette, such as Peter Liccardello, who served as an Integration Manager, basically a go-between from engineering to manufacturing. "It's really cool to own the car that GM people like Peter can identify."

Of course, Yager would like to have all five phases in his collection for posterity. "I'm definitely interested in getting those," he admits. "I saw No. 19 of the '97 pilot cars at Bloomington and didn't buy it, but I wish I had." On the other hand, at least he has the last C4 produced, as sort of a segue into the CERV-4b and Alpha and Beta platforms. Obtaining that finale took some doing, as he wrote to then-GM manager Jim Perkins to inquire about purchasing it during a special ceremony. He agreed, and allowed Yager to bring in a film crew the night before in order to document that car's swan-song construction.

"Most people are interested in the first car built, not the last ones," he observes. "I like having the end of one, and the start of another." So now most of the C4-to-C5 nexus is safely on display at Mid America's HQ for all Corvette owners to relish for themselves.

SOURCE
Mid America Motorworks
Effingham
IL
866-866-0856
www.mamotorworks.com