1968 Corvette Coupe Structure and Availability
Below is an interesting response to a letter published in the December 2009 issue of "Corvette Enthusiast" magazine regarding 1968 Corvette coupe availability and why 1968 Corvettes with vehicle identification numbers under 11,000 are difficult to find. The response is from John Hinckley who was on the "front line" of 1968 Corvette development as he was employed by General Motors and part of the Chevrolet Corvette Group for the buildout of the 1967 Corvette model year and stgart of the 1968 Corvette at the St. Louis Corvette Assembly Plant.
Reader's Question: I've always lied the '68 coupe as the first year of the Shark series, and plan to sell my '79 when I find a '68 that's in good shape as a cosmetic restoration cadidate. I've looked at many 68's over the last year or so, both on-line and in person, and I have yet to see a coupe with a VIN under 11,000 or so; is there some reason why coupes with VINs lower than that are so hard to find?
Response: Yes, there is; it's an interesting story, and it isn't generally known.
Although the 1968 Corvette program was already a year late (it was originally supposed to launch for the 1967 model year), only the convertible model appeared in September, 1967 for the 1968 model year start of production. Why?
The original design for the '68 couple had a one-piece targa removable roof panel, with no "T"-bar. However, prototype development testing showed that due to body and frame torsional deflection (twist), unless the car was parked on a dead-flat surface, it was nearly impossible to remove or install the one-piece removable roof panel.
This was obviously unacceptable, and it resulted in a last-minute redesign of the coupe body structure for additional torsional stiffness, which required adding the "T"-bar from the windshield header to the rear roof bow, and splitting the removable roof panel into two separate pieces. This was a major change, adding many new steel birdcage members, trim parts, moldings, roof panels, and weatherstrips, plus new welding fixtures and assembly tooling.
All of those new parts had to be tooled-up from scratch, and the revised design had to be tested and validated with a second group of development prototypes; the development/validation cycle took time, and resulted in production parts and assembly tooling for the revised design not being available until late January of 1968.
The coupe structural redesign meant that only convertibles could be produced at launch, so the first five months of '68 Corvette production (10,000 units) were all convertibles; the first coupes weren't built until late January. This had a major impact on the outside convertible top assembly supplier, who had to produce 120 tops per day instead of the originally-planned 50-60 per day; he had to hire more people and add a third shift, and ran seven days a week for the first five months of production to support the 100% convertible built.
That's why you won't find any '68 Corvette coupes with VIN numbers below 10,000 or so; there weren't any!
I've also attached an illustration of the '68 coupe birdcage from the 1968 Shop Manual, which was printed before production started; you'll note that it's the originally-released (and subsequently cancelled) one-piece roof design with no "T-bar".
 |