“We’d already developed a lot of fiberglass technology, starting from the 1968 program on,” Vogelei recalled. "Even that far back we were wanting to do more plastic-to-metal bonding, and we challenged the adhesives industry to work with us. They were a little slow in responding, because of the Corvette’s low volume. It took a lot of time, money, and R&D to convince our suppliers to produce a special adhesive for ‘only’ 25,000 cars a year.
“Our first task with the ’84 was to (develop) a structurally sound, stiff, mass-efficient uniframe. Before, the conventional frame used to belong to the chassis group and my guys did just the body, but for this car we inherited responsibility for the total structure.
“I’d like to give you an example of what I mean. When Don Urban did the 1963 car, Don and four or five engineers did a whole brand-new body, and Walt Zetye plus a handful of engineers developed the entire 1963 chassis. In 1968, my staff put an updated, restyled body on that same ’63 chassis: Four engineers and I did that whole job.
“For the 1984 car, I had three assistant staff engineers, 11 Chevrolet engineers, and an equal number of outside contract engineers supporting the body activity. It used to be that one of my guys or I would be confronted by a problem at eight in the morning, and by 8:15 we could make a decision and be on our way.” No longer: By the C4 era, even body engineers had to “…worry about how it affected the emissions people or the safety people, etc.”
Also new was the plastic parts’ final finish. Explained Paul Huzzard, who was in charge of panels and trim under Vogelei, "One of the problems we ran into previously with our fiberglass panels was porosity. There were microscopic pits that resulted from air trapped by some of the molding techniques. When the panel went through the painting process, it tended to trap volatiles in these tiny pores, and then when the panel went through the paint oven the volatiles expanded and ended up with a cratering effect on the paint.
“Well, GMMD, along with some of our molding suppliers, principally General Tire & Rubber’s Chemicals/Plastics/Industrial Products Group, figured it might be neat if we could mold a panel, open the die up a few millimeters, inject a sealing material, close up the mold again, and heat-cure the panel. That way we’d end up with all the porosities sealed. The (final) process was perfected in the late ’70s.”
FROM T-TOP TO TARGA
As most Corvette fans know, midway through the C4 program Chevrolet changed its mind and decided to go from a T-bar roof to a full targa. This created plenty of anxious moments, especially amongst the lead engineering teams. Bob Vogelei again: “We started by doing this car with a T-strut roof, like the previous Corvette’s. We used the strength of the T in all our original structural analyses. Lloyd Reuss, before he left to become general manager of Buick, was leaning on Dave McLellan and the rest of us pretty heavily to get that T-bar out of there. He wanted the more open look; the targa openness and feel.”
Reuss confirmed that view of the events. “I felt very strongly about the one-piece roof,” he said, "but (so did) others…! I remember sending (Dave McLellan) a Ferrari ad out of the Wall Street Journal. The ad said something like, ‘If you dream about it, it can be done….’ I said, ’We’ve got to do this targa roof.’ It was a pretty arbitrary decision.
“My engineers came back and told me we’d have to add weight to compensate for the missing T-strut, that we’d have a big structural problem. I said, ‘Yes, I agree with that, but it’s such an important element in this new car to get rid of that T-member that we’d better find a way to do it.’ It threw the whole program into a real tither for a while.”
Vogelei noted that “…some of us resisted the deletion of the T-strut for a time, but finally, after we deepened the rocker sections and such, we changed our minds and agreed we could take the central roof strut out and still get a good, sound car. But I think we overlooked a couple of variables earlier in the program. The first car we put on the road without that strut was pretty bad, and that worried me. It kept (Corvette’s) development guys busy for quite a few months, but between us we identified the problems and managed to solve them.”
In truth, identifying problems and solving them virtually defined the C4 program, which was Chevrolet’s last and best chance to prove it still had the know-how and manpower to engineer its own world-class product. By using the latest technologies available and never confusing fashion with real-world results, it was able to keep the Corvette all to itself.