This article originally appeared in the January 1971 issue of Road & Track. At the time, what we now know as the XP-882 prototype fooled a lot of us, since it truly was nearly production-ready. Sometimes history repeats itself, as information about a mid-engined C8 Zora has surfaced in recent months—compelling, reliable, difficult-to-ignore information—as well as photos of a mule out in the wild. Read what we thought in 1971, and draw your own conclusions about the C8. - Ed.
When Chevrolet rushed a mid-engine Corvette prototype into the New York Automobile Show last April, we knew there was more to it than the usual show-car routine. It was all a little bit too real. Chevrolet gave out vital information like curb weight and weight distribution and the press releases talked not so much of how exciting the car was but how practical it was.
At the time we speculated that it was a production prototype and surmised correctly several details of its powertrain that Chevrolet did not reveal: that its engine was transversely mounted, that the transmission was ahead of and parallel to the engine and that the differential was a separate unit behind the engine. We have now established beyond a doubt that the car was indeed a prototype for future production—1973, to be exact—and can report full details on the 1973 Corvette. At this time, all major mechanical parts of the production car are "locked in" and no more basic changes are likely to occur though smaller items are not final yet. Likewise, the basic shape of the prototype, as shown in the photographs, is very close to the final form of the production car; but all styling details haven't been decided upon yet and Werner Biihrer's drawings, based on our latest and best information about it, indicate its general final appearance.
For any mid-engine sports car with a many-cylinder powerplant, the transverse engine position seems to be the coming thing. By so locating the power unit the designer can utilize the car width fully at that point instead of wasting a lot of space to either side of the engine. The space freed at the rear of the car can then be used for a good-sized trunk, like the Lamborghini Miura. It would seem that the Miura bought by General Motors a couple years ago was put to good use.
The Miura has a unit transaxle with a gear transfer drive at the left end of the engine and the transaxle entirely behind the engine. Chevrolet engineers, a bit more cost-conscious than those at Lamborghini as they're shooting for semi-mass production and a price well under $10,000, wanted to retain the existing Corvette differential in the mid-engine car. For Chevrolet Division it's expensive business to tool up a unit like this, entirely exclusive to a model, built in several ratios in quantities of only about 30,000 annually. So the power package was designed to use this differential assembly.
Another production component influencing the power lay out was the Oldsmobile Toronado-Cadillac Eldorado version of GM's Turbo Hydra-Matic transmission. In these cars the engine is mounted up front, facing in the conventional direction; the torque converter is also conventionally positioned behind the engine. A Morse Hy-Vo silent chain takes the drive from there left and down to the "front" of the planetary gearbox, which is on the left side of the engine. A differential directly ahead of the gearbox passes the drive out to the front wheels, with a shaft for the righthand wheel passing under the shallow sump.
The whole automatic transmission and transfer drive from the Toronado will be used on the Corvette. It fits the layout perfectly. This puts the transmission on the front side of the transverse engine and as it snuggles close to the bottom of the engine block, it projects no farther forward than the exhaust manifold on that side of the engine. On the Corvette, instead of the Toronado differential there is a simple gear transfer drive to turn the transmission output 90 degrees and aim it toward the differential behind the engine. A shaft, splined for thermal changes, passes through a small tunnel through the sump and under the 2nd main bearing taking the drive from the transmission to the differential. There is at least one universal joint, type not known, to allow for engine motion.
Some people at Chevrolet Engineering felt that the automatic transmission was sufficient and that no manual transmission need be offered. Others insisted that a car like the Corvette just couldn't be marketed without a manual option. The latter won and a 4-speed manual box will be optional. It should present some tough problems for the linkage designers but at least the linkage won't have to pass under or around the engine. When the manual box is specified the clutch will be in line with the gearbox rather than on the engine, but a chain drive (rather than the Miura's gears) will be used here too. The chain as used on early Toronados probably wouldn't have survived the shock loads imposed on it by a brutal clutch engagement, but recent developments in torsional damping and the chain itself have produced a chain that will take it.
Which engine? Well, right now it looks as if the big-block advocates have it and the 455-cu-in. monster will be the only choice. But there are some more weight-conscious people on the engineering staff and a smaller engine (the present 350 or its 1973 equivalent) could be substituted. I hope so.
The structural platform for the new Corvette will be a 3-dimensional welded steel unit, perhaps partially tubular, thus getting the Corvette away from the weight-wasting, marginally rigid ladder frame it has used since its beginning.
But the outer panels will be fiberglass, continuing a feature that has become part and parcel of the Corvette image—and, I might add, a feature that is particularly valuable in areas like Detroit where salt is used to melt snow and steel-bodied cars. The fiberglass will be only a skin, though, the steel structure doing all the work. The weight saving is really significant: the prototype with 454 engine weighs 2900 lb, compared with nearly 3300 lb for a stripped LS6-engine 1971 Corvette coupe. That's the aluminum-head 454, by the way, which weighs only 82 lb more than the iron 350-cu-in. unit. The regular iron 454 has a 182-lb weight penalty.
We can assume that the present Corvette front suspension, shared with Chevrolet sedans, will be used: unequal-length A-arms, coil springs and an anti-roll bar. At the rear the present Corvette layout will be continued—with trailing arms for longitudinal location, a simple lower transverse link and the axle halfshafts serving as upper links—but the transverse leaf spring is certain to be replaced by two coil springs. An anti-roll bar will be standard.
The show car's wheelbase was 95.5 in., 2.5 in. shorter than the present Corvette's, and its front wheels were well back in their body cutouts to allow for exit of air from the front-mounted radiator. As the hot-air exit is likely to be moved to the top front surface the wheelbase could go up slightly—to, say, 96.5. The car is shorter than today's Corvette by half a foot and almost that much lower but as the track has been widened to 61.4 in. front and rear to accommodate this and the extremely wide 60-series tires, the body is also a half-foot wider than the already wide present one. The show car uses wider tires and wheels in the rear than in the front (E60-15 on 8-in. rims front, G60-15 on 9-in. rims rear) and I'll be surprised if this is continued on the production car because of the impracticalities of using the spare tire with unequal front-rear sizes.
The present Corvette has ventilated disc brakes, 11.75 in. in diameter front and rear with identical calipers and pads at both ends. As the weight distribution of the mid-engine car (44 percent front/56 percent rear) is not extreme, these brakes probably can be used with no changes except in the hydraulic proportioning between front and rear.
For the first time in years the new Corvette will have an external trunk opening—as on the Miura, there will be a lid at the rear of the rear body section which also lifts up to reveal the mechanical innards and takes the trunk along with it. The spare tire is carried up front behind the radiator as is standard practice on mid-engine cars and the battery is carried in a well ahead of one rear wheel. The show car had a minimal steel bumper over its out-front air opening; the production car will have an Endura plastic front-piece (see drawings) forming the air opening and serving the bumper function—if Federal bumper laws in effect by that time don't demand something to meet a 5-mph crash standard. Endura is also used for the rear bumper, as shown in the photos, but represents more of the rear bulk than on the show car.
Interior details have yet to be worked out. The show car had a bare-bones panel in front of the driver with Camaro speedo and tach four austere small gauges in a center panel. We know GM Styling will do better than that, and I also expect them to replace the prototype's 1970 Corvette seats with some that are adjustable for rake. Intriguingly, all the control switches in the prototype are labeled with international symbols rather than lettering and with this feature appearing on the Vega I'd expect it on the production car.
Electric window lifts surely will be standard. Air conditioning will be at least optional, maybe standard; and we can expect it to be really adequate, well designed air conditioning with fresh-air intake as on American sedans. That is a refreshing thought for owners of current mid-engine sports cars!
The mid-engine Corvette isn't the only exciting project underway at Chevrolet Engineering, but it's the one we'll see in production first. The other one: a Vega-based 2-seater. Meanwhile, rejoice in the immediate future: a Corvette to challenge the best efforts of Lamborghini, Ferrari and De Tomaso!