Corvette Custom Chassis - Vintage Is Only Skin Deep
Dissecting Street Shop's C1-C3 Custom Chassis
February 01, 2010
By Jeremy D. Clough
http://www.vetteweb.comVery few cars can match the style of the Corvettes that came with chrome bumpers. From the frank, wide-eyed front end of the late-'50s C1s to the muscular smugness of the early sharks, they embody the central tension between elegance and raw power that has always defined America's sports car. Unfortunately, for those accustomed to modern performance vehicles, driving one of these vintage Vettes in "spirited" fashion can be a truly terrifying experience. Indeed, given the heart-pounding fear that comes from combining razor-thin tires with sudden rear-wheel camber shifts while cornering, perhaps it's no wonder Chevy long called itself "The Heartbeat of America."
There are modifications that help, but they never quite fix the problem. In 2004, I was in the throes of modifying a 1971 Chevy Corvette 454 convertible to make it more amenable to the sinuous roads of the North Georgia mountains where I lived, and had only mixed success. Poly bushings and hard springs helped, but they also revealed massive frame flex-until I put in a heavier rear sway bar, going over an uneven road would pop the rear of the convertible top up out of its latches.
It was around that time that I was wandering around Knoxville's Corvette Expo and noticed a tent exhibiting Corvette frames. Built by a company named Street Shop, they looked like C2 and C3 frames, only they weren't-they had C4 suspension . . . and rack-and-pinion steering . . . and Dana 44s. And they had my attention.
Laying The Framework Like many great ideas that seem to suddenly burst on the scene, Street Shop is the result of several years' labor by a committed entrepreneur-in this case, Tray Walden. Walden, an Alabama native with a bachelor's degree in mathematics and computer science from Auburn (and a matching MBA to go with it), was working at a CD-manufacturing plant when he made the decision to leave the corporate world in 2000. "I've been gone almost as long as I was there," he tells me about going into business for himself, "and I haven't missed it for a day." And so it was that he was in a position to create and sell the aftermarket frame that he first showed at Carlisle in 2001.
The idea for the frame, however, goes much further back. An inveterate racer, Walden had been taught to weld in his teenage years, and had been building frames and rollcages for drag cars even while working at the CD company. What he had not done, however, was anything for a Vette, even though he owned two. It hit him one day when he was standing in his garage between his black '67 coupe and his matching black '94.
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A fairly "standard" rolling chassis from Street Shop: LS3 engine, Classic Chevy five-speed, C4 rearend and suspension, and rack-and-pinion steering [/align]
"You know," he mused, turning first to the midyear, then to the C4, "if I could have that, and make it drive like that, I'd be pretty happy." After combining his engineering experience with his ability to fabricate what he designed, he had the first frame. Intended as a one-off for his own use, the frame fit under his '67 without modification and accommodated C4 suspension and brake parts.
Enter Jim Hornaday, a Corvette aficionado par excellence who lived nearby. Hornaday managed to talk Tray into displaying the frame at Carlisle. Several orders, hundreds of frames, and three patents later, Street Shop is alive and well, and still making the latest incarnation of that frame, along with several more-advanced variants. Available for '53 through '82 Vettes, all of the Street Shop frames start as a pair of mandrel-bent framerails made from 4x2x0.120-inch tubing. From there, though, almost anything is possible.
What Lies Beneath The standard chassis kit is much like the one Walden originally created for his '67. Designed to be a complete drop-in replacement that requires no modification to the car, it comes with rack-and-pinion steering, a complete C4 suspension (front and rear), and a new Dana 44 rearend. Although some components are refurbished, many of the parts are fabricated specifically for the kit, including the halfshafts, "dog bones" (the two camber bars on either side of the rear that replace the trailing arms of the C2/3), and "batwing" diff cover, which is fully CNC-machined from billet to fit the new frame.
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The elemental beginning for a Street Shop chassis, the 4x2x0.120-inch mandrel-bent frame-rails are welded, ground, and welded again as they slowly become something much greater.[/align]
One advantage of the C4 setup that's not readily apparent is that it allows you to use deeper offsets-and therefore wider tires-than a stock C3, without flaring the fenders. Wider to the tune of 9-inch wheels up front and 11-inchers in the rear. Although both the front and rear suspensions do follow the late-C4 pattern, the shocks and springs are replaced with coilovers from QA1 as part of the standard package. In fact, the only things omitted from the standard kit are the powertrain, wheels, and brakes.
Engine mounts are available for whatever configuration you intend to use-SBC, BBC, or LSX-and the removable crossmember easily lets you install a variety of transmissions. Of course, since this is a custom shop, you can order these things along with the frame, with a choice of any GM Performance Parts crate engine and a variety of manual and automatic gearboxes.
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While red is not the favored color-black powdercoating is standard-almost anything is possible at Street Shop, including this midyear frame that combines a fuel-injected 502 with C6 Z07 running gear. Stand back.[/align]
Similarly, although they don't come standard, you can pick from a dizzying array of brake options that stretch from "standard" Grand Sport C4 calipers to massive six-piston Wilwoods with two-piece rotors. It also bears noting that while Wilwood offers a factory C4 front-brake conversion, the company does not produce one for the rear. Street Shop, however, does. The kit includes a parking brake, and yes, C4 guys, it's available separately.
What Price Performance? The standard package costs around $15,300 fully assembled, or about $7,400 for the bare frame. That sounds a little steep until you start adding up what it would cost to do the job piecemeal. With a rack-and-pinion conversion for a stock C3 running about $1,300, a complete coilover conversion coming in at $2,300 to $2,700, and a five-bar conversion for the rear suspension at $2,700, you're knocking on $7,000 in parts alone. If you want your diff to take the same abuse as the 44, you'll also need to add in a 12-bolt conversion and heavy-duty halfshafts for another $2,600 to $3,200, all of which gets us ominously close to $10,000. Offset trailing arms for wide tires tack on another $400, so once you add in heavy-duty upper A-arms and sway bars, the Street Shop frame is getting pretty competitive with what it would cost to upgrade a stock frame. And even then, the effectiveness of these aftermarket parts will unavoidably be compromised by the inherent weakness of the factory chassis.
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This new C4 "batwing" is custom-made for Street Shop. Instead of using refurbished parts, many of the components used at Street Shop are CNC-machined from billet.[/align]
Don't think I'm throwing rocks at aftermarket suspension kits. Some brilliant engineering has gone into many of these packages, making it possible to have up-to-date technology applied to a vintage Vette. Besides that, doing it one part at a time is more financially feasible for a lot of folks, because it spreads out the cost over time. Some people simply may not want to do everything to their car, preferring to pick and choose which mods to apply, and what parts to leave stock. For those who want the ultimate, though, the frame package gets you someplace you otherwise can't get from here.
For those like Dick Dawson (whose "Z067" convertible appeared in these pages in August 2008), who aren't averse to cutting fiberglass, there's no reason to act like the Corvette quit advancing in 1996. Street Shop also offers frames with C5 front and rear suspensions (including the rear-mounted six-speed transaxle), as well as one compatible with C6 underpinnings. The last time I was at Street Shop, Walden and company had just finished assembling a midyear chassis that had C6 Z06 running gear backed up to a fuel-injected big-block 502-a mighty amalgamation of the nastiest of both breeds.
Ultimately, that's what the Street Shop chassis is all about: combining the best features of each of the generations into the single car that best suits your needs.
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This chassis is set up for C6 Z06 running gear. It's difficult to conceive of a more ferocious package than a midyear with 500-plus hp and this sort of suspension. Well, maybe the LS9-powered C2 they're working on now . . .[/align]
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Some of the proprietary parts-such as brackets-are produced in-house, using a plasma cutter.
The standard chassis kit comes with C4 suspension and rearend hardware, including new heavy-duty halfshafts and a quartet of coilovers. C5 and C6 rear packages are also available, but they aren't a drop-in fit.
The front suspension on the standard chassis offers as many advantages as the rear: C4 upper and lower control arms, coilover shocks, and rack-and-pinion steering in place of the original recirculating-ball design.
While factory C4 brakes are standard equipment, there are many upgrades available, including Wilwood six-piston front calipers with two-piece rotors.
Street Shop began as an attempt to create a chassis that would combine the elegance and style of a midyear with the driveability and performance of a C4. It worked.
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Phone 0438 658 458
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