There is what I thought was a very interesting article about the car in the Jan 13 New York Times. I dont know how to post a link, but Googling "Corvette XP-819 ny times" will get you there. I'd be curious what our own experts think of it.
Corvette XP-819 Article
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Re: Corvette XP-819 Article
The Rear-Engine Corvette That Was Never to BeG.M. Media ArchiveTIME LAPSE The 1964 XP-819 had the unmistakable proportions of a rear-engine car, but its shape previewed the third-generation Corvette of 1968.
By STUART SCHWARTZAPFEL
Published: January 11, 2013- [*=left]FACEBOOK
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ON Sunday evening, just ahead of two press preview days for the 2013 North American International Auto Show
Multimedia
Slide Show
The Corvette XP-819
As details of the new car are being revealed in Detroit, some 600 miles to the east a storied Corvette engineering prototype will be progressing toward the final phases of a restoration. The XP-819, a one-of-a-kind research vehicle developed by General Motors engineers in the 1960s, is one of the cars that has given rise to recurring rumors that each new generation of Corvette may be the breakthrough model elevating the Chevy to supercar status. Long out of sight after a crash during testing, the XP-819 is being brought back to life at the Long Island shop of Kevin Mackay.
Mike Yager, founder of Mid America Motorworks, a Corvette and VW parts and accessories supplier based in Effingham, Ill., bought the XP-819 at a Monterey, Calif., auction in August 2002.
Still, G.M. built, tested and, in some cases, displayed at public shows more than a dozen experimental prototypes that featured mid- or rear-engine layouts from 1958 to 1973. The period was a long, dreamy exploration into advanced sports car design and reflected the optimism of the times.
Despite all of the noteworthy innovations and forward-looking design cues that came out of these experimental vehicles, Corvette has retained the same basic front-engine V-8 layout.
Duntov provided basic mechanical specifications for coming research cars but did not have direct involvement in the XP-819 design. That was the responsibility of Frank Winchell, a top engineer who had worked on rear-engine sports-racing cars and the Corvair production model.
For legal reasons relating to the Corvair lawsuits that were starting to appear and the handling challenges that arose when rear-engine vehicles were pushed to the limit, those who worked on the XP-819 knew that mounting the engine behind the rear axle, rather than in the middle of the car, was not necessarily the best plan. Instead, they viewed the project as a way to learn more about optimal engine placement.
The remains of the XP-819 were left in one concentrated huddle in a paint booth inside the shop. Years later, a Chevrolet dealer named Steve Tate recognized the unique XP serial number in the parts pile and promptly bought the car from Yunick, eventually reassembling it. The car changed owners a number of times and was displayed at the National Corvette Museum in Bowling Green, Ky., for several years.
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Re: Corvette XP-819 Article
The XP-819 was a product of Frank Winchell's Chevrolet R&D. Duntov had nothing to do with it. In fact, Duntov and Winchell often butted heads.
As you may expect this car exhibited, ah... "unusual" driving dynamics.
There is discussion about this car in Van Valkenburgh's "Chevrolet Racing: Fourteen Years of Raucious Silence", which has been reprinted after decades of being out of print and is available from the SAE Bookstore.
Winchell's R&D organization were the guys who worked with Jim Hall of Chaparral Cars and were the brain trust behind the many innovations introduced on Chaparrals, and the whole story is in the book.
The article contains a major error, which is typical of mainstream publications and the public at large. They don't understand the difference between a "rear engine" car and a "mid engine" car.
Duntov absolutely never, ever proposed a rear engine car. He understood the dynamic behavior issues, but he was a strong advocate during his entire GM career of a mid engine Corvette.
Duke- Top
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Re: Corvette XP-819 Article
Winchell was credited (?) with two major mistakes during his tenure as VP of the corporate Engineering Staff - the unwieldy XP-819, and the Vega engine (Chevrolet Engineering had nothing to do with the design of the base Vega engine - it was done by Winchell's staff, to Ed Cole's design). Interestingly enough, Winchell was the only GM Engineering executive who didn't have an Engineering degree.- Top
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Re: Corvette XP-819 Article
Mike- Top
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Re: Corvette XP-819 Article
It's interesting that the Reynolds/GM 390 high silicon alloy and the manufacturilng technology that allowed "linerless blocks" is widely used, primarily by European OEMs, to this day.
My understanding is that the cylinder wall scoring problems were due to an inconsistent etch. The electo-chemical etching process was supposed to remove about .0005" of aluminum from the bores leaving a pure silicon wear surface, but it wasn't consistent like it was supposed to be. In areas that were unetched or insufficiently etched, the rings would tear off small bits of aluminum, which would score the bores, and the blocks were very intolerant of overheating.
My '72 Vega GT never overheated but I ran it hard. On a cross country trip returning from a Vanderberg Minuteman test launch the engine developed a ticking sound. I can't recall, but I may have also been pulling my Honda SL350 on a trailer on that trip.
The noise became progressively worse - from ticking to knocking - and by the time I got to Omaha were I planned stopping to see friends, I didn't think it would live much longer. A buddy drove down from Grand Forks, and we flat towed it home. Disassembly at the auto hobby shop revealed scored cylinders and a disintegrated thrust side skirt on one piston.
I bought a fitted block and put it back together. Later, after I transfered out to LA AFS and was buying parts for the Corvette and Vega, the parts guys told me about the "secret warranty" that got GM in trouble.
I still had my receipt for the fitted block and other parts I needed to put it back together and got a refund. As I recall it was something on the order of $350.
Porsche used the same technology for the 928, which I recall was introduced in 1978 - a year after the Vega died, and I assume they were able to improve the etching process. Mercedes followed suit circa 1981, and BMW followed. AFAIK their current engines still use a development of the same technology.
I've always thought that one of the problems with the Vega engine was that GM tried to do the etch too fast. I recall it took about 30 seconds for the whole process, and I assume Porsche slowed it down so it was more consistent. They didn't have the cost limitations on the 928 that GM had for the Vega.
Duke- Top
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Re: Corvette XP-819 Article
The Vega was built to a very tight manufacturing cost in order to compete with the low price imports. The die cast linerless aluminum block was supposedly less expensive to produce than a conventional sand cast iron block, but the head was done in cast iron because aluminum would have been more expensive due to the requirement for valve guide and seat inserts.
Chevrolet did develop an aluminum SOHC cross flow hemi-head for the Vega block - similar in layout to the contemporaneous head on the BMW 1600/2002 - dubbed "L-10". A handful were built and in development when the project was abondoned in favor of the Cosworth DOHC 4V design, which was a scaled up version of the DFV F1 V-8 head.
Duke- Top
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Re: Corvette XP-819 Article
The Vega was built to a very tight manufacturing cost in order to compete with the low price imports. The aluminum block was supposed to be less expensive than an iron block, but the head was done in cast iron because aluminum would have been more expensive due to the requirement for valve guide and seat inserts.
Chevrolet did develop an aluminum OHC cross flow hemi-head for the Vega block - similar in layout to the contemporaneous head on the BMW 1600/2002 dubbed "L-10", but this cylinder head was abondoned in favor of the Cosworth design for F2 racing engines..
Duke
Yep...I had a '75 Cosworth and the analog EFI kicked ass. It was so cool to hear the engine go off cold fast idle automatically. Sadly the body was still Vega...Up in the frozen north they would rot away in 4-5 years. I ended up giving mine away.
Mike- Top
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Re: Corvette XP-819 Article
Here's a photo of one of the (12) L-10's that were built - that SOHC cylinder head was smaller, lighter, and made significantly more power than the original iron "Heron-head" Vega engine, and we even had Assembly Manual sheets for it; however, Ed Cole refused to approve the appropriation for the tooling, as "You already have a cylinder head - you don't need another one", and that was the end of the L-10. After Engineering Staff dumped the Vega engine design on Chevrolet's doorstep for production, it became instantly known as "the world's tallest, smallest engine".
L-10VEgaEngine.jpg- Top
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Re: Corvette XP-819 Article
Duke -
Here's a photo of one of the (12) L-10's that were built - that SOHC cylinder head was smaller, lighter, and made significantly more power than the original iron "Heron-head" Vega engine, and we even had Assembly Manual sheets for it; however, Ed Cole refused to approve the appropriation for the tooling, as "You already have a cylinder head - you don't need another one", and that was the end of the L-10. After Engineering Staff dumped the Vega engine design on Chevrolet's doorstep for production, it became instantly known as "the world's tallest, smallest engine".
BTW, what vehicle is that L-10 installed in? It's definitely not an H-body.
Do you know if any L-10s survive to the present day?
Duke- Top
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Re: Corvette XP-819 Article
To address the early cylinder scoring problem, Chevrolet modified the block dies to include, among other minor changes, trasverse cooling slots at the top of the siamized bores, and in 1976 mounted a major ad campaign for the new "Durabuilt" Vega engines that carried a 5 year, 50K mile engine warranty - by far the best in the business at that time.
These "Durabuilt" engines were painted classic Chevrolet Orange, from the oil pan to the cam cover.
Duke- Top
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Re: Corvette XP-819 Article
What about the 1973 Aerovette? I kind of like the look of this mid engine Aerovette
One thing is that the front end and rear end is very similarAttached Files- Top
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Re: Corvette XP-819 Article
Mike- Top
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