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Illustrated Corvette Series No. 132 - 1970-1/2 - 1972 ZR-1 Corvette
"The Original ZR-1"

By 1970, the Detroit horsepower party was largely over, and GM management was planning radical changes for ‘71 and beyond. There was a growing awareness of the health hazards of breathing fumes from leaded gasoline, along with increased pressure from insurance companies to curb the escalating output of domestic cars. But while the GM brass were putting the kibosh on performance, Zora Arkus-Duntov was doing his best to keep it alive.

In February of ’69, John DeLorean was top dog at Chevrolet. Knowing the direction that GM president Ed Cole had mandated, DeLorean and his Corvette product planners were tasked with creating a new theme for the Vette: the luxury sports car. The Custom Interior Trim option cost just $158 and included leather seats, woodgrain trim on the console and door panels, and special carpeting. This was just the beginning of the added creature comforts that would define the Corvettes of the ‘70s. .

But Duntov wasn’t about to let the hard-core performance crowd go without some goodies to race with. The L-88 was history, and the ZL-1 was only available as a crate motor. The hot new performance engines were the LT-1 350 small-block and the LS5 454 big-block. If racing was your intention, there was the LT-1–based ZR-1 option, along with the (planned) LS-7-based ZR-2. Unfortunately, the ZR-2 never made it into production in ‘70, but it did make a brief appearance in ’71 with a somewhat detuned 454 LS-6. The ‘71 model year was the only one for the $1,747 ZR-2 option, with just 12 units produced. The cure for the lower-compression LS6 was simply a set of dome-top pistons. The ZR-2 was the base car for John Greenwood’s entry into road racing in the ‘70s.

The ZR-1 and the ZR-2 Corvettes were officially designated as “off road,” which translated to ”racing only.” Like the ’67 to ‘69 L-88 cars, the ZR Corvettes were not happy on the street, but they did provide an excellent base on which to build SCCA Class A or Class B racers. The ’70 ZR-1 package cost $968 and included the following: the solid-lifter, 370-horsepower LT-1 engine; an M-22 four-speed transmission; heavy-duty power brakes; a transistor ignition; a special aluminum radiator; a metal radiator shroud; and special springs, shocks, and front and rear stabilized bars. There was also a long list of options that were not available. These included power windows, a rear-window defroster, air conditioning, power steering, deluxe wheel covers, an alarm system, an AM/FM radio or stereo, and an automatic transmission. Racing fender flares were included in the trunk space, and a cold-air scoop and header-type side exhausts were sold separately. As with the L-88 package, Duntov wanted to discourage customers from buying a car that wasn’t designed for street use. There were 25 ZR-1 units built in ‘70, 8 units built in ’71, and 20 units built in ‘72. When the 454 ZR-2 option was released in ’71, only 12 units were built. All of the "ZR" Corvettes were built by Chevrolet’s “Repair Department” in St. Louis.

The ‘70-1/2 Corvette also received a minor makeover. There was the revised, egg-crate grille that matched the new egg-crate side vents, square front turn-signal lights, rectangular exhaust tips, and flares on the back edges of the front and rear wheel openings. The LT-1 and ZR-1 options included the big-block hood with special pinstriping and “LT-1” lettering. Positraction and tinted glass were standard, and there was no charge for transmission choice.

It would be 18 years before the ZR-1 name would resurface in ’90, and another 19 years before the ‘09 version showed up. It was definitely worth the wait! - K. Scott Teeters

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Illustrated Corvette Series No. 43 - 1970-1/2 Corvette
"Lots of Hot Stuff"

Corvette lovers had much to catch up and get very warm over for the 1970 Corvette. There were subtle, but significant, body and interior changes, and big changes under the hood.

 By the numbers, sales for the '69 model was the best ever, due to then Chevrolet General Manager John DeLorean's decision to extend the sales year of the Corvette, Camaro, and Firebird to make up time lost to a worker's strike earlier in the year. Sales for the '69 Corvette was 38,762 units, up from '68 production of 28,566. Bean counters were very happy. Consequently, sales numbers for the '70  model were only 17,316 units. It seemed like it took a year for the public to warm up to the new Shark body style. The extra time actually allowed the Corvette team to better refine the new model.

 The body changes weren't a total surprise, as the Aero Coupe Show Car tipped the hand for the new styling. But it was a fresh change that few complained about. The new front grille was an eggcrate design that had rectangular turn signals with amber lights in the corners of the grille. The front fender vents used a similar eggcrate design.

All four wheel openings were flared at the back to protect the sculpted sides from road debris. Exhaust outlets were now rectangular shaped. Interior mods included reshaped seats for more headroom and an optional trim package that included cut-pile carpet and imitation wood trim on the console and door panels.

 The really hot news was under the hood. The trusty 327 was stroked to 350 cubic inches and the beastly 427 was stroked to 454 cubic inches. The LS5 engine had 390 horsepower and 500 lbs-ft of torque. Duntov scored a victory with his LT-1 option. Zora wanted to do whatever he could to keep the weight down and the power up. On the street the LT-1 was only a tick slower than the big-block. However, it handled more like the sports car Duntov wanted the Corvette to be.                

 For the first time, Corvette's base price was over five thousand dollars. $5,192 was the new entry price for a Corvette. The most expensive street option was the $447.60 for the LT-1. The LS-5 454 engine option was only $289.65. A loaded LT-1 could cost over seven grand!

 Duntov never wanted his legions of Corvette racers to be without the latest racing parts. The ZR-1 option cost $968.95 and included the LT-1 engine, transistor ignition, the M22 four-speed, power brakes, an aluminum radiator, and beefed-up suspension. With this package, you couldn't get power windows, power steering, air conditioning, or a radio.
Only 25 were ordered. Planned, but not sold, was a ZR-2 option that included all of the
ZR-1 parts, but with a 465-horsepower 454!

 This was the  big-block's best year. With insurance and emissions concerns, the rip-snort'n 454 was history by '75. However, the LT-1 sowed the seeds of the C5's power-plant. - K. Scott Teeters   

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llustrated Corvette Series No. 44 - 1970-1/2 LT-1 Corvette
"Balance of Power"

Corvettes have always had something of a split personality. Defined as a "sports car", but with musclecar straight-line, scare-you-to-death acceleration. Detroit learned early in the performance game that there's no substitute for cubic inches. But the penalty is extra weight. When the Corvette went "big-block" in '65, the split widened between the sports car and musclecar groups. The 1970 LT-1 option gave buyers the best of both worlds.

Although Zora Arkus Duntov loved the brutish big-blocks, his "ideal" for the Corvette was a balanced, mid-engine, small-block layout. After many attempts, the mid-engine Corvette just wasn't to be. His plan-B was to make a high-revving, high-performance, lightweight small-block, with a 50/50 weight distribution. The resulting LT-1 option just blew everyone away.

The LT-1 engine had about every trick part a production car could have. Designed as a high-revving performer, everything was stout. The cast-iron block had four-bolt main caps and a forged crankshaft at the bottom end. The connecting rods and pistons were forged and had 11:1 compression. A dual-plane aluminum manifold and 4150 Holley four-barrel rated at 800 cfm handled the intake side. Over-sized valves in performance heads and solid-lifters along with a high-life cam gave the LT-1 a lumpy, "don't mess with me" idle, and cast-iron manifolds with 2.5 inch pipes. The ignition system was the latest transistor Delco model.

It all added up to 370 ponies at 6,000 rpm, and 380 ft-lb of torque. With the relative light weight of the small-block, the LT-1 was just a tick off the straight-line performance of the 454. Quarter-mile-times were around 14.10 seconds at 102 mph, with zero to 60 times around 6.5 seconds. But the best part was that because of the balanced arrangement, the LT-1 could be driven as deep into corners as Europe's finest. Some publications reported that the LT-1 was as fast, if not faster, through the curves than the 1970 911 Porsche!

The LT-1 option wasn't cheap though. At $447.60, it was $10.50 more than the '69 L71, 427/435 engine and $157.95 more than the '70 LS5, 390-horsepower 454. For 1970, Chevy sold 1,287 LT-1 Corvettes. Interestingly, the air conditioning option was $447.65, 5 cents more than the LT-1, but not available with the LT-1, as was an automatic transmission.

There was an option called the ZR-1, that was a small-block "package" version of the off-road L-88. Only 25 were ordered. For some, the 1970 LT-1 was the finest C3 Corvette made. Corvettes have always had something of a split personality. Defined as a "sports car", but with musclecar straight-line, scare-you-to-death acceleration. Detroit learned early in the performance game that there's no substitute for cubic inches. But the penalty is extra weight. When the Corvette went "big-block" in '65, the split widened between the sports car and musclecar groups. The 1970 LT-1 option gave buyers the best of both worlds.

Although Zora Arkus Duntov loved the brutish big-blocks, his "ideal" for the Corvette was a balanced, mid-engine, small-block layout. After many attempts, the mid-engine Corvette just wasn't to be. His plan-B was to make a high-revving, high-performance, lightweight small-block, with a 50/50 weight distribution. The resulting LT-1 option just blew everyone away.

The LT-1 engine had about every trick part a production car could have. Designed as a high-revving performer, everything was stout. The cast-iron block had four-bolt main caps and a forged crankshaft at the bottom end. The connecting rods and pistons were forged and had 11:1 compression. A dual-plane aluminum manifold and 4150 Holley four-barrel rated at 800 cfm handled the intake side. Over-sized valves in performance heads and solid-lifters along with a high-life cam gave the LT-1 a lumpy, "don't mess with me" idle, and cast-iron manifolds with 2.5 inch pipes. The ignition system was the latest transistor Delco model.

It all added up to 370 ponies at 6,000 rpm, and 380 ft-lb of torque. With the relative light weight of the small-block, the LT-1 was just a tick off the straight-line performance of the 454. Quarter-mile-times were around 14.10 seconds at 102 mph, with zero to 60 times around 6.5 seconds. But the best part was that because of the balanced arrangement, the LT-1 could be driven as deep into corners as Europe's finest. Some publications reported that the LT-1 was as fast, if not faster, through the curves than the 1970 911 Porsche!

The LT-1 option wasn't cheap though. At $447.60, it was $10.50 more than the '69 L71, 427/435 engine and $157.95 more than the '70 LS5, 390-horsepower 454. For 1970, Chevy sold 1,287 LT-1 Corvettes. Interestingly, the air conditioning option was $447.65, 5 cents more than the LT-1, but not available with the LT-1, as was an automatic transmission.

There was an option called the ZR-1, that was a small-block "package" version of the off-road L-88. Only 25 were ordered. For some, the 1970 LT-1 was the finest C3 Corvette made. - K. Scott Teeters

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lIlustrated Corvette Series No. 45 - 1070-1/2 454 Corvette
"Gobs of Power and Confusion"

Nothing exceeds like excess, and the '70-454 Corvette was a perfect example. Between the car magazines, published brochures, and what was really available, there was almost as much confusion as there was power.

What John Q. Public was actually able to drive home from the Chevy dealer was the 390 horsepower, LS5 454, which wasn't too shabby. The LS5 option was reasonably priced at $289.65, and 4,473 LS5- equipped Corvettes were sold in the half-year of 1970. The extra cubic-inches pumped up the torque to 500 lb-ft. Even though on paper, the LS5 looked like it had lost 45 ponies from the 427/435 '69 big-block; on the street, the difference was nil.

Power figures for General Motors cars was kind of a black magic shell game. For years GM wouldn't sell cars with more than 400 cubic inches. That changed in '66 when the 1965's 425 horsepower L78 396, became the L72, 427 that pulled 425 horsepower. So what was the real power of the 427? The L72 almost got a decal reading "450 horsepower," but corporate politics downplayed the figure. The '67, '68, and '69 L71, 427/435 tri-carb engine was rated at 435 horsepower, but was closer to 450 to 475 horsepower. All of the Detroit power numbers were somewhat misleading because published figures were "gross" power ratings. Engines were tested without mufflers, accessories, or even a fan. Real cars have all sorts of power-robbing aspects, but it all makes for great bench racing.

There were several 454 variants that were very interesting. The 450-horsepower, LS6 454 never made it into the Corvette for '70- , but was an option in the Chevelle. Then the LS6 showed up as an option for the '71 Corvette, but was de-tuned to 425 horsepower. Even more exotic was the LS7 454, rated at 465 horsepower. This option was listed in the Corvette shop specs, but only one was "officially" made. The LS7 was a stroked version of the L88. Supposedly, Duntov gave a wry wink, and signed the order to have all LS7 prototypes destroyed. Sometime between 1973 and 1975, an LS7 was stolen from Chevy Engineering by a few guys who jumped the fence.

Perhaps the most unusual 454 prototypes were the LT-2 and the LJ-2. The LT-2 was a 454 version of the all-aluminum ZL-1. Increasing the stroke on a high-revving racing engine probably wasn't a good move. The LJ-2 was a 454 version of the solid-lifter 427/435 tri-carb L71. This beauty was rated at 460 horsepower.

By the end of 1970, the party was over. Rising insurance rates, tougher emissions regulations, and no-lead gas put a lid on things. In the long run, big-block engines took the Corvette away from "sports car" to "street bruiser." Duntov liked the power, but didn't miss the weight of the big-block. But oh, the wonderful sound of a big-block Corvette! - K. Scott Teeters   

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lllustrated Corvette Series No. 40 - 1970 XP-882 Corvette Show Car
"Experimental Corvette - Bad Timing

It was a great day for Corvette fans. When the crowds piled into the New York Auto Show on April 2, 1970, they had no idea what Chevrolet was proposing as the next Corvette. The XP-882 Mid-Engine Experimental Corvette had almost everything a Vette lover would want... big-block power, huge wheels and tires, exotic suspension, drop-dead looks, and the engine located in the middle of the car, exactly where an exotic car engine should be.

But we all know how the story ended; they didn't come close to making the car. Forward thinking just couldn't overcome bad timing. Duntov's design team started working out the mechanical challenges for the XP-882 in 1968. Styling penned up a new look that screamed "Corvette!" It was crisp, edgy, modern, yet it "looked" like a Corvette.

New Chevy General Manager John Z. DeLorean stopped work on the XP-882 to pursue making Corvettes based on the new, inexpensive Camaro chassis. DeLorean met with fierce resistance from styling, engineering, and sales to NOT take the car in that direction. So the project was stopped in 1969 and was warehoused until 1970. When Ford announced a similar mid-engine project with DeTomaso, DeLorean resurrected the XP-882 and had it finished for the show car circuit. Because there were no press releases, everyone was stunned. The car magazines were all over it, initiating a feeding frenzy of speculation.

Mid-engine cars were very exotic in the '60s. Not only was the engine midship located, but it was transverse mounted. By using the front-wheel drive, automatic transmission from an Olds Toronado, Duntov was able to quickly get a working prototype. Suspension and brakes were obviously independent and disc. Wheels were spun-aluminum, with vent slots, and tires were E60x15 on the front and G60x15 on the rear. The interior of the car was basic prototype fashion, no frills and no real design at that point. The XP-882 was never officially tested for speed and performance.

Many other Corvette show cars have been more thought out than the XP-882, but the car was rushed into service and not fully developed like show cars of the '60s. But the timing couldn't have been worse for an all-new Corvette. The new platform was going to be expensive to make, requiring new transmission, suspension, body, and interior parts. Actual production wouldn't have started until '72 or '73, just in time for the first Arab oil embargo. Also in the brew was a GM internal push to develop a Wankel-engined prototype, so the second XP-882 chassis was made into the 1973 4-Rotor Aerovette.

All things considered, the XP-882 didn't have a chance, but it sure was exciting. - K. Scott Teeters   

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lllustrated Corvette Series No. 41 - 1070 Aero Coupe Corvette Show Car
"It's Good To Be Sr. V.P."

Being the Senior V.P. of Design at General Motors sure had its perks for Bill Mitchell. The actual car that was made into the "Aero Coupe" was born as an off-the-assembly line 1968, small-block Corvette. Over the next seven years the car lived through three incarnations: the "Aero Coupe", the "Scirocco", and the "Mulsanne." When the car wasn't on-duty at car shows, it saw duty as Bill Mitchell's personal ride. What a job!

The first thing that Mitchell's Design Staff did was to remove the 327 small-block and drop in one of the new ZL-1, all-aluminum Can-Am engines. For several years the ZL-1 used an experimental Rochester fuel-injection unit and an experimental, four-speed Hydra-Matic transmission. The ZL-1 was awesome, but the four-speed automatic was replaced with a Turbo 400 unit. And what Bill Mitchell show car wouldn't be complete without side-mounted exhausts? Mitchell described the Aero Coupe as a "bear!"

With plenty of power under Bill's right foot, the Design Staff started work on the body. It may have been slightly overdone, but that's what show cars like the Aero Coupe were supposed to do. They are "officially" called "Research and Development Vehicles." The Aero Coupe had many interesting styling cues. The egg-crate front grille and side vents were the only design elements that made it into production. The front end had a deep, "shovel-style" front spoiler that wrapped around its chin. At the rear, there was a matching, wrap-around spoiler similar to the '70-1/2 Z-28 Camaro. The side pipe covers were similar to the optional, production side pipes, except for the section under the doors that had six groups of vertical scribe lines. The windshield and roof were interesting. The A-pillars were curved at the top corners, allowing the glass and roof to have a smooth, continuous line. The removable roof panel was a single piece and hinged at the back. Since the car was using Chevrolet's ZL-1, the ZL-2 hood option was used. And continuing with the Can-Am influence, fat Goodyear tires were monuted on wide, Chaparral-style alloy wheels.

The interior was very plush for a Corvette. It was completely trimmed in tan leather and deep-cut carpet. Years later a crude digital unit was added to the dash that projected the car's speed on to the windshield. The Aero Coupe was completed with a deep, candy apple red paint with heavy gold metalflake, gold striping, and Corvette, and ZL-1 badges.

This very special Corvette went on to delight Corvette fans for 7 years, with each version getting more wild. When if finally became the Mulsane in '74, only insiders knew that it was really a '68 small-block Vette on steroids. - K. Scott Teeters