Here's the story:
lllustrated Corvette Series No. 148 - 'Zora Arkus-Duntov's Mule Corvettes - Pt. II"

Zora Arkus-Duntov was the perfect man for his time at GM. As his friend and coworker Gib Hufstader explained, “Zora was always anxious for more of everything.” Had Duntov come along 20 years later, it’s unlikely he could have gotten away with building the kinds of cars he did. But while only a small percentage of Corvettes ever get close to a race track, we all get to enjoy the fruits of Duntov’s automotive passions. Most of his test, or “mule,” Corvettes were never seen by the public, but those that were made long lasting impressions of what a Corvette could be.

The introduction of the L88 in ‘67 floored everyone. This was as close to an all-out, factory-built racing Corvette as the public would ever see. America had moved from the jet age to the space age, and race cars were using more and more exotic lightweight materials such as magnesium and aluminum. Duntov had been wanting an all-aluminum engine for the Corvette since 1956. (Engineers were even working on an all-magnesium engine for the car. Can you imagine how much that would have cost?) Bolt-on aluminum chassis and engine components were one thing, but an all-aluminum engine was another. The alloy-headed L88 was definitely a step in the right direction, but it would take 30 years for the all-aluminum LS1 to arrive.

When the automotive press arrived at the Milford test facility in the summer of 1968 to preview the ’69 models, they weren’t prepared for Duntov’s latest toy: the ZL1-powered Corvette. The only things missing from Zora’s white ZL1 car were sponsor graphics and numbers. The car had killer looks and grunt to match. The objective was simple: take one Corvette roadster, all the latest performance parts, and build it like a racer would. Everything that didn’t belong on a race car was removed. By the time they were done, Duntov and his crew had reduced the weight of the car by about 400 pounds, to approximately 2,965 pounds. The ZL1 engine alone was worth a 175-pound reduction. Missing production items included the radio, heater, insulation, headlights, radiator shroud, upholstery, rear bumpers, and cast-iron exhaust manifolds. Racing equipment included 15 x 9.5-inch magnesium wheels with 10.5-inch front and 12.5-inch rear Goodyear racing tires, a ZL2 cold-air-induction hood with hood pins, and L88 fender flares. Header side pipes really opened up the breathing of the radical ZL1 engine.

Duntov himself gave journalists “believer” rides. When coaxed to make a drag-strip run, Duntov clicked off a 12.1-second e.t. at 116 mph, this despite the car’s tallish 3.60 gearing. Lower 4.11 or 4.88 gearing would surely have put the car into the low 11s. Earlier, Duntov had the hood blow off while performing speed test at 180 mph! Later, at GM’s Phoenix test track, journalists got to drive the white mule ZL1 on a short road course. Road & Track writers described its performance as being close to that of a Group 7 race car they had driven shortly before. Duntov’s quasi-ZL1 racer was a shining example of the engine’s potential.

Also on hand at the ‘69 press preview was a menacing-looking Monaco Orange ZL1 wearing 9-inch drag slicks. Although Corvettes were never developed for drag racing, many were quite successful, including the Astoria-Chas L88 and several other Vettes built and raced by Bo Laws. The pumpkin-colored beast at the press event was set up with open headers, a Turbo-400 automatic with a high-stall torque converter, and 4.88:1 gearing. Those lucky enough to be on hand couldn’t have been prepared for the awesome power of the uncorked, big-block ZL1. According to Gib Hufstader, who did the transmission work, powertrain engineer Tom Langdon had tuned this particular ZL1 to produce 710 hp!

So how good was the quarter-mile ride? About 30 guys clicked off 11-second-flat runs, with a best time of 10.89 at 130 mph. Trap speeds are an indicator of plenty of power. Several guys even did neutral starts by revving the engine up to 6,000 rpm and dropping it into gear. Proving grounds PR man Bob Clift said, “We all enjoyed driving that car. Zora used to keep us all excited back then. That was back in the good ol’ days.” A similarly equipped ZL1 Camaro prepared by Dick Harrell went on to run a 10.21 at 133 mph at Kansas City International Raceway.

Duntov turned 65 on December 25, 1974, and a month later he retired from GM. But just six months before retirement, he was thundering around the GM test track in the wildest-looking Corvette mule ever: his wide-body “silhouette racer.” Corvettes were doing quite well in Trans-Am and IMSA racing at the time, with John Greenwood leading the charge. Working with Hufstader and Greenwood, Duntov‘s team developed a body kit to cover the ever-wider racing tires being used in the mid-’70s. Chassis and suspension mods on road-racing Corvettes had progressed far beyond the Z07 off-road suspension and brake packages, but racers were still using variations of the ZL1 and L88 engines.

The silhouette mule was based on a production ‘74 Corvette but was powered by a balanced-and-blueprinted cast-iron ZL1 variant with open-chamber heads, header side pipes, a big Holley double-pumper carb, and an L88 cold-air-induction hood. Clear plastic headlight covers over quartz-iodine headlights were employed, and oil coolers were installed behind the mesh-covered front grille openings. The body-kit parts were riveted on and covered over with 200-mph duct tape. Lowered and wearing magnesium racing wheels, this was one bad-looking Corvette. CARS Magazine editor Marty Schorr got a ride in Zora’s beast and reported, “One day, he took me out on the high-speed oval test track. We were going full tilt, with the tail slightly out, while he had a cigarette in his mouth and was explaining suspension geometry and big-block engine development. He had great control of this animal car.”

As we stated in the beginning of this two-part story, mule Corvettes live hard lives. After tests and evaluations are completed, they always end up in the crusher. Sadly, you just can’t save everything. - KST

Here's the story:
Illustrated Corvette Series No. 54 - 1974 Corvette
"Happy Bean Counters"

While the automotive world was in the doldrums over the death of performance cars, Chevrolet couldn't make enough Corvettes to satisfy customers! Duntov's objective was to make the Corvette a quality car. Obviously, his efforts paid off. And despite major social changes, Chevrolet sold 37,502 Corvettes in'74, that's up 7,038 from '73 sales of 30,464. This made the bean counters very happy!

The name of the game in business is sales. If nobody is buying, it won't be sold for long. Remember the Fiero? The marketplace was changing and Duntov made enough changes in creature comfort and quality to strike a chord with the buyers. Demand was so high that the production was bumped from 8 to 9 hours. And even then, there were 8,200 orders returned to dealers "unfilled." Buyers wanted Cadillac quality for their $6,000. A major car magazine awarded the Corvette Best All-Around Car in '73 and '74. Considering the performance drop, this was amazing!

The obvious visual difference on the '74 Corvette was the new rear bumper. While other cars had huge chrome railroad ties for bumpers, the Corvette's new look was smooth and clean. The '74 rear bumper cover was made of two pieces, later year cars used a one-peice cover.

In an effort to improve life inside the Corvette, two small resonators were added to the exhaust system to tone things down. 1974 was also the last year for non-catalytic exhaust, as well as the last year for real dual-exhausts. The big-block 454 would be gone in '75.This was also the last year for leaded gas.

Under the hood there were three engines available. The base 195 hp 350, the optional $299 L82 350 with 250 hp, or the $250 LS4 454 with 270 hp. The standard transmission was a four-speed or Turbo Hydramatic. The option buy of the year was the $7 "Gymkhana" suspension that got you a thicker front anti-roll bar and high-rate springs. This was available on all Corvettes, but only 1,905 were ordered.

All of the extras added cost and weight to the Corvette. The base price for the '74 Corvette was now 6,001.50, But it didn't seem to matter to buyers. The Corvette was over 20 years-old and now had a solid performance image even though the rip snort'n, mean machine days were over. The three most popular options were now power steering, power brakes, and telescopic steering column. Buyers taste had changed and Duntov was right on target. The car still had untapped potential, you just had to extract it yourself. But, it was better than no Corvette at all. - K. Scott Teeters

Here's the story:
lllustrated Corvette Series No. 55 1974 - Mulsanne Corvette Show Car
"Recycled Again"

Only Bill Mitchell could get away with this. Bill always managed to have a hot daily ride. Engineering prototypes that weren't street-legal stayed behind the fence, but many of the show car Corvettes managed to go home with Bill. His usual statement on his "design study" cars was, "This thing runs like a bear!" For the Mulsanne Bill added, "This is the best Stingray ever."

The Mulsanne actually had three previous lives. Born as a stock 350 '68 Corvette, the car was originally the '69 "Aero Coupe" show car used to preview the '70-1/2 styling changes. It had a ZL-1 all-aluminum engine and a prototype four-speed automatic and was, well, a "real bear."

A short time later the Aero Coupe received the slim, Manta Ray-style side pipe covers, got a new paint job with the front bumper-grille assembly painted body color, and was renamed the "Scirocco." For the next four years the car worked as a pace car at Can-Am races. These were the days of heavy ZL-1 powered McLarren dominance. Mitchell thought it was cool that his Mulsanne pace car had the same basic engine as the McLarens. Like all of the Mitchell show cars, the Mulsanne had a large crowd around it at the '75 New York Automobile Show. Bill didn't pen every line on the Corvette, but his style was always present.

Painted bright metallic silver, the Corvette Mulsanne wore '75-style front and rear bumper covers. The pop-up headlights were replaced with four rectangular lamps under body-fitting clear plastic covers. The new hood had a raised center section with recessed, functional scoops on both sides. The curved
A-pillar, high-mounted racing mirrors, and electric rear window were all carry-overs from the Scirocco exercise. Since the Mulsanne was made to be a pace car, Mitchell kept the removable one piece roof panel, but added a periscope rearview mirror system. The interior was completely trimmed in leather with fixed seats and adjustable pedals and steering wheel.

Bill couldn't have a "stock" ZL-1, this engine was bored out to 454 cubic-inches and wore an experimental Rochester fuel injection system. Chaparral lace wheels and flames exiting the fender vents added show car splash.

Mitchell wanted the speedometer to look like a gunner's site. So a roller-type speedometer reflected speed numbers on to the windshield. This was so that the driver could watch the road while "blasting" past lesser cars. Designer Chuck Jordan said, "The man had flair!" - K. Scott Teeters