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lllustrated Corvette Series No. 149 - '69 427 ZL-1 Corvette
"The Rarest Corvette Ever?"

We have come a long way since the hey-days of the muscle car era - in fact, much farther that we realize. Through the ‘50s and ’60s, all-aluminum high-performance were the province of small, exotic, European sports car companies, such as Ferrari, Porsche, and Jaguar. Zora Arkus-Duntov was fully aware of the advantages of lightweight engines and started pushing aluminum engine parts into production Corvettes by ‘56. An all-aluminum small-block Chevy engine and a trans-axle were part of the proposed 1960 Q-Corvette. The first version of the ’63 Grand Sport was supposed to have an all-aluminum engine. One version had hemi heads and double overhead cams! But “durability” was always an issue.

While Duntov was busy playing with his aluminum blocks, Chevy NASCAR racers were getting clobbered by the big-block Fords, Mopars, and Pontiacs. Even after being opened up to 427 ci, the 348/409 “W” truck engine just couldn’t cut it. A totally new engine was needed, something similar to—but bigger and more advanced than—the W-based motor. The Mark II 427 big-block was first unleashed in early 1964 in one of Smokey Yunick’s specially prepared Chevelles. Nicknamed “The Mystery Motor” by car magazines, the experimental engine touched off a fire storm of anticipation among Chevy fans.

The rest, as they say, is history. The big-block was released into production in 1965 as a 396 and grew into a 427 the following year. But Duntov wasn’t keen on the big engine. Zora was a racer first, and he always wanted the Corvette to be leaner so it would be meaner on the race track. He felt that the extra weight over the front wheels was wrong, but he sure liked the extra horsepower and torque. Being the “big picture” man he was, Duntov immediately began working to introduce aluminum into the new engine. By 1966, a preproduction aluminum-headed L88 was released to Roger Penske for “field testing” at the ‘66 Daytona race. The L88 racer kit performed so well that plans were set into motion to make the L88 an option in 1967. But as Gib Hufstader once said, “Zora always wanted more.”

Creating an aluminum block was more involved than simply substituting material. The larger-displacement engine created all sorts of heat-related problems not experienced with smaller aluminum engines, such as those used in the air-cooled Corvair and VW Beetle. A beast like the big-block Chevy was a completely different animal. Since the new ZL1 engine was specifically designed for racing, Duntov started where the L88 ended. The block was cast with 356 T-6 heat-treated aluminum alloy. To compensate for the softer material, the main-bearing bulkheads were beefed up, two additional hold-down bolts were included, and longer bolts were used where possible. Cast-iron sleeves were used for the cylinder bores, and provisions were added for a dry-sump oil system. The L88 combustion chambers were opened up to be as close to a hemi configuration as they would ever be. The new “open chamber” heads were worth about 40 horsepower. The rest of the engine was made up of stout L88 hardware. Packing 12.5:1 compression with a big 850-cfm Holley double-pumper carburetor, the basic ZL1 generated between 550 and 585 horsepower. Chevy engineer Tom Langdon built a special ZL1 for a ’69 mule Corvette commissioned by Gib Hufstader. The car would be used to make drag-strip passes at a ‘69 press review. Langdon’s ZL1 cranked out 710 horsepower!

The ZL1 package was released for ‘69 as an option on top of RPO L88, making it, on paper, as unstreetable as any L88 Corvette. Worse, the 100-pound weight savings was hardly noticeable on the street. The official published horsepower figure was 430—the same as the L88—so to the uninitiated, the ZL1 didn’t look like anything special. And if that wasn’t enough of a turn-off, the $4,718 price tag sure was. A Corvette already cost twice as much as a regular Chevy, and the complete ZL1/L88 package pushed the bill to almost $11,000! That’s why only two ZL1 Corvettes were officially sold. But there’s more to the story.According to former VETTE editor Marty Schorr, about 20 or so ZL1 Corvettes were built for the press, factory officials, Duntov, and GM exec Vince Piggins. In fact, the ZL1 that Schorr drove in ‘69 was not one of the three currently identified surviving ZL1 Vettes. Schorr nailed it when he wrote that due to the ZL1’s extreme price, the car was a street-performance machine. But the car and engine were never intended for street use. The yellow Roger Judski and the white Kevin Suydam ZL1s were almost totally unwanted in their day. The Judski car once sat at a gas station for two years with a $3,000 price tag and no engine. Both cars were bought, raced, abused, and resold many times before finally being restored.

On the track, however, the ZL1 was a tremendous success. John Greenwood’s BFGoodrich ZL1 Corvette was almost unstoppable in road racing. Grumpy Jenkins took Pro Stock drag racing by storm in 1970 with his ZL1 Camaro. The most successful use of the ZL1 was in the McLaren Can-Am cars, which dominated the series for five years. The most unusual use of the ZL1 was found in Jim Butcher’s ultra-lightweight Top Fuel dragster. The car set the NHRA national e.t. record at the ‘73 Gatornationals, with a 6.09, and scored a Top Fuel win at the ’74 Summernationals. Of the 20 or so ZL1 Corvettes that were actually built, only three have been accounted for. It’s too bad the ZL1 package didn’t get a few more years of development time. But who knew that 28 years later, all Corvettes would have aluminum engines? The cars that no one wanted would some day become some of the most valuable Corvettes of all time. - KST

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lllustrated Corvette Series No. 148 - '69 - 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

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lllustrated Corvette Series No. 135 - '69 - '71 Phase III GT
"60s Style GT Corvette"

The term “GT” is arguably one of the most misused automotive designations. The term dates back to the ‘30s in Europe and is an abbreviation for the words “grand touring,” or as they say in Italy, “grand turismo.” In the classic sense, a GT car was a road going , lightweight, semi-luxurious coupe, built on a high performance chassis. If your plan was to take a big trip, you needed a performance car with enough power, a strong chassis to deal with the rough roads, and creature comforts to make the journey more pleasant. Car makers such as Ferrari, Lamborghini, Austin-Martin and others, all offered GT cars for their affluent customers.

In the ‘60s, American car makers started to apply the GT term to their new pony and intermediate-size cars. But some enthusiasts wanted more from their cars. Some sought out the help of specialty shops that would super tune or build a package car for a price. The original Shelby Mustangs were the most noticeable of the turn-key super cars. But at a small shop in Baldwin, New York on Long Island, Motion Performance speedshop owner, Joel Rosen was making his own brand of performance cars called the Baldwin-Motion SS and Phase III Supercars.

Rosen was a successful drag racer and turner with a proven reputation for building dependable, high-horsepower big-block Chevy engines. He partnered with local Baldwin Chevrolet to build brand new, under warranty, enhanced versions of Chevy muscle cars. A few others were making similar cars, but Rosen’s cars were much more extreme. And Baldwin-Motion was the only brand building Corvette Supercars.

Phase III Supercars were reasonably priced for a turn-key car that was guaranteed to run 11.5 in the quarter-mile, or quicker with a Motion-approved driver at a NHRA or AHRA drag strip. In Joel’s limited spare time, he was dreaming of his own GT car, a machine that would put a hurt’n on Europe’s best. Within the Chevrolet lineup, there was one obvious place to start - the L71 427/435 big-block Corvette.

Rosen’s Phase III GT began where the regular Phase III Corvette ended. Since every car was built to the customer’s specs, we’ll examine Joel’s prototype GT. First the engine was disassembled and blueprinted. A low-restriction air filter was used with a 1,050-cfm Holley three-barrel carb on an aluminum high-rise manifold. The engine had tube headers, a Motion Super/Spark CD ignition, and M/T finned valve covers. The exhaust was a factory side-pipe system with chambered pipes. Horsepower was rated at 500 on Rosen’s dyno. The suspension received special shocks, bushings, and springs, along with a single traction bar. The wheels were 15-inch slotted alloy on wide Goodyear Polyglass tires.

What rocked everyone at the GT’s ‘69 New York International Auto Show debut was it’s stunning, muscular good looks. The Monza red ‘68 donor car had a distinctive black stripe that wrapped around the back end of the car, up the rear deck, over the roof and ended on the ’67 427-style scoop. All four wheel opening were flared to cover the wide tires, the side vents were reversed, and remote controlled mirrors were used. Most noticeable was the fastback rear window that opened up the rear storage area and a Le Mans quick-fill gas cap replaced the stock gas cap door.

Zora Arkus-Duntov was at the show and spent time with Rosen talking about big-block engines and gave the GT his blessings. Rosen’s promotion literature quickly ran out, but he got two deposits to build cars. The starting price for the GT was $10,500, over double the cost of a stock ‘69 Vette. When Rosen started building GTs, two major body changes were incorporated. The stock pop-up headlights were replaced with single, fixed headlights that were faired into the front fenders. And at the back end, the classic four round Corvette taillights were replaced with two sets of three slotted taillights.

The Phase III GT Corvettes were only built from ’69 to ‘71. Rosen anticipated building 10-to-12 cars per year, but it turned out that he only made approximately 12 cars total and no two cars were alike. No doubt, the maga-buck price was a major factor back then. A 1970 Phase III GT turned out to be one of the most expensive, costing a mind-bending $13,000 in ’70. The car was Daytona Yellow and packed a 535-horsepower 454 engine with open-chamber heads, a modified automatic trans with a Hone overdrive, 4.88 gears, and air conditioning.

In the late ‘80s Rosen began looking for one of his old GT cars. He was able to locate the ‘70 Daytona Yellow GT , had the car fully restored and displayed it at the ’93 New York Auto Show. Joel later sold the car to a private collector in ‘01. Specialty Corvettes have come a long way since ’69 and many others have applied the same concept to their dream machines. Only five of the Phase III GT cars are known to still exist, making this one of the rarest of all the specialty Corvettes ever made. - KST

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lllustrated Corvette Series No. 32 - 1969 Corvette
"Getting Its Act Together"

After all the brouhaha over the new Corvette's Mako Shark styling, reality set in and the magazine testers and customers figured out that the 1968 model wasn't really done. Quality, fit, and finish were a major concerns. There was a lot that wasn't right - so much so that the 1968 Corvette never enjoyed the same status as the first 1963 Sting Ray.

Designers knew that the '68 Corvette was a transition model. Much of what they'd hoped to have on the '68 car made it into the '69 car. The Stingray name was back, however, instead of being a two word name, it was now just, "Stingray." Visually the Stingray had minor changes. The most obvious one was the "Stingray" script lettering over the front fender vents. The front grille was completely blacked out and the tailights had integrated backup lights. The door handles were flush mounted and operated by squeezing down. The Rally Wheels didn't look much different, but now measured 8 inches in width. Perhaps the hottest option was the off-road exhaust pipes. These were the same pipes that were available in '67, but with beautifully styled covers that fit the coke-bottle shape of the rocker panel perfectly.

The small-block engines grew from 327 cubic inches to 350, but power ratings remained the same. The 427 engines were unchanged for 1969 except for the $3,000, optional, all-aluminum 427 ZL-1. Transmissions and suspension options weren't changed, either.

The interior saw new door panels for additional shoulder room and a small- diameter steering wheel, since most Stingrays had power steering. The dash now had map pockets and the seats had built-in headrests. The console area had a few new warning lights and there was a plate indicating which of the five engines was under the hood. An alarm systems was a new option for '69.

The changes were mostly well received. One magazine described the small-blocks as "marginally fast and very civilized, while the big-blocks were marginally civilized and very fast." The Stingray was still criticized for having a "harsh" suspension. Duntov explained that it was tuned for speeds between 80 and 120 mph. He didn't want to, "penalize the man who's going to drive fast." Wise words from the Godfather. KST

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Illustrated Corvette Series No. 33 - 1969 ZL-1 Corvette
"The $10,000 Mega-Buck Corvette"

Imagine having a new Corvette with more power than a big-block, and the weight of a small-block. That was the basic idea behind the all-aluminum, 427 ZL-1 Corvette. The idea of an all-aluminum engined Corvette was first outlined in 1957 as the "Q-Corvette." What finally emerged was more than anyone ever expected.

While everyone loved the 427's power, Duntov was not happy to have 51% of the Corvette's weight over the front wheels. Some calculating showed that if the engine was completely made of aluminum, the weight would be close to a small-block. So it was decided to go-for-broke and make the ZL-1 a monster.

Duntov started with a "stock" L88 and added an aluminum block that was fitted for a dry-sump oil system, larger main bearing bulkheads, extra cylinder head bolts, 12:1 compression pistons, a new camshaft, and open-chamber aluminum heads. Cast-iron sleeves were installed in the piston bores to solve the wear problem with the aluminum block. With a set of headers, the ZL-1 made over 585 horsepower at 6,600 rpm! Since the L88 was already void of unnecessary street hardware, the ZL-1 optioned Corvette weighed in at only 2,908 pounds, about the weight of a 1957 Vette.

The big hitch for the ZL-1 was its price. The ZL-1 option alone cost $3,000 on top of the L88 option. That made the ZL-1 cost over $10,000 in 1969! That was almost twice the cost of a normal 427 street Corvette.

Only two ZL-1 Corvettes were ever made, making them the rarest Corvettes ever. Performance was amazing: 12.1 quarter mile time and 180 mph top speed. This was really Chevrolet's all-out racing Corvette! KST

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lIlustrated Corvette Series No. 34 - Zora Arkus-Duntov's 1969 ZL-1 Corvette

Being Chief of Engineering for the Corvette surely had its perks. In 1969, Zora Arkus-Duntov showed the press his latest "mule car", a completely optioned-out for road-racing ZL-1 Corvette. The public finally had a glimpse of what it was like being in the beast.

Duntov was the best friend that any Corvette owner ever had. First and formost, he was a sports car racer. His "vision" for the perfect Corvette was a lightweight car with a high-revving, high output engine. The big-block 427 was not his ideal. However, the all-aluminum 427 made more power than anything at GM, plus it weighed as much as a small-block!

To show off what the '69 Corvette was capable of at the high end of the performance spectrum, Zora and his team built a Corvette the way any racer would. Starting with a "stock" L88 optioned Corvette, he then added the optional ZL-1. Like racers, they removed anything that didn't look like a race car.

All non-essential parts were removed: bumpers, upholstery, radio, spare tire, headlights, and heater. Then the good stuff was added. Cast-iron exhaust manifolds, mufflers, and pipes were replaced with steel header side exhausts. Racing mag wheels were 15 inches in diameter by 10.5 inches wide with non-D.O.T. approved, racing tires. Using the roadster body with a fixed hardtop roof, the only body mods were huge fender flares, the optional ZL-2 domed hood, and a lip along the leading edge of the hood to keep it from blowing off at 180-plus mph! This car was never driven on a public road, as it was a "research vehicle" only.

Needless to say, Duntov's toy ran like no other Corvette ever had up to that time. With 3.70 gears and a close-ratio four-speed, and not shifting like a drag racer, Duntov could hammer the quarter-mile in 12.1 seconds at 116 mph. In tight corners and heavy braking the '69 ZL-1 would pull over 1g. The suspension was set up to understeer slightly, but a controlled drift was possible. Top speed was somewhere over 180 mph!

Costing over $10,000, Zora's ZL-1 was twice as much as a stock Corvette. The cool thing was that so much great stuff was available from your local Chevy dealer. KST

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lllustrated Corvette Series No. 38 - 1969 Manta Ray Show Car Corvette

The 1965 Mako Shark II may well have been the most exciting Corvette show car of all time. This one show car had more direct impact on future production Corvettes than any other. The car was a world traveler as General Motors trotted the Mako Shark II all over the automotive globe, wowing car lovers everywhere it went.

By 1968, with the debut of the new C3 Corvette, the Mako Shark was old news. But when your pockets are as deep as GM's, why not make a great thing even greater? Even though $2.5 million had been spent on the Mako Shark II, the General spent almost another $3 million on the Manta Ray!

The biggest change was the long, tapered tail, a 'la the Astro Vette Show Car. Endura bumpers gracefully covered functional metal bumpers. The roof line featured a beautiful, sweeping, tapered style, similar to a Sting Ray roof, but scooped out with a small slot for a rear window. For hard braking and turn signaling, flip up lights popped out of the rear deck. Four taillights were fared in under the rear bumper line with a center-located license-plate holder.

An awesome show car should have an awesome engine. The Manta Ray used the new, all-aluminum, ZL-1 engine with a special air cleaner. Side pipes were beautifully crafted into the side rocker panels and sounded great. This was part of the Bill Mitchell trademark.

The nose of the car was basically unchanged, except for an extended bumper ring around the air inlets and a small chin spoiler. Normal sideview mirrors were deleted in favor of small, bullet-shaped mirrors that were attached to the top of the A-pillers. Like the previous Mako Shark cars, the Manta Ray was painted dark blue with pearl white fogging along the lower edges. Special badges and Corvette crossed-flags insignias completed the car.

This may have been the last "pure" show car Corvette. Later show cars were serious engineering studies. Cars like this sure got a lot of us juiced up for the "next" Corvette. Ah, the stuff of daydreams! KST

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lllustrated Corvette Series No. 39 - Baldwin Motion 1969 Phase III Corvette
"The Shelby Mustang of Corvettes"

From 1967 to 1969, the hottest street Corvette was the 427/435 L71. Not a bad ride for most folks. But Joel Rosen isn't "most folks."

Rosen owned Motion Performance in Brooklyn, New York in the late '50s and '60s, and was having considerable success as a local drag racer-tuner. In '67 Joel struck a deal with the owners of Baldwin Chevrolet, in Baldwin, New York, to make 427-engine versions of the new Camaro. When the '68 Corvette came out, Joel knew that he had to make a special red-hot version. The '69 Baldwin-Motion SS-427 Phase III Corvette was born.

The deal with Baldwin Chevrolet was that Motion would perform all of the conversion work and the car's warranty would still be maintained. To keep everything balanced, the car was beefed up, inside and out! You simply could not miss these cars. Even sitting still they looked nasty and serious. A '67 427-style hood scoop was grafted on top of the stock 427 hood along with a Pontiac hood-mounted tachometer. The wider tires were covered with wheelwell flares. Side pipes were either '65-'67 style, '69 style, or Hooker Header side pipes. An optional fastback window opened up the luggage space. Finished off with a unique stripe design, the car looked like a killer.

The 427 received an 850 Holly three-barrel on top of a high-rise manifold. Ignition used a modified Mallory setup with Ramcharger wires. Other goodies included a close-ratio Muncie four-speed, blow-proof clutch, heavy-duty suspension, and 60-series tires on Anson Sprint wheels. Every Phase III car was guaranteed to run 12.50 et @120 mph with a M/P approved driver at a NHRA or AHRA track.

Unfortunately, Rosen was a high-profile, big fish in a small pond. In 1974, after seven years of building super cars, the Feds threatened to shut down and fine Rosen $50,000 per car for violation of the Clean Air Act. Rosen's lawyer explained that he wasn't operating a huge assembly line. Luckily, Joel got off with just a $500 fine, but the party was over. That's what a little too much success, publicity, and horsepower can do to you.

Recently, Rosen was able to buy back the last Phase III Corvette he made, a 1974 model. KST