1969 Corvette ZL1 - Checkered Past
‘Super Chevy’ Magazine - June 14, 2006
An Article By Paul Zazarine

The ZL1 was a midyear engine release for the '69 Corvette and was slated to replace the legendary L88. It boasted a beefier, all-aluminum block; stouter connecting rods; and open-chamber heads that flowed better than the L88's. The ZL1 was also lighter, weighing about the same as the L46 small-block. And it was expensive.
The ZL1 option also required a handful of mandatory options-the F41 Special Front and Rear Suspension ($36.90), G81 Positraction rear axle ($46.35), J56 Special Heavy Duty Brakes ($384.45), and K66 Transistorized Ignition ($81.10)-raising the total price of the ZL1 package to $5,267.15. And that was on top of the Corvette's base sticker, so if no other options were ordered, the tab for a ZL1 Vette was a hefty $10,048.15. Radio and air conditioning were not available with the ZL1 engine.
With that nosebleed price tag, not many ZL1s were produced. Records from the Tonawanda engine plant revealed 94 - ZL1 engines with Corvette prefixes were built-80 coded for use with manual transmissions and 14 for use with automatics. It's acknowledged among Corvette historians that the majority of these engines were sold to racers, but a few went over dealers' parts counters to private parties. Although two ZL1s were sold to the public, only one has provenance and pedigree. The other has never been fully documented.
Before these engineering cars were retired, both Popular Hot Rodding and Road & Track magazines got their editorial mitts on one. PHR was able to run an 11.0 at 129.45 mph in the quarter-mile. R&T took the 2,945-pound ZL1 and recorded 0-60-mph acceleration in 4.0 seconds, while the quarter-mile was over in a short 12.1 at 116 mph. These were mind-boggling speeds and took the standard Corvette chassis and brake systems beyond their design limits. Unfortunately, all this Saturn-rocket stuff was quickly over. Duntov and his staff knew the ZL1 would have to be cut in 1970 to meet stringent new EPA guidelines. But it was glorious while it was around.
There are also a handful of ZL1-equipped '69 Corvettes in the hands of the Chevrolet Engineering Department, including one once piloted by Chief Engineer Zora Arkus-Duntov. The story goes that these cars were used as performance test-beds for driveline and suspension upgrades. What happened to them remains a mystery, although it's believed the engines were yanked, the production big-blocks reinstalled, and the cars put up for sale. And where did the ZL1 engines go?

One Corvette is now in the hands of Rick Treworgy, of Punta Gorda, Florida. Rick's owned the car since 2001, and he's researched the car's provenance. He believes it started life as a big-block, perhaps an L88, especially since it was minus the radio straight from the factory. Some of the numbers on the Corvette and the ZL1 look tantalizingly close, but no cigar.

The owner of record in the mid '70s purchased the '69 in baskets, and the Holy Grail of Corvette restorers - the tank sticker - was long gone. The tank sticker is a copy of the build manifest and contains information about the car, including the options and accessories as equipped from St. Louis. With it, you have full documentation. Without it, well, you have supposition. Like the yellow ZL1 that belongs to Roger Judski, Rick's car has the black stripe that runs the width of the headlamp panel and up along the rise of the front fenders. It's been there since the car was restored in the '70s. Also still fitted on the roadster is the RPO C07 Auxiliary Hardtop.

Rick isn't hung up on the '69 roadster's mysterious past and how it ended up with the most exotic and most powerful production engine Chevrolet ever sold to the public. All he knows is that it's one hell of a car to drive. The restoration done years ago has held up well, with the only visible change being the replacement of the Western turbine wheels for a correct set of Rally road wheels. One thing that hasn't changed is the curiosity that surrounds this car. Did it start life as an L88? - only Chevrolet knows for sure.

The 1969 Corvette RPO – ZL 1
If Corvette history and the elusive lore of ZL 1 and L 88 blows you away, then please CONTINUE READING a true account by Ken Kayser's take on it.

The 1969 ZL1 all aluminum 427 cubic inch Corvette motor was the most powerful engine that was ever offered in an American built automobile. It was the direct descendent of the L88 427 engine and the all aluminum Can Am racing engine of the same era. Although factory rated at 430 HP, the actual output was more like 585 HP after tuned headers were installed in place of the restrictive factory exhaust manifolds. When delivered from the factory, the standard exhaust manifolds may have suited quick assembly line techniques, but they only slowed the Corvette's true acceleration potential. So to resolve this problem, the factory contracted Kustom Headers to build several sets of header/sidepipes for the true racing enthusiast, which could be purchased via the local Chevrolet parts department. But due to the low production quantity of these headers, the prices were extremely high. Hooker Headers quickly bent a set of their own and offered them at a much more reasonable price than the Kustom set. Hooker established its own niche with that marketing move.

A dome hood was necessary for intake manifold clearance. This hood was released in 1968 with the cast iron block L88. Cowl induction was used at the rearmost base of the dome for improved air induction to the Holley 850 double pumper 4 barrel carburetor. This cowl induction trick alone cut seven seconds off the car's zero to 140 MPH acceleration times!

To truly experience this car's handling and acceleration potential, it was to one's advantage to install the factory designed fender flares, which were also available through the parts department of the dealership. Larger, wider tires could then be used for improved cornering and acceleration.

Two factory test mules were made available to the press. A white convertible, which was set up for road racing duty, and a red coupe, which was set up as a "Saturday Night Special" for 1/4 mile drag racing action. The red ZL1 was equipped with a "beefed-up" automatic transmission and 4.88:1 rear end gears. With 9" slicks and open headers, every automotive reporter at the session was running the 1/4 mile in 10.9 Sec. @ 132 MPH!!  This is an incredible feat considering that all you had to do was to get in a car, buckle up, load up the torque converter a few thousand RPM's,take your foot off the brake, and in less than 11 seconds you've already driven through the traps at the strip at a speed that most other street cars could barely achieve with highway gears!! This red ZL1 was set up by Corvette engineer Gib Hufstader.

The white ZL1 was equipped with an M-22 "rock-crusher" 4-speed transmission and 3.70:1 rear end gears. Even with this "road racing" setup, it could cut the quarter mile in 12.1 Sec @ 116 MPH! - 200 MPH could be attained with the proper higher rear end gears (lower numerically). This white car was set up by chief Corvette engineer Zora Duntov.

One of the most successful Corvette racers to use the ZL1 motor consistently was John Greenwood.  He achieved many victories in the SCCA, including a  national championship, and competed quite successfully in long distance endurance racing.

1969 Chevrolet Corvette Stingray ZL1

One of the rarest Corvettes is the C3 Stingray fitted with the all-aluminum ZL1 engine. Only a handful of Vettes originally came equipped with the ZL1, but many racecars were later upgraded to include the ZL1 and produced upwards of 750 bhp.

Like the L88 racing engine, Zora Duntov made the ZL1 available as a regular production option (RPO) but was rarely ordered because of its high price of $3,010 on top of the $1,032 L88 option. This made the ZL1 option the most expensive engine ever offered by GM. Furthermore, the engine wasn’t as thoroughly tested as the L88 which had already proven itself in 1967 by winning at Daytona.

The all-aluminum engine was cast entirely differently than the 427 in L88 model, having larger block thickness and increased support webbing. It was developed from the ground up and benefited from the lessons learned with the 283 in all-aluminum engine. The first versions were used in 1967/68 by Chaparral for the Can-Am season. Suffering from major leak issues due to the porosity of aluminum, the ZL1 reached final specification in 1968 and was sold in certain Camaros and Corvettes or sold over the counter for about $2000 USD.

A Yellow ZL1 is owned by Roger Judski of Florida; this car is the only one that features black ZL1 stripes and it is the most famous of the three known cars. In the 1980s it was restored in Texas and eventually auctioned by the state in 1991 for $300,000 USD. The car was displayed at The 2009 Blooming Gold.

The White ZL1, also ordered with J50 power brakes, J56 heavy Duty Brakes, F41 suspension, K66 Transistor Ignition, G81 Posi Rear Axle, M22 Muncie Four Speed, F70x15 Red Stripe tires, A01 Tinted Glass and Front Louver Trim is currently owned by The Kevin Suydam Collection in Washington.

An Orange ZL1, ordered new by John Maher in 1968 was traded for a used L88 roadster. With a Gulf Oil sponsorship, the car was delivered with an automatic transmission. Eventually the original engine was replaced by an L88 unit. In 1972 the car was parked and hardly used until 1989 when another new L88 engine was installed. By 2002 John Maher still owned the car and he decided to rebuild the original engine as well as a new ZL1 to place in the car. With this configuration he  uses it at drag races and slaloms.
1969 Corvette ZL1 427-430HP
The ZL1 engine was as exotic of an engine that could have ever been developed given the parameters Chevrolet had to work with 30 plus years ago. The all aluminum 427 - ZL1 was patterned after the cast iron 427 - L88, but it wasn't merely just a change of the block casting material. The ZL1 had beefier bearing journal web areas, and external web braces at places such as the front of the block where the intake manifold bolts down. There are extra bolt pads inside the lifter valley under the intake manifold to allow for extra head bolts. The aluminum block had iron cylinder sleeves, capability for dry sump oil system and optional gear drive for the camshaft. The ZL1 camshaft was a higher lift and different duration than the L88.

The ZL1 motor was developed by Chevrolet with the intended purpose of racing. Therefore it was necessary for Chevrolet to produce it as a regular production motor to qualify it. But it is likely that without the efforts of Zora Duntov the engine would never have made it to production. Chevrolet produced the ZL1 motor as a RPO (Regular Production Order) option in 1969 only, and only available as a RPO option on the Corvette. Additionally, there were ZL1 Camaros produced during the same year, but only as a COPO (Central Office Production Order).
The ZL1 Corvette is one of only two 1969 ZL1's sold to the public. Why were only two sold when it was such a great engine option? It was the added cost of approximately $6,000 for the ZL1 option that discouraged sales. This more than doubled the cost of the Corvette resulting in a total cost over $10,000. It would be a good guess that prospective buyers opted for the more cost effective L88 cast iron motor, which appeared to have the same horsepower; for a lot less than the $6,000 that Chevrolet wanted for the ZL1. This particular ZL1 was delivered new to a Chevrolet Dealer in Salt Lake City Utah, as shown through NCIB Bureau records; they list the original dealerships to which new cars are delivered. The first owner of this ZL1 Corvette was Jack Cheskaty, former US Treasury IRS Director for the Rocky Mountain District of five states. In phone conversations, Jack Cheskaty, talks about his purchase and ownership of this factory original ZL1. He remembers the original Chevrolet window sticker on his Corvette with the ZL1 option, and he states: "There was no mistaking that option as it essentially doubled the price of the car.” Jack's regret of course; is having let go of this ZL1 Corvette in 1970, not realizing what a valuable car it was destined to be.

Jack traded his ZL1 late in the year of 1970, after drag racing it and only owning it for a year and a half. The last time he saw his old gem, it was headed for circle track racing and was highly modified, flares, fuel cell and all. The car was not seen again until 1978 after Jack wrote a letter to ‘Vette Vues’ editor, Errol McCoy telling the story of his ZL1, but not knowing where it was, or who currently owned it. That letter was published in ‘Vette Vues’, 1978 and it set off a nationwide hunt for the car. It was eventually found by Dick Ferrando by finding the second owner, and by obtaining the owner history through DMV records.

More history in the file of this ZL1 is the racing contract between Jack Cheskaty and Woody Walcher & Associates Racing team. Woody provided a signed affidavit of this Corvette as being a factory original ZL1. There is a 1970 Race Program from Midway Dragstrip in Grand Junction, Colorado with this Corvette under Cheskaty's name and several original photos of the car on the drag strip with the name "Predator" on its side.

This ZL1 is presently restored to original showroom condition. Along with its ZL1 option are the J50 power brakes, J56 heavy Duty Brakes, F41 suspension, K66 Transistor Ignition, G81 Posi Rear Axle, M22 Muncie Four Speed, F70x15 Red Stripe tires, A01 Tinted Glass and Front Louver Trim. It has been Bloomington Gold certified and featured in many magazines and numerous books. Through the years in magazines such as Motor Trend, Corvette Fever, Vette Vues, Classic Auto Restorer, Corvette Quarterly, Vette, Musclecars, and hard back books such as Automobile Quarterly, Corvette-The Complete Illustrated History, Corvette-Americas Sports Car, and American Muscle to name a few.
So What is an L88 Corvette?
Dr Peter J. Gimenez, writer for ‘Corvette Racing’

The L88 option package for the Corvette was the result of years of developmental work which resulted in a factory racing option package that could be ordered from Chevrolet in a brand new Corvette. The L88 option was only available for three brief model years from 1967 through 1969. The L88 Corvette was so potent, that it could not only allow the new owner or driver to win a race in local competition, but it also could propel a properly prepared Corvette to stunning finishing positions in world class International races, such as the 12 Hours of Sebring and the 24 Hours of Daytona. These racing victories with the L88 option package, made the Corvette an overnight hit. The L88 nomenclature became synonymous with Corvettes and champions. Although only 216, L88 Corvettes rolled off the St. Louis Corvette Plant assembly line during three model years, namely 1967 – 20 units. 1968 – 80 units. 1969 – 116 units. 

The L88 created an image of power and prestige that would live on with the Corvette for decades. Most of the race prepared L88 Corvettes that competed on tracks in the United States and Europe are featured in my text book, and so are the predecessors that led up to the creation of the L88 factory racing option.

These are the Corvettes that started the legend. These are the Corvettes that shaped a generation of Corvettes and Corvette enthusiasts. They are the Corvettes that shaped the future generations of Corvettes.

So what exactly is an L88 Corvette? It's a special order ultra high performance Corvette that was equipped with the 427 cubic inch L88 full competition engine and its trademark L88 hood, a heavy duty M22 four speed transmission, J56 heavy duty disc brake calipers, J50 power brakes, F41 heavy duty suspension, K66 transistor ignition, and C48 heater delete (1967). These were all mandatory options that the buyer had to select in order to receive the L88 engine. It was an option package.

Additional options were available such as power windows, leather seats, bolt on hardtop, tinted glass, speed minder, side pipes, engine block heater, rear window defogger, head rests, tilt-telescopic steering column, and for late 1969, a heavy duty dual disc clutch, and a heavy duty turbohydramatic 400 automatic transmission. Comfort options such as a radio, air conditioning, and power steering were not available with the L88 engine option package.