This One-Off Corvette ZL-1 Could Bring $3 Million
While General Motors has built over 1.75 million Corvettes since 1953, but not all Corvettes are equal. This 1969 Chevrolet Corvette Stingray Convertible offered at RM Sotheby’s upcoming Phoenix auction is unlike any other. That’s because this drop-top, fiberglass-bodied two-seater packs the astonishing, all-aluminum, 427-cubic-inch (7.0-liter) big block V-8 engine known as the ZL-1. Only two Corvettes that received this race-ready motor were released to the public, with this one the only ZL-1 convertible. It is expected to sell for between $2.6 million and $3 million.
It's the ZL-1 V-8 engine that is responsible for the sky high valuation. The engine is a lighter and more refined variant of the mighty all-iron L88 big block V-8 that found in other high-dollar Corvettes from this era. An evolutionary step beyond the L88, besides the aluminum block and cylinder heads the ZL-1 has upgraded pistons, stronger connecting rods, a reworked crankshaft, and a higher lift camshaft. Later iterations featured open chamber cylinder heads, but this particular example retains the pre-production closed chamber heads. Every ZL-1 V-8 also has four additional head bolts to help keep things stuck together. GM rated the ZL-1 at 430 hp, but that's a blatant lie. Later testing revealed the open chamber version was actually good for closer to 560 hp. That made the ZL-1 the most powerful engine GM had ever produced up until that point. And it was also among the very lightest, weighing less than a comparable iron Small Block V-8.
The ZL-1 was designed as an FIA and NHRA homologation experiment, and was never intended to be sold to the public. In testing of a ZL-1-powered Corvette, R&T recorded 0-60 mph times of 4.0-seconds, as well as ¼ mile sprints of 12.1 seconds at 116 mph.
The ZL-1 engine was also installed in a limited run of Camaros to certify the combination for NHRA drag racing competition. Only 69 were built under Central Office Production Order (COPO) 9560 during the 1969 model year. Naturally, they're considered the most desirable and collectible Camaros of all time.
If you wanted an L88 to power your Corvette back in 1969, you forked over $1032 for the RPO L88 upgrade. That was a significant chunk of the base Corvette coupe’s $4781 MSRP back in the day, with only around 200 customers opting for the spendy race motor. And RPO ZL-1 was a huge thump up from that, requiring buyers to spec the L88 package and adding another $3000 or so more beyond that. That $4718 option box for the all aluminum big block about doubled the base price of the Corvette.
The ZL-1 package also omitted such luxuries as a radio, heater, air conditioning, power windows, power steering and the fan shroud. This particular car was later fitted with a fan shroud due to overheating concerns, however. RPO ZL-1 did bring some nice performance parts too, including the heavy duty suspension package, a positraction rear end, and heavy duty stoppers. That knocked the total chit for RPO ZL-1 and its accessories to reach $5267.15.
This particular car was the first Corvette ordered with the ZL-1 engine. Originally ordered by John W. Maher of Leechburg, Pennsylvania from Harold Breman’s West Penn Garage in December 1968. According to RM Sotheby’s, this decision came after Maher’s friend Don Yenko began talking up the experimental ZL-1 motor. Maher was specifically interested in the fact that the engine could be mated to GM’s M40 automatic transmission, which was perfect for drag racing. Despite his knowledge of the engine program and his interest in shelling out the necessary cash, Maher initially struggled to get his order in. That changed when he got a little help from his friend and two time SCCA champion Grady Davis. Davis was a senior vice president at Gulf Research, who worked alongside GM on its secretive racing operations. GM would approve the ZL-1 / M40 powertrain configuration for production on November 21, 1968. Maher’s order for a Monaco Orange convertible would be accepted the next day. The exterior hue was selected as a nod to Davis’ involvement in securing the car.
After taking delivery of the car in early 1969, Maher would campaign the Corvette ZL-1 in a number of drag racing, hill climb, and autocross events. Often he ran L88 engines supplied by Gulf Research with the ZL-1 set aside and stored. The car’s original ZL-1 engine would have its short block replaced in September of 1969, which remains the only racing injury that the car ever received. In place of the numbers matching engine now sits a factory-correct, date-coded ZL-1 V-8 installed by GM.
The car’s most recent restoration came in 2014 at the hands of Kevin Mackay and Corvette Repair. It looks better than it would have in 1969. Combine the history, rarity and condition of this car, and its seven-figure estimated price isn’t so shocking. This is the first time in 30 years that a ZL-1-powered Corvette has been offered for public sale, and it marks the only time the sole drop trop has ever been offered. The car will cross the block during RM Sotheby’s Arizona auction on Thursday, 26 January 2023. If it does reach that upper estimate, the car will become the third most expensive Corvette ever sold. That title currently belongs to a 1967 L88-powered coupe, which sold for $3.85 million. Second place is currently held by a 1967 L88 convertible that previously sold for $3,424,000. You’d think a genuine ZL-1 would bring even more.
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