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.