Cohort Classic: The Corvette C4 ZR-1 Convertible

This beautiful yellow C4 was posted at the Cohort by chrisjcieslak , under the title “Did they make a ZR-1 convertible?”. That’s actually a very interesting question and one which I decided to find an answer to. As it turns out; yes. A couple of them, actually.

There have actually been several ZR-1 convertibles across the four Corvette generations with such a model on their lineup. Pedantry forbids me from including the C6 and C7 ZR1’s thanks to the lack of hyphen in the name. But the older C3 models had a ZR-1 package if you decided to opt for the LT-1 engine between 1970 and 1972. Eight people added infinite headroom to the heavy duty suspension components, power brakes and a heavy-duty manual transmission. Should make up for the lack of air conditioning. And the unencumbered V8 rumble should make an adequate substitute for the radio.

Compared to the 53 C3 ZR-1s ever made, 6,939 C4 ZR-1s rolled off the assembly line in Bowling Green. I’ve gone on record saying that the C4 is my favorite of all the Corvette generations. A completely new design after the evolutionary C3, it set the design template from which all future Corvettes were built. And yet, it was unmistakably a product of the decade that spawned it.

Sure, the digital gauges were a bit unfortunate. And nowadays they carry an air of…middle age about them. Doesn’t matter, they have remained my favorites since I’ve got memory. And out of all the C4s, the ZR-1 is my favorite of all. Twice the price of a normal Corvette with only wider wheels, upgraded suspension, steering and brakes, a unique rear end (which stopped being unique after the 1991 facelift) and a small badge to distinguish it visually, as most of the changes were done under the hood.

Thanks to the 375 horsepower V8 (designated LT5, designed by Lotus and assembled by Mercury Marine), the ZR-1 could crack 60 in 4.4 seconds. Today that is the domain of the Camaro SS, but back in the 1988, a mormal Corvette would run 6.1 to 60 (According to either C&D or R&T). The ZR-1 gave some much needed bite to the corvette. 4.4 Seconds was reserved for 911 Turbos and Lotus Esprits at the time. The Testarossa would do it in 5, which means it could be out-dragged by a good driver on a turbo V6 Pontiac Firebird.

And thanks to the brake and suspension upgrades done in collaboration with Lotus, you could keep going at transcontinental speeds even if the roads got twisty. There were only two compromises. The price, and the fact that you would have to make due with the coupe and its targa top. GM discovered that the convertible body just wasn’t stiff enough to handle the power of a ZR-1.

And how did they discovered that?

With this! Meet the Corvette DR-1, the only GM backed C4 ZR-1 convertible. DR stands for Don Runkle, then Vice-President of Advanced Engineering and the man who requested that this convertible ZR-1 was built. Naturally, after he had discovered that production of a ZR-1 convertible would not be viable, he took it upon himself to discover the long term effects of LT-5 use in a convertible by using it as his personal car. Truly a man who thoroughly validates his work. Last we heard of it, it was sold at a 2009 Barrett-Jackson collector car auction for a not-inconsiderate $265,000.

So that was it for convertibles made by GM themselves. However, ASC also decided to have a go at it. Their result is this, the ASC ZR-1 Spyder. is a much more involved affair including a chopped windshield. Originally presented in silver with a yellow interior, it picked a coat of purple paint and a red retrim before making its way to the Bowling green Corvette museum.

Then that sinkhole kicked in.

Do not let the horrifying image scare you though. It’s okay now, back on the plinth where it was supposed to be.

Finally, there is this, a 1991 C4 done by Metalcrafters, an outfit in Fountain Valley, California. The vehicle was originally done for Dr. Larry Bartschi. He also decided to send the engine for some custom work which bumped it up to 475 horsepower. It has gone through three owners and at least 175,000 miles.

And…that’s it, there have indeed been several C4 ZR-1 convertibles. But this particular one, I’m afraid, isn’t one. It’s just a very well kept Corvette C4 convertible being enjoyed on a clear night. It’s the best time to have the roof down anyway.