In the Barrett-Jackson studio, I caught sight of a Mosport Green 1966 Chevrolet Corvette roadster. It looked perfect with the turbine-like aluminum knock-off wheels and unusual gold stripe tires. The domed hood told me it was a big-block car, specifically a 427 since 1966 was the first year for that engine. Taking a peek inside, I noticed the automatic shifter. “390 horses,” I remarked to myself.

From 1965-68, all solid-lifter big-block engines available in the Corvette required the four-speed transmission. As such, the presence of an automatic means this C2 couldn’t be powered by the L72 425-horsepower 427. If you wanted an automatic, you had to make do with the L36 390-horse 427. What’s interesting about this combination is that it was paired with the two-speed Powerglide.

Wait  — didn’t General Motors introduce Turbo Hydra-Matic (TH400) in 1964? Why saddle the Corvette with some old-fashioned tranny? Come to think of it, the TH400 transmission didn’t appear in mid-size cars until 1967, yet the Corvette didn’t receive it even then? Those questions are valid, and there are two explanations.

• When the C2 Corvette was designed, it was not engineered for a transmission that had yet to debut, so it did not fit. Plus, automatic transmissions were a small percentage of Corvette production, with buyers overwhelmingly preferring the optional four-speed.

• General Motors did not put automatics behind solid-lifter engines. Sure, GM built some fast cars through 1968 — Ram Air GTO and Firebird, and 4-4-2 W30 to name a few — but the ones with revving ability were stuck with manual transmissions.

When the redesigned Corvette appeared for 1968, it was engineered to handle the TH400, but the L71 and L88 big-blocks (both solid-lifter engines that first appeared in 1967) were still restricted to a four-speed. That all changed for 1969.

Fred Gibb (the owner of the same Illinois-based Chevrolet dealer who became famous for creating the 1969 ZL1 big-block in conjunction with GM) and champion racer Dick Harrell had discussed the idea of how perfect an L78 Chevy II would be in SS/Automatic. They worked with Chevrolet’s Vince Piggins to create a 1968 Nova SS powered by a solid-lifter, 375-horsepower 396 paired with the TH400. Normally, only a three- or four-speed was available, but Piggins had engineers create a TH400 with a modified torque converter and improved clutch packs. Gibb placed a COPO fleet order for 50 Nova SSs with the L78 and beefed-up TH400 to satisfy the NHRA’s homologation requirement.  

Thanks to this COPO order, GM was equipped to allow the TH400 to play a role with solid-lifter big-blocks in Chevrolet’s roster starting in 1969. It was also used in GM’s stronger performance cars, including Ram Air IV Ponchos and W30 Olds.

The aforementioned 1966 Corvette will be headed to the Barrett-Jackson 2026 Las Vegas Auction, which takes place September 10-12, 2026.