When you think of the name Thumper, is the first image that pops to mind of a cute, cuddly, and furry bunny rabbit friend of Bambi? Well, you can quickly forget that Disney cartoon character and meet the new Thumper-a bad-to-the-bone, race-prepped, street-legal '78 Corvette with a big-block and LOTS of attitude!
When Dr. G.R. Richards of Lubbock, Texas, purchased his '78 bubble-back coupe over the Internet a couple years ago, it was already a mild hot-rod with a 383-cid stroker small-block and a Turbo 350 automatic, and it had lots of chrome under the hood. After the car made its journey from Southern California to its new home in northwest Texas, though, Dr. Richards soon realized that the Vette wasn't everything he wanted as it was. The ill-tempered 383 was hard to start and didn't run well, plus the Shark just didn't handle like a Corvette should due to an awkward, "nose-in-the-air attitude." It only took a few weeks before he called up Scott Arnold at Scotty's Vettes in Dickens, Texas, to remedy its vices. Because Scotty's shop was already in the middle of a couple major builds, they couldn't start on the '78 project at once, but Dr. Richards had another Vette to drive. So the '78 sat on the rear burner for a while.
Over the following year, Scotty and the good doctor came up with a wild but moderate game plan for the '78. Impressed by a radical big-block '63 split-window project that Scotty had just finished, Dr. Richards asked him to replace his 383 small-block with a brand new ZZ502 big-block crate motor. Scotty agreed to this new project and prepared to build an "average" big-block 502 street machine when Dr. Richards changed his mind. Can too much ever be enough? Obviously not when you're talking about anything in Texas where bigger is always better. Richards soon decided that a mere 500-horsepower big-block wasn't enough, so he called Scotty back a week later and pulled out all the stops.
Instead of the GMPP crate motor, the doctor had to have the seriously built 548-cid monster motor he'd seen in the back room of Scotty's shop that was slated for another project. Why settle for 500 horses if you can get 790! Dr. Richards was undaunted by the fact that much more would have to be done to the '78 for it to withstand yet another 300 horsepower (basically the equivalent of adding an additional small-block engine!), but he instructed Scotty not to change out the chassis and to keep the noise "down to a low rumble." Thus, with all that in mind, Scotty dove into the ever-expanding project to build one extremely bad street Shark-which became nicknamed Thumper!
Scott and his partner Mike began by pulling the small-block and trans out and scoping out the immense amount of fabrication necessary. Scott reinforced, cut, and boxed the frame for clearance; lowered the front suspension with Monroe gas shocks and Bell springs; added a Hotchkis front anti-roll bar, and converted the steering to a Speed Direct Steeroids rack-and-pinion system. The rear suspension received Bilstein gas shocks, and strengthened half-shafts were connected to the 3.73:1-geared third member.
Scotty managed to make the huge motor look like a natural fit in the tight confines of the late C3's engine bay, but wedging it in there was anything but easy. "We installed the engine with moderate difficulty and with mods that edged on the extreme," Scotty tells us. "The oil pan would not work with the rack-and-pinion, and the valve covers would not work with the A/C box, nor would the vacuum booster be able to stay. So the oil pan was changed, and the vacuum booster was history." It took a bunch of reengineering to make everything fit, but the big-block now sits happily perched upon its Moroso solid motor mounts.