Sunset Racecraft in Lubbock, Texas, built the huge-displacement, 790hp powerhouse that Scotty and Mike shoehorned into Thumper, starting with a machined Dart Pro-1 548-cid big-block with Dart Pro-1 ported and polished aluminum heads. They fortified its innards with a steel crankshaft, SP 11.5:1 compression pistons, Clevite bearings, and gold roller rockers. The motor, which is dressed-to-kill in a black satin aluminum finish, is decked out with natural aluminum Merlin valve covers, an Edelbrock Victor intake, and a massive 1,150-cfm Holley
Dominator carburetor. A complete MSD ignition system fires the 548, including an electronic billet MSD distributor, MSD Blaster coil, MSD wires, and MSD 6AL box.
March Performance pulleys spin the accessories that are mounted on custom billet and handcrafted brackets, including a black-satin-finished 100-amp alternator and a Sanden A/C compressor. Since there wasn't enough vacuum from the engine for headlamp actuation, Scotty replaced the vacuum system with a set of electric linear actuators-which "work smooth and are quiet, and are not as violent as the originals." Scotty made the necessary modifications to make a high-capacity 8.5-quart oil pan fit around the steering rack, and he employed a Melling sump pump to lube the motor.
To cool the big-inch engine, Scotty chose an Edelbrock aluminum water pump and a large polished Be Cool radiator with a Be Cool electric module. Scotty installed a custom-fabricated stainless steel fuel cell from RCI with a sending unit and vents, along with a Holley Red electric fuel pump and BG fuel filter to feed the carb at a regulated 7.0 psi. The battery was relocated to the back of the car, so the high-voltage yellow-top Optima battery needed to juice this hellacious Corvette, no longer hangs near the RCI tank.
Hedman 2.5-inch headers wearing Thermotech heat wrap dump spent gases into the custom 2.75-inch exhaust that was fabricated by Joe at A&B Muffler and Brake Shop in Lubbock Texas. Dr. Richards specified that Thumper must be quiet enough to drive across town to the hospital at 2:00 a.m. if necessary, so Joe muzzled the big motor's thunderous bark to a low rumble using two pairs of mufflers-passing first through a pair of Magnaflows and then a pair of Flowmasters.
Considering the engine cranks out nearly 800 horsepower, losing approximately 60 ponies to make it civilized enough for Doc Richards' driving chores really is just a drop in the bucket. The meager 730 or so horsepower that remains is channeled through a GM Performance Parts lightweight flexplate and a strengthened Sullivan Turbo 400 transmission with a 2,500-rpm TCI torque converter and a billet B&M shifter.
Scotty and Mike gutted Thumper's interior with visions of a "full-on comp look" to replace it. They began with safety by selecting Kirky racing seats, G-Force Racing Gear five-point harnesses, and a CE roll cage kit. "The original dash was cracked and the door panels were ragged, but there was room to get everything together," Scotty says. So they fabricated a custom aluminum-paneled dash which houses a full array of Auto Meter Ultralite gauges, a high-tech Sony MEX-5DI MG-MS/FM/AM CD Player, the factory A/C controls, power window switches, toggle switches for the fuel pump, and a pre-wired NOS cutoff ("just in case" wretched excess is not enough!).