LokJaw is not just an engine swap with a blower on top. The whole truck was built around making a supercharged 6.6L Duramax work as a complete system. That starts with air. We fed the engine through Ram-Air inlets and custom airboxes, then built a billet front drive with dual 5-inch inlets for the Whipple 3.8L supercharger. Just as important, we added pressure and temperature sensors on both sides of the blower so we can see whether it is actually increasing air density, not just making heat. That data matters. With Banks iDash handling the sensor network and logging, we can monitor what the engine is getting, what the blower is doing, and how the whole package responds. From the chassis and suspension to the exhaust routing and hood design, the truck was engineered around the size, torque, airflow, and heat demands of a supercharged Duramax. That is why LokJaw behaves like its own animal instead of a typical diesel swap.
Lockjaw is a 1966 Chevrolet C20 that has been transformed into a slammed custom truck powered by a Banks supercharged Duramax. The build had previously appeared at the annual Duramax company picnic in Marion, Ohio, but progress paused when the team took on a defense contract to hybridize a Humvee. With that project wrapping up and AMSOIL inviting Banks back to SEMA 2023, the truck became a priority again and represented a final opportunity to finish it properly.
The project began with a rough, rusted C20 purchased for just one dollar. The goal was never restoration. Instead, the idea was to preserve the truck's weathered exterior character while filling it with modern, state-of-the-art engineering and a highly unusual engine swap. At the center of that concept is a Banks supercharged Duramax L5P, supported by a fully custom chassis and a long list of one-off fabricated components.
To handle the power of the Duramax, the truck needed far more than its original frame. Roadster Shop in Chicago 3D scanned the body and built a completely custom chassis around it. The reasoning was straightforward: the engine tries to twist the chassis in one direction while the ground resists that rotation, so the structure underneath had to be exceptionally stout.
From there, the build moved to Strange Engineering for a full-floating 9-inch rear end fitted with custom eight-lug axles. Braking was equally serious. Wilwood TX6R brakes were adapted to those eight-lug axles, which required KibbeTech to design custom spindles that would package the large brakes while preserving proper suspension geometry. The challenge was to create a very strong component in a very confined space because of the forces involved during braking.
The driveline was matched to the engine with an Allison six-speed transmission handbuilt by Clint at ATS Diesel. That transmission was built to hold up to 1,200 horsepower, making it a suitable partner for the supercharged Duramax. To cope with the torque while also reducing weight, the truck uses a QA1 carbon-fiber driveshaft. The team noted that the carbon fiber is not only lightweight but also somewhat forgiving under load.
One of the most distinctive elements of Lockjaw is its set of custom 22-inch billet wheels. Designed by Spark Industries, each wheel was machined from a single 500-pound piece of aluminum. These wheels were not created purely for appearance. Their fins were shaped to act like fan blades, an idea driven by Gale Banks to help extract heat away from both the brakes and the engine bay.
That combination of form and function runs throughout the truck. The wheels are visually aggressive, but they also serve a thermal-management purpose, reinforcing the engineering-first approach behind the build rather than treating styling as a separate exercise.
Because so many of the truck's parts and mechanisms were custom, the team wanted the finished vehicle to reveal its engineering rather than hide it. To do that, they worked with designer Jeffrey Transou of Transou Designs to create a body that opens dramatically. Both the hood and the bed were redesigned to expose the truck's structure and powertrain.
The fabrication work was extensive. The floorboards were stripped out, and the truck bed was split and rebuilt with custom six-bar, spring-assisted hinges so it could open and close smoothly. The bed also required a rigid supporting frame to maintain its shape. The inner fenders, firewall, and transmission tunnel were completely replaced as well, giving Empire Fab the freedom to reshape the sheet metal around the oversized powertrain.
The hood received the same level of engineering attention. After 3D scanning and CAD design work, the team built a reverse-opening, six-bar, spring-assisted hood intended to showcase the engine bay. This was not simply cosmetic bodywork; it was a structural and packaging solution developed around the realities of fitting a massive diesel engine and supercharger into a vintage truck.
Performance on Lockjaw is driven by measurement and airflow science, not just visual impact. Inspired by Gale Banks' land-speed-record Studebaker, the team replaced the 1966 front grille with a 1960 grille, removed the lights, and added Ram-Air inlets. Those inlets feed directly into custom-fabricated airboxes designed to induce vortex motion and surround the truck's large air filters.
To ensure the supercharger receives the coolest and densest possible air, Banks engineered a billet front drive with dual 5-inch inlets, informally nicknamed the granny panties because of their shape. The intake system also includes a one-off billet adapter plate that houses Banks pressure and temperature sensors. Those sensors are connected to Banks iDash units for live monitoring and data logging.
By logging pressure and temperature on both sides of the supercharger, the team can calculate the air-density gain across the blower. That matters because the objective is not merely to make the air hotter under pressure, but to confirm that the supercharger is delivering denser intake charge. The truck also carries an extensive sensor package with numerous analog and thermocouple modules, plus a Banks AirMouse mounted in the grille to record ambient conditions. All of that information is displayed and recorded through the iDash system, which is integrated into a custom billet dashboard alongside a MoTeC digital display.
Lockjaw rides on air suspension using an RCH air system and Billet Flow air tanks, allowing the truck to drop all the way to the ground. The iDash system also monitors airbag pressures, tying suspension behavior into the same data-focused philosophy used for the engine.
Lowering the truck this aggressively created major packaging problems, especially around wheel clearance. To make the 22-inch wheels fit, Sean at Empire Fab fabricated matching rear tubs so the wheels could tuck inside the body. This was one more example of how the truck's stance was not a simple bolt-on styling choice; it forced substantial structural and sheet-metal changes throughout the build.
As SEMA deadlines approached, the team worked through the remaining interior and exhaust details. The cabin was finished with TMI seats and mounts, a Flaming River steering column, and a custom billet steering wheel from Spark Industries. The dashboard was already a major custom piece because it had to house the Banks iDash units and the MoTeC display cleanly within the truck's redesigned interior.
The exhaust system required especially careful fabrication because space in the engine bay was extremely limited. For that work, the team brought in Dragos from Candela Manufacturing, described as a master header fabricator. He built 1 3/4-inch primary tubes that transition into a 5-inch exhaust system. The routing had to clear the steering shaft, the inner fender, and the front wheel, all within a very tight package.
The finished exhaust exits through Banks exhaust tips ducted out the side of the truck. That routing was chosen so the hot exhaust gases could be discharged safely away from the bodywork.
The centerpiece of the build is the Banks 6.6-liter supercharged diesel engine. The engine was finished in Cerakote Banks red and built around a Whipple 3.8-liter supercharger. Supporting hardware includes a custom Comp Cam camshaft for the supercharged L5P, upgraded valve springs, Trend pushrods, 50-percent-over injectors, and pulley sizing selected to achieve the desired supercharger drive ratio.
Packaging was so tight that the hood had to be cut, leaving the billet supercharger visible even when the truck is on the road. That exposed hardware became part of the truck's identity: an aged, rusted exterior wrapped around an extremely dense concentration of modern diesel performance engineering.
The team emphasized that Lockjaw is more than a collection of shiny parts. It is a machine built from metal, fabrication skill, and engineering intent, with contributions from people of different backgrounds and experience levels. The result is a diesel that revs and sounds unlike a typical truck, with a level of power and mechanical intensity that the builders felt is difficult to capture fully on video.
At the current stage of the project, the truck has recently returned from teardown and refinishing work. After being picked up from storage, it was taken back to Empire Fab, which handled the major task of disassembling the truck, coating the raw metal surfaces, and reassembling it.
That leaves the final push focused on reinstalling the powertrain and completing the remaining mechanical and electrical details that were not addressed during the earlier 2021 phase of the build. With SEMA 2023 as the deadline, the truck is close to completion, and the expectation is that Lockjaw will soon move from fabrication and assembly into running, driving, and tire-burning reality.
