A Rat-Rod ’41 Chevy School Bus with a P-pumped 12-Valve
In the midst of his busy life managing multiple businesses, Jason Bliesner, an entrepreneur from central Illinois, found solace in his unique escape vehicle—a modified 1941 Chevy school bus. Taking on a rat-rod approach, Jason transformed the bus into a head-turning machine, while still maintaining its original appearance. The bus now boasts a powerful 12-valve 5.9L Cummins engine with compound turbos, as well as a full air-ride suspension, allowing for a smooth and enjoyable ride. With an updated interior, Jason can also bring along a dozen friends on his much-needed weekend excursions. Although the bus may not always be cruising in the fast lane, it impressively achieves 15 miles per gallon at 80 miles per hour.
Jason Bliesner had always intended to replace the original six-cylinder engine in his ’41 Chevy school bus with a 5.9L Cummins from the start of his rat-rod project. He acquired a P-pumped 6BT engine from a Ford school bus and proceeded to rebuild and enhance it to achieve higher horsepower. Various reputable shops, including Quality Engine Machine Shop, Scheid Diesel, and DeClerck Custom Machine, contributed to the engine build, with local truck puller Drew DeClerck assembling the components. Upgrades such as ARP main and head studs, a Hamilton 188/220 street cam and tappets, fire-rings, and 180-pound valve springs were incorporated into the engine build.
The adventure began when Jason and his father embarked on a mission to find a school bus for their rat-rod project. They attended an auction 700 miles away from home, hoping to secure an old Ford bus. However, when the bidding price reached $9,000, they shifted their attention to a lead for a Chevy bus. Jason managed to purchase the ’41 Chevy bus for a cool $2,700 and subsequently traveled to Iowa to acquire the 5.9L Cummins engine he had already procured. His inclination towards a diesel-powered project was evident from the beginning. “I like anything weird,” he admitted. “I wanted to do a rat-rod project but do it differently.”
To bring the engine to life, Jason installed an S363 turbo from BorgWarner in a compound arrangement. This wastegated charger, with a T3 flange, is mounted on a flipped factory exhaust manifold. Boost is then channeled through 3-inch intercooler piping fabricated by Jason himself. After passing through the Treadstone Performance intercooler, the boosted air enters the ported and polished head via a unique individual runner intake manifold.
While Jason was aware that the 5.9L Cummins engine ran before it was removed from the Ford school bus, he knew it was an eBay purchase and had limited information about its condition. Therefore, instead of pushing the engine to its limits without proper knowledge, he decided to disassemble and upgrade it. Much of the machine work was entrusted to the nearby Quality Engine Machine Shop. Scheid Diesel performed the fire-ring installation on the block, and Drew DeClerck of DeClerck Custom Machine meticulously assembled the refreshed 5.9L engine. The list of upgrades included ARP main and head studs, a Hamilton 188/220 hot street cam with tappets, heavy-duty pushrods, and 180-pound valve springs. Additionally, the head received extensive porting and polishing work.
Inside the cabin, Jason opted for a simple yet functional layout. He installed an instrument panel with various gauges on the left side, featuring an ididit steering column and an Auto Meter Pro-Comp series
tachometer. The area under the driver’s seat serves as storage for the compressors used in the air ride system. While the exterior of the bus remained largely original, the interior underwent an upgrade to enhance driver and passenger comfort. The seats were sourced from an ’85 Chevy school bus and professionally reupholstered by Mac’s Custom Interiors in Decatur, Illinois. Before the upholstery work, Jason sand-blasted the interior, applied an epoxy primer, and painted it in a vibrant school bus yellow. The floor was treated with a durable Line-X coating.
To fuel the powerful machine, Jason turned to the experts at Scheid Diesel for their expertise in 12-valve engines. They supplied him with a potent P7100 injection pump capable of delivering full fueling up to 4,500 rpm. Custom-bent injection lines were fitted to work seamlessly with the unique intake manifold Jason had fabricated. Additionally, a set of 5×13 injectors was installed. To ensure sufficient airflow, a compound turbo setup was implemented. This configuration consists of an S472 turbo mounted above the engine and an S363 turbo attached to the stock, flipped exhaust manifold. Generating 60 pounds of boost is effortless, thanks to a Treadstone Performance intercooler effectively compressing the intake air.
Simplifying the transmission setup, Jason opted for a TH400 automatic transmission to handle the power of the Cummins engine. Steve’s Transmission Service in Springfield, Illinois reinforced the
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