Sleeper 1991 First-Generation Cummins Hits 660 HP On The Dyno

Tim from Decent Garage built a truck that tricks the eye. His 1991 Dodge W250 wears its original paint scheme and looks like a well-preserved farm truck, but the mechanicals tell a completely different story. This first-generation Cummins is a sleeper in the truest sense, hiding a massive power transformation beneath a vintage exterior. Power Driven Diesel brought this truck into the shop to prove that old iron can run with modern machines.

The Art Of Deception

The build started with a philosophy of restraint on the outside and excess on the inside. Tim explained his approach clearly: “The goal with this build was to keep it looking very original, but have it be anything but that.” He swapped the factory VE pump for a P-pump 12-valve setup, which was a necessity for making real power. The engine bay features a Banks Twin Ram intake and a compound turbo setup using a K27 and 369. To avoid a flashy look, he anodized the billet Kingspeed valve covers to black. Tim noted that he didn’t want it to be a flashy truck, so they powder-coated the parts to keep it subtle.

Tuning A First-Generation Cummins

Getting the truck ready for the rollers involved installing an AFC Live system to manage fueling. The team faced an immediate hurdle when the pre-boost setting proved too aggressive, locking the minimum power at 500 horsepower. Since the truck needed to work for a living, they dialed back the base pump settings. Tim stated, “In this truck, we want to use it for towing.” With the adjustments made, the truck hit the dyno. It put down a massive 660 horsepower and nearly 1,500 lb-ft of torque at just 47 psi of boost.

Built To Haul

Peak numbers are great for bragging rights, but reliability matters more on the street. The team set up a specific tow tune that delivered a clean 485 horsepower. This map featured a flat torque curve designed to keep exhaust gas temperatures in check during long hauls. Under the chassis, a G56 transmission and a Dana 80 rear axle handle the load, while a custom three-link front suspension modernizes the ride quality. The efficient compound turbo setup ensures the first-generation Cummins stays cool even when pulling heavy grades.

A Masterclass In Restraint

This Dodge W250 stands as a perfect example of purposeful building. It lacks the neon lights and chrome that usually flood car shows, preferring to let the torque do the talking. The combination of a sorted chassis and a P-pumped inline-six creates a truck that drives as good as it looks. It proves that you do not need to sacrifice classic style to get modern performance.