All-Billet 6.4L Powerstroke Debuts in Pro Mod Mustang — Bullseye Power Turbo Keeps the Program Grounded
When Nathannial DeLong of Rudy's Performance Parts rolled into the 2026 Rudy's Spring Truck Jam at Rockingham Dragway, he swapped the familiar four-wheel-drive F-250 that had chased records in the ODSS series for something completely different: a purpose-built Pro Mod Mustang packing an all-billet 6.4L Powerstroke. The goal was simple to state and hard to achieve — find out how much power a 6.4L Powerstroke can truly handle once every major structural limitation is engineered out.
The Cast Block Hit Its Ceiling
The prior combination — a factory-based block reinforced with concrete fill and cast cylinder heads — had already run in the 4.60-second range in eighth-mile competition. But rising cylinder pressure exposed the limits of that architecture: cracks between cylinders and material breaking away from the outer casting became a recurring, program-defining problem. To survive, Rudy's had to tune conservatively, even keeping engine speed elevated around 4,500 rpm through the pass instead of using converter lockup, sacrificing efficiency just to protect the block.
Billet Block and Billet Heads Remove the Weak Links
The fix came from a billet block supplied through Warren Diesel Injection, validated across multiple pulling seasons by Jesse Warren before being released for high-horsepower applications like this one. Paired with it are new billet cylinder heads developed with Kill Devil Diesel and machined from raw billet stock by Jeremy Wagler of Wagler Competition Products — using steel-insert technology proven in high-output Cummins builds to keep valve seats stable under combustion loads that cast aluminum heads couldn't handle once water jackets were removed.
The Turbo That Doesn't Need to Change: Bullseye Power's GT55-Frame
Here's the part that stands out most about this build: with nearly every major structural component reinvented, the induction side stayed exactly where it was. Rudy's intentionally carried over its proven Bullseye Power GT55-frame turbocharger from last season rather than introducing a new turbo combination alongside the new engine architecture — a deliberate choice to isolate variables while validating the billet block and heads.
That's a strong statement about the Bullseye unit's headroom. After working through several compressor wheel sizes during development — including an 88mm option — the team settled on a 94mm compressor on the GT55 frame, and it's been comfortably supporting the program's power levels ever since. Historically, this Bullseye Power turbo has operated in the 90-95 psi boost range while holding roughly 70-75 psi of backpressure — numbers that indicate the turbo is running well within its operating window without needing aggressive wastegate intervention to stay in check.
In other words, while the block and heads were the bottleneck holding this program back, the Bullseye turbo never was. It's the one major subsystem that's already proven it can support DeLong's target of more than 2,500 horsepower as the billet architecture is unlocked to full power over the coming test sessions at Rudy's Spring Truck Jam and the Ultimate Callout Challenge. That kind of margin is exactly why the team could confidently bolt an unfamiliar, all-new bottom-end architecture into an unfamiliar Pro Mod chassis and not worry about the turbo being the thing that holds them back next.
Everything Else Stayed Proven, On Purpose
Fuel delivery also carried over unchanged, with the same Dynomite Diesel Products injectors that powered the truck combination through multiple seasons — DeLong notes considerably larger injectors are available whenever the program needs them, but for now the focus is validating the new architecture, not chasing more fuel. The rotating assembly tells the same story: a factory-based forged crankshaft, Wagler connecting rods, and forged Mahle pistons all transferred directly from last year's engine because they'd already proven reliable.
Why the Mustang
The move from a four-time-record four-wheel-drive truck to a lighter, two-wheel-drive Pro Mod Mustang chassis reflects the same philosophy driving the engine build — shed the components holding back performance, keep what works. The nearly year-and-a-half build was completed almost entirely in-house at Rudy's Performance between customer projects, from chassis fabrication and wiring to bodywork and final assembly.
What's Next
Initial passes will focus on chassis setup, suspension tuning, and baseline data before the team restores the engine to full power. DeLong believes the billet package should comfortably support more than 2,500 horsepower — and with the Bullseye Power turbo already sitting comfortably within its 90-95 psi boost window on the 94mm compressor, the turbo side of the equation looks like it has room to spare as that power climbs.
