Cuda Powered By A Mind-Bending 1,500hp Turbo 6.7-Liter Cummin…

Most diesel-swapped muscle cars announce themselves with zip-tied plumbing and a cowl hood hiding the mess underneath. This Plymouth Cuda carries a compound-turbo 6.7-liter Cummins that looks like it was cast for the engine bay, backed by a reported 1,500 rear-wheel horsepower and a torque figure north of 3,000 lb-ft. The parts list explains the numbers. The fabrication explains why anyone took the build seriously.

Pop the hood on most diesel-swapped muscle cars and the illusion falls apart immediately. Pipes routed wherever they would fit, brackets fabricated on the fly, an oversized cowl hood bolted on for the sole purpose of hiding what could not be made to clear. This Plymouth Cuda does none of that. It carries a drivetrain that has no business fitting inside an E-body engine bay, and it wears that drivetrain like the factory intended it, with clearances and finish work that hold up to the kind of inspection most swap builds cannot survive. The horsepower number attached to it is the sort of figure that makes experienced engine builders ask to hear it again. The way it got there is more interesting than the number.

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The Swap That Usually Goes Wrong

Diesel swaps into classic muscle cars have a reputation, and it is not a flattering one. The engines involved are physically enormous compared to the V8s these cars were designed around, taller through the block, longer between the front cover and the bellhousing, and heavy enough to change how the front suspension behaves before the car has moved an inch. The usual result is a build that works mechanically and fails visually: intercooler piping routed through whatever gap presented itself, a firewall cut back further than anyone wants to photograph, and a tall cowl hood bolted on at the end to cover the compromise. Most owners accept that trade because the alternative is months of fabrication for a result the average onlooker will not consciously notice. The car in question refused that trade entirely.

A Cummins Where a 426 Hemi Belongs

The engine is a 6.7-liter Cummins inline-six, built by Weaver Customs and tuned by Gorilla Performance, and it wears the nickname Torc. That displacement arrived in Ram heavy-duty trucks for the 2007 model year as the successor to the 5.9, and in factory form it was rated somewhere in the neighborhood of 350 horsepower with an emphasis on low-end pulling rather than revs. What builder Randy Weaver did to it bears almost no resemblance to that. The bottom end runs Carrillo connecting rods and Mahle pistons, the cylinder head has been ported and polished, and a dual-fueler system keeps the injectors supplied. On a 500-shot of nitrous, the combination reportedly puts down 1,500 horsepower at the rear wheels, with torque said to top 3,000 lb-ft.

Compound Turbos and 80 PSI of Boost

The boost side is where the packaging problem gets genuinely difficult. Up front sits an 80-millimeter BorgWarner turbocharger, large enough to identify from across a parking lot, paired with a smaller 66-millimeter unit behind it in a compound arrangement. The airflow runs the other way around from what most people assume: the big turbo swallows atmosphere and hands a pressurized charge back to the small one, which squeezes it a second time before any of it reaches a cylinder. On the exhaust side the little unit spools first and lights the big one off, so there is no waiting around for boost. Together the pair can force as much as 80 psi into the cylinders. Both are wastegated and blanket-wrapped, the latter as much for the sheet metal and wiring nearby as for exhaust gas temperature management. Fitting two turbochargers of those sizes, plus the crossover piping between them, into a bay designed around a 426 Hemi and a pair of exhaust manifolds is the sort of problem most shops decline politely.

Feeding an Engine That Drinks This Hard

An engine consuming that much air needs fuel delivered at a rate the factory system was never designed to approach. The build carries a PPE dual fueler, a Fuelab lift pump, and Industrial Injection 5×18 race injectors, a combination aimed squarely at keeping the air-fuel ratio survivable at full boost rather than at any kind of efficiency. Diesel engines make their power by dumping more fuel into an abundance of compressed air, which is why boost and fueling have to scale together. Get that relationship wrong at 80 psi and the failure mode is not a misfire; it is a piston.

The Transmission Problem Nobody Talks About

Behind all of it sits the component that quietly decides whether a build like this is a running car or a static display. A reinforced 48RE four-speed automatic handles the output, built with a triple-disc torque converter, a manual valvebody, and a shortened output shaft to fit the E-body tunnel. The 48RE is a heavy-duty Chrysler unit designed for diesel trucks, and even so, 3,000 lb-ft is well beyond anything it was engineered to see. The manual valvebody removes the transmission’s own shift logic and hands it to the driver, which matters when the torque curve arrives all at once and a computer-commanded shift at the wrong moment breaks parts.

Why Fitting It Properly Was the Hard Part

What actually separates this Cuda from the usual diesel swap is the fabrication discipline, and that is harder to photograph than a turbocharger. A Cummins 6.7 is a tall, long, iron-block inline-six weighing somewhere around 1,100 pounds, roughly 250 more than a 426 Hemi and shaped nothing like it. Making it sit low enough to clear a stock-height hood, far enough back to keep the front axle from carrying all of it, and centered enough that the steering box and headers do not fight each other requires moving crossmembers, rebuilding the firewall area, and refabricating mounts from nothing. Weaver spent years on that puzzle specifically so the finished car would not need a cowl hood to hide the answer.

What 3,000 lb-ft Actually Does to a Chassis

The torque figure has consequences that extend well past the engine bay. A number above 3,000 lb-ft applied through a unibody E-body chassis will twist the car itself if the structure has not been addressed, which is why builds in this class run subframe connectors, roll cage tubing tied into the chassis, and rear suspension geometry that keeps the axle from winding up under load. Traction becomes the limiting factor long before power does. Diesel torque arrives at low rpm and stays there, which is superb for a truck pulling a trailer and brutally difficult to manage through a tire on pavement.

Where a Build Like This Fits in Mopar Culture

Builds like this one occupy an odd position in Mopar circles, and the reaction to them tends to split cleanly. Purists point out, correctly, that a numbers-matching E-body Cuda is a genuinely rare car and that the 426 Hemi cars in particular trade for sums that make any engine swap look like vandalism. The counterargument is that this level of fabrication is doing something the restoration world never does, which is asking what the platform is capable of rather than what it originally was. Both positions are defensible. What is not really arguable is the execution, because the standard for judging a swap has always been whether it looks like it was meant to be there, and this one clears that bar more convincingly than nearly anything else built on the idea.

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