One Week With: 2017 Ford Shelby GT350 Mustang

The 2017 Shelby GT350’s 5.2-liter Voodoo V8 used a flat-plane crankshaft, revved to 8,250 rpm, and made 526 horsepower without a turbo or a supercharger anywhere in sight. It was hand-assembled by two-person teams on a dedicated line, sounded more like a Ferrari than a Mustang, and lasted five model years before Ford moved on. Owners still treat surviving examples as a limited-run specialty engine rather than an ordinary Mustang V8. Read on for why.

There is a moment in a GT350 that reorders your expectations of what a Mustang is. The tachometer needle is climbing, the exhaust has stopped rumbling and started shrieking, the whole car is vibrating with an urgency that feels faintly unsafe, and then you register that there are still two thousand rpm left before the limiter. American V8s are not supposed to do this. They are supposed to make their case in the first four thousand revolutions and then hand the job to a taller gear. Ford spent real money and real political capital inside the company to build an engine that behaves the other way, kept it in production for a handful of years, and then quietly stopped. What went into it, and why it disappeared, is a better story than the horsepower figure suggests.

The Engine That Rewired the American V8 Sound

The 5.2-liter engine Ford named Voodoo used a flat-plane crankshaft, a configuration far more common in Ferraris than in anything built in Michigan. Instead of the traditional American cross-plane layout, where the crankpins are spaced ninety degrees apart, the Voodoo’s four throws all lie in a single plane, paired off at a hundred and eighty degrees. That change trims rotating mass and lets the engine spin to a factory-rated 8,250 rpm redline while producing 526 horsepower and 429 lb-ft of torque, entirely naturally aspirated. It also completely rewrites the exhaust note, swapping the familiar V8 burble for a high, hard shriek that either thrilled or unsettled everyone within a block of it.

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What a Flat-Plane Crank Actually Changes

The reason for that sound is not styling, it is firing order. A flat-plane crank alternates combustion evenly between the two cylinder banks, which means each bank fires at regular intervals and the exhaust pulses arrive cleanly spaced rather than in the lopsided pattern a cross-plane V8 produces. That even spacing improves exhaust scavenging at high rpm, which is a large part of how the engine breathes well enough to make useful power that far up the range. The famous American rumble is, in engineering terms, a byproduct of an uneven firing pattern that the flat-plane design deliberately eliminates.

The Price You Pay for Eight Thousand RPM

Nothing about this is free. A flat-plane crank generates secondary imbalance forces that a cross-plane layout naturally cancels, which is why the configuration usually lives in exotic cars with small displacement and buyers who accept vibration as part of the experience. Building one at 5.2 liters for a car expected to commute meant engineering around that harshness with careful mounting, balancing, and structural work, all on a program that had to survive normal emissions certification and a normal cost sheet. The result still transmits more character through the seat than a Coyote does, and owners overwhelmingly consider that a feature.

Two People, One Engine, One Dedicated Line

Assembly was handled with unusual care. Each Voodoo was built by two-person teams on a dedicated Niche Line at Ford’s Romeo Engine Plant, a level of hand assembly rare for a mass-produced American engine and closer to how a low-volume European manufacturer operates. It powered the GT350 and GT350R from 2016 through 2020 and, in the process, became the longest-stroke flat-plane crank engine ever put into series production.

The R Model and Its Missing Equipment

The GT350R took the concept further by removing things. It shipped with carbon fiber wheels, among the first fitted to a mass-produced car, and deleted the rear seat along with a list of comfort equipment that buyers could optionally add back. Less unsprung mass at each corner does more for how a car changes direction than almost any spring or damper change, which is why the R drives noticeably differently rather than simply lighter. The carbon wheels alone were a genuine engineering risk for a mass-produced car, since a composite wheel has to survive potholes, curbs, and the general abuse of American roads without the forgiving failure behavior of aluminum. Ford shipped them anyway, on a Mustang, which tells you how seriously the program was taken internally.

A Chassis Built Specifically Around the Engine

Ford also built the chassis specifically around the engine rather than adapting an existing one. Magnetic adaptive dampers, a widened track, unique aerodynamic work, and a set of Michelin Pilot Sport Cup 2 tires developed specifically for the car meant the GT350 was not a Mustang GT with a better engine. It was a coherent package where the suspension calibration assumed a driver would actually use the top two thousand rpm. That coherence is what separates it from the long history of American cars that received a strong engine and little else. The brakes, the damping, the tire compound, the aerodynamic balance, and the gearing were all specified with the same rev range in mind, and the result is a car that feels engineered rather than assembled from a parts bin.

Retired in Favor of Something Louder

The engine’s retirement had less to do with failure than with direction. Ford’s attention moved to the GT500 and its supercharged 5.2-liter Predator, a cross-plane engine making 760 horsepower and chasing a very different kind of performance: overwhelming force rather than mechanical rev-happiness. On any objective measure the GT500 is the faster car. On the measure enthusiasts actually argue about, plenty of people still prefer the one that has to be wrung out to give up what it has.

What the Market Decided Afterward

The market has quietly sided with them. Clean, well-documented GT350s, and particularly R models and the final-year cars, have held their value far better than a five-year-old Mustang has any right to, and the reason is straightforward: nothing has replaced this engine and nothing is going to. Emissions and efficiency pressure make a high-revving naturally aspirated V8 an increasingly difficult thing to justify inside a modern product plan, and every manufacturer that still builds one treats it as a halo rather than a volume item. That gives the Voodoo a specific kind of scarcity that has nothing to do with production numbers and everything to do with timing. Owners and tuners already treat surviving examples as a limited-run specialty engine rather than a garden-variety Mustang V8, and after five model years, no successor, and a clear industry direction away from the entire concept, that reading looks less like enthusiasm and more like an accurate forecast.

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