Dodge Charger 1970 SpeedKore TANTRUM 9L Twin Turbo

SpeedKore built this 1970 Dodge Charger around an engine that was never intended for a road: a 9.0-liter, quad-cam racing V8 from Mercury Racing’s boat program, twin-turbocharged to 1,650 horsepower on race fuel. It debuted at SEMA, appeared in a Fast & Furious film, was gifted to Vin Diesel, and has been offered at $699,000. Here is how a marine engine ended up in a muscle car body.

Most high-horsepower builds start with a decision about which engine family to use. This one started with a decision to ignore the entire question. When SpeedKore set out to build the Charger that became known as Tantrum, the team did not go shopping among crate Hemis and aftermarket blocks. They went to a company that builds engines for offshore racing boats, and they came back with a nine-liter, double-overhead-cam V8 that had never previously been fitted to a street car. Two 94mm turbochargers and a tank of 110-octane later, the number on the dyno sheet was 1,650 horsepower. Everything else about the car had to be built to survive that.

The Shop That Made That Phone Call

SpeedKore is a Wisconsin shop whose entire identity is built on composites rather than on any particular brand of car. The team came at the business from carbon fiber first and vehicle building second, which is the opposite of how most high-end shops evolve, and it shows in what they choose to do with a project. Where a traditional hot rod shop asks what engine and what stance, SpeedKore tends to ask what the body panels should be made of, and the answers get expensive quickly. That orientation is also why an engine nobody had used before was an attractive problem rather than a disqualifying one.

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What a Marine Racing V8 Actually Is

A marine racing V8 is a genuinely different animal from a drag engine. Boat engines run at sustained high load for long periods with no gear changes, no coasting, and no letup, which forces a design philosophy built around thermal management and durability rather than short bursts. Mercury Racing’s four-valve, quad-cam architecture reflects that: it breathes far better at high rpm than a two-valve pushrod engine of similar displacement, and it is engineered to hold together while doing it. What it is not engineered for is fitting between the shock towers of a 1970 Chrysler B-body.

Why Not Just Build a Hemi

The obvious question is why not simply build a Hemi. A supercharged 426 in the 1,500-horsepower range is a well-trodden path with a mature parts supply, and it would have been considerably cheaper and easier to package. The answer is that Tantrum was never primarily an engineering exercise, it was a statement piece, and a supercharged Hemi in a Charger is a sentence people have heard before. A quad-cam marine engine in the same car is not. The build’s entire value proposition rests on doing the thing nobody had done.

Carbon Fiber Where Sheetmetal Used to Be

The bodywork follows the same logic. SpeedKore built its reputation on carbon fiber, and on this car the hood, fenders, doors, and bumpers are all recast in it rather than stamped steel. The front sections were left with the raw weave visible, fading rearward into paint, which is now a widely imitated treatment but was not when the car appeared. The weight savings are real but secondary. The point is that carbon fiber reads instantly as modern and expensive, and applying it to a shape that everybody associates with 1970 creates exactly the tension the build is selling.

The 1970 Charger as a Starting Point

The 1970 Charger is a shrewd choice of canvas. The second-generation Charger’s 1968 restyle gave it the Coke-bottle flanks and full-width tunneled backlight that made it one of the most recognizable American shapes of the decade, and the 1970 update brought the full-width chrome loop bumper up front. It is also, importantly, physically large, with a 117-inch wheelbase and generous underhood volume, which a nine-liter engine and a pair of turbochargers genuinely need. A smaller car would have made the packaging a nightmare instead of merely difficult.

Turbocharging on That Scale

Turbocharging at this output level is its own discipline. Two 94mm turbos are enormous by street-car standards, and feeding them requires exhaust routing, wastegate placement, and charge-air cooling that all have to coexist inside a body that was designed around a carburetor and a single air cleaner. Then there is fuel: 110-octane race gas is not a lifestyle choice, it is a requirement at the boost levels involved, which means the car’s stated output is a race-fuel number and the way it behaves on anything from a pump is a separate conversation entirely.

The Driveline Behind 1,650 Horsepower

Behind the engine sits a driveline chosen for survivability rather than brand loyalty. A built T56 Magnum six-speed manual handles the shifting, and a Ford nine-inch-derived rear end handles the torque, which is an unusual pairing to find under a Mopar body and tells you something about priorities. Purists will note that none of it is Chrysler. Anyone who has tried to put 1,650 horsepower through a period-correct Mopar driveline will note that purity and durability were not both available.

SEMA, and the Award That Followed

The car made its public debut at the 2015 SEMA show in Las Vegas, where it took the Gran Turismo award, one of the more prestigious honors at an event where thousands of builds compete for attention. SEMA is a difficult room, because everything there is finished to a high standard and everything there is trying to be memorable. Winning requires either flawless execution of a familiar idea or a genuinely unfamiliar one done competently, and Tantrum arrived with both.

Hollywood, and a Birthday Present

What happened next is the part that made the car famous outside the build community. It appeared on screen in The Fate of the Furious, and was subsequently gifted to Vin Diesel as a birthday present during production on the following film. That is a peculiar kind of provenance, one that has essentially nothing to do with engineering and everything to do with value, because a car with screen credits and a celebrity chain of custody occupies a different market than an identical car without them.

What a Car Like This Is Actually Worth

That market has been tested. The car has been offered publicly with an asking price as high as $699,000, which sounds outlandish until you total the components, the fabrication hours, the one-off engine installation, and then add the film history on top. High-end restomods from name builders regularly trade in the mid-six figures now, and the ones with genuine stories attached lead the field. Whether Tantrum is worth that number is a matter for whoever writes the check. What is not arguable is that no one had put a boat engine in a Charger before, and that remains the only reason any of the rest of it happened.

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