The Ford Mustang has never had an engine with more than eight cylinders, but in the early 2000s, Ford considered upping the cylinder count. Engineers briefly worked on an aluminum V-10 for the Mustang, according to a recent DrivingLine report.
The Mustang V-10 would have been based on the 6.8-liter Triton V-10, used in the F-Series Super Duty pickup truck and Excursion SUV at the time, as well as E-Series vans and buses.
The Triton engine was an outgrowth of Ford's modular line of V-8 engines; it was effectively a 5.4-liter V-8 with two cylinders added on. To create the Mustang V-10, engineers at Ford's Powertrain Research and Advanced Engine Development group took the same approach, but with the smaller 4.6-liter V-8. This resulted in a 5.8-liter V-10 that was easier to package under the hood of a Mustang.
In addition to its smaller displacement and aluminum construction, the experimental V-10 featured quad cams from the Mustang SVT Cobra R, a short-stroke design, and a pair of ECUs to run the fuel injection and ignition. Ford reportedly didn't have a single unit available that could handle 10 cylinders and the odd-fire crankshaft used for this engine.
Executives were impressed by early test results, which is why you saw so many V-10-powered Ford concept cars in the early 2000s.
The top brass commissioned a 605-horsepower, 7.0-liter version for the Ford 427 sedan concept, while a 6.4-liter version powered the Shelby GR-1 concept, and a hydrogen-fueled version appeared in the Ford F-250 Super Chief concept.
The development team also pushed for the V-10 to be used in the 2005 Ford GT—reportedly with support from Carroll Shelby and then-Special Vehicle Team (SVT) boss John Coletti. However, the GT got a supercharged aluminum-block 5.4-liter V-8 due to cost considerations. Ford also scrapped the 427—the only one of the V-10-powered concepts with a chance of production—for the same reason.
Needless to say, the V-10 never found its way under the hood of a production Mustang either. However, the 5.2-liter supercharged V-8 in today's Shelby GT500 makes 760 hp—more than even the 7.0-liter version of the experimental V-10 engine.