Jay Leno’s Merlin-powered Rolls-Royce proves there’s no replacement for displacement

Your big-block might seem downright burly compared to today’s small, turbocharged four-cylinder engines, but it might as well be a toy when stacked up against the goliath piston-powered aircraft engines of WWII. That fact is made abundantly clear on this week’s episode of Jay Leno’s Garage, which features a gargantuan Merlin V-12 encased in a custom-built aluminum Rolls-Royce wrapper. Drool.

Rolls-Royce’s Merlin engine is a wartime legend, powering dozens of military fighter planes, the most iconic of which being the American P-51 Mustang. At 1650 cubic inches, these powerhouses could deliver as much as 2000 horsepower in supercharged guise. Not requiring the additional complexity of a boost-fed motor, Leno opted to keep his V-12 beast naturally aspirated, limiting its output to only 1000 horsepower and 1750 pound-feet of torque. More drool.

Leno has owned the car for almost 30 years, and its restoration took nearly that long to complete. It started life as just an engine, an original 1934 Rolls chassis, and a basic wooden body, so a good amount of custom work was needed to get it to its current condition. The garage’s chief fabricator, Jim Hall, created a bespoke intake manifold for the six-Weber-carb setup through the use of 3D scanning and printing technology. A swooping aluminum body was formed using cues from period Rolls-Royce styling. Shockingly, the goliath only weighs 4800 pounds, barely more than a contemporary Hellcat Charger.

Driveline mechanicals were a bit trickier during the restoration. A Jaguar XK120 gearbox was the original transmission that came with the car, and simply shifting to second gear caused the box to essentially shatter like glass. Not wanting to go with an automatic option (as on his Merlin-powered Bentley), Leno consulted friend and diesel-whisperer Gale Banks for a solution. The two sourced a six-speed, New Venture NV5600 transmission, used in heavy-duty Ram pickups, to withstand the brutal twist from the V-12.

The starting process is nearly as intense as an aircraft’s—Leno needs to flip switches, prime with oil, and fire it off with a hand-cranked magneto located on the dash. Roaring to life, the beast sounds identical to that of a WWII warplane taxiing to the runway. Though not his only aero-engined vehicle, the theater of driving such a car isn’t lost on Leno.

“The torque is unbelievable. It’s like the hand of God is just pushing you,” Leno says. It’s easy to believe, as the Rolls sounds virtually unfazed by its on-road duty, basically idling around in whatever gear you please. This lack of stress is the beauty of Merlin power; anything you ask of it is more or less an effortless task. It might just be the only powerplant you’d choose instead of that new 572 big-block.

What do you think of Leno’s airplane-infused powerhouse? Given the chance, what would you swap a Merlin V-12 into? Let us know below.