Masters of the V-12
They're like highly specialized surgeons: there are few of them and they're in great demand.
- By Stephan Wilkinson
- Air & Space magazine, March 2002
(Page 2 of 7)
Thorn’s specialty is replacing Rolls-Royce rods with beefy, never-run Allison connecting rods and adapting them to fit Merlin crankshafts and pistons. This allows the engine to operate at 135 inches of supercharger pressure but at lower rpm because of the rods’ greater mass. Before Thorn’s imaginative fix, racing Merlins with their lighter connecting rods turned as much as 3,800 rpm, the propeller spinning so fast the blade tips were supersonic, which meant they weren’t creating thrust. Now racers can back the revs down to 3,300 or 3,400, allowing the prop to get a better bite but sending cylinder pressures into the stratosphere.
Most of Mystery Aire’s clients aren’t racers. “We’re dealing with a different kind of customer now,” Thorn says. “Back in the 1960s and ’70s, the majority of the owners worked on their airplanes, had military experience, some had even flown the P-51 in the service. Today it’s the nouveau riche. They’re like the Ferrari guys—people who’ve bought something they assume will appreciate in value.”
Between Rolls-Royce, Packard, and Ford of England, 165,000 Merlin engines were made during and after World War II—second only to the approximately 178,000 R-1830 Twin Wasps turned out by Pratt & Whitney and its licensees. Today, enough Merlin parts survive to make perhaps a few thousand. In the ’60s, acres of Los Angeles were carpeted with Merlins and Allisons owned by a speculator who had bought them for pennies a pound. When land prices shot up the engines were sent to Japan, melted, and recycled.
Thorn’s best engines are built with what the cognoscenti call “transport banks.” Between 1948 and ’50, Rolls-Royce turned out the strongest and most durable Merlins ever for Canadair-built Douglas DC-4s known as Northstars. These 1,760-horsepower engines could pound away for hours without missing a beat, and they made use of every trick Rolls had learned about building durable V-12s. They are the gold standard, and if you want a racer, they are what you need.
What about nitrous oxide? The Luftwaffe used it to augment its simple, single-stage superchargers, and hot-rodders inject it for instant acceleration. (NOX is a powerful oxidizer that “thickens” the air—and therefore the amount of fuel—that an engine can inhale.) Thorn will provide nitrous if asked but says, “It’s hard to carry enough to make it worthwhile. A hot-rodder can fit a five-gallon tank and go play all night, but with an engine this size, you’ve got to have a lot on board.”
Scattered throughout Thorn’s warren of shops are shelves, boxes, racks, and pallets of Merlin parts, many still in sealed Rolls or Packard packaging. “I’ve been able to buy a couple of complete [shop] inventories over the years,” he says. “I could probably build 20 complete engines from scratch. Not counting the things that wear out, like bearings, I probably have 200 engines’ worth. But someday there will be one little widget that nobody has anymore, and you won’t be able to finish an engine unless somebody steps up to the plate and manufactures it.” Part of the problem, Thorn points out, is that a Merlin has six times as many parts as an Allison. “I blame it on socialism,” he says. “The more parts they had to make, the more hours of labor were needed and the more make-work the government achieved.”
Thorn’s protégé, Mike Barrow, builds his own engines alongside Thorn and pitches in to help when needed. When Thorn retires, it’s likely that Barrow will take over the business. “I had a cousin, Louis Norley, who was an ace with the Fourth Fighter Group,” Barrow says. “I’ve always had a thing about P-51s and Merlins. It’s neat to be able to work with this stuff, and I like the air racing too. I’ve been a crew chief, though when you’re both the crew chief and the engine guy, no matter what breaks you’re in trouble,” he says with a grin.
“People my age—I’m 40—when I tell them that I overhaul Rolls-Royce V-12s for a living, they don’t know what I’m talking about.”