Sam Torvik and Bill Moja have worked together for 30 years and still argue about whether the shop radio is too loud. Torvik is small, tightly wound, and wears a trimmed beard. He’s the Merlin specialist. Moja is a big, shuffling, mustachioed galoot, the kind of man whose shirttails are usually out. He prefers Allisons. “The English engines…,” he shakes his head. “Full of lousy rubber seals and way too many pieces. They’re like Jaguars burning out at the side of the road all the time. I don’t know why we’re still doing Merlins. There’s so much labor in ’em.”
Torvik and Moja are the V-12 masters at JRS Enterprises, which is housed in an old brick building next to some automobile dealers in suburban Minneapolis. The “R” has fallen off the JRS sign, and a constant stream of traffic rumbles past on a four-lane highway. This was once the hobby shop of racer John Sandberg, who was killed in 1991 in his remarkable homebuilt Unlimited racer Tsunami, a mini-Mustang that was the smallest airplane ever to have carried a Merlin. Today, JRS Enterprises is basically a fabrication shop fulfilling small contracts for the aerospace industry, but the engine building continues almost as though nobody knows how to stop it.
“Why are we still doing this? Because we always have,” Moja says. “Nobody’s making much of a living doing this stuff, because it’s just for rich boys and their toys—that and flying museums. But it’s warm in here during the winter, and you get to go home at 3:30.”
Torvik is happiest left to himself. He has his own small engine assembly area, where he’s finishing up an early Merlin that will go to a collector in England. (Early Merlins and Allisons are far rarer than the later more powerful and sophisticated variants.) “I don’t know what it’s going into, either a Spitfire or a Hurricane,” Torvik says.
He is impressed by what he’s seen of German World War II engines, having recently worked on a BMW radial from a Focke-Wulf Fw 190 fighter. “Their technology was so far ahead of ours at the time, it was easy to see,” he says. Moja demurs, of course. “They were way too complicated,” he says. “You didn’t have to be a rocket scientist to work on an Allison.”
Amid piles of engine parts and tools, Moja is building an Allison for a P-40 restoration. Hanging on a wall nearby are a huge Merlin connecting rod bent a good 10 degrees from straight and a supercharger impeller that looks as though somebody had punished every blade with a hammer. They’re from Tsunami’s Merlin, and they show what happens when an anti-detonation injection system fails. “If the ADI system fails, you can’t reach anything in the cockpit fast enough to keep the engine from blowing up,” Mystery Aire’s Mike Barrow had told me, and this display proves it. The explosion nearly blew Tsunami’s cowling off.
JRS does 15 or so engines a year, most of them radials for collectors and restorers and a few commercial operators. They do only one or two V-12s a year but are usually at work on several at a time while they wait for overdue supplies or missing parts. “The commercial stuff, that’s a push, because those people need their engines,” Moja says. “A V-12, the worst that happens is a rich boy misses an airshow. We haven’t worked on a weekend since September ’91.” Which, as it happens, is when Sandberg died and JRS was out of the air-racing business.
“The round motors are probably more reliable than the V-12s,” Moja admits, “but remember, the V-12s were made for an entirely different purpose. [The radials] were the truck engines, hauling bombs for the most part. The V-12s were the hot rods, made to go balls-out all the time. You’re asking me to fly behind it? I’ll take the radial every time.”
A variety of ailments can afflict a V-12 when it’s asked to do too much—even Moja’s Allisons. They’re prone to cylinder-liner distortion if overboosted, because the liners are locked to the block both top and bottom, and when uneven expansion is exacerbated by sudden overheating, the liners deflect slightly and let the combustion charge sneak past the rings. That is invariably fatal to that piston, which destroys the head with its shrapnel. “The Merlin’s liners, even though they’re thinner, stay pretty much round, because they float at the bottom end, where they’re sealed by O-rings,” Moja points out.
Imagine a soup can with both its top and bottom cut out and you have a small, very thin cylinder liner. Grab it by each end and twist, and it distorts—becomes slightly oval. Grab it by only one end and you can’t do that.
“See that semi out there?” Moja asks, pointing to a battered white trailer outside the shop. “It’s filled with cylinder heads that prove you can overboost an Allison.” Sandberg began his short air-racing career with an Allison-powered Bell P-63 Kingcobra. An inveterate tinkerer, he continually had its engine modified in a variety of ways, never leaving well enough alone. “We modified and modified that engine and kept blowing it up,” Moja says. “Then we finally took it back to stock and it ran better than ever.”