Tom Langdon is the inline-6 expert

It’s a decades-old story: Someone gets hold of an old General Motors car or truck from the ’50s, ’60s or ’70s, and immediately replaces the original inline-6 for a small block V-8 (I’ve done this myself). And why not? For the money, nothing produces more power for less money than a small block.

But not everyone goes this route. There are many people who either want to keep the vehicle’s original engine or like the idea of getting performance out of something other than the ubiquitous V-8. Most people who look into making improvements – major or minor – to a GM-built inline-6 will eventually encounter Tom Langdon’s name. Simply put, he’s the Chevrolet inline-6 engine guru.

From its introduction in the 1950s until the oil crisis two decades later, the modern overhead valve, small block V-8 enjoyed cultural dominance across the American auto industry. By the mid-’60s, everything from compact cars to light trucks could be had with one. Their popularity in motorsports since then has been unparalleled.

But a handful of enthusiasts, dedicated to inline-6 restoration and racing, have persevered. Langdon caught the six bug early in life, attending races in the 1950s at the US 30 Dragway, in York, Pa., not far from where he grew up.

“There was a guy racing a ’39 Chevy coupe with a big GMC six-cylinder in it,” he said. “It sounded different from the V-8 cars and was really fast on the first half of the track. I just really loved the way it sounded and fell in love with it.”

His older brother drove an inline-6-powered ’53 Chevrolet Bel Air, and Langdon said he talked him into letting him hop it up with dual exhaust manifolds from an early Corvette (they all came with inline-6 engines) and dual glasspack mufflers.

“When we fired it up for the first time, our mother came out and said, ‘What have you done to that car? Turn it off before you break the windows,'” Langdon recalled, chuckling. “A six-cylinder engine with a split exhaust has a really unique sound quality. Some people really love it and some people don’t like it at all. My mother was one of the ones that didn’t like it.”

It was the beginning of a lifelong obsession with inline-6 engines. Langdon went on to become an engineer, spending his 36-year career with General motors, testing and developing engines.

“A large part of my experience was dynamometer and durability testing, spending time in the dyno cells with technicians and inspecting the results of failed engines,” he said, explaining that he liked to take a hands-on approach to his work. “I didn’t do it singlehandedly, but I supervised the operation.”

He joined GM in the early ’60s, so working with small block V-8s was unavoidable. But in his personal time, he went racing, his passion for inline-6 engines honing his understanding of a unique powerplant. One feature that couldn’t be avoided, he said, was harmonics. Langdon said that at a certain rpm – close to 6,000 – vibrations in the engine cause the crankshaft to twist back and forth in opposite directions at each end. The motion can cause the flywheel to come off and the rubber ring in the vibration damper mounted on the front of the crankshaft to melt. In racing, this meant crankshafts had to be replaced frequently, a problem not seen as often in V-8 racing.

“The Ford guys had a much better design on the crankshafts, but when they get really competitive, they start to feed the engines crankshafts throughout the racing season,” he said.

From Fanatic to Guru

All those years of engine testing, number crunching and recreational racing weren’t for naught. Several months before Langdon retired from GM, in 1999, he found out through his membership in Inliners International – a club for inline engine aficionados – that a business specializing in inline Chevrolet parts was for sale.

“The guy who owned it basically couldn’t make a financial go of it,” he said. “I was nearing retirement, so I thought it would be a perfect match of my background and interests.”

Langdon and his wife, Joyce, bought the business – Stovebolt 6 – and its remaining inventory. Thus was born Langdon’s Stovebolt Engine Parts Company. The Langdons have been running it out of their house, in Utica, Mich., ever since.

Google anything about inline-6 engines – Chevrolet models in particular – and his name is bound to pop up. He doesn’t do anything V-8-related, and won’t even spend time offering advice on how to set them up, but he does sell hard-to-find parts for GM and Mopar inline-6 engines. His cast-iron exhaust manifolds, which he has manufactured for Mopar flathead and Chevrolet engines, can’t be found anywhere else. His small company also builds unique ignition upgrades for the engines. Plus, Langdon is always willing to go into great detail about what works and what doesn’t for any particular inline-6 application.

“We’re always getting calls from Australia and California,” he said, “I’m the guru of inline-6 cylinders and I get communication from everywhere. There’s probably no one else involved with inline-6 engines with the engineering background to be able to understand what’s going on with them.”

Looking forward, Langdon has gotten his son, Steve, his daughter-in-law, Doni, their children and a couple of Joyce’s brothers involved in the business, too. Langdon said he still works 10-12 hours a day, but Doni puts in four hours a day helping out with paperwork, emails, building the company’s social media presence and working in the shop.

“She’s getting very technically competent, and she’s able to answer 75 percent of the questions people ask,” Langdon said, adding that his son will step in when he retires in 5 years. “I’m 74 now, so hopefully I’ll make it until then.”

The children help out in the shop, with Doni’s 12-year-old son, Michael, building carburetor linkage kits, soldering pigtail connectors and disassembling distributor cores. His younger brother, 10-year-old Carter, helps out with the linkage kits. Bruce and Elmer Stange, Joyce’s brothers, take care of shipping and paperwork. Even Langdon’s neighbor, Doug Turner – who, although he’s not a member of the family, has known the Langdons for 40 years – helps out.

“Tom’s so busy that everyone pitches in,” Doni said. “Everybody’s very comfortable with each other.”

It helps that everyone in the family is a gearhead. Doni Langdon said that between the bunch, they have about 20 old cars. Michael is already building himself a 1950 Chevrolet 3/4-ton truck. That he has the best technical help anyone could dream of doesn’t hurt either; Langdon is assisting the boy in building a GMC 302-ci engine for a truck much like the ones he saw when he watched drag racers tear down the York, Pa., strip so many years ago. Doni said that Carter is beginning to collect parts for a similar project.

“That’s our family; this is our life,” Doni said.

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    Hello Tom ,

    I Know you are busier than a long tail cat, in a room full of rocking chairs, but since you are the 235 261 expert I thought Id just ask you a quick question if you had time.

    I m building a 261 to put in a 49 chevy truck
    I’ve got your Webber carb set up on a 60 over 261.

    I’m trying to set up the gearing and wheel size for the best general torque and hp for an efficient rpm.

    My question is, what is that sweet spot RPM for these motors?

    I’ve looked at piles of web sites and the answer is all over the board, of a good rpm that the 261 can proficiently run down the freeway all day long. Some say 2000 rpm all the way to 3300!

    Thanks for any input.


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