Engines Used To Be So Weak Some Trucks Needed Two Engines To Make Real Power

The internal combustion engines of today are technological wonders benefiting from over a century of development. Today, you can buy pickup trucks that make over 1,000 lb-ft of torque and highway semi-tractors can comfortably pull heavy loads from sea to shining sea. That wasn’t always the case. In the earlier decades of the automotive industry power demands sometimes outstripped technology. To meet demand, some companies did something simple and just filled trucks with two engines. One of these trucks is the Thorco Dual Motor. A couple of these mighty twin-engine Ford trucks have come up for sale and they’re a rare piece of history.

The Thorco Dual Motor has been at the back of my mind for at least a year, maybe two. Sadly, I’ve never been able to write about it because I’ve never been able to confirm who owns what few historical photos of it that exist today. That changed last week when the owner of the suspected two surviving examples decided to list them for sale, also catching the eyes of the folks over at The Drive. Now, not only do we know that these trucks still exist, but there are glorious high-definition photos of these oddities now in existence.

The crazy part is that strapping two engines into big trucks wasn’t all that of an anomaly. There were times when highway coach buses also had two engines for the same reason these trucks on your screen have two engines.

The Thirst For Power

Heavy hauling in the 1930s was very different than it is today. The 1930s were the dawn of diesel power in highway trucks. The first diesel truck sold to the public was likely a Kenworth sold in 1933, which had a Cummins diesel.

Back in those days, both gasoline engines and diesel engines weren’t making a ton of power. As Heavy Duty Trucking notes, a 1939 Peterbilt Model 260 had a Cummins 6-HB diesel making 125 HP. Step up to a Model 270 just a few years later and you got 150 HP. Over at Ford, the automaker boasted about the V8 power of its Cab-Over-Engine trucks. How much power did a Ford V8 punch out in 1939? 95 HP.

While these power figures were just fine for countless customers, some particularly needy organizations needed far more power than was offered at the time. As Mac’s Motor City Garage writes, trucking companies of the late 1930s faced a conundrum. The gasoline engines of the day were reliable but were coming up short on desired pulling power. Diesels made more power, but the tech wasn’t proven yet and it was also much more expensive.

A slew of companies came up with a bizarre solution that seemed logical. If existing gasoline engines are cheap and reliable but don’t make enough power, why not just double them up?

One of the early examples of a dual-engine semi was introduced in February 1939 by the Gear Grinding Machine Co. of Detroit, Michigan. The Grico Twin-Motor, as it was called, started life as a 1939 Ford COE with a 239 cubic inch Flathead V8 good for 95 HP. Grico then added power by doubling the Flatheads.

As an advertisement noted, the Grico Twin-Motor featured two engines with one mounted in its normal position and a second bolted into a growth behind the cab. Both engines had their own independent controls and even their own driveshafts to the rear wheels. However, the truck still required just one driver as the engines’ clutches and throttle linkages were set into singular pedals.

Grico advertised the Twin-Motor as doubling the horsepower and doubling the hauling capabilities of a Ford COE. The company also said that wear and tear on the braking system would be reduced thanks to double the engine braking.

As Mac’s Motor City Garage writes, America’s truck manufacturers experienced a dual-engine fever of 239 times two. In 1940, the Merry-Neville Manufacturing Company of Delphos, Ohio presented its own twin-engine Ford COE. Just like Grico, the Merry-Neville twin-engine tractor added a second Ford 239 inside of a Ford COE.

However, the Merry-Neville interpretation of the same thing was slightly different as it featured the two engines in tandem without requiring the weird growth on the back of the cab. Otherwise, the Merry-Neville twin-engine still featured two transmissions, two driveshafts, and linked controls. Both the Merry-Neville and Grico trucks were advertised as being able to run on just one of the engines or both of the engines at the same time. In theory, that meant higher uptime because a driver could keep trucking even if one engine failed.

These companies weren’t alone. Competition came from the D.H. Spangler Engineering and Sales Company of Hamburg, Pennsylvania, which produced the Spangler Dual.

As you can guess, the Spangler Dual worked by doubling up Ford engines. Spangler was also pretty crazy in how it implemented its dual engines, in some situations creating beasts with two steering axles containing dual wheels.

Even more dual-engine trucks would come in the mid-1940s through the Eisenhauer Manufacturing Company of Ohio creating the Eisenhauer Freighter. But for a twist, those trucks weren’t double Fords, but twin Chevrolet 235 cubic inch sixes. Later, General Motors would double up 4.7-liter Detroit Diesel 4-71 straight-fours into the engine bays of its Scenicruiser buses of the 1950s. The Diamond T 730C of the 1950s was also available with a second engine.

The Thorco Dual Motor

While tons of companies were all making their own variations of the same idea, it’s believed that few examples from any company were built. Even General Motors converted its Scenicruiser buses to single-engine setups. As it turned out, only some companies were willing to pay the cost of running two engines and eventually, single-engine power rose high enough to make the setups obsolete, anyway.

That’s what makes this pair of Thorco Dual Motors for sale pretty special. These trucks were rare and weird when they were new. It’s impressive that they’ve somehow lasted 84 years to make it to today.

According to Hemmings, it was Thorco, a brand of the Thornton Axle Company, that came up with the idea of the dual-engine semi. But, the Thorco Dual Motor didn’t become a reality without some help from the E&L Transport company. From Hemmings:

As it turns out, both Thorco and E&L were involved in the project. We contacted Tom Warren of Amarillo, Texas, who in 1988 took on the restoration of one of the only – if not the only – such trucks to still exist. Tom noted that Thorco did come up with the dual-motor design of the bomber haulers; he notes, however, that it was simply a matter of routing the power from the left engine to the rear axle and the right engine to the front axle, then ensuring that both engines received the same amount of vacuum and that their four-speed transmissions were shifted in synchronization. E&L then took on the construction of the trucks, with total production at less than 100.

While twin-engine trucks managed to get some interest from transport companies, their real claim to fame was working for the U.S. Army. The Army used Thorco Dual Motor trucks and other dual-engine rigs to carry Consolidated B-24 Liberator (above) parts across the nation. From Fred Crismon, author of the book U.S. Military Wheeled Vehicles:

Early in 1943 this highly specialized vehicle was shown to the public, identified as a tractor designed to pull a 60-foot-long “supertrailer” in which 34 complete tail cone assemblies could be carried. The tail cones were for the B-24 bomber of which Ford was one of several builders. The assemblies were carried between several manufacturing plants according to contemporary sources, including runs between California and Texas, Willow Run, Michigan, and Tulsa, Oklahoma, and Fort Worth, Texas, and between Loudonville, Ohio, and Buffalo, New York. Two Mercury V-8s were used, driving into synchronized transmissions.

The paragraph above points out why the Army used these beastly trucks. A regular Ford COE wasn’t going to cut it to pull a 60-foot trailer hauling bomber parts. Reportedly, the special trailers were built by Mechanical Handling Systems and had to be loaded from the top using cranes. Each dual-engine tractor could pull 10 tons of airplane parts and it’s noted that their drivers had to take special routes that could accommodate the 60-foot trailer plus the length of its monster tractor.

Of the fewer than 100 examples of these dual-engine semis believed to be built, it’s believed that Thorco was responsible for 46 of them. Of those, it’s believed that only two exist today. One is broken down and unrestored while the shiny example you’ve seen here today was restored by Tom Warren of Amarillo, Texas back in 1988. Tom has held onto the truck ever since then. Now, he’s decided it’s time to pass these pieces of history on.

Tom says that the Army’s fleet of 96 dual-engine trucks logged over 3,800 trips across America, aiding in the construction of over 1,600 B-24 Liberators over the course of a year and a half. Tom also believes that the Thorco Dual Motor “is the pinnacle of design for the Dual Engine Bomber Haulers.”

Both of the Thorco Dual Motors that are believed to exist are in Tom’s possession and he wants to sell both as a package deal. He wants $1,250,000 to take both of the trucks home from his Amarillo property. Normally, I would scoff at a price like that. However, as I figured out by finding zero other examples over more than the past year, it really does seem like Tom has the very last examples of a wild period of trucking history. It also helps that one of them still looks so good that it’s practically a time capsule. I can see them going for that asking price.

The drivers of today might take their abundance of power for granted. Today’s pickup trucks make multiples of the amount of power that highway trucks made in the 1930s and 1940s. My wife’s Scion iQ makes about the same power as a 1930s Ford V8 truck did. For a brief moment in time, the solution wasn’t forced induction or greater displacement, but by multiplying the number of engines in one truck or bus. The Thorco Dual Motor and its competition will hopefully be remembered as creative ways engineers used to solve problems.