Go-Devil L4-134
The engine known as the Willys “Go-Devil” L4-134 represents one of the most important components in Jeep history and one of the key reasons the Willys MB won the competition in the 1940 US Army competition. Although not revolutionary on paper, this engine combined reliability, simplicity and extremely favorable low-rpm torque, which made it ideal for military and later civilian use.
Engine development is tied to the Willys-Overland company and its chief engineer Delmar "Barney" Roos. Before the competition, Willys already had a flathead four-cylinder engine, but it was weak and unreliable for serious off-road use. Roos and his team decided to improve the existing concept instead of developing a completely new engine, because there was no time for that. The result of that work was an engine with a volume of 134.2 cubic inches, or about 2.2 liters, which would later be nicknamed the "Go-Devil".
The basic construction of the engine was simple: an in-line four-cylinder with an L-head (side valve) valve arrangement, where the valves are located in the block next to the cylinders. This design was not the most efficient in terms of power per liter, but it was extremely robust, easy to manufacture and tolerant of poor fuel quality, which was crucial in wartime conditions. The engine had a compression ratio of about 6.48:1, developed approximately 60 horsepower at about 4000 rpm, and about 105 lb-ft (about 142 Nm) of torque at relatively low rpm.
The Go-Devil engine's key advantage over the competition wasn't maximum power, but the way it delivered power. Unlike the Bantam's Continental engine of about 112 cubic inches and about 45–48 hp, as well as the Ford four-cylinder of about 119.5 cubic inches and about 45 hp, the Willys engine produced significantly more low-speed torque. This meant that the jeep could more easily climb hills, haul loads and get out of mud without the need for high revs. This very characteristic was crucial in military tests, where real driving conditions were much more important than laboratory specifications.
One of the lesser known reasons for this engine's success was its internal build quality. Roos insisted on technical improvements that were not common for cheap engines of the time: a fully counterbalanced crankshaft reduced vibrations and increased durability, insert bearings (replaceable bearings) allowed for easier maintenance and overhaul, aluminum pistons reduced the mass of moving parts, and a full pressure lubrication system ensured even lubrication of all key components. This combination allowed the engine to withstand long-term operation under full load, which was confirmed in tests where it worked for tens of hours without interruption.
Another important characteristic was tolerance to poor exploitation conditions. The Go-Devil could run on lower quality fuel, withstand dust, mud and large temperature differences. Its simple construction meant that soldiers could repair it in the field with minimal tools. In wartime conditions, where logistics and availability of spare parts were often limited, this feature was as important as performance itself.
The engine was relatively compact and easily fit into the short wheelbase of the Jeep, but at the same time it was powerful enough to compensate for the increase in vehicle mass that occurred during development. It is important to emphasize that the original military specification required a very low overall vehicle weight, but all manufacturers quickly realized that this requirement was unrealistic. When the military cracked down on weight, the Willys' more powerful engine became an even greater advantage, as it could carry the extra mass without losing functionality.
In operational use during World War II, the Go-Devil proved extremely reliable. It was capable of driving a jeep in various roles: from a scout vehicle, through the transport of soldiers and equipment, to the towing of light weapons. Its elasticity allowed driving at low speeds without shutting down the engine, which was especially useful in off-road and combat conditions. This is precisely why the soldiers often considered the engine "stronger than the numbers show".
After the war, the same engine continued in civilian use through the CJ-2A and later the CJ series. This is an additional proof of his quality, because he moved from military to civilian working conditions without major changes. In civilian applications, the Go-Devil was used not only for driving, but also for powering additional devices via the PTO (Power Take-Off) system, such as agricultural machinery, pumps and generators. With that, the jeep became a real working machine, and the engine became its central element.
Although the L-head design was later obsoleted by OHV (overhead valve) engines, the Go-Devil was remembered as one of the most successful engines in its class. Its power was not impressive by modern standards, but its reliability, simplicity and adaptability made it ideal for the time in which it was created. It is precisely because of this that it can be said that the Willys MB won not only because of the design of the vehicle, but above all because of the engine that gave it character and capability - an engine that proved in practice that power is less important than usability.
Go-Devil L4-134 is thus remembered as the heart of Jeep, a technical solution that allowed a relatively simple vehicle to become a legend and set the standard for generations of off-road vehicles that followed.