Dan Mihalascu is an accomplished automotive journalist with over two decades of automotive media work both internationally and in his home country of Romania.
He holds a bachelor’s degree in journalism from Lucian Blaga University of Sibiu, and he has reviewed (sometimes even raced) cars for most of his professional life.
Prior to joining HotCars.com in July 2025, Dan worked as a news writer and editor for InsideEVs.com, CarScoops.com and Autoevolution.com. He also has bylines at DriveMag.com and ConsumerAffairs.com, among other international media outlets.
In Romania, he wrote for car magazines, sports newspapers and even a TV news station.
Writing and cars aside, he loves reading, cycling, hiking and spending quality time with his family.
The flat-eight engine, also known as an eight-cylinder boxer or horizontally opposed engine, is a rare configuration that was never used on a production car, although it was relatively successful in racing, with Porsche using it in its 908 series racers.
The flat-eight engine lost the battle with the V8 in production cars mainly because it’s too wide, complex and costly to integrate into a mainstream vehicle architecture. But when it comes to specialty cars, there is an American boutique company that has developed a flat-eight engine – a very spectacular and very expensive one.
We’re talking about Runge Cars, a small company based out of Minnesota that was born 14 years ago when founder Christopher Runge began building his dream car in a small barn. After he showed the car publicly a year later, he was approached to build another, and that’s how Runge Cars came to be. It has come a long way since then, as the company recently announced an air-cooled 5.3-liter flat-8 engine destined for a new ultra-lightweight, mid-engined supercar it will soon start building, called the Runge R3.
Nicknamed the Hetzer, the new engine has been years in the making, according to Runge Cars. Developed together with British engine specialist Swindon Powertrain and air-cooled engine expert Sol Snyderman using state-of-the-art technology, CNC-machining and motorsport-grade materials, the 32-valve, double-overhead cam 5.3-liter flat-8 is a technological tour de force.
The engine’s four-cam architecture and 32-valve layout allow it to rev “with the urgency of a race engine while delivering a broad, usable power band ideal for spirited road and track use.” That’s because it has a redline of 9,000 rpm and a rev cut off at 10,000 rpm. Imagine the sound this thing will make! Runge Cars says the engine is purpose-built to deliver “the most visceral, analog driving experience available today.”
But that’s not all: since the engine is the same size as Porsche’s legendary M64 3.6-liter flat-six engine, it’s a bolt-on replacement for it, fitting perfectly into the engine bay of air-cooled 911s. Company founder Christopher Runge says the engine was packaged within the M64 flat six architecture and no modifications will be required to the body of air-cooled 911s that the engine fits in, though oil system and ECU upgrades will be needed.
The engine was also designed to adapt to the bell housing of some of Porsche’s most iconic manual transmissions, the G50, G96/50 and G96/88, allowing both rear-engine and mid-engine applications. Now imagine a 964 or a 993 fitted with the Hetzer flat-8 motor – wouldn’t that make the ultimate air-cooled Porsche 911 engine swap?
So what are we talking about in terms of performance? Runge Cars hasn’t released dyno results for the flat-eight engine yet, but given that the company has already developed a 2.4-liter flat-4 engine that produces 300 hp at 8,600 rpm and accounting for more than double the displacement, the 5.3-liter flat-8 should deliver 600 hp, if not more.
Still not impressed? Well, that’s a lot of power for the Runge R3 lightweight supercar, which is projected to weigh just 1,720 lbs. It’s also more horsepower any air-cooled 911 project will ever need. But wait, there’s more. The engine will be paired with a 6-speed manual transmission in the Runge R3, making it the purist driver’s dream.
“This engine is more than a machine—it’s a statement. Working with the engineers at Swindon Powertrain and air-cooled specialist Sol Snyderman, we’ve combined modern technology with old-world craftsmanship to create something truly unique. It’s an engine that not only pushes boundaries but fits seamlessly into the legacy of air-cooled performance.”
Christopher Runge, founder, builder and designer at Runge Cars
Type
Custom air-cooled horizontally opposed eight-cylinder
Displacement
5,328
Valvetrain
Double overhead cams with four valves per cylinder (32 total)
Bore & stroke
102.7 mm x 80.4 mm
Compression ratio
12:1
Power
Over 600 hp
Torque
N/A
Transmission
6-speed manual
Compatibility
Designed for a direct bolt-in fit for air-cooled Porsche 911 platforms
And now for the less pleasant part, pricing. The flat-8 engine is going to be an extremely expensive piece of kit. Runge’s flat-4 motor we mentioned earlier costs more than $250,000, so you can imagine that the new flat-8 will exceed that. It’s an insane amount of money, but then again, this is not an ordinary engine. A kit of cylinder heads for this engine alone costs more than $30,000! Despite the steep price, we’re pretty sure Runge will find buyers willing to put this jewel of an engine in their air-cooled 911 project cars.
Both the Hetzer flat-8 engine and the Runge R3 supercar will be available for customer orders in late 2025, with the first three engines being exclusive to Runge, which will be testing them over the coming 12 months in a prototype test mule and two pre-production units. This is to ensure customer engines will offer an ideal blend of maximum reliability and high performance, according to Christopher Runge. He says the simulations run by the company have virtually tested the engine at 14,000 rpm for extended periods of time.
The Runge R3 is a major step forward from the cars the company has built so far, both in terms of design and powertrain. It looks like an old-school Le Mans race car for the road, and that’s intentional because its hand-formed aluminum body is inspired by Group C Le Mans Racers. We can definitely see some Porsche 962 influences there. It has a low, wedge-shaped nose and slab sides, as well as gullwing doors.
Developed over a seven-year period, the R3 is inspired by mid-century race cars and shaped by modern dynamics, according to Runge Cars. “This synergy between the chassis and Flat 8 powertrain marks the beginning of a new era for Runge—one that celebrates craftsmanship, innovation, and analog performance,” the company says. Not much else is known about the Runge R3, as the full specifications, performance specs and pricing will be announced in the coming months.
One thing is certain: if you have to ask what it costs, you probably can’t afford one.
Source: Runge Cars
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