Runge Cars, the Minnesota-based artisan carmaker known for its handcrafted 1950s-inspired creations, has revealed its most ambitious project yet; a bespoke 5.3-litre air-cooled flat-eight engine.
Developed entirely in-house, the engine, named Hetzer, is a double overhead cam, four-valve-per-cylinder powerhouse designed to rev to 9000rpm, with a cut-off at 10,000rpm. Power is estimated to be around 600hp, though final figures are yet to be confirmed. The Hetzer will power the upcoming Runge R3, a lightweight, mid-engined machine expected to weigh under 800kg. It looks a little like a shrunken 917 to us.

Despite its bespoke design, the Hetzer’s dimensions apparently allow it to slot into the engine bay of a 964-generation Porsche 911. For enthusiasts, that opens up a tantalising prospect: an air-cooled 911 with the howl of a 1960s Le Mans racer.
Company founder Christopher Runge, a former professional snowboarder turned coachbuilder, began the brand more than a decade ago after discovering a trove of vintage metalworking tools alongside an old Porsche 912. His first creations, hand-formed aluminium sports cars inspired by post-war endurance racers, quickly gained international attention, even attracting actor Gary Oldman as a customer.
Runge’s craftsmanship harks back to Porsche’s early days, when cars were shaped by hand rather than automation. The company’s latest engine continues that philosophy; air-cooled, naturally aspirated, and built with painstaking precision.

While modern supercars chase hybrid systems and electronic trickery, the R3 and its Hetzer flat-eight offer something rarer; pure, mechanical connection. “Handmade. Precision crafted,” Runge says of its ethos, and with production expected to be limited to fewer than 100 units, exclusivity is guaranteed.
Pricing hasn’t been confirmed, but with Runge’s existing four-valve head conversion for Porsche’s M64 flat-six already costing US$30,000, the full Hetzer engine is likely to command a serious premium.
Still, in a world dominated by SUVs and crossovers, Runge’s latest creation is a welcome throwback.