Are flathead engines still made, well yes they are!
As everyone in the hobby knows flatheads were widely used internationally by automobile manufacturers from the late 1890s until the mid-1950s but were replaced by more efficient overhead valve and overhead camshaft engines.
They are currently experiencing a revival in low-revving aero-engines such as the D-Motor.
D-Motor is a technology company founded at the end of 2010 to produce and market engines that have been researched and developed over a period of many years.
Based on existing and well proven technology, our 4 stroke side valve (flathead) boxer engine was developed using the very latest technology including multipoint fuel injection, electronic ignition and liquid cooling giving a maximum continuous power of 93.68 HP at 3100 RPM (58 Kgs) for the 4 cylinder LF26 and 125 HP at 3100 RPM (78Kgs) for the 6 cylinder LF39. Combine this with high quality materials machined on the latest precision CNC machines, this ensures that crank shafts, connecting rods, camshafts and all engine parts are produced to the highest standards.
Our engines are most wanted for Helicopter and DRONE applications, because of their light weight, low consumption of MoGas @ 2.850 RPM, low RPM (Low noise) and performant nearly flat Torque capabilities continuously.
D -Motor delivers engines ONLY to OEM aviation manufacturers.
But I guess if enough interest is generated, you never know!
Take a look at the D-Motor site here