"the previous VW-based 1,100 cc (67 cu in) flat-four, used in the contemporary 356 and rated at 38 hp (28 kW), hit the limit of its potential.[4] Porsche realized it needed something all-new.[2] The brainchild of Dr. Ernst Fuhrmann, later Technical Director, it was hoped to achieve an "unheard of" 70 hp (52 kW) per 1 litre (61 cu in),[4] relying on hemispherical combustion chambers (what would be called hemi in the U.S.) and 46 mm (1.8 in)-throat 46IDA2 two-choke[6] Weber carburetors to generate 112 hp (84 kW) from the 1,500 cc (92 cu in) four-cam engine.[4] The 1.5 liter weighed 310 lb (140 kg) dry, eventually producing 180 hp (134 kW). A complex design that proved "very taxing" to build and assemble,[4] but very durable, it was used in 34 different models, including 550 Spyders, 356 Carreras, and F2/1s.[4]"

"probably the most complex four-cylinder" ever