largest single-cylinder production engine: Karl Benz's 1.7L 1-cylinder engine from 1885, EXTREMELY popular in its day. 103.2ci. Bore/stroke was 4.56x6.3, and it made upwards of 1.5hp


also interesting: the Lancia Lambda featured what was considered the roughest running production engine of all time, was a 13-degree V4 (!!). It was 2.1L (129ci). Made ~38hp. They made no effort to correct the balancing issues a 13-degree V-engine had.... you know how an old V8 like a Chevelle fires 1-2-3-4, 5-6-7-8 and shakes the frame when it's revved? This Lancia did the same thing...