Production four-cylinder pushrod engines first appeared on American roads in the early years of the 20th century, and they were available in new cars and light trucks here until… when?

BMW has patents on two, bizarre three-cylinder engine designs meant to improve on the classic V-twin. One splays out the pistons in a fan shape, adds a cylinder to the traditional design.

The beating heart underneath that sinewy bodywork is known as the Motus Baby Block MV4. This pushrod engine, with design help from such well-known engine builders as Katech and Pratt and Miller ...