The orignal Cherokee had 150 horsepower. A few years in, Piper came out with the -140, intended for use as a trainer. Before it went into production, they bumped the horsepower up to 150 but held on to the -140 model number.
The first PA-28 to be certified and go to market was the four-seat PA-28-160 in mid 1961, followed a few months later by the PA-28-150. Despite somewhat lower performance, the -150 proved more popular because it could use less-expensive 80-octane fuel. The PA-28-180 came along in late 1962, and the -235 at the end of 1963.
Piper had planned a new two-seat, low-wing trainer (PA-29 Papoose) to replace the Colt, but its plastic-composite construction was not ready for prime time (or even direct sunlight, as it turned out), and it was scrubbed. To get a trainer to market as quickly as possible, Piper took the rear seats out of a PA-28-150, moved the rear bulkhead forward by one station and eliminated the baggage door, and put a cruise prop on it which derated power to 140 hp (2450 rpm), and
voila, the PA-28-140 "Cherokee 140" was introduced in early 1964. MGW was initially limited to 1,950 lb., which seemed plenty for a two-seater.
Within a year, though, Piper added optional snap-in rear seats (the "2+2 Cruiser" option package), repitched the prop so power was equivalent to the PA-28-150 (2700 rpm), and raised the MGW to 2,150 lb., also equivalent to the Cherokee 150.
The "2+2" Cherokee 140 (intended for the flight school market) and full four-seat Cherokee 150 and 160 were built side-by-side until 1967, when the -150 and -160 were discontinued. Beginning in 1964, though, the Cherokee 150, 160 and 180 had the restyled fiberglass cowl that made them easily distinguishable from the -140.
