By 1922, the Model E had been developed; this could be said to be the "classic" Doble, of which the most examples have survived.
The initial monotube boiler design was perfected into the "American" type. This produced steam at a pressure of 750 psi (52 bar) and a temperature of 750 °F (400 °C). The tubing was formed from seamless cold drawn steel 575 ft 9 in (175 m) in total length, measuring 22 inches (560 mm) in diameter by 33 inches (840 mm) in height when coiled and assembled. The boiler was cold water tested to a pressure of 7,000 psi (480 bar). Two 2-cylinder compound cylinder blocks were in effect placed back-to-back as the basis for a 4-cylinder Woolf compound unit with high pressure cylinders placed on the outside. A piston valve incorporating transfer ports was fitted between each high-pressure and low-pressure cylinder in an arrangement similar to Vauclain's balanced compound system used on a number of railway locomotives around 1900.
Stephenson's valve gear replaced the previous Joy motion. This engine was used on all vehicles developed thereafter. Again, the car neither possessed nor needed a clutch or transmission, and due to the engine being integrated directly into the rear axle, it did not need a drive shaft either. Like all steam vehicles it could burn a variety of liquid fuels with a minimum of modification and was a noticeably clean running vehicle, its fuel being burned at high temperatures and low pressures, which produced very low pollution. Price ranged from $8,800 to $11,200 in 1923. The Model E ran on a 142-inch (3,600 mm) wheelbase. Twenty-four E's were made between 1922 and 1925 with a variety of body types from roadsters to limosines. Owners included Howard Hughes and the Maharajah of Bharatpur. One the Hughes cars, a roadster engine number 20, is currently owned by Jay Leno. Abner Doble owned the last one - number 24.
The E cars still known be in existence are 9 (at the Ford museum), 10, 11, (in Australia) 13 (in New Zealand), 14, 17, 18, 19, 20, 22, 23, and 24.