Packard 1A-1500 was an American 12-cylinder liquid-cooled 60-degree Vee piston aircraft engine designed in 1924. Test flown in the second prototype  Douglas XO-2 it proved to be unreliable. Only 29 engines were built.
Liquid-cooled V-12 piston engine
Applications Edit Specifications (1A-1500) Edit
Data from STATISTICS OF ALL THE AERO ENGINES OF PACKARD 
Type: V-12 liquid-cooled piston aircraft engine
Bore: 5 in (136.5 mm) + 3⁄ 8
Stroke: 5 in (140 mm) + 1⁄ 2
1,498 in Displacement: 3 (24.5 L) 720 lb (326.5 kg) Dry weight:
Power output: 500 hp (370 kW) at 2,000 rpm maximum continuous;520 hp (390 kW) at 2,200 rpm for takeoff
0.347 hp/cu in (15.8 kW/l) Specific power: 0.722 hp/lb (1.187 kW/kg) Power-to-weight ratio: See also Edit
^ Gunston 1989, p.109.
Neal, Bob. "STATISTICS OF ALL THE AERO ENGINES OF PACKARD" (pdf). Aircrqaft Engine Historical Society. Washington D.C . Retrieved . 20 January 2018
World Encyclopedia of Aero Engines. Cambridge, England. Patrick Stephens Limited, 1989. ISBN 1-85260-163-9 Aircraft Engine Historical Society