Packard 1A-2500 is an American V-12 liquid-cooled aircraft engine designed by Packard in 1924 as a successor to the World War I-era Liberty L-12. Five aero variants were produced, of which the  3A-2500 was the most numerous. Three marine versions, used most prominently in American World War II PT-boats, the 3M-2500, 4M-2500, and 5M-2500, were also derived from it.
1924, 800 hp. Six built.
1925, 800 hp. 75 built.
Huff-Daland XHB-1 3A-2500
1926, Geared propeller drive option, 800 hp. 175 built.
1927, fitted with a
supercharger, 900 hp. One built. 5A-2500
1930, experimental use only, 1500 hp. One built.
Marine version, 1200 hp (895 kW), subsequently upgraded in stages to 1500 hp (1,150 kW).
Marine version, larger supercharger, aftercooler, and power output of 1850 hp Specifications (1A-2500)
Data from Aircraft Engine Historical Society and Race With the Wind By Birch Matthews  General characteristics
^ Gunston 1989, p.109.
"Packard 3A-2500". National Museum of the United States Air Force. 8 June 2015 . Retrieved . 26 June 2020
"Packard 3A-2500 Geared Drive, V-12 Engine". National Air and Space Museum. Smithsonian Institution . Retrieved . 26 June 2020
"Packard 3A-2500". New England Air Museum . Retrieved . 26 June 2020
^ Aircraft Engine Historical Society - Packard Archived 2015-03-25 at the
Wayback Machine Retrieved: 30 January 2009 Bibliography
World Encyclopedia of Aero Engines. Cambridge, England. Patrick Stephens Limited, 1989. ISBN 1-85260-163-9 Aircraft Engine Historical Society - Packard Engines
Matthews, Birch. Race With the Wind. Osceola, WI. MBI Publishing, 2001. ISBN 0-7603-0729-6
Wikimedia Commons has media related to Packard 3A-2500.