Packard 3A-2500 Note: This item is currently in storage. The 3A-2500 is a 12-cylinder, liquid-cooled, direct-drive engine. Packard developed this engine, an improved version of the Packard 2A-2500 used on the Huff-Daland Keystone LB-1 bomber, in the late 1920s. This basic engine also was produced in geared and inverted configurations. TECHNICAL NOTES: Displacement: 2,500 cu.in. Rated rpm: 2,000 Weight: 1,223 lbs. Click here to return to the Featured Accessions index.