Bring a Trailer auctions sold this for $13,450 On 8/17/20.
This Packard 4M-2500 engine is one of approximately 12,700 built and is believed to have powered a US Navy patrol torpedo (PT) boat during World War II. The supercharged 41-liter V12 produced 1,200 horsepower when new and features overhead camshafts and four valves per cylinder. It is not in running condition and sits in a wooden box equipped with castors. Retained equipment includes a Holley downdraft carburetor, centrifugal supercharger, and a Delco-Remy electric starter. The engine was donated in 2008 to the seller, the Tahoe Maritime Museum, and is now sold on a bill of sale at no reserve in Carson City, Nevada.
Originally developed by Packard in the 1920s for use in aircraft, the water-cooled 1A-2500 V12 was eventually developed into a marine engine. The 4M-2500 was the fourth marine variant, succeeding the 900 horsepower 1M-2500, 1,000 horsepower 2M-2500, and the 3M-2500, which debuted in 1939. Only 15 examples of the 1M, 2M, and 3M versions were built, but 4M production ramped up ahead of the United Statesâ€™ entry into World War II, resulting in 12,700 examples being manufactured between 1940 and 1945.
With a 6.375â€ bore and a 6.5â€ stoke, this gasoline-powered OHC V12 displaces 2,490 cubic inches (40.8 liters). A Holley 1685FR downdraft carburetor, crank-driven centrifugal supercharger, and Delco-Remy 841 electric starter motor are retained. The 4M variant produced 1,200 horsepower when new.
Serial number P3255 is stamped in the crankcase base as pictured above. 4M engine serial numbers range from 701 to 13,400, and the seller states this unit was likely built during the early portion of US involvement in World War II. The engine and ancillaries are finished in gray paint, which is peeling throughout.
It was evidently purchased by an enthusiast who is rebuilding a WWII PT-Boat. The discussion at the bottom goes into a lot of interesting technical details.