http://www.acmp.com/blog/ford-aviation-division.html"During World War II the Defense Department placed orders for Navy engines with similar specification to the Merlins and Allisons. Ford responded with their design. Ford had developed an aircraft engine similar to that of the Rolls-Royce Merlin and Allison engines of that era. It was a 60 degree V-12 with aluminum block and head, dual overhead camshaft, and 4 valves per cylinder. The intention of this design was to help Ford break into the anticipated large market for fighter engines. This engine was built to typical aircraft standards: it was light, high performance, and highly reliable. Everything was safety wired or staked with close attention to detail on every part. Available information suggests this design performed well.
However, this engine never went into production as an aircraft engine due to the US Navy’s decision to only use radial engines for its aircraft, and the Army’s contractual commitments to existing engine manufacturers. With the approach of war, increasing orders for the M4 tanks were causing supply issues with the existing engine. The U.S. Army decided they needed to source an engine supplier, so Ford removed 4 cylinders from the design and it went into production as a V-8."
Earlier, the Harry Miller 1200 cid V16 (for Ford's 1935 Indy 500 entry) was also a twin cam design (and supercharged). That engine was then adapted as an IV-1200 for the proposed Rider-Miller racing aircraft. Did the later Ford aircraft V12 owe anything to Miller's V16s, I wonder?