Chrysler A57
"Five Chrysler 250.6 cu in (4.1 L) (bore 3.4375 in, stroke 4.5 in) flat-head inline six cylinder engines were arranged around a central shaft, producing a unique 30-cylinder 21-litre (1,253 cu in) engine in a relatively compact but heavy package. The crankshafts were fitted with gears, which drove a sun gear arrangement. With iron block and head,[1] it featured Carter TD-1 carburetors and 6.2:1 compression ratio, for an output of 370 hp (280 kW) at 2400 rpm."
Interesting, but with dismal output:
I guess we were so unprepared for war, so that were open to anything...