The Citroën DS demonstrated many innovations in styling, materials, and hydraulics. Originally conceived to be powered by an air-cooled flat "six", cash flow problems at Citroën resulted in the cancellation of that program leaving the DS to soldiered on till the 1970's powered by an ancient design that dated to the 1930's. Originally displacing 1,911cc (75hp), it continued to be developed with changes in displacement, different carburetors, an Aluminum cylinder head, and eventually even Bosch D-Jetronic fuel injection (2,347cc). The advantage? It is pretty sturdy making it a pretty reliable engine that is relatively easy to maintain.
Cutaway drawing showing engine internals (
source).
Valve train is nicely highlighted in this front view (
source).
This side view highlights most internal components (
source).
Engine sits behind the transmission to provide enough clearance under the hood (
source).
Late model DS with carburetor (
source).
