Originally Posted by
Jhieminga
The last semi-successful car-to-aircraft engine conversion (just my opinion of course) is the Thielert / Continental range of diesel engines, based on Mercedes automotive engines.
To me, as a former automotive engineer, one of the obvious issues with a car-to-aircraft conversion is that modern car motor model cycles are likely to be far shorter than aircraft engine designs. Car motors change every few years and even the underlying designs no longer last many decades as some post-war designs did. (BMC A series for example).