Who invented the first all aluminum engine for passanger cars?

There is no all aluminum engine in production, for any passenger car. They may have aluminum blocks and cylinder heads but most have cast iron or cast steel cylinder sleeves: What probably come closest to all aluminium are the most modern petrol engines which have "parent bores" in which the cylinder running surface is impregnated locally with aluminium silicate during casting.

Most of the internal parts like the crankshaft, connecting rods, camshaft, valves and timing gears are in iron and steel, including castings, forgings rollings and sintered components, because aluminium and its alloys can't stand up to the mechanical stresses and thermal loading - an exception being pistons which take the full force and heat of combustion.

But to answer the underlying question, several claim the honour of being first with aluminium blocks, heads and casings etc. As a saying goes, everything has an inventor and a German inventor.