Technical aluminum engine?

When I was a wee young lad I came across an old car carc*** that I believe was a Buick or Olds or some type of gm make though not really sure. It had an aluminum engine in it. It was a straight 6 if I recall, and was overhead valve. I'm pretty sure it had an aluminum head on it as well, but I know for sure the block was aluminum. It was approx early to mid 20's Era. Anybody have any idea what I might have seen and how rare it is/ was? It went for s**** a very long time ago so it's lost to history but I have always been curious what it might have been.
I should add that my memory tells me it was a 6 cyl, but it could possibly have been a 4. So include any of those possibilities too.

 

Marmon was a car of that era, that had an OHV aluminum six cylinder engine. Marmon used an aluminum six from 1916 to 1928.

They were an expensive car in the Cadillac cl*** and were known for their easy riding and performance qualities. Extensive use of aluminum in engine, ch***is and body made them light in weight for their size. F. Scott Fitzgerald wrote a story about a trip he and Zelda made in one.

 

My fathers 29 hudson 6 cyl had an alum crank case with cast iron cylinders and head.

 

Buick had an aluminum crank case in the 20s also.

 

Many crankcases were aluminum in the Teens/ealry 20's to keep weight down. When I was apprenticing in a shop back in PA, one of the cars wee worked on was a 1911 Simplex. The crankase was aluminum and was pretty badly deteriorated. The shop owner was able to locate the original bucks for the case and had it recast- that was a FUN project!