I don't know if it will turn up by using a web search but years ago I read an article about a plastic Indy type proto-type motor.
It was called a "Poly-Motor" or Poli-Motor or something like that.
It had, (if I remember right), plastic/carbon fiber block, a carbon fiber crank, c/f rods and maybe even ceramic valves and piston tops and ceramic valve springs and I THINK it ran without oil??
I never did hear how it finally turned out but just maybe the R&D on it ended up in this block now offered by GMPP???
PS., totally off the subject unless it is lightweight block construction is that the late '40's Crosley Hot Shot SOHC motors were actually brazed together sheetmetal and sleeves and was a very light little gear drive SOHC motor.
Here is something on it.
"The most revolutionary feature, though, was the method of block construction. First of all, this was in unit with the cylinder head and detachable from the crankcase. Secondly, and more important, instead of being cast as all other engine blocks were and are, it was built up from an assembly of steel tubing and stampings. These parts were assembled in a jig, then copper brazed together at high temperatures, which also served to heat treat the cylinder walls and valve seats to bring them up to a high degree of hardness. Water jackets and passages were lined with a plastic material for anti-rust purposes, and all outside parts had some kind of stiffening ribs or fins cast into them for high rigidity. Machining operations consisted of trueing the bottom of the block where it meets the crankcase, boring the camshaft bearings and boring and honing of cylinder walls and cam follower guides. The block was bolted to the aluminium crankcase, with the hold-down bolts also serving as bolts for the main bearing caps.
The result of all this innovation was a 44-cu.in. engine that weighed only 59 lbs. without accessories. It put out 26 hp at 5200 rpm, and had a compression ratio of 7.5:1. The copper brazing process gave it its unusual name, COBRA."
Interesting reading to say the least even if corrosion finally ruined the little motors before they went to cast-iron!!
More reading at;