Is a carbon fiber engine block possible? Have the cylinder sleeves steel and every other component in a steel surrounding. Might be a thing.

Nein

Carbon fibre doesn’t conduct heat. Also a block is mostly hollow because of channels which would be hard to make with fber

Depending on what Carbon fiber. If it’s CF reinforced plastic, it’s impossible. If it’s CF reinforced ceramic ( a.k.a. carbon ceramic, as what you see in expensive supercars ), I think it’s possible. It can take lots of heat, it’s very strong, and it’s not flexible. Also I read once that a company had made CF reinforced aluminium.

well its reality now :)