Small 4 cyl engine that turns.
2-56x 1/2 screws for the bottom end .
2-56x1/4 screws for the pistons.
One can stop the print close to the top of the sleeves and drop in steel nuts to secure the head. The nuts are #2-56 hex nut.
Update..
use crank 5 as it fits and can be printed with out support.