This inline 4 cylinder engine block is designed to use with my rotating assembly parts. I cut away part of the front of the block to allow for easy viewing of the internals in motion.

The color picture is of the whole lower end minus the hand crank adapter, but this thing is just the block and stand. Get the rest of the parts here:

Engine Crankshaft:
http://www.thingiverse.com/thing:102180

Piston and Rod with bolts, nuts, and pins included:
http://www.thingiverse.com/thing:100282

Hand crank for the crankshaft:
http://www.thingiverse.com/thing:103329

I have all the parts translated into position in the scad files but commented out to allow for playing with the fitment but it should all line up with minimal gaps to allow for freely moving parts right out of the box.

If the tolerance is too tight, a nice acetone bath for the pistons and crank should grease things right up!

The block prints deck-first (vertical but upside down) and prints 102mm tall, but it's not very wide/long. I have an 8x8 bed and I don't even use the whole thing yet I still have no problem printing everything. The biggest print is the crank.