There is a engine on thingiverse I'm not sure how big it is but its the complete engine....... Lots of parts

um, yeah - not going to be able to print that at 1/64 scale....1/64 is a pretty tiny scale.

the engine with all the parts on thingiverse is more like 1/6 - 1/4 scale and is a moving model (pistons move in the cylinders, etc)...

however, you may be able to find something suitable (static model) that you can scale down in your printer software - might take a bit of tinkering to get it sized right, tho.

or try modeling one of your own with some of the free 3d modeling software out there. there are plenty to chose from, some easier to use than others, just depends on what you find easiest to learn.

I personally use 123D Design from Autodesk, others like Google Sketchup... and there are others, too. A search will give you lots of options to choose from.