Love those miniature engines......and also the BIG ones.
Here is one of my favorites. It's a 140 ton, double acting tandem natural gas pumping engine from the PA oil fields.
It's rated to make 600 HP continuously at 80 RPM, and displaces about 86,800 cubic inches (1420 L) (376 Gallons
The engine now resides in Rollag, MN (near Fargo) at the WMSTR show grounds, where they run it and thousands of other antique engines every Labor Day weekend.
I realize this is a photo thread, but all I have is video of this engine. Please forgive me.