Info about the worlds largest piston aero engine second link in case you miss the first articles link or got bored,sorry i just love engines lol.Not as air proven as the russian Dobrynin VD 4K engine though.
http://people.virginia.edu/~rjr/engines/ and http://people.virginia.edu/~rjr/engines/x7restored/
http://people.virginia.edu/~rjr/engines/ and http://people.virginia.edu/~rjr/engines/x7restored/