The main thing that separates Unleashed from the other Lancair aircraft is the engine.  The Superior Air Parts XP-400SRE.  For starters, this is NOT just a bored out IO-360.  Far from it.  The XP-400 has a 1/8″ larger bore and a 1/4″ longer stroke.  It also shares the same roller cam system that other Superior XP-360 engines have, but with a different cam profile.  Unleashed has the one and only SRE version of the 400.  SRE (Superior Race Engineering) adds a few things that other engines do not.  The biggest thing is 10:1 compression ratio and the cam profile to take advantage of the higher compression.  Also, the XP-400SRE is rated for 3,400 rpm.  I have yet to find a prop that will accept that rpm, unfortunately.  Specs are as follows:


  • Model: IO-400-J4AD3 SRE (XP-400SRE)
  • Horsepower: 250+
  • Displacement: 400 cubic inches
  • Number of cylinders: 4
  • Maximum RPM: 3,400
  • Bore x Stroke: 5.25” x 4.625”
  • Compression Ratio: 10:1
  • Fuel: Avgas
  • Weight: 310 lbs
Also, be sure to check out many of my engine related projects. I have made some modifications, and continue to do so, always check back for the latest!

For a flyby sound, check out this video at 1:57