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IO470 To IO520 Engine Conversion STC

IO470 To IO520 STC

STC SA02363CH $1995 (Single STC)
STC SA02262CH $2995 (Twin Engine)


Allows installation of IO520 cylinders on your IO470 engine.


This STC conversion applies to:



  • J35 through P35, G33


  • 55 through B55


  • C-310C through C310Q.

Modifications for Conversion:

  • 470 case is bored to accept the larger diameter IO520 cylinders and oil nozzles if not already installed

  • 520 cylinders of your choice are installed

  • 520 counterweights are installed on the existing 470 crankshaft

  • Fuel injection divider at the top of the engine is replaced with the 520 version

  • Fuel controller is set up for the 520 fuel flows

  • New cam shaft gear will be in compliance should this become an AD

  • 520 inter cylinder baffles replace the 470 versions (4 small sheet metal parts)

  • Same propeller is retained

  • Engine data plate is replaced per the STC

  • TBO becomes 1700 hrs

  • Flight Manual Supplement update


Bottom Line:

This is the most economical performance increase to your IO470. It makes a lot of sense to do this when overhauling an IO470, increasing the displacement by installing larger cylinders.

Increases TBO to 1700 hours.


Gain IO520 performance at wide open throttle settings

Cygnet provides the STC permission and data for your engine shop to convert your engine.

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