Swapping the O-470 for IO-390 Source: 2013 Q1 Beartracks, Merv Hargraves After having some trouble with the old Continental O-470 APU engine, I decided to bite the bullet and replace it with a new Lycoming IO-390 and Constant speed Hartzell propeller. This article is available for purchasers of 2013 Beartracks access. Click here to purchase access or validate your prior 2013 subscription. Multi-year bundles are available here. Username Password Remember Me Forgot Password