Engine Break-In

Monday, November 23, 2020 at 10:57 AM ET

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On The Cover: A new, or freshly overhauled engine - including top overhauls - needs to be broken in. we're primarily concerned with seating the piston rings, but anytime an engine has undergone major work, it's appropriate to treat it as unproven. For more details see the article beginning on Page 16. Image by Patrick Allen/Dreamstime.com.

Key Takeaways:

Engine overhauls carry "infant mortality" risks due to new components, requiring extreme caution, thorough inspections, and a structured test flight plan during initial operation.
The core of engine break-in involves seating piston rings against cylinder walls, best achieved by running at high power settings to maximize internal cylinder pressures while carefully managing heat.
The break-in period extends for approximately 25 hours, including initial test flights over the airport, subsequent flights alternating power settings, and regular oil/filter inspections to monitor engine health and ensure full ring seating.

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By the time you read this, my Debonair should have a freshly overhauled engine holding down its nose. The story of how all that came to be is best told with a few adult beverages, but the bottom line is I will soon have a new hole in my wallet and a zero-since-major-overhual IO-520.

This isn’t my first engine overhaul with this plane, but it has been a while, so I sat down recently to review how I handled the previous one, update myself on the various recommendations and develop a plan for the plane’s next few flights. I came away with new appreciation and respect for test pilots.