Engine break in

[Vlakvark]

Hope all is well with my fellow mooney friends. Flew under the radar for the last few months. 
How much hours to break in a rebuild engine?

[carusoam]

If they have been run on a test stand, very little...

See if you can get the break-in instructions from your engine rebuilder...

They usually state how many flights should be done early on... what the purpose is... and what to look for...

 

Then there is the usual statement that says break in will occur over time that may last 100 hours...

If you have an engine monitor... you will be watching CHTs that stay elevated until the rings work in...

 

My factory reman IO550 was run on a test stand for a couple of hours... when installed it had two flights circling the airport... a couple more hours...

Then the Long, low, high MP, sweeping rpm flights began...

All in... probably 10hours of break-in related flying... never saw a shift in CHTs...

I was hoping to see an obvious sign that everything was done correctly...

Follow the steps, claim success!  

Best regards,

-a-

[Bravoman]

My  experience with the factory reman was much the same as Anthony‘s, above. Didn’t see much indication of change on engine monitoring. Lycoming runs their remans on a test stand, so I would imagine that the break in  process was well underway way by the time the engine was installed on my plane. The proof is in the pudding though, because I have excellent oil consumption and compressions have stayed at 78/80 or better for the almost 600 hour since it was installed.

[Awful_Charlie]

I followed the Lycoming instruction for running in except for oil changes, which I did at +4 and +13 hours before going to the regular 25 hour intervals. There wasn't a magic number when it was suddenly "broken in",  just as I got more hours on the engine I would be a little less conservative on limits and expectations. By 40 hours I was back to using the limits I used on the old engine. (which are pretty much book, except for CHT and TIT where my limits are lower))

However, what are you expecting with "broken in" - at 1000 hours some parts/fits will still be getting sweeter and some other parts will be wearing out!

[Bravoman]

And don’t use Camguard during the break in process. I didn’t resume using it until about the 50 hour mark just to be on the safe side. Also for Lycoming turbo engines use ashless dispersant oil vs mineral oil for break in as per the Lycoming directive.

Edited December 4, 2020 by Bravoman