Help! 1 Rebuilt CYLINDER Break in

[pete tynning]

Just had my #3 Cylinder Rebuilt and back on my 170

I am finishing up the rest of my Annual.

Question? When I get ready to fly, do I

1. Start the engine Without the cowling for 2min and check for leaks
2. Then, button the cowling up and fly it hard at 75% power for one
solid hour to Break in the cylinder ??

OR


Is there a more Precise Schedule that I need to Follow??


Please jump in and give me your Opinion, the more the better!


Thanks !

Pete

[GAHorn]

The engine should be filled with 100% mineral oil (SAE 50 recommended above 60 degrees F OAT.)
The engine should be pre-oiled and oil pressure obtained before startup.
Engine baffles (and cowls too in my opinion) should be in good condition and installed.
Accurate instruments should be available.

Head the aircraft into the wind.
Start and observe oil pressure within 30 seconds, or shut down and determine the cause.
Run the engine only long enough to detect leaks and make any necessary fuel sustem adjustments.
If not already installed, install the cowls.
Start the engine and run it at 1000 rpm until oil temp has reached normal (above 135F). This time can be used to taxi to the runway if necessary.
Perform a full runup and mag check.
Shut down and check for leaks.
Start engine and make a normal, full power/full rich takeoff. Climb at shallow angles.
Fly the first hour at 75% power or more and change the power setting at least every 15 minutes from 75%, to 65%, to full power, stopping at each setting for 1 minute minimum, and then back to 75%.
Avoid long, low power descents.
Land after one hour and remove the cowl, checking for security and leaks.

Make the next 10 hours of flights at 75% power with mixture slightly richer than usual (minimum of 100 degrees rich of peak).
Notice when the cyl head temps drop and oil consumption stabilizes. This is the sign your cylinders have broken in.

Change to ashless dispersant oil, making certain to clean/change the screen/filter and examine it for excessive contamination or metal, expecially large magnetic material. (larger than the "o" in this sentence.)
Do another oil change in 15 hours additional, checking again for excessive material and performing a compression check. Now you're back to the ordinary/regular 25 hour oil change periods.

Be especially observant for excessive oil disharge thru the breather during break-in, a sign of broken or incorrectly installed rings.

Avoid breakins during frigid weather or at high altitudes, as they can lead to cylinder wall glazing and failed break in.

My 2 cents.

[Bruce Fenstermacher]

Georges break in sounds pretty good to me except I think he missed the fact that you only replaced/repaired one cylinder. I don't think you'll see much change in your oil consumption with just one new cylinder. I'd run it for 15 hours as George discribed then change the out the mineral oil at 15 hours.

[GAHorn]

I see your point, Bruce, but with one new cylinder, or 6 new cylinders, the break in should be the same and the time-frame allowed should be the same. (Just because only one cyl is new, doesn't shorten the time that cyl needs to break in.) The change to AD oil at 10 hours is important for the other 5 cylinders more than for the one that's new. Too long of operation on mineral oil can allow the older cylinders to begin a buildup of contaminants, while not breaking in on mineral oil can do two things, both of them adverse. 1) AD oil may contribute to premature cylinder wall glazing on the new cylinder and 2) AD oil will circulate minute particles of metal at a time of high wear rates on the new cylinder. Therefore the rest of the engine may be subjected to lubrication with oil contaminated with metal particles unless straight mineral oil is used. The mineral oil allows the particles to seperate out into the sump. The next short-period of AD oil operation should restore a cleansing effect to the lubrication system and allow the particulates that the filter misses to drain out. That's the theory at least.