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#3 Break In

Manchu16

Manchu16

Active Member
I figured I would post my experience breaking in my reworked #3 superior millennium nitrated cylinder.

Followed the Mattuck ground run process. Had to stop two of the cowled runs due to getting close to 350 CHT. Waited to cool down and finished them.

First flight saw CHTs about 50* hotter than the rest. 350 or so at WOT and full rich. Could just about get 2575 RPM. Have a 2600 placarded prop. Ran WOT for 1 hr, then 15 at 2400 then another 15 at 2575. Finished up with a fuel stop and a short, but hard 10 min run back to base. Total of 2 on the Hobbs. Used 1/2 qt of which some was on the belly from the breather. Oil stayed about 165 due to OAT. Flt was at 2500’

Flight 2 saw CHTs about 50* hotter than the rest until I started to lean to peak RPM (roughly 70* LOP). One of the cylinders came up to the same 360F egt as #3. Ran at 2550 for another hour then went back to 15 at 2450 and 15 at 2550. Oil was up to 188 during high rpm and 169 at the lower rpm. Flight at 2500’ MSL. Put another 1.7 on the Hobbs. Oil consumption was just under a half qt. Now down 1 qt since the start of ground runs. I haven’t seen anything about 385F on the CHTs and that was right after take off due to having to wait for two twins to depart with the wind at my back.

Pulled the plugs because I was getting some roughness during the post flight mag check. All looking good. The auto plug (bottom) had a yellowish hue on the electrode. Outside of that all normal and dry. Gapped and cleaned them all. Finding some case or pan leaks up front. Not the main seal. Always been very minor, but the hard running has been making them more evident. Checked the torque of the oil pan and the case half’s. One nut moved about a 16th of a turn.

Will post some of the borescope pics of the #3. Not an expert so would love opinions on if this is looking good.

Off for a few days and then after this next front pushes through going to put some mileage on the #3 and take a trip down to FL. Hoping to get 4 hrs in or so between 65 and 75%+. I used a power app, imputed the MP (27), RPM (2550) the alt (2500) baro (30.38) and the oat of 12c and I got that I was pushing 90.2% power. Not sure if I buy that, but great.
 
Pictures

Here are the two pictures. One from the front camera and one on the side of camera in #3. There are a few shiny areas in the middle of the bore that I am guessing are a part of the break in process. Fingers crossed all is progressing like it should. Good news is no oil pooling like it did before the oil control ring was replaced.
 

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Are you concerned that a CHT > 350 deg is too hot??? For a newly overhauled cylinder it is expected to get over 400° during breakin which could take a couple hours or so. You are supposed to run the engine as hard as possible as long as you’re below 420° or so. After breakin as long as the CHT’s are below 400° in cruise, all is good.
 
Break in

I am following Mahlon’s break in process. CHT below 350* during the ground break in then 350*+15% or roughly 400* for flight. So yes, stopped on my ground run when I reached 350*.

The max I normally see in low alt WOT cruise is 385* or so. Outside of extended Vx/Vy climbs not sure I could hit 400*

Right now, I have no significant concerns with the break in. Seems like +50* CHT on a new cylinder isn’t out of the ordinary. I am running leaned near WOT now because I was fouling my plugs running full rich and I could feel it in the mid ranges during approach. If I run WOT and lean to best RPM I will exceed 2600, so I am targeting 2550-75 as a safety margin. Not sure if it really matters if I am WOT and overly rich to get 2550 vs near WOT and 70* ROP to get 2550.

I have read, you should see the CHTs drop in an hour or two with nitrated cylinders, so I am a bit surprised I haven’t seen the CHT drop the 50* yet. Will be nice to have some of the breather puking slow down a bit as well to get back to normal

As I say all of this, last airplane I broke a single cylinder in was a 172 with a very basic CHT gauge on one cylinder. I flew that WOT and full rich for 25 hours. Was a nitrate cylinder as well. So I am happy to have folks poke holes in my approach.
 
Quick update

Went out to fly today and noted 0 oil burn after flight number 3. Was glad to see that normalize. CHTs are still 45 to 50* higher on the cylinder, so still waiting for that to drop. I did get oil temps knocking on 200* during the last flight but that was probably due to 70* air temps with the cooler blocked off still. Total of 5 hours of engine time and 4.5 of that in the air.

Quick question for the group. Can I pause my break in?

Meaning, I have a friend that wants to head out on a flight while he is in town. Going WOT down low means I get to snug up my belts quite often this time of year. I would like to slow it down, 2300 RPM or so for an hour to have him enjoy a smooth flight to breakfast. Will taking a break from running it hard do anything but delay my final break in?
 
BMEP is what seats the rings, nothing wrong with keeping it below 2300 if you keep HP between 65-75% IAW Lycoming guidance
 
avrojockey said:
BMEP is what seats the rings, nothing wrong with keeping it below 2300 if you keep HP between 65-75% IAW Lycoming guidance
Click to expand...
Thanks! Unfortunately my calcs show 2300 is about 60% hp.

Had to bag the trip anyways. Found a small nick on the leading edge I am dressing tomorrow.

IMG_5149.jpeg
 
Update

About 10 hours Hobbs, No tach timer, on the new #3. Estimating about .5-.75 have been on the ground in-between flights and doing the ground testing prior to return to flight. Used just about 1QT over that time. Before the issues started I was about 1 QT per 7 hours. So I am not sure I am going to get any better than 1 QT every 10 or so. CHTs on #3 are still slightly elevated, but #3 was normally the hottest cylinder before the overhaul. So that just may be a difference in the sealing of the baffles or I could still be breaking it in.

My plan is to pull the filter, K&P S-15, this weekend and look for any metal. If it looks clean I am going to continue to run the engine as is on this oil until my condition inspection in late Feb, probably another 10 hours or so of Hobbs time. At my CI, I will drain the oil, check the screens, clean the filter,... and refill with the Phillips 20/50 XC I have been using for break in. That will get me to about 40 - 45 hours total on the 20/50 before my next oil change. Plan on going back to Phillips Victory 100 after that.

I have read, stick with break in oil until the temps and oil burn stabilizes, 50 hours is the minimum you need to stay with break in oil, AD oil is bad for break ins,.... All the different documents from the different sources really makes it confusing when you go through this process. The shop that did the cylinder overhaul recommended that I wait until the 10 hr oil check then ok to top off with Victory 100 when I run out of the XC oil. Rationale was the low compression O-320 (150 HP) engines break in very quickly with the superior cylinders.
 
Pulled my filter today for my CI. A total of 17 hrs on the new number 3 cylinder. I noticed a magnetic sludge on the oil filter magnet on that just covered the surface. I am assuming that I should expect some ferrous material after new rings and a honed cylinder. Sound normal?
 
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