A3B6 Engine Break In

[201er]

Please chime in if you've ever broken in an engine and haven't broken it (aka had major problems down the line). The lycoming service instruction SI1427C says you should break in at 5000ft and 75% power for the first hour. Meanwhile I've heard guys recommending max power and low during the first hour. Anyone have good sources/experiences on this topic to share and which you used, why, and how it affected things in the long run.

[garytex]

Lycoming cylinders are steel, and break in easily at 75%. The 100% guys are trying to break old straight or channel chrome barrels in which it is harder to get the wear necessary to polish down the ring. They are trying to get very high break mean cylinder pressures. The high pressures actually get under the ring and press it forcefully against the cyl. wall, and polish off a tiny bit of the slightly angled face of the ring, making a good contact interface.

The nickel ceramic bores from ECI break in so easy that I know of successful break ins that used as little as 50% of power, and are as tight as a drum.

When one hears of break in problems with IO 360 engines in our Mooneys and also in Cardinals usually there are reported "hot spots" which come from poor baffling. Uneven heat distribution in the barrel causes differential expansion, and here is the kicker, I think that the true cause is un-round barrels. The rings can't follow the out of round contours and lose contact with the cylinder walls, and the cylinder promptly glazes over in that area, the observed "hot spot", so the rings then can't ever break, and they pump oil. It isn't the heat per se, it is the change in form that accompanies it.

I assume that you and your mechanic have exhibited obsessive-compulsive disorder in tending to your new baffling for your engine, OATs have come down a little, fire it up and go. 75% works. Watch the cht's, sometimes you actually can see them come down in the first hour or so on steel cylinders. It is fun to watch.

Good luck

Gary

[Parker_Woodruff]

As much power as you can get, LOP.

I've broken in a new IO-360 before. Then the second time I "broke it in" was when I had new rings put on it at ~2300 hours.

[jetdriven]

The SI also recommends operating the engine at maximum power for 30 minutes. We broke in ours at 95% power for 1 hour, then another two hours of 75% power with a half hour of 95%. Then the next 25 hours at 75% power. Then the next 20 hours at 55-75% power. We just rolled over 50 hours today. It has burned 3 quarts.

ROP is going to be 15-18 GPH for cooling. LOP is 10-11.

[201er]

The SI also recommends operating the engine at maximum power for 30 minutes.

Yeah but on the SI, maximum power is step 8 which comes after 2 hours 75% (and 65% cycles in 2nd hour), not beforehand.

How's it going after 50 hours? Did you get your speed back?

[jetdriven]

Its still off ~5 knots but about the same as the old engine was at 20 degrees, this one is timed at 22. It has cooled off over the 50 hours and it seems about broken in fully. We just put 17 hours on it in the past 4 days. There are two air races coming up. We are going to see what it does .

[201er]

So it sounds like the engine is fine and just needed some time? When are you cranking up the timing to see what it's really got for you?

[jetdriven]

We have the correct used Bendix S4LN-1227 mags and need to get them overhauled. We just blew through nearly 40K on this thing after including 50 hours of flying in one month, and need to recover. So we suffer for now.

However, it is the smoothest running 4 cylinder engine I have ever flown behind. This thing purrs like an electric motor, and its not even dynamically balanced.

[fantom]

However, it is the smoothest running 4 cylinder engine I have ever flown behind. This thing purrs like an electric motor, and its not even dynamically balanced.

I want a quick ride in your baby when we're in Fredericksburg

[ProprAire]

Is it just my imagination or are more of us getting new engines this year? This is all great info and gives me confidence my 15 hrs of breaking in time on a Zero Time A3B6 seems to be proceeding well.

Cheers!

Dan

[jetdriven]

I woulndt cal it good news that I know of 5 folks includingt myself getting new engines this summer. Thats a hell of a lot of work and money for something that is supposed to last 2000 hours and only goes half that

[201er]

Thats a hell of a lot of work and money for something that is supposed to last 2000 hours and only goes half that

Actually it's supposed to last more than 2000 hours! That is just a recommended point of overhaul. So there really shouldn't be any excuse for a properly maintained engine not making it that far.

From talking to a few guys with this going on, the one thing that seems common is that it took 200 hours after buying a sitting engine for the wear to show. It is really sounding like this is the amount of time it takes for corroded lifters to break off sufficiently to be noticeable in the oil filter. I guess as it corrodes, it just sits there and it takes some motion to actually exploit that weakness and break it off such that we could detect it in the oil.

[Txbyker]

Just picked up my plane with the new A3B6. The engine is real smooth. Oil temp on trip home was 190-ish running 125 ROP at 6000 ft, 12C OAT. CHT's peaked about 390 and stayed around that until I opened the cowl a bit. TAS was at normal 163 kts. I was expecting slower. Like I said it is smooth so I don't know if I will dynamic balance the prop, at least for a while. Oil pressure stays high green. Oil cooler was rebuilt.

The fuel pressure is in the high green now. When I cycle the fuel pump at altitude I don't see a deflection at all on the gauge. Does this sound normal? Also, is everyone still shooting for 50 hrs at 75% power?

[fantom]

Your engine should be broken in, with lower and stabile temps in a lot less than 50 hours, and I would vary the power between 65 and 75%.

Of course this learned advise is worth no more than you paid for it.