Pulling cylinders.

[Lood]

I took my F in to have the tanks stripped and resealed and had the engine shop investigate a minor oil leak on the engine. While at it, I asked them to also do blow by's and a boroscope because since day one, I was not happy with the oil consumption. All temps and pressures always ran fine, except for an occasional highish oil temp, but I had to add 1 quart every two hours to keep the level at 6. Still within Lycoming limits, but not acceptable to me.
The leak turned out to be a failed o-ring where the cylinder joins the crankcase - nothing major. However, the blow by's were 64, 64, 66, and 68. After pulling the cylinder with the failed o-ring, the boroscope's findings were confirmed. The cylinder is severely glazed looks like a morror. It seems that whoever ran the engine in, after its previous overhaul, did not do it correctly.

So, I instructed the engine shop to pull all the cylinders. Unfortunately, they're already at plus 10 and there might not be enough meat left to hone them and install new piston rings. I'll know the outcome by this afternoon. On the positive side, I found first life cylinders that are still standard and complete with pistons and valves for ZAR2k - which amounts to $300! Depending on their condition, the engine shop can overhaul and certify them for around another ZAR5k - $750. According to those who know, these cylinders should last the rest of the 1300 hrs left on the engine, if treated well and ran in correctly. I am quite excited on the result this excersize is going to have on my Mooney's performance.

I have the Lycoming manual regarding engine break in procedures in hand, but would appreciate and advice on the best and most correct way to do this.

 

[jetdriven]

Those break in procedures from Lycoming are pretty much IMHO spot on.  Limit ground running time and fly it at 75% power for the first 50 hours, or till oil consumption stabillizes.  Keep CHT under 400. 

[Shadrach]

I am confused as to what your saying with regards to "meat left".  "Honing" is not the same as "boring", if your cylinders are in spec, they should be able to re-hone and re-ring the hole affair. If the barrels are out of spec @ 700hrs, then I don't think that they were likely at new service limits when the engine was OH'd.

Lyc's break in proceedures have been in practice since and working well since....well since Lycomings started being produced.

Some folk break engines in LOP.  I would break my engine in this way if I had a new engine install and was at my current locale.

However, IIRC, your field is subject to higher DAs. If that is the case, you will need to do the break-in at a min 75% power controlling CHT with mixture on the rich side... I would personally not try to break in an engine at with DA's above 3000. It would probably work out fine at times, but is not ideal.  If the DA is high enough to necesitate significant leaning to achieve 75% power, I would avoid flying that day.  I would not my alter my personal CHT redline for break in - 380 is about the max I would want to see. Follow the Lyc procedures and you'll be fine.

With steel cylinders, you're rings should seated inside of 5 hours...if they're not seated inside 10hrs, they're likey glazed again.

[KSMooniac]

I freshened my cylinders a few hundred hours ago and broke them in flying LOP at ~80% power at 3000' and they were broken in after about 4 hours.  I stayed low and ran with the cowl flaps open and it worked great.

[The-sky-captain]

Lood- I had the same problem that you described with high oil consuption of 1 qt per 2 hours. I had them pulled and honed and saw my oil consumption dropquite a bit. Needless to say a short time later my engine started making metal so I had it OH'd and got new cylinders with the overhaul. 

[Shadrach]

yup, 3000 is fine, but would you have tried it on an August afternoon?

What RPM were you running?

[Shadrach]

god, it is painful to reread some of my posts without editing capability... Ouch!

[sreid]

"Lood- I had the same problem that you described with high oil consuption of 1 qt per 2 hours. I had them pulled and honed and saw my oil consumption dropquite a bit. Needless to say a short time later my engine started making metal so I had it OH'd and got new cylinders with the overhaul. "

I don't understand why you say "needless to say".  Why did your motor start making metal after honing?  Did you hone and re-ring?

Steve

[The-sky-captain]

Yes I honed and re-ringed. I misspoke, I just meant that it was all for naught because soon after that my camshaft went bad and I had to OH. It had nothing to do with the re-ring.

[Lood]

Thanks all for your replies. Shadrach, the way I understood it is that at plus ten, the cylinders might be beyond the allowable limits after being honed or even before that. I'm not sure if they can get worn out over time. In my case, however, it seems that the cylinders will just be re-honed and they will fit new rings. All the valves, seats, guides and pistons are good.

Regarding the break in procedures, I am in a bit of a dillemma. The airfield where the work is being done sits at 5300ft. The nearest low ground is about 30 minutes flying time away and there we'll be able to maintain 4000ft or below. Luckily, it's winter here and that will help a bit with the DA. It shouldn't reach more than 6000ft at take off, decreasing immediately. The major part of the flight will take place at a DA of not more than 3800ft. I sure hope that the break in will be successful.

[sreid]

Yes I honed and re-ringed. I misspoke, I just meant that it was all for naught because soon after that my camshaft went bad and I had to OH. It had nothing to do with the re-ring.

Ok, thanks for clarifying!  Was just unsure if something went wrong with your re-ring.  Sad to hear about the cam, but at least you've got a fresh engine now.

[jetdriven]

Lood I would fly it at 5000 DA.  Just run it 125 ROP at pattern altitude.  4-5 hours of that or two tanks the rings wil be seated.  Just take the maximum cylinder pressure you can make.

[Shadrach]

I'm not saying it can be done. However, if it were me, I'd head for lower ground if possible. I'd prefer to run at a lower RPM then Redline.

[jetdriven]

Your engine can run essentially forever at redline, 2500 RPM is only 7% less than 2700.  Acutally that brings up an idea.  full throttle and 2300 RPM will create more cylinder pressure.

[DaV8or]

"Your engine can run essentially forever at redline, 2500 RPM is only 7% less than 2700."

Really? How about your prop? What about all the things that are attached to your engine? Why do they have a "red line" if it's so harmless?

[Shadrach]

"full throttle and 2300 RPM will create more cylinder pressure"

In the future, please try and refrain from seeing my point before I get to post an explanation; it's not as much fun for me...

[Shadrach]

Dave,

Engines are certificated to go to TBO at max power...

Our 2700 RPM redlines are pretty slow with regards to engine technology.  The prop does not seem to care about the differnce between 2700 and 2500 except that it tends to transfer engine power to thrust more efficiently at lower RPM... All of the other accessories (mags, alt/gen,vec pump,etc...) have spun far faster for long periods of time in alternate aviation and non aviation applications...

[Shadrach]

Vec = Vac

[jetdriven]

"Your engine can run essentially forever at redline, 2500 RPM is only 7% less than 2700."

Really? How about your prop? What about all the things that are attached to your engine? Why do they have a "red line" if it's so harmless?

Dave

 

Yes, everything in the aircraft is certified in that configuration to run at redline RPM with no time limit.  That is the limit, do not exceed it.  But don't think you are harming it there while "saving it" at 2500 RPM.

[Shadrach]

However, if your're using tach time, you will be spinning your way towards TBO faster, as most mechanical Tachs are calibrated for true time at about 2500rpm...

[jetdriven]

Ours is actually calibrated for 2300 RPM.  1977 J.  Yours might be too.  Which is a rip off. We might change ours for a  2500 RPM version.   Wonder how the Horizon digital tack counts tach time? 1:1 same as hobbs?  What does that cost you?

[danb35]

The Horizon tach counts time 1:1 when the engine is over 800 RPM.  The EI tach is also 1:1, but starts when the engine is over 1300 RPM.  Either one is around $500 and an easy install (I did mine myself, with a friendly IA's approval).