What to expect for TBO

[6930]

I’m at 1050 hours since an extensive overhaul - which included new ECI cylinders, cam and crank- in 2011. Compression is still running 76-78/80 cold. No apparent issues.

I have the logs for my plane from day one, and the engine has never made it past 700 hours until now. Most overhauls over the years were done much more frequently than that. I have a C85 with the O-200 crank STC.

Anyway, I’m curious what others have seen for TBO. Anybody make it to 1800 hours? I’m trying to get a handle on what to expect over the next few years.

Thanks,

Mike

[6643]

Any indication as to why the other overhauls were performed? I believe Continental says 1800 hours OR 12 years, whichever comes first.

If you fly 500 hours a year it's much more likely you'll reach TBO than if you fly 20 hours per year. (20x12=240).

Most C-series engines I've seen have solid bottom ends even after 25 years and 1800 hours. The top end won't usually last that long. So, if it needs 4 cylinders and it's been 15 years, a complete overhaul might be a good idea even if the hours are a lot less.

[6930]

Hi John,

Thanks for the input. I don't know why so many overhauls were done. I suspect that one of the first ones was done because the airplane went up on end back in '48. The others are probably the result of "not so good" overhauls that were performed over the years which needed to be redone before their time. The plane had periods of regular usage, but then there were periods where it sat...and sat....and sat.

For the first 6 or 7 years I owned the plane I was flying at about 150 hours per year. Lately, down to 50 or so. Since the overhaul in 2011, I've put an average of 105 hrs/year on the plane. The plane is kept in a heated hangar and flown regularly....once or more per week generally unless mother nature decides to not cooperate. I change the oil every 25 hours to keep the lead from building up in the oil and use Phillips X/C with Camguard. All my oil analysis reports (done at least once per year) at Blackstone are excellent. No chunks of metal when I cut the filters.

I just did a compression check this morning and cold the cylinders were all 76/80 or higher. With the new crank and cam and all new cylinders in 2011, I'm thinking that this engine is a good candidate for 1800 hours. I may try a top within the next 500 hours....but I'm not a big fan of top overhauls in general. We'll see.

Regards,

Mike

[6298]

My engine has been overhauled three times, with 1800 hours between. It has 1900 hours since the last one and I’m about ready to do it again.

[6930]

So it is possible!

Thanks Randy. Good info.

Mike

[6183]

Hi Mike,

I agree totally with my fellow forum moderator John Cooper about how to get the most longevity out of an engine, you have to operate it. I fly for a utility company performing aerial power line patrol, and I used to put approximately 350 hours a year on the engine in my airplane. When the engine time got to 2,100 hours my wife calmly told me that it was time for an overhaul when I commented that I was beginning to see an increase in oil weeping out of the gaskets, pushrod tubes, as well as the fact I discovered some broken rings in the number 3 cylinder when it was removed for an exhaust leak issue. At that point on the calendar, the engine had been in service approximately 20 years since the last overhaul.

Overhaul on my engine consisted of the following:

(4) four new Superior Millennium Cylinders
Overhaul of the case by Divico
All new internal gears i.e. mag, main crankshaft, camshaft, oil pump
New camshaft
New cam followers and lifters
New starter
New magnetos
New overhauled carburetor

Was all this needed, yes, only the crankshaft was serviceable, all of the other steel parts were unserviceable.

BTW, Randy Thompson helped me immensely. He's a great one to talk to.

[6930]

Hi Mike.

Great input! It is interesting how regular flying can really impact the longevity of an aircraft engine. I’m not flying anywhere near that much, but I am getting up regularly.

So far, as I noted, all indications are good for a long and healthy life for my engine. Seeing others make it to TBO is encouraging.

Thanks!

Mike

[8359]

I’m new to aviation in general, but I’ve done a bit of research on engines and maintenance. Mike Busch has a great book on the topic. He’s not a fan of top overhauls. In his mind if you have a bad cylinder replace that one, not all of them arbitrarily. He’s a big fan of on condition maintenance rather than timing things out. Thankfully as Part 91 operators we have that flexibility.

[e thomas]

I am just getting to a major overhaul on my C-85. It was overhauled in 1974 at a technical high school. I am at 1400 tach hours since overhaul. Over the last 21 years of ownership, I have chased a few cylinders, done the mags a few times, and the carb once. I have had it apart enough to check inside, and it ls fine. It still runs very well, has 40 PSI oil pressure, and produces power "to book" It is starting to weep oil from every corner, and one of the cylinders is down on compression.

It is clearly time to go all the way though it, new crank, new whatever. Then get another 40 years out of it. - E

[6643]

I don't think anyone was recommending a top overhaul for any other reason other than a on condition. My point was more that you may have one or more cylinders that don't make it to TBO but the bottom end of the engine can still be fine. Also, the less you fly, the more likely it is you'll have early cylinder issues, IMHO.