PhredPhantom Posted March 10, 2014 Report Posted March 10, 2014 I'm negotiating for an Ovation and I have a question for you more experienced guys. The airplane looks good except for one concern that I have. The compression on the last annual a year ago was 60/80 on three cylinders, 62/80 on one, and 64/80 on the remaining two. I don't have personal experience with big-bore Continentals and I'm not an A&P but I wondered if that might be a little low with a little over 800 hours. One factor may be that the airplane hasn't flown much at all in the last 2 years. The owner said it doesn't use any significant oil. Should I be concerned? Thanks in advance for your thoughts. Phred Quote
jetdriven Posted March 10, 2014 Report Posted March 10, 2014 Big Continentals aren't a simple pass/fail at 60 PSI. They can go down as low as 40 per the service letter. If it hasn't been flown, go fly it at 75% power for 30 minutes then recheck. Quote
PhredPhantom Posted March 10, 2014 Author Report Posted March 10, 2014 That's what I've asked the owner to do. Since it's not my airplane yet, it's his place do fly it and then re-check. The annual is due next week and I asked him to fly it 3 or 4 hours before they pull it in for the annual when the compression will be checked again. My concern is not that the engine is airworthy now but I wonder if these compression numbers are indicative of a top overhaul being required sooner rather than later. That will have an effect on the fair selling / buying price of the airplane. Quote
DonMuncy Posted March 10, 2014 Report Posted March 10, 2014 As a matter of fact, compression tests are just about worthless on Continentals. They go up and own seemingly at random. Listen to Mike Busch's archived webinars; Google Saavy Aviation. Let me know if you don't find them. 1 Quote
carusoam Posted March 10, 2014 Report Posted March 10, 2014 There have been a couple of threads regarding top overhauls and when to expect them... 800hrs is very low for even a turbo normalized version of the IO550. I would take Byron's advice to help you feel better about what you have. Big bore Continentals are difficult to quantify using compression testing. Something about the rings aligning, maybe. They burn very small amounts of oil. See if you can determine the operation characteristics of the previous owner. Running LOP at altitude on long trips is more difficult to wear out cylinders than full throttle TNGs on a short field. Best regards, -a- Quote
harrispa Posted March 10, 2014 Report Posted March 10, 2014 If you really want to read about others experiences with the big Continentals, Beechtalk under "engine" forum has much on the subject. I just had to have 2 cylinders removed and repaired at 690 hours. The valve guides were found to be worn significantly. Much has been written about Continental's valve guide problems. Other than that the cylinders were in great shape. Continental has an extensive SB on how to do a compression and Borescope test. Compression leaking past the rings is not as significant as leaking past the valves. I believe many are factoring in cylinder work about mid time, but if you make it to TBO without it consider yourself one of the lucky ones. Paul. 1 Quote
DAVIDWH Posted March 10, 2014 Report Posted March 10, 2014 My 550 G ran 2400 flawless hours before compression on #4 cylinder dropped to 10/80. If I were you I would buy it and drive it with an oil analysis and filter cut on every change. Great plane, great engine. Oh yes, on that annual, make sure inspection plates are pulled and fuel tanks are checked for leaks. I found out about Mooney fuel leaks the hard way. 1 Quote
Beskra Posted March 17, 2014 Report Posted March 17, 2014 As others have said, lower compressions on a Continental IO-550 are not concerning. Compressions in the 60s (assuming good oil analysis, no metal in the filter, and low oil consumption) are fairly typical. It is really not an extremely useful parameter and tells you very little about the overall health of the engine. Sent from my iPhone using Tapatalk Quote
N222VS Posted March 19, 2014 Report Posted March 19, 2014 I agree with all the others about compressions being meaningless, our IO-550G had great compression consistently @ every annual & then @ around 1,000 hrs the cylinder with the best compression @ last annual stuck a oil ring. If I were you I would negotiate with the seller to deduct the price of a top overhaul because I it appears most ovations with the 550's make it to the 1k hr mark & then need the top done. My partner & I could have had only the one that failed the oil ring done , but we both fly often so we decided to have all 6 cylinders overhauled & chromed , we also had the connecting rods rebuilt & the parts & labor total was $12k Buy it & fly often , you will LOVE it!!!! Quote
PhredPhantom Posted March 19, 2014 Author Report Posted March 19, 2014 If I were you I would negotiate with the seller to deduct the price of a top overhaul because I it appears most ovations with the 550's make it to the 1k hr mark & then need the top done. That's the main point in the current negotiations. Yours are not the first comments that I've seen that indicate that Continental IO-550's typically need a top overhaul at the midway TBO point (about 1,000 hours). This particular airplane has nearly 850 hours on it right now. 1 Quote
carusoam Posted March 19, 2014 Report Posted March 19, 2014 I have seen Ovations with recent engine OH for sale with a $200k price tag. Currently there are none listed at AAA. Not all Ovations use their cylinders prematurely. Flying LOP @ 165 KIAS, 10,000' could make a difference...compared to 175KIAS @ 50 degF ROP, 6,000' David above is reporting past TBO. My cylinders were fine at 1800 hrs when the engine got swapped out for a 310 hp IO550 (N). Negotiate your best, but the cylinder argument depends on the current owner. Insist on a PPI at an MSC. All airworthiness issues get fixed at the owners cost. All others belong to the buyer, unless there are specific issues that you negotiate. The TOH is in the 5% range of the going price of Ovations. Quick review... 1 ) the market is low on supply. AAA doesn't have any. Normally they have 2 or 3. 2 ) O prices with recent OHs can be $200k and above. 3 ) There are a few new owners here compared to this time last year. The market has been moving... 3 ) It's been 5 years since the economy tanked and people were forced into selling planes, cars, boats etc. 4 ) Unemployment is turning around faster than Putin can take over countries... 5 ) What are you waiting for? A better price? A better plane? Your choice...O1, O2, O3, Screaming Eagle? Or new from the factory, like that other Phantom guy??? Best regards, -a- Quote
N222VS Posted March 19, 2014 Report Posted March 19, 2014 was it the #5 cylinder? Yes I think it was #5 , it was the one behind the alternator (possibly due to lack of airflow??). I'm certain that we could have "patched it" by just doing that one?? After seeing how deep you have to go to get a single cylinder off it seemed like a no brainier to do the rest. Also we viewed it as a capital investment , adding more value to the airplane?? It's in for annual now & we just got the prop back from overhaul ,no problems with prop but it was @ the recommended overhaul time. We are thinking about putting it on the market & upgrading possibly in the next few months now that the market seems to be getting better?? Quote
carusoam Posted March 19, 2014 Report Posted March 19, 2014 What would be the next plane after the O? #5 is behind the alternator. The known pixie hole is worth consideration. Best regards, -a- 2 Quote
jetdriven Posted March 19, 2014 Report Posted March 19, 2014 Yes I think it was #5 , it was the one behind the alternator (possibly due to lack of airflow??). I'm certain that we could have "patched it" by just doing that one?? After seeing how deep you have to go to get a single cylinder off it seemed like a no brainier to do the rest. Also we viewed it as a capital investment , adding more value to the airplane?? It's in for annual now & we just got the prop back from overhaul ,no problems with prop but it was @ the recommended overhaul time. We are thinking about putting it on the market & upgrading possibly in the next few months now that the market seems to be getting better?? Old wives tales. It adds zero value to the plane, whether it's one cylinder or 6. If one doesn't meet the standards of the Continental SB, repair it. Changing the others makes no sense. And it's more invasive. And far more expensive. Same with the prop. Run it until you need to pull it, then do an IRAN unless it obviously needs an OH. The only difference is they grind the blades to limits which means next time it will need replaced. Quote
BigTex Posted March 19, 2014 Report Posted March 19, 2014 Old wives tales. It adds zero value to the plane, whether it's one cylinder or 6. If one doesn't meet the standards of the Continental SB, repair it. Changing the others makes no sense. And it's more invasive. And far more expensive. Same with the prop. Run it until you need to pull it, then do an IRAN unless it obviously needs an OH. The only difference is they grind the blades to limits which means next time it will need replaced. +1... Check out Mike Busch's webinar called "All About Cylinders." He's strongly recommends only changing out one cylinder out at a time and then only when it calls for it. 1 Quote
N222VS Posted March 20, 2014 Report Posted March 20, 2014 Old wives tales. It adds zero value to the plane, whether it's one cylinder or 6. If one doesn't meet the standards of the Continental SB, repair it. Changing the others makes no sense. And it's more invasive. And far more expensive. Same with the prop. Run it until you need to pull it, then do an IRAN unless it obviously needs an OH. The only difference is they grind the blades to limits which means next time it will need replaced. I'm not a A&P but I personally saw enough to persuade me to pull the other 5 cylinders due to the invasiveness of pulling just one cylinder. Like I said it seemed like a no brainer to me, I will argue the point about zero value added. I'm sure going to pay more for something with a top overhaul than one (everything being the same) with a mid time engine with one new cylinder, but that's just me. As far as the prop goes, the manufacture recommends overhaul based on many factors & like I'm not an A&P I'm not a test pilot either. All that being said the bottom line is I like my mooney & I like me & whoever is along for the ride , and @ the end of the day I like the feeling I have done everything possible to keep the fan blowing. Quote
aaronk25 Posted March 20, 2014 Report Posted March 20, 2014 I'm not a A&P but I personally saw enough to persuade me to pull the other 5 cylinders due to the invasiveness of pulling just one cylinder. Like I said it seemed like a no brainer to me, I will argue the point about zero value added. I'm sure going to pay more for something with a top overhaul than one (everything being the same) with a mid time engine with one new cylinder, but that's just me. As far as the prop goes, the manufacture recommends overhaul based on many factors & like I'm not an A&P I'm not a test pilot either. All that being said the bottom line is I like my mooney & I like me & whoever is along for the ride , and @ the end of the day I like the feeling I have done everything possible to keep the fan blowing. Just remember extra elective maintenance creates a opportunity for something to not get torqued right or a part manufactured wrong. How do you know your safer for because you replaced the other cylinders? A cylinder with some hours on it is a proven known, or as close as it gets but new parts are unknowns. It's not a big deal but if I launched in to IFR with new or low time cylinder I'd have a very uneasy feeling. Just limit the type of flying you do until the new parts and workmanship are proven. The only time I would change good functioning cylinders is if there was a flaw in manufacturing for example the rocker arms we mis-aligned with the valves (which I experienced) and the remaining cylinders were starting to show signs of oil consumption though the valve guides, I believe that warrants changing them all. The trouble with trying to put a value on a top overhaul is that there is a reason it didn't make overhaul and even if a plane is listed with 300stoh it doesn't mean much if the operator got CHTs hot. Ask a ferry pilot which type of single engine airplane they would rather fly across a ocean a zero time or 2000hours since overhaul. Most likely you won't have any issues and you will "feel better" because you have new parts upfront making the fan spin. 1 Quote
BigTex Posted March 20, 2014 Report Posted March 20, 2014 N222VS, As I stated above do yourself a favor and watch the webinar by Mike Busch who know's of what he speaks around changing out perfectly good cylinders. Here's the link to the webinar. http://www.eaavideo.org/video.aspx?v=1204537102001 Watch this first, then if you still wish to move forward changing out all your cylinders at least you're going into it with your eyes open. Report back after watching it. Quote
Txbyker Posted May 28, 2014 Report Posted May 28, 2014 Just got my O back from annual. 3 cylinders in the low 60's, 3 cylinders in the high 50's. This is after a year of reportedly low 70's at annual prior to my ownership. Borescope all clear in the cylinders. Oil analysis normal. Oil consumption normal. I have 700 hrs on the engine of which I have put 200 on in the last year so it gets used. Any worries here? Russ Quote
KSMooniac Posted May 28, 2014 Report Posted May 28, 2014 Did you borescope the valves themselves, or just the cylinder walls and pistons? Post some pics if you can. Quote
carusoam Posted May 28, 2014 Report Posted May 28, 2014 Be familiar with the data and the method of testing in regards to Continental cylinders. Many people report going 2000 hrs... Many people report difficulty measuring Continental compression... How has it been operated? LOP at 10k' or WOT @ 5,500' leaned to peak. No, I'm not saying you burned it up. But you could if you wanted to. The next question is what is the best preparation for doing the compression test? A good flight and return to the MX hangar for testing may be required. If they pulled it into the hangar without running it. That may explain what you got.... Best regards, -a- Quote
Txbyker Posted May 28, 2014 Report Posted May 28, 2014 Scott, no I don't have pics. Our good MSC at GGG did the work and he believes all is well and I think they looked at pistons, cylinders and valves. I left out some info, one cylinder was in the teens but the valve was leaking due to carbon points holding the valve up. Once cleaned it went to 60. Everything internally reportedly still looking new. Anthony, I run ROP 8000-10000, 90 degree over, WOT, 2400 rpm. I am not sure what method they used to check but they probably know the routine pretty well for Continentals. I might have them checked and borescoped again in about 50 hrs. If no drop in compression I will keep it going. Russ 1 Quote
carusoam Posted May 29, 2014 Report Posted May 29, 2014 MSC at GGG should be good enough. 90dF should be cold enough. 8-10k' develops lower ICP. Everything looks in order. I would lean toward the compression test not working very well for Continentals. It takes extra effort to generate half decent numbers. Other things to look for is dark colored oil. If things are worn and leaking, the oil won't stay golden. Oil starting to burn at higher levels. IO550s are tight and hardly burn any oil. Burning a quart in 10 hours is usually unlikely. Talk to the good people at the GGG and see what their take is on this? Trying to purchase a plane with an IO550 is a bit challenging. Acceptable numbers are much lower than Lycoming. Getting decent numbers from the test is challenging. I let a good Missile get away once because I couldn't get up to speed on this issue fast enough. As you know I'm a pilot, not a mechanic. Best regards, -a- Quote
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