The O-470 L in my 182 had a field overhaul in the 1970's. The engine runs strong, makes 70+ compression, doesn't burn much oil or blow much through the breather, although it does leak a little around the crankcase and valve covers (valve cover gaskets will be replaced at next annual). By all accounts, the engine sounds healthy to myself and anyone on the ground, I have no complaints. The mechanic that did the prebuy commented it was one of the best looking engines he's seen considering the age of it, and I had an excellent mechanic do the first oil change look for issues, and he was happy with it. I've flown it 75 hrs and it has not even given me a stumble in that short time.

But... it's approximately 1000 SMOH, and has never been topped. There's nothing to indicate it's been opened up since the overhaul according to the logbooks, and the engine itself doesn't show any appearances of having been opened up. The engine logbooks begin at overhaul, I have no clue how many runs the cylinders have on them. According to 470 folklore, I'm getting close to being on borrowed time concerning the cylinders, even though it doesn't show any signs of slowing down.

My question is, what would you do when the time comes for a top? I'm undecided on what I'll do when it comes time for a major, considering a P-Ponk or the Norland STC's. This plane spends 90% of it's time at sea level, and the 470 honestly makes plenty of power for my mission, so leaving it stock is a strong possibility. Assuming I might have to do something in the next 200 hrs, should I try to get these old cylinders overhauled and live with them till MOH, or spring for new cylinders and potentially spend $10k I might not recoup at OH, especially if I decide on a bigger engine. I'm not going to put my family at risk flying behind sketchy cylinders, so I have no problem buying new cylinders if that's the consensus of the cylinder shop and my mechanic, but I don't want to buy new cylinders that I might only fly behind for a short time and then toss at overhaul if it's not necessary.

What would you do?

I think it's a no-brainier when it comes to the PPonk. Give it a good hard look!

CenterHillAg wrote:The O-470 L in my 182 had a field overhaul in the 1970's. The engine runs strong, makes 70+ compression, doesn't burn much oil or blow much through the breather, although it does leak a little around the crankcase and valve covers (valve cover gaskets will be replaced at next annual). By all accounts, the engine sounds healthy to myself and anyone on the ground, I have no complaints. The mechanic that did the prebuy commented it was one of the best looking engines he's seen considering the age of it, and I had an excellent mechanic do the first oil change look for issues, and he was happy with it. I've flown it 75 hrs and it has not even given me a stumble in that short time.

But... it's approximately 1000 SMOH, and has never been topped. There's nothing to indicate it's been opened up since the overhaul according to the logbooks, and the engine itself doesn't show any appearances of having been opened up. The engine logbooks begin at overhaul, I have no clue how many runs the cylinders have on them. According to 470 folklore, I'm getting close to being on borrowed time concerning the cylinders, even though it doesn't show any signs of slowing down.

My question is, what would you do when the time comes for a top? I'm undecided on what I'll do when it comes time for a major, considering a P-Ponk or the Norland STC's. This plane spends 90% of it's time at sea level, and the 470 honestly makes plenty of power for my mission, so leaving it stock is a strong possibility. Assuming I might have to do something in the next 200 hrs, should I try to get these old cylinders overhauled and live with them till MOH, or spring for new cylinders and potentially spend $10k I might not recoup at OH, especially if I decide on a bigger engine. I'm not going to put my family at risk flying behind sketchy cylinders, so I have no problem buying new cylinders if that's the consensus of the cylinder shop and my mechanic, but I don't want to buy new cylinders that I might only fly behind for a short time and then toss at overhaul if it's not necessary.

What would you do?

Start doing oil analysis and keep flying, no reason you won't get another 1000 hrs unless I'm not reading this correct?
I would not even mess with the Cyls. until they let you know it's time!
Just my .02!!

I am on my second overhaul on my engine. Made 100hrs between. Keep running it on condition. An overhaul does not mean you get another 1000-1400 hours.

I would keep flying it. In my experience, the 470 series will start talking to you if something is going wrong. Pay attention to your cht's & egt, oil consumption, speeds etc.

When it is time, consider the Pponk. It is an amazing engine that performs. There are several prop options that you can choose to suit your mission.

mghallen wrote:I am on my second overhaul on my engine. Made 100hrs between. Keep running it on condition. An overhaul does not mean you get another 1000-1400 hours.

Why did you only make 100 hours? And to what extent was it overhauled?

The "experts" who teach the Advanced Pilot Seminars don't believe "top overhauls" of Continental engines are a cost-effective maintenance technique. If you had a knee joint go bad, would you have the doctor replace both knees and both hips "just in case" the others might also go bad? Why replace six cylinders when only one cylinders is indicating a problem? Why even replace it, if it's repairable? Borescope examination of the valves (Google search for articles by Mike Busch and Adrian Eichhorn) can tell you more about the condition of the exhaust valve (and guides) than even a compression check, and will definitely tell you when it's time to replace a cylinder (or at least have it rebuilt by an expert).

Otherwise, if your engine is running well, not burning an excessive amount of oil, and is not "making metal" (assuming you're doing oil sample analysis), why would you ruin all that by doing unnecessary maintenance? The vast majority of engine failures occur very early in the engine's life or very shortly after a major overhaul or repair. (The term "infant mortality" applies aptly to this phenomenon.)

For more information on this topic, you should read Mike Busch's series of articles on engine "euthanasia" (his terms)... He believes there is absolutely no reason to pull a cylinder (much less "top" the engine) unless there are specific indications of conditions that render it unsafe for flight.

But when it IS time to replace the engine or rebuild it, I personally would give serious consideration to Pponk-ing it!

Yup! What he said. Watch the stuff from Mike Busch. It's on the EAA site or his Savvy Analysis site. If it's not broken, don't "fix it". You've got a proven solid engine. Failure rates are higher for lower time engines. Do oil samples, put an engine analyzer in it if you don't already have one, learn how to use it, and scope it like mentioned above. In the club I used to be in, we'd routinely take our 470s to 3,000 hours. Don't fall for the wives tales, but make decisions based on condition. Like mentioned before, by keeping a finger on the pulse of the engine, you'll most likely know when something is starting to go south. And I'd be willing to bet it will be way past 200 hours.

My current plane had a top overhaul and that was actually one of the negatives I had to come to terms with in deciding to buy it. Like mentioned before, Mike isn't a fan of them for various reasons.

Thanks for the replies, always appreciate the wealth of knowledge on this site. I guess my biggest concern will be what a cylinder shop will say about those cylinders if I send one in. I don't have an engine monitor, I had planned to get one this year but some business purchases might push a monitor to the back burner.

My previous plane had an IO-470 in it. It was overhauled in '89 and had about 600 hours on it when I bought it. 300 hours after I bought, the number 6 cylinder started loosing compression. We watched it closely, checking it every 25 hours. After talking to Adrian (with whom I work) and Mike, I decided to have it pulled by Western Skyways...for piece of mind. They found that the valve guide was wearing and causing the valve to burn. If I could have found a good camera to scope it, I would have found the signature burn pattern that Adrian has published with the help of AOPA. They also found a cracked cooling fin that was heading to the case...not repairable. So, they swapped the cylinder out and life went on.

I guess I thought to share this to just illustrate that with some attention to anything that changes, I think you'll typically have some time to evaluate and make a good informed decision that is appropriate to the issue at hand. Hopefully you've got a good mechanic that isn't prone to just "pull & replace" too.


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Thanks, that's definitely helpful. I really don't have much experience with cylinder monitor and repair, knowing what to look for and establish trends will be a big help. I couldn't ask for a better mechanic for this kind of work, he spent years working on and flying Ag Wagons, so big bore Continental's are definitely in his wheelhouse. If there's a chance to repair over replace, he'll be the first to recommend it.

First thing is have an engine monitor installed for all six cylinders. Then fly the crap out of it. At below 65% power setting lean aggressively. Then lean it a bit more. If Cessna Pilots Association is till putting on the 182 systems seminars you ought to sign up for one.

Tim

I couldn't agree more with Tim. Make the analyzer a priority and you'll have it for every engine here on out. And I think there is some peace of mind that comes from being able to be in tune with what is going on with your engine on a more detailed level.


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Electronics International make really good stuff and there after sale tech help is excellent

Tim

CenterHillAg wrote: According to 470 folklore, I'm getting close to being on borrowed time concerning the cylinders, even though it doesn't show any signs of slowing down.

"Folklore" is exactly what that is, and how it should be handled. I wouldn't borrow trouble...just run it and watch it like any other engine. I've seen them go all the way to TBO and past with nothing but oil and plug changes...but I've seen them go just a few hours and have trouble too....sounds to me like yours is just fine. Go flying and have fun.
JH

On engine monitors, they are great! But there have been 1000's of these engines fly past tbo with out them!! Cruise below 75%, lean to stumble or rough as advised and back in to smooth!

I recently bought a 1974 T310Q, (TIO520's) has over TBO engines in it Both have great compressions, Both just have 1974 as installed single point CHT and EGT.
Probably the lowest TT 310 out there, been sitting in a hangar for 16 years!
Wish the fuel bladders were in as good shape as the engines!!
Just going to fly it and do oil analysis and see where it goes.
GT

According to the logs, my old 170's C-145 did ~2300 hours TBO prior to the overhaul that I (and Rob) flew on.

Despite the common comments that these engines are old 40's technology and dirt simple, there is a long list of "gotchas." Sure, they're designed with relatively low compression ratios and some slop in the ring fit to allow for thermal expansion, but on the inside they are quite precisely engineered mechanical marvels.

It's too bad that splitting the crankcase is such a major event. One thing I liked about the Franklin 6 series was the case access panel and replaceable sleeve cylinders. They had some good ideas.

One commonly held truth is that frequent use is critical for longevity of an engine. Quality of the overhaul too. Anyone who buys an airplane with X hours since overhaul has no control over those factors.

I recently tore down an IO-540 with 2440 hours on it; same cylinders since new. Of course a few cylinders had valves lapped for some reason or other of that time, but the time period covered 1976 to 2014. The bottom end looked very nice, relatively corrosion free, which is what most people fear as it's the first stage in wearing shit out. Most wear was in some bearing journals and cups for stuff like ignition drive gears, and some gear teeth wear here and there.

One eye opener, which several trusted people commented was standard, was the amount of metal-based sludge and chips and shit in the oil sump. I assume it's actually carbon but there were some big chunks. When you look at the oil pump pickup, you realize it wouldn't take all that much to block and starve the oil system.

I forget where I was going with this. /stream of consciousness end

I'm on board with run it frequently until it requires you to actually intervene. Sometimes cylinders with low compression/leak down test results can recover after frequent use and engine management.

I was in damn near the exact same position as you a year ago or more. I just flew the shit out of it until the compressions started dipping and the oil burn got excessive. Now I'm waiting on the pponk to arrive.

qmdv wrote:Electronics International make really good stuff and there after sale tech help is excellent

Tim

EI is currently having a $1000 rebate turning the CGR-30P from $3500 to $2500 is pretty attractive. But it's only for the basic version. the "premium" version is only $400 discount - which is still pretty good. It can replace 5 primary instruments in a certified plane - like the tach/manpress/egt etc.

CenterHillAg wrote:T
My question is, what would you do when the time comes for a top? I'm undecided on what I'll do when it comes time for a major, considering a P-Ponk or the Norland STC's. This plane spends 90% of it's time at sea level, and the 470 honestly makes plenty of power for my mission, so leaving it stock is a strong possibility. Assuming I might have to do something in the next 200 hrs, should I try to get these old cylinders overhauled and live with them till MOH, or spring for new cylinders and potentially spend $10k I might not recoup at OH, especially if I decide on a bigger engine. I'm not going to put my family at risk flying behind sketchy cylinders, so I have no problem buying new cylinders if that's the consensus of the cylinder shop and my mechanic, but I don't want to buy new cylinders that I might only fly behind for a short time and then toss at overhaul if it's not necessary.

What would you do?

I guess it depends on what precipitates the top end overhaul. Valve issues? Are they easily lapped? Are the valves themselves gummed up and getting sticky in the guides? Is it burning more oil? Is it due to contamination or metal? Are you losing a wrist pin? The why is everything.

No one wants to find out the hard way that a cylinder can fail spectacularly, but I'd think good careful maintenance could prevent a surprise of this kind.

It's a tough question, I agree. A full overhaul of a 470 is not cheap, probably 3-4 times the cost of a top overhaul, as most of the parts and labor are in the bottom end, so if you think you can make that go to a full 2000 SMOH and beyond, a top overhaul might be worth it.

But like most everyone else in this thread, I say run it and watch it. I think it will give you ample warning.