What do you think about a Continental 0-300D with 40 years SMOH?

German guy

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Thoughts on a Continental 0-300D with 40 years SMOH?

I received today the result of the pre-buy inspection of the Cessna 172 we want to buy. Besides of a nuber of smaller issues, the plane is in a good shape for its age.

It turned however out that its O-300D engine had been overhauled almost exactly 40 years ago and ran only 1,500 hours since then. When I spoke with the seller, hew claimed that is had around 1,400 hours on the clock and that he does not remember exactly when it had been overhauled, but that it was relatively recently. Well, this is obviously in the eye of the beholder. ;) To his defense I have to say that the discrepancy of the hours was caused by a past error in the logs.

According to the guy who did the pre-buy inspection, the engine log shows all kinds of past trouble with the engine, including two replaced cylinder and a number of stuck valves. Compressions were 69/80 58/80 78/80 70/80 69/80 78/80. My understanding is, that these values are not great but OK for this type of engine. He also expressed his low opinion on the O-300D in general and suggested that we should replace the engine shortly. Not because there is something wrong with it right now, but because of its age and the because O-300Ds would be generally troublesome.

I spend the entire evening with additional (I had already done quite a lot of reading before) research on the O-300D. Besides of the sticking valve issue, of which I was aware of and which seems to be related to insufficient leaning and the high lead content of today's AVGAS, I was still not able to find anything negative about the engine. Quite the contrary - the consensus seems to be that it is not exactly a race horse but very reliable and smooth.

My questions are, whether I missed something about this engine in general and what you think about it age? Do we HAVE to replace it immediately or could we run it with good conscience another 2 or 3 hundred hours, as long as runs nice and doesn't excessively leak or burn oil?

We'd be willing to have it overhauled, an upgrade to a different type of engine would IMHO however be cost prohibitive.
 
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O-300s are Smoooooooth.

40 years and 1500 hours = 37.5 hours/ year. Combine that with signs of wear and you're looking at overhauling/remaning the engine for sure.
 
Is it making metal ? Are you planning on using it in any kind of commercial operation ?
 
Thank you for your quick replies.

Art VanDelay said:
Is it making metal ? Are you planning on using it in any kind of commercial operation ?
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No (from what I was told) and no.

Admittedly, I have no experience with aircraft engines. From working on cars and motorbikes, my understanding is however that old age alone does not lead to catastrophic failures but rather to hardened polymer seals, what again leads to oil leaks and an increased oil consumption. Another potential risk is corrosion inside the engine, if the engine sat for longer times and especially if condensation was an issue.

I don't want to take risks but don't want to have it sitting in a shop for multiple weeks during the best time of the year either. And, admittedly, I don't want to spend money on a not yet necessary overhaul.

The hope is to be at least able to fly with the engine until next winter. If an immediate danger exists, I would however eat the pill and have it done right away. This is however assuming, that the seller accepts my new, lower offer... :rolleyes2:
 
It sounds airworthy. If it is, you can fly it indefinitely (for at least till the annual) unless it develops symptoms. I would consider it a run-out, I would plan and budget for an overhaul or replacement, and I would fly it with careful monitoring for as long as it seems to be ok.

That IS a smooth engine.
 
After sleeping on it for a night and a discussion with my wife, we decided that we want to fly it for this summer, but to pull the engine next winter, no matter how nicely it runs. Mainly for the peace of mind.

The seller wants to let us know by this afternoon, whether he accepts our revised offer.

So, assuming we will actually buy this plane and fly it until next winter – is there, other than temperatures and oil consumption, anything in particular we need to monitor? I would not expect catastrophic failures, based on what I read about when and how such things happen over the life of en engine. Any thoughts / experiences on this?
 
Oil analysis and bore scope would help estimate time left on the engine. Factor in either a new engine or overhaul to be on the safe side. Good luck.
 
I have a 1420 hr since new engine put in in 1979. As part of the pre-buy we did the standard compression test, but also boroscoped the cylinders. The values were so clean, that we could read part numbers. The faces all looked good, and they seated without any "wobble". BUT, I priced the plane at O SMOH, and subtracted the cost of an overhaul, made the offer, and the owner agreed. My AnP/IA, basically said not if, but when, and the engine owes you nothing. I will probably take it down this winter and OH the first run cylinders. There is no metal in the filter, and all constituents are very much in the normal range on the oil analysis. We will look at the cam with the cylinders off, but don't expect to see any spalling. YMMV. But, I would definitely boroscope through the sparkplug wells, and begin oil analysis.
 
German guy said:
After sleeping on it for a night and a discussion with my wife, we decided that we want to fly it for this summer, but to pull the engine next winter, no matter how nicely it runs. Mainly for the peace of mind.

The seller wants to let us know by this afternoon, whether he accepts our revised offer.

So, assuming we will actually buy this plane and fly it until next winter – is there, other than temperatures and oil consumption, anything in particular we need to monitor? I would not expect catastrophic failures, based on what I read about when and how such things happen over the life of en engine. Any thoughts / experiences on this?
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Don't even worry about it, when the 0-300 has good oil pressure the lower end is good, the cylinders are replaceable, no worries there, When the engine has good compression good oil pressure it's good to go.

40 years ago, no problem. Fly it. when the compressions drop, replace all 6 cylinders and fly it again.

the 0-300 was the best engine ever put in a 172.
 
Rcmutz said:
I have a 1420 hr since new engine put in in 1979. As part of the pre-buy we did the standard compression test, but also boroscoped the cylinders. The values were so clean, that we could read part numbers. The faces all looked good, and they seated without any "wobble". BUT, I priced the plane at O SMOH, and subtracted the cost of an overhaul, made the offer, and the owner agreed. My AnP/IA, basically said not if, but when, and the engine owes you nothing. I will probably take it down this winter and OH the first run cylinders. There is no metal in the filter, and all constituents are very much in the normal range on the oil analysis. We will look at the cam with the cylinders off, but don't expect to see any spalling. YMMV. But, I would definitely boroscope through the sparkplug wells, and begin oil analysis.
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Never overhaul a factory 0-300 / 0-200 cylinders. use ECI nickel cylinders and forget ever doing it again. Factory cylinders will crack at or about 3000 hours total time, with cylinders being changed over the life of the engine, you have no clue what you have. simply because we don't track time on cylinders.
 
warthog1984 said:
O-300s are Smoooooooth.

40 years and 1500 hours = 37.5 hours/ year. Combine that with signs of wear and you're looking at overhauling/remaning the engine for sure.
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yep.... in about 20 years :)
 
Tom-D said:
the 0-300 was the best engine ever put in a 172.
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Lolz

They are the least desirable engine.

Yeah they are smooth, having two more jugs will do that.

Best engine in a 172 is the fuel injected 180hp, next would be the XP conversion, last would be the 300d.

Personally I wouldn't buy the plane, the overhaul isn't a big deal, just go off compression (which is iffy shy of it not running for a while) and filter cut plus general exam. Fact is there are tons of 172s, more so than any airplane ever, why get the bastard step child 172.

Heck if it were me I wouldn't buy a 172, nothing wrong with em' just s very blah aircraft.


As for the plane not flying much, frankly with most all of the fleet, if it doesn't have over 10,000 hrs on it, the plane didn't fly much, which is a good thing, you'll notice not many people pay top dollar for a 10,000+hr 172/PA28/etc
 
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Tell your mechanic to look closely at the oil pan and poke at with a screw driver. Some of them are so corroded they develop a hole and leak. Its fairly labor intensive to replace.

Pictures are worth more than a paragraph. You can tell a lot about what is worth just by posting a few pictures.

Rotten exhaust? Bad baffling seals? Lotta rusty fasteners? Holey ducts? ancient ignition harness and magnetos? Corroded spark plugs? The list goes on and on. Any oil filter adapter?
 
Engines are a crap shoot. You could fly it a long time with little trouble or it could fail 15 hours after you buy it.
 
Re: Thoughts on a Continental 0-300D with 40 years SMOH?

German guy said:
It turned however out that its O-300D engine had been overhauled almost exactly 40 years ago and ran only 1,500 hours since then. When I spoke with the seller, hew claimed that is had around 1,400 hours on the clock and that he does not remember exactly when it had been overhauled, but that it was relatively recently.
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What does the engine log say? In any event, you should make your purchase offer based on planning to spend about $20K on an overhaul immediately. Then, any hours you get out of the engine before a need for overhaul is indicated by how the engine is running or the like are freebies.

Quite the contrary - the consensus seems to be that it is not exactly a race horse but very reliable and smooth.
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That's a reasonable statement. But reliability only goes so far, and 40 years with less than 40 hours/year utilization isn't a good thing.

My questions are, whether I missed something about this engine in general and what you think about it age? Do we HAVE to replace it immediately or could we run it with good conscience another 2 or 3 hundred hours, as long as runs nice and doesn't excessively leak or burn oil?
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No way to say based on the information available. One would need to have a good engine mechanic examine the engine (maybe including pulling one jug to look deep inside), as well as a series of oil analyses.

We'd be willing to have it overhauled, an upgrade to a different type of engine would IMHO however be cost prohibitive.
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No need to change engine types, but plan for an overhaul of this one in the near future, and value the plane accordingly.
 
I wouldn't put much faith in the engine. Underuse is not good for an engine ,unless itis pickled during long periods of non use.i like the 0 e300 ,one smooth engine.
 
James331 said:
Lolz

They are the least desirable engine.

Yeah they are smooth, having two more jugs will do that.

Best engine in a 172 is the fuel injected 180hp, next would be the XP conversion, last would be the 300d.

Personally I wouldn't buy the plane, the overhaul isn't a big deal, just go off compression (which is iffy shy of it not running for a while) and filter cut plus general exam. Fact is there are tons of 172s, more so than any airplane ever, why get the bastard step child 172.

Heck if it were me I wouldn't buy a 172, nothing wrong with em' just s very blah aircraft.


As for the plane not flying much, frankly with most all of the fleet, if it doesn't have over 10,000 hrs on it, the plane didn't fly much, which is a good thing, you'll notice not many people pay top dollar for a 10,000+hr 172/PA28/etc
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I'd follow this advise. Makes sense to me. But.....if you do purchase it, it will be exciting each time you take off especially if your based at a short runway, wondering if it will get a hair in its throat and quit. I'd move on. It's old and tired. (You might call charlie at zephyr and see what a major would cost and his opinion on the engine. He's a pro.)
 
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Tom-D said:
Don't even worry about it, when the 0-300 has good oil pressure the lower end is good, the cylinders are replaceable, no worries there, When the engine has good compression good oil pressure it's good to go.

40 years ago, no problem. Fly it. when the compressions drop, replace all 6 cylinders and fly it again.

the 0-300 was the best engine ever put in a 172.
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Tom wrote what I would write. Anybody who says that the O300 is a lousy engine never flew one for 4000 hours like I did. I overhauled it at 2600 more because I came by a hell of a deal on fresh jugs and other parts from a feller that sold his airplane and was going to rebuild his engine but sold it as is instead.

Jim
 
Thank you very much for all your replies, very much appreciated. :yes:

We have a few dozen hours in a Cessna 172F, which is pretty much identical with the 172G, we want to buy. We therefore know what to expect regarding the aircraft's performance and have only the best memories - even though it wasn't the fastest, it was smooth and handled like a dream.

Our initial offer already took into consideration, that the engine will have to be overhauled in the next few years. The new, revised offer is based on the assumption that this needs to be down now. We also have budgeted in the overhaul and have sufficient $$$ in the bank.

Speaking of $$$ - I would love to fly a Mooney, for the around $50k which we have currently available, we could get a really nice M20C and possibly still have a few $ left. After some discussions, we however dropped the idea and conciously decided that we want to have a basic 172. The reasons are, that my wife just got her instrument rating and that I want to work on mine in our own plane. Minimal complexity in combination with nice IFR avionics woud therefore be preferred. An older 172 is as simple as a plane can get, the lower acquisition costs also allow to have some money left for an avionics upgrade and / or other expenses like the overhaul of the engine.

This will also be our first own plane. I know that everybody says that one should buy his last plane first. In our case, this would be a brand new Mooney Ovation. Not only that we could not afford it, I would also continuously be behind the aircraft. A 172 fits our today's mission, and if weekend trips or the occasional flight to Florida take longer, because we are cruising at 105 instead of 140 kts, so be it. The advantages of a 172 outweigh, at least for us as new owners, the speed penalty that comes with it - it is dirt simple, what reduces the risk of unexpected expensive repairs and the availability of spare parts is second to none. The idea is therefore to fly the 172 as a low risk, low cost airplane for a few years and to gain experience as pilots and as owners along the way. If we then still find that the 172 is just the perfect plane for us, great. If not, we will by then have a much better understanding of which plane suits our needs the best.

Listening to what Tom-D ans Weirdjim said, but also based on my own additional digging into this topic, I came to the opinion that the age itself does not create an immediate danger. If the seller accepts our offer, we'll fly it home, closely watching oil consumption and pressure, as well as temperatures. Once home we'll have, with an A&P, a very close look at the oil, borescope the engine and run another compression test. Then, we'll move from there...
 
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I don't think " everybody says" buy your last plane first. My first plane was an 85 hp aeronca , then a mooney super 21. Then a Stearman, etc. A doctor on the field learned to fly in a mooney, got his instrument ticket in the mooney then traded it for an aerostar. I would buy a mooney 201 instead of a very old tired 172 but that's your prerogative for sure. Of all the people I've flown with, none bought their last plane first. Press on!
 
One thing I didn't see mentioned but is pretty important. Where's this plane been over those 40 years? There's a big difference 'twixt Phoenix and Tampa.

German guy said:
the engine log shows all kinds of past trouble with the engine, including two replaced cylinder and a number of stuck valves. Compressions were 69/80 58/80 78/80 70/80 69/80 78/80. My understanding is, that these values are not great but OK for this type of engine.
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A couple of cylinders and a few stuck valves don't constitute "all kinds of past trouble" considering it's been forty years IMO. I've OH'ed two cylinders in 12 years SMOH on my plane. No biggie. And those compressions are just fine, except possibly for the 58 but that one might come back once you start flying it more regularly.

Hint: Get a MoGas STC and start running a 75% MoGas/25% 100LL blend and the stuck valve issues will go away. Old Continentals love this mix...if you can find 0E MoGas in your area. (It looks like your closest option is 17 miles down the road at the Sunoco on W. Grand River Ave in Brighton.)

German guy said:
After sleeping on it for a night and a discussion with my wife, we decided that we want to fly it for this summer, but to pull the engine next winter, no matter how nicely it runs. Mainly for the peace of mind.
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That's some very expensive (and false) peace of mind. If the engine's running good, if oil analysis is good, if compressions are good, if the bore scope shows no ills, and if the filter is clean, then there's absolutely no reason to OH. In fact, you'll be increasing your chances of engine failure if you do...not lessening it. Worse case scenario, if the soft cylinder doesn't come back up then only OH that one cylinder but even it is well above Continental's allowable minimums.

Unless, of course, you like to spend money just for the sake of spening money!
 
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Good gully....it's a Continental, no wonder the compressions are low. 58/80 doesn't scare me....I'm more concerned with what the valve faces look like.

TCM SB03-3 spells all this out....and 58/80 is more than acceptable when following the SB.
 
Since there are a lot of C145/0300 engines in Cessna 170's take a ride over to the www.cessna170.org forums and ask, lots of good knowledgeable people there that fly these engines, I have a C145, same engine basically and it purs like a kitten,

Yes stuck valves do happen but it has more to do with 100LL from what I have read, use TCP, and or car gas to help that issue.

I will bet if you fly it a lot those compressions will come up some, they are not that bad really.

40 years is a long time but where is this airplane, humid climate, or dry?
 
My io-360 was installed new in 1981, 34 years ago and has about 1400 hrs, it's a Lycoming and has had one jug replaced for low compressions in that time.

Most engines will tell you when they need attention. Yes, catastrophic failures do happen but it is usually more prevalent in recently overhauled engines, not engines that have ran for many years.

I plan to keep flying mine but with a constant ear to how it starts and runs. Oil analysis at every oil change and cam guard because it is a Lycoming.

And for the record I am NOT a big Risk Taker.
 
You are going to find that maybe 40% of the typical single engine piston personal airplanes, such as an old 1966 Cessna 172 or a 1982 Cessna 182, all have old engines and/or propellers.

I have yet to work on an airplane that didn't have a >20 and yes even a 48 year old engine.

What's really shocking is seeing cams crapping out 15 years since new. while others are original >40 years old and never been overhauled.

Some things are predictable but most isn't.
 
My aircraft is a case in point. The brand new engine in a brand new aircraft started making tons of metal at about 700 hours and 4 years. Lycoming and Piper bellied up and put a brand new first run engine in it 1981. It has performed well. Reading through the log books I am not even sure the replaced jug made sense as it hadn't been flying much and that can lead to low compressions. One of the cylinders was showing 68# for a couple years but now routinely runs in the low 70's.
 
My standard question for guys who defend running old and tired engines-

Does that 40 year-old engine run as well and perform as well as a newly overhauled and broken-in engine? Guys who've replaced engines at TBO with remans or other overhauls know that answer. In the overwhelming majority of cases the new engine runs smoother, makes more power, and has better temp spreads. So how does that fit into the advice for somebody else to fly an old engine til it quits? I'd rather fly the best engine I can. I guess different people have different requirements and different expectations. Establish yours.
 
strangebird said:
Yes stuck valves do happen but it has more to do with 100LL from what I have read, use TCP, and or car gas to help that issue.
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I have been repairing, overhauling the 0&C series for a very long time, I remember when they were new. and I've never seen a stuck valve in one. the guides wear, allowing the valve to not seat properly, the valves will warp, and not seat properly, I've even seen a bent valve stem. but for one to stick in the guide. that is very rare. The guides wear too fast for that to happen.

Lycoming's yeah that happens often.
 
Stewartb said:
My standard question for guys who defend running old and tired engines-

Does that 40 year-old engine run as well and perform as well as a newly overhauled and broken-in engine? Guys who've replaced engines at TBO with remans or other overhauls know that answer. In the overwhelming majority of cases the new engine runs smoother, makes more power, and has better temp spreads. So how does that fit into the advice for somebody else to fly an old engine til it quits? I'd rather fly the best engine I can. I guess different people have different requirements and different expectations. Establish yours.
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Do you believe in infant mortality ??
 
Your silly question has nothing to do with the topic or my attitude towards it. In one thread you whine about deferred minor maintenance issues and in another you advocate running old and tired engines. I really don't care what others think and I wasn't looking to argue about it. I was just sharing my thoughts with the OP. He can consider them, dismiss them, or ignore them as he chooses.
 
Stewartb said:
Your silly question has nothing to do with the topic or my attitude towards it. In one thread you whine about deferred minor maintenance issues and in another you advocate running old and tired engines. I really don't care what others think and I wasn't looking to argue about it. I was just sharing my thoughts with the OP. He can consider them, dismiss them, or ignore them as he chooses.
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A tired engine has yet to be proven, just because it is 40 years old. the engine in question has 1400 hours, and there are many more out there operating well over that.
 
Hello everybody,

I am aware that the high lead content of 100LL and insufficient leaning cause the sticking valve issue and that it can be avoided by using mogas and proper leaning. I therefore already conducted some research on where to get mogas ( http://pure-gas.org/extensions/map.html for those who are interested), made sure that Petersen offers an STC (just paperwork, no modification of the aircraft required) and how to safely fuel an aircraft from a can, without blowing myself up.

The Cessna 170 forum as well as Backcountrypilots.org were very resourceful in this regards and also regarding the O-300 engine in general. The many happy O-300 pilots in these and other forums, were also the reason why I was so surprised about the mechanic's negative opinion on this engine type. As I said - other than the manageable sticking valve issue and the lack of power, I could not find anything negative about this engine. Quite the contrary, actually.


When it comes to the overhaul I am, frankly, on the fence. We already factored into our offer that the engine need to be overhauled NOW. We have the money, if it needs to be done, no big deal because this is what we expect. However, now that I slept another night on it ;) , before we actually pull the engine, we will thoroughly inspect it with one of our EAA chapter's mechanics and then make the decision whether we'll have it overhauled right away or not.
Even though I dug even deeper into this topic, I still could not find any reason for failures related to age, other than stiffened polymer parts and possible corrosion issues. I understand that both can be discovered by inspection.

There was also a report in the AOPA magazine a while ago, in which they analysed the relationship between the hours on an engine / its age and accidents. Looking at the result, one should be the more nervous the fresher an engine is:
ulrich_hours-300x202.png


ulrich_years-300x202.png

Source: http://blog.aopa.org/opinionleaders/2014/03/13/do-tbos-make-sense/

In case of 'our' engine (the seller is still thinking about our offer), all cylinders have also been replaced withing the last 20 years, I however don't know whether this means that the cylinder heads were also overhauled at this occasion.
 
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Stewartb said:
My standard question for guys who defend running old and tired engines-

Does that 40 year-old engine run as well and perform as well as a newly overhauled and broken-in engine? Guys who've replaced engines at TBO with remans or other overhauls know that answer. In the overwhelming majority of cases the new engine runs smoother, makes more power, and has better temp spreads. So how does that fit into the advice for somebody else to fly an old engine til it quits? I'd rather fly the best engine I can. I guess different people have different requirements and different expectations. Establish yours.
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In answer to your question I had noticed a drop in performance a year ago. It had me thinking that the engine was talking to me. Shortly after that I started seeing a higher than expected drop in rpm at run up. A new set of plugs took care of that but still didn't have the power I once had. Finally the symptom presented itself to a friend flying my airplane in the form of high CHT and a rough run. Found a clogged fuel injector so all were cleaned and since then the engine has came back to full power and makes book speeds again.
 
First, I'd price the Skyhawk as one that needs a major. Wouldn't do it any other way.

Second, if I had the money for a Mooney I'd be all over it. Damn things are fast, and have a nice price point for aircraft that are. That said, you have to be mindful of your mission, what you're going to do when you're done with your IR. I assume you guys are doing this because you want to go places. That Mooney is going to do that far more quickly than the Skyhawk.
 
If it runs good, it runs good, the chances that you get a few more years out of it with minor expenses is pretty high. If it is blowing by a lot of oil out the breather, you may need a new front crank seal, no worries, they are not an expensive proposition, I had both done on my 310 for $300 some.
 
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