New Engine or Just Heads?

[rmciottijr]

Well we just found out the we lost two cylinders in our 172H with a Continental O-300 and 150 hours until recommended TBO. At our last annual the compressions were a little low but we have not been flying much and the mechanic said they may increase a little if we fly it more. Well we put a lot more hours on it this year (thanks Rob) and we all know that is better for the plane. Well after a long 23 hours round trip out west we went to take the plane out the next weekend and found the problem. Now we are at a crossroad we have an engine the lost two cylinders with TBO in 150 hours. we could just replace them for $3500 but with a lot of hours on 3 of the 4 good cylinders. Or we could replace the engine for $18,000-$25,000. I need to add a little more info to the post like compression # before and after the annual, hours on the other cylinders but I would looking for any suggestions. also money is an issue.

 

[flyersfan31]

Be more specific with the "problem" you found, and the rationale for needing new cylinders. I think this will turn into a very interesting discussion.

 

[ScottM]

TBO is not a magic number that requires you, for part 91, to immediately overhaul or replace your engine. If you are getting good compressions and things look ok for the engine bottom then getting two new cylinders and running for another 1000 hours may be possible. Of course depending on the engine and a bunch of other variables.

But you are seeing that there may be more things that will have to be worked on as the engine gets used more. Those first two cylinders might be the canary in the coal mine for the other two that you say are starting to show lower compressions. By the time you give a good inspection to them and the bottom you will be in it for more the 3 or 4 grand. So perhaps it is time to do a major overhaul and get a little piece of mind.

 

[rmciottijr]

Well, I wanted this to be a Poll but for some reason I can not get the polls to work. if the MC could make this a poll that would be great.

1. Replace the two cylinders and hope the other last longer the 150 hr.

2. Replace the engine.

Thanks

 

[poadeleted20]

With 1650 on that engine, and two cylinders gone, the general rule is you'd be penny-wise but pound-foolish to do anything but a full overhaul now, especially if the engine is more than 12 years old. OTOH, if your oil analyses are good, and oil consumption is low, and the other four cylinders check out fine, you can do this. However, if in a couple of hundred hours you find need of a full overhaul, you will end up having to overhaul those two cylinders along with the other four in order to be able to describe the engine as "overhauled." While there is no regulatory need for an "overhauled" engine, down the line, if you want to sell it, the engine will show like 2400 SMOH even if it was "almost" overhauled at the 1800 hour mark.

Also, my experience with the O-200/300 series engines is that they usually need a "top" at around the 1200 hour mark, so if you've made it to 1650 without any cylinder work, you're probably ahead of the game even if you overhaul it now.

 

[rmciottijr]

Be more specific with the "problem" you found, and the rationale for needing new cylinders. I think this will turn into a very interesting discussion.

Well I was not able to sit with Tom (form Wing) today but what I got form him in our first conversation was that one Cylinder has 0/80 compression and the second one had 50/80. They did not dig into the engine yet until I talked to the other members.

 

[gismo]

Well I was not able to sit with Tom (form Wing) today but what I got form him in our first conversation was that one Cylinder has 0/80 compression and the second one had 50/80. They did not dig into the engine yet until I talked to the other members.

Chances are the cylinder with 0/80 has a valve that's missing a chunk of metal or a valve is stuck open. Either way a borescope inspection would easily identify the source of the problem and would be a very good idea before anyone starts removing cylinders or removing the engine for overhaul. And most importantly, if you're thinking of repairing or replacing the "bad" cylinders have the other two borescoped before making that decision and take a good look at the cam once the two cylinders are removed.

Are both of the problem cylinders on the same side of the engine? Does the plane have a multi-cylinder engine analyzer? What's the condition of the baffles?

 

[Rob Schaffer]

flyersfan31Re: New Engine or Just Heads?
Be more specific with the "problem" you found, and the rationale for needing new cylinders. I think this will turn into a very interesting discussion.

Little further Info:
June Annual - 1596 Tach Hrs on Engine
The engine had the two rear jugs replaced on it already. It has been running fantastic and super smooth, just like the O-300D is known for. Engine performance comparing my flying to Windwood WV and Bob's Kansas trip shows nearly book values for fuel burn and mph speeds at 4500, 5500, and 7500 feet altitudes.

Oil was changed at Annual (june) and just changed at the beginning of November before Bob's trip. Oil was lower than typical after the last leg of the return from Kansas. Didn't think much of it at first, since it was quite a long series of legs that day.

Plane sat for 1 week, till I went out this past Sunday to go meet you guys for Lunch at Chester County. Primered the engine with 3 strokes, and she started right up, but was extremely rough and sounded very different. Barely held 1000 rpms. Oil pressure in green, temp needle didn't move yet. Thought maybe a fouled plug, but it still didn't feel right. Set rpms at 1200 and leaned while in the parking spot. Checked Left mag, and she quit. Started up right away again when put back on both mags. Let it idle at 1000 for about 30 seconds, verified again the oil pressure on lower half of the green on the guage, but in the green. Leaned again, raised rpms to 1200 for 30 seconds or so. switched to left mag, ran really rough but continued to run, back to both, smoother than initial startup, but very rough and abnormal. Went to right mag, very rough, something definitely not right. So I shut her down as I didn't want to try to push anything on the engine not knowing what this could be.

Unloaded Ally and buttoned up the plane, drove for lunch.

After lunch, Bob met me back at the airport. He just started it up as I was walking across the ramp, and it really wasn't sounding right. Almost like it was missing or a light 'backfire'/popping sound in a rythmic timing. He shut it down as well within about 45-60 seconds. He checked mags too, and had the same vibration/sound/etc with the engine.

The plane now has 1640 tach hrs on engine. Tom pulled it in and apparently ran it too, briefly, and checked compression. Apparently the middle cylinder on one side and one of the back ones are the problem ones. The loss of oil more than normal on the last leg may be an indicator of oil passing out of the cylinder, not sure.

So, if two cylinders are replaced, the engine will have 3 originals, two new, and one with a decent number of hrs on it.



No engine anylizer or EGT temp guage. Typically run with leaning right after startup, and once reaching cruise or level flight above 2500 feet. Lean the mix while watching rpms and listening.

 

[gismo]

Little further Info:
June Annual - 1596 Tach Hrs on Engine
The engine had the two rear jugs replaced on it already. It has been running fantastic and super smooth, just like the O-300D is known for. Engine performance comparing my flying to Windwood WV and Bob's Kansas trip shows nearly book values for fuel burn and mph speeds at 4500, 5500, and 7500 feet altitudes.

Oil was changed at Annual (june) and just changed at the beginning of November before Bob's trip. Oil was lower than typical after the last leg of the return from Kansas. Didn't think much of it at first, since it was quite a long series of legs that day.

Plane sat for 1 week, till I went out this past Sunday to go meet you guys for Lunch at Chester County. Primered the engine with 3 strokes, and she started right up, but was extremely rough and sounded very different. Barely held 1000 rpms. Oil pressure in green, temp needle didn't move yet. Thought maybe a fouled plug, but it still didn't feel right. Set rpms at 1200 and leaned while in the parking spot. Checked Left mag, and she quit. Started up right away again when put back on both mags. Let it idle at 1000 for about 30 seconds, verified again the oil pressure on lower half of the green on the guage, but in the green. Leaned again, raised rpms to 1200 for 30 seconds or so. switched to left mag, ran really rough but continued to run, back to both, smoother than initial startup, but very rough and abnormal. Went to right mag, very rough, something definitely not right. So I shut her down as I didn't want to try to push anything on the engine not knowing what this could be.

Unloaded Ally and buttoned up the plane, drove for lunch.

After lunch, Bob met me back at the airport. He just started it up as I was walking across the ramp, and it really wasn't sounding right. Almost like it was missing or a light 'backfire'/popping sound in a rythmic timing. He shut it down as well within about 45-60 seconds. He checked mags too, and had the same vibration/sound/etc with the engine.

The plane now has 1640 tach hrs on engine. Tom pulled it in and apparently ran it too, briefly, and checked compression. Apparently the middle cylinder on one side and one of the back ones are the problem ones. The loss of oil more than normal on the last leg may be an indicator of oil passing out of the cylinder, not sure.

So, if two cylinders are replaced, the engine will have 3 originals, two new, and one with a decent number of hrs on it.



No engine anylizer or EGT temp guage. Typically run with leaning right after startup, and once reaching cruise or level flight above 2500 feet. Lean the mix while watching rpms and listening.

Running OK before last shutdown and then being very rough on the next start after cooling down sounds very much like a stuck valve. If a pushrod hasn't bent the could potentially be fixed without removing the cylinder. Pulling the rocker cover would likely allow confirming this diagnosis.

 

[rmciottijr]

Running OK before last shutdown and then being very rough on the next start after cooling down sounds very much like a stuck valve. If a pushrod hasn't bent the could potentially be fixed without removing the cylinder. Pulling the rocker cover would likely allow confirming this diagnosis.

When I was landing and taxing I didn't feel a thing. As posted before I am going to see it the mechanic can do a bore-scope inspection and see if that shows anything.

 

[SCCutler]

If the engine is otherwise sound, I'd put on two overhauled cylinders.

 

[Bob Bement]

In Barnstormers.com there is a complete engine 145-2 cont. with a top overhaul of 254 hours complete with price of $3700. Not only do you get 6 cylinders, but mags, carb, harness, and all. Page eight under Cont. Engines. ( no offer refused and non prop strike.)



Recommend This Ad to a Friend •

 

[timwinters]

If the engine is otherwise sound, I'd put on two overhauled cylinders.

+1

but, that "if" is a big if.

We need much more info on the engine to make an informed recommendation.

How long ago was it overhauled?

How's the oil analysis been?

Has it sat idle for extended periods?

What's the borescope look like?

etc?

With 1650 on that engine, and two cylinders gone, the general rule is you'd be penny-wise but pound-foolish to do anything but a full overhaul now.

That must be a "general rule" that I'm not aware of and that Mike Busch definitely doesn't espouse. http://www.savvyaviator.com/

I don't agree with everything that Mike advocates but he makes many good arguments (backed up with data) that if your engine isn't telling you that it's about to die then don't kill it just because it's near TBO.

 

[kmead]

I may be cheap, but I would repair the two cylinders and put the engine back in service.
The big problem with a high time engine is that you may find a bad cam or lifter once the cylinders are removed, then it's time for the major overhaul.

The second engine on my Malibu went for some 2600 hrs and only one cylinder pulled since factory reman. It only had 1 CHT and 1 TIT (factory original) indicators up to that time. The turbocharged engines don't always show a dead or very low compression cylinder.

Kevin

 

[GMascelli]

In Barnstormers.com there is a complete engine 145-2 cont. with a top overhaul of 254 hours complete with price of $3700. Not only do you get 6 cylinders, but mags, carb, harness, and all. Page eight under Cont. Engines. ( no offer refused and non prop strike.) Recommend This Ad to a Friend •

CONTINENTAL C145-2 ENGINE ​

 

[d.grimm]

What's your plan for the airplane? A long time keeper or going to turn it?
In my experience, running the little Continentals above TBO cost you more because of bearings that start digging into cranks and cams, etc,etc.
If I was keeping the airplane I would do more than cylinders. I like the used engine idea, a friend just rebuilt his 170's engine and it cost close to $18,000.
Dave

 

[Gary]

Bob and Rob:

This is a bummer! For what it's worth, seems as though you are going to spend some $$ to find out how many $$$$ you are going to spend to get it fixed AND get the confidence to fly behind the engine.

If it was running fine before the shut down and then had the problems you mention, rough running, backfire and a 0 compression on one cylinder leans me in the direction of a stuck/burned/chipped exhaust valve (at least on that cylinder). The borescope idea (all the cylinders) as a first step is easy and may help a lot in determining the problem. Although the total hours are a concern, I don't think that, with the information at hand, the engine is trashed and requiring a complete overhaul.

Guess I'd find out the answer to the failure of these two before making the decision. Although not exactly cheap, pulling a cylinder or two will give you a look opportunity to inspect the case, you can then decide if a overhaul is necessary and what other items may need replacing. Not sure what overhauled O-300 cylinders are going for nowadays, and I'm not sure what cylinder work Tom at Wings can do, but it's worth the time to explore. The engine on Barnstormers isn't a bad deal, of course that's a bit of a crap shoot as well. All this will take is time and money!

Gary

 

[Tom-D]

With 1650 on that engine, and two cylinders gone, the general rule is you'd be penny-wise but pound-foolish to do anything but a full overhaul now, especially if the engine is more than 12 years old. OTOH, if your oil analyses are good, and oil consumption is low, and the other four cylinders check out fine, you can do this. However, if in a couple of hundred hours you find need of a full overhaul, you will end up having to overhaul those two cylinders along with the other four in order to be able to describe the engine as "overhauled." While there is no regulatory need for an "overhauled" engine, down the line, if you want to sell it, the engine will show like 2400 SMOH even if it was "almost" overhauled at the 1800 hour mark.

Also, my experience with the O-200/300 series engines is that they usually need a "top" at around the 1200 hour mark, so if you've made it to 1650 without any cylinder work, you're probably ahead of the game even if you overhaul it now.

Pretty much agree, with a couple thoughts.

oil consumption is determined by the oil control rings, replacing the cylinders with new ECIs will cure that. NEVER overhaul the 50CI cylinders from Continental. It's been proven many times they will crack at or near 3000 TT on the cylinder. plus the cost of overhauling a cylinder is near the cost of new plus the "ECI Titon" has exhaust valve rotators STCed into the new cylinder, which makes the cylinder go to TBO with no major problems.

We don't know (or I missed it) the total time on the lower end. the 1600 may be time since last overhaul. If so we don't know if the crank will be usable again. nor do we know the sump is good, early 172's have a habit of corrosion in the sump.

How do you prove the lower end is good? oil pressure is a clue, but not proof.

spending the money of the new cylinders and not have a "0" since overhaul entry in the log is nota smart move in my humble opinion.

 

[ScottM]

the "ECI Titon" has exhaust valve rotators STCed into the new cylinder, which makes the cylinder go to TBO with no major problems.

Except for the airworthiness directives telling you that you need to remove them from service after 300 or so hours TIS

Sorry, could not resist. After getting burned twice by ECI ADs and having to top my engine twice in 3 years, I am not by any stretch an advocate of their products.

 

[Dan Thomas]

Those little Continentals have several habits:

1. Their exhaust valves burn easily, usually when the guide wears and lets the valve whack the seat a little off-center and start leaking.

2. The valve stems sometimes varnish up and stick in the guides. Common morning sickness.

3. Infrequent use causes sludge formation in the engine, and that sludge makes the lifters' internal hydraulic pistons stick and hold the valve off the seat when the engine's cold. More valve leakage and burning.

All of this could be fixed with a top O/H, but you'd want to do all the cylinders. But if it's an old engine with lots of short flights on it, you'll probably find pitted lifter faces, pitted cam, and if the oil pump leaks down, maybe worn rod bearings near the front of the engine.

Seems to me that O-300 cylinders are the same as the O-200's?

Dan

 

[Tom-D]

Those little Continentals have several habits:

1. Their exhaust valves burn easily, usually when the guide wears and lets the valve whack the seat a little off-center and start leaking.

2. The valve stems sometimes varnish up and stick in the guides. Common morning sickness.

3. Infrequent use causes sludge formation in the engine, and that sludge makes the lifters' internal hydraulic pistons stick and hold the valve off the seat when the engine's cold. More valve leakage and burning.

All of this could be fixed with a top O/H, but you'd want to do all the cylinders. But if it's an old engine with lots of short flights on it, you'll probably find pitted lifter faces, pitted cam, and if the oil pump leaks down, maybe worn rod bearings near the front of the engine.

Seems to me that O-300 cylinders are the same as the O-200's?

Dan

They are known as the 50CI cylinders, do the math 50X4 = 200, 50 X 6 = 300?

If the engine is a first run core, I'd expect none of what you advocate will be seen in the engine.

 

[Dan Thomas]

They are known as the 50CI cylinders, do the math 50X4 = 200, 50 X 6 = 300?

If the engine is a first run core, I'd expect none of what you advocate will be seen in the engine.

I had already done the math. And what I proposed as possibilities are all from my experience with the things. First-run cores aren't immune to corrosion, sludging, sticking valves, and worn guides, especially at 1640 hours, and especially if that's 1640 since it was new 40 years ago.

Dan

 

[steingar]

Wow, you guys sure are brave. If it were me flying over all those big nasty mountains I'd want the new engine and would mortgage my eye teeth to get it. You really have nads of adamantium, willing to fly behind a questionable engine over hostile terrain.

 

[Rob Schaffer]

I had already done the math. And what I proposed as possibilities are all from my experience with the things. First-run cores aren't immune to corrosion, sludging, sticking valves, and worn guides, especially at 1640 hours, and especially if that's 1640 since it was new 40 years ago.

Dan

It's not the origional, IIRC from the logs, it is the third.

 

[Tom-D]

It's not the origional, IIRC from the logs, it is the third.

Then you don't know what size crank you have in it. might as well get as much time from that crank as it will allow, put 6 new cylinders on it and go for as much time as you can.

 

[Rob Schaffer]

Wow, you guys sure are brave. If it were me flying over all those big nasty mountains I'd want the new engine and would mortgage my eye teeth to get it. You really have nads of adamantium, willing to fly behind a questionable engine over hostile terrain.

It was never questionable till Sunday. It ran very smooth and reliable. Leaned the same with respective flight altitudes and air temps, climbed predictiblly with weight and DA's. In SE PA here, we're pretty flat, and going to Windwood was 27 hrs ago. we'll get it fixed and fly behind it for a while to trust everything before the next big trip.

Then you don't know what size crank you have in it. might as well get as much time from that crank as it will allow, put 6 new cylinders on it and go for as much time as you can.

Bob is going to get the logs Monday and go through them to list out when specific items were done/by who/and when. Thanks for talking to him today, shareing your knowledge is very much appreciated. I'm sure we will be in contact again once we gather more facts and info.

 

[flyingcheesehead]

Wow, you guys sure are brave. If it were me flying over all those big nasty mountains I'd want the new engine and would mortgage my eye teeth to get it. You really have nads of adamantium, willing to fly behind a questionable engine over hostile terrain.

Sheesh. It sure sounds to me like once the engine became questionable, they didn't fly it AT ALL.

A "new" engine is by no means a panacea - Until it's got a bunch of (400?) hours on it, you don't really know that everything was properly installed at the overhaul - It may shake itself to pieces any second. I felt quite all right with flying a TBO+800 engine over the Rockies, because it was a known quantity.

*Always* pay attention to the engine, it will talk to you. Whether it's fresh out of the engine shop or TBOx2, it may quit at any moment.

Bob and Rob, definitely haven't seen enough info on this thread to make a decision other than "keep investigating."

FWIW if you do need an overhaul, I highly recommend you consider Poplar Grove Airmotive - I know Penn Yan is a lot closer, but I wouldn't be surprised if they charge the big-name price. PG is one of the top 4 or so overhaulers by volume, but I haven't heard the name outside local circles and out of the 5 options considered for our latest overhaul, they came in the least expensive. The engine had previously been overhauled by PG, and made it to TBO + 951. Post-overhaul, it's been clear that their use of a test cell helped immensely, the rings must have been seated before the engine even was hung on the airplane - We've only burned 2 quarts in 31.3 tach hours since the overhaul, and the engine just hums - I don't think it could possibly run any smoother. We'll certainly go back to Poplar Grove next time we need an overhaul.

 

[Trapper John]

How much over the $18-25k would it cost to do a fixed-pitch O-360 conversion?


Trapper John

 

[Tom-D]

How much over the $18-25k would it cost to do a fixed-pitch O-360 conversion?


Trapper John

How much can you get the engine for?

 

[Tom-D]

FWIW if you do need an overhaul, I highly recommend you consider Poplar Grove Airmotive - I know Penn Yan is a lot closer, but I wouldn't be surprised if they charge the big-name price.

Why not have your local A&P do it ?

These engines are not that difficult to do, disassemble, clean, send the cases to Chuck Ney, send the crank, rods and cam to Aircraft services, buy new crank/rod bearings/ 12 new hydraulic units and 12 new lifter bodies, 6 new ECI cylinders, a gasket kit repaint, inspect the other parts and reassemble IAW the overhaul manual.

That is the same engine you'll get from any body. get involved with your engine, control the parts bought and the money spent at the local level.

 

[SCCutler]

See, I think I want a genuine Downey overhaul.

 

[flyingcheesehead]

Why not have your local A&P do it ?

Because our "Local A&P" is a big expensive FBO that would probably charge as much or more, for lower quality work.

Seriously, when the engine goes to 951 over TBO, and the shop that did the overhaul gives you the least expensive quote to do it again - You go back there.