TOP OVERHAUL ON MIDLIFE CONTINENTAL

[Alan Maurer]

Having read Mike Busch's essay on tops called "Be Afraid" and one of several issues being preload on the assorted. bolts ....he talks about proper lubrication of 

the fasteners that attach a cylinder to the case. We spoke of this at Sarasota Avionics and was told that the instructions from Continental to attach a cylinder

call for doing this "dry" .......Mike says any cylinder work is scary business. Has anyone done a top overhaul on a mid life IO550  lately?  And WHY?

Cheers

Alan

N913ND

[DonMuncy]

I do not think a top overhaul is ever a good idea. In my opinion, cylinders should only be changed when there is a proven need to replace one, and then only the one that is bad. I adhere to Mike Busch's theory that cylinders are bolt-on accessories. If you had two alternators, would you replace both when one goes bad. 

[carusoam]

Hmmmm….

The way to need a top OH for an Ovation….

Is to enjoy high speed cruising in flaming dragon mode….  

 

If you are part of the CB club of LB owners…. And you cruise LOP above 10k’… keeping CHTs below 380°F… and climb ROP using the blue or white box technique….    Cylinders go way past the halfway point before needing service…

TC’d engines are more likely to live the life of the flaming dragon… because their MPs are much higher than the NA engines… and cooling is harder to come by in the FLs…

 

As far as following the procedure… expect that the cylinder shop or Continental have easy to follow instructions… including the order of execution… and other fine details…

PP thoughts only, not a mechanic…

Best regards,

-a-

[kortopates]

....he talks about proper lubrication of 
the fasteners that attach a cylinder to the case. We spoke of this at Sarasota Avionics and was told that the instructions from Continental to attach a cylinder
call for doing this "dry" .......

Something got miss communicated because Continental does Not call for using “dry” torques but the “wet” torques that Mike talks about.

It’s much more complicated than wet vs dry. Some mechanics have been known to not even torque the cyl thru bolts on the opposite side, because a significant amount of dismantling must be done to get access to them. Yet other mechanics are very thorough in doing this and will also replace the cylinder fasteners to ensure proper torquing using a calibrated torque wrench as well as keep the thru bolts torqued with torque plates while multiple cylinders are off.
But every once in awhile we’ll see an engine shed cylinders that weren’t properly torqued so Mike is doing his best to educate us on risks. When you consider that a good number of cylinders are replaced well before necessary, on the basis of a single compression test, the added risk of top overhauls is seldom warranted.


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[carusoam]

Great details Mr. K!

Thank you for sharing them…

Best regards,

-a-

[Guest]

Cylinder replacement is more commonly a Continental issue than a Lycoming issue. Continental cylinder have never been as good as a Lycoming cylinder.  They suffer from head cracking, and poor compression.  Replacing one is not rocket science if you’re willing to read and follow the instructions.

[A64Pilot]

Top overhauls are a fact of life with big bore Conti’s, they should be expected and are I’m afraid normal.

Some cylinders do go until engine overhaul, but they are the exception not the rule.

You can Top one at a time, but it will cost WAY more to do that, and you open yourself up to being more likely to get an incorrect torque.

If all are done at once them almost certainly your done until TBO at least, and as they are ALL off then ALL nuts are torqued. The exception to that is infant mortality, if one goes bad in a couple of hundred hours, I wouldn’t replace them all, just the bad one, but if your approaching say 1500 hours, you did well actually.

Next door neighbor had his Bo topped with all six a few months ago, with no issues.

Another neighbor had all four cylinders overhauled on his O-360 Lycoming that is only a few hundred hours from a Lycoming overhaul, Lycoming had already paid for one maybe two cylinders due to leaking valves, this time he wanted them all done.

Having to replace jugs every so often is a fact of life owning an airplane, just as exhausts are. Just be sure an experienced professional does it and other than a hit in your wallet you will be fine.

[Pinecone]

18 hours ago, A64Pilot said:

If all are done at once them almost certainly your done until TBO at least

Maybe.

One airplane I looked at, a 252 with TSIO-360 was overhauled in 2010.  Overhauled again in 2011.  Then was topped (all 6) in 2019, then have one removed and reworked in 2020 and another one in 2021.

I passed.

 

[Fly Boomer]

38 minutes ago, Pinecone said:

Maybe.

One airplane I looked at, a 252 with TSIO-360 was overhauled in 2010.  Overhauled again in 2011.  Then was topped (all 6) in 2019, then have one removed and reworked in 2020 and another one in 2021.

I passed.

 

I would pass on the mechanic/shop/cylinder provider OR examine how it was flown.

Ham Fist=Many Cylinders

Especially Continental TSIO.

[DonMuncy]

In my opinion (and experience) many Continental top overhauls and cylinder replacements are a waste of money. Many have been done on the basis of one -time low compression numbers, rather than following Continental's recommendations when low compression numbers are found.

[DonMuncy]

Just to clarify, after I had my 231 for a nunber of years, I went back through my log books and found about 5 cylinder replacements. (One during my ownership). As near as I can determine (and in my case, I know), it would go in for annual and the A&P/IA would check the compressions. They would find one low and reccommend replacement of the cylinder. 

Continental says, if you find a low cylinder, go fly the plane for a an hour or so and re-check the compressions. Chances are, it will be back up within normal range. If one continues to read low, do a borescope and find out why. Only when a non correctable problem is found should you replace the cyinder.

I have not replaced a cylinder since.

[Fly Boomer]

1 minute ago, DonMuncy said:

Just to clarify, after I had my 231 for a nunber of years, I went back through my log books and found about 5 cylinder replacements. (One during my ownership). As near as I can determine (and in my case, I know), it would go in for annual and the A&P/IA would check the compressions. They would find one low and reccommend replacement of the cylinder. 

Continental says, if you find a low cylinder, go fly the plane for a an hour or so and re-check the compressions. Chances are, it will be back up within normal range. If one continues to read low, do a borescope and find out why. Only when a non correctable problem is found should you replace the cyinder.

I have not replaced a cylinder since.

Good man!  I don’t agree with everything Mike Busch says, but replacing cylinders “on condition” if, and only if, they can’t be saved just makes sense.

[A64Pilot]

4 hours ago, DonMuncy said:

Just to clarify, after I had my 231 for a nunber of years, I went back through my log books and found about 5 cylinder replacements. (One during my ownership). As near as I can determine (and in my case, I know), it would go in for annual and the A&P/IA would check the compressions. They would find one low and reccommend replacement of the cylinder. 

Continental says, if you find a low cylinder, go fly the plane for a an hour or so and re-check the compressions. Chances are, it will be back up within normal range. If one continues to read low, do a borescope and find out why. Only when a non correctable problem is found should you replace the cyinder.

I have not replaced a cylinder since.

While Conti does have an SB that’s years old about how to correctly do a compression test, I’d say it’s applicable for all engines, you shouldn’t replace a cylinder based solely on compression, I’ve staked valves and that “fix” a valve another said needed to be replaced. But for instance if you find a burnt exh valve, the Jug’s coming off.

Maybe it was just a stuck rotator and the others are fine.

No matter what a good mechanic always determines most likely cause of failure

Now as I can DIY this stuff and my times free, if it’s just a valve then I’d have just the valve and probably guide replaced and put it back together.

But average guy has to pay labor, and sometimes if you have to it’s cheaper in the long run to overhaul the cylinder and or if all are weak to just have the whole lot done.

Sometimes you can be penny wise and pound foolish.

But it’s common to have to top Conti’s mid time, especially if they are run hard habitually.

[BDPetersen]

My 310 had an IO-470D with Cermichrome cylinders. One at a time, they got replaced. They let you know. It’s less financial stress  than all at once and you always have something to do in your spare time. The last cylinder had a broken ring and made serious metal. The engine went to IRAN. But I miss that plane . . .

[Guest]

One of my clients had his Cirrus engine overhauled by Powermaster Engines in Tulsa.  They disassemble all of the new Continental cylinders, fix the many issues then reassemble them.  300 plus hours later the compression reading are as good as any Lycoming cylinder.

[Phil EF]

Is there a specific issue with one or more cylinders that prompted the question?

Both Continental and Mike offer sound, specific, reasonable procedures to deal with a variety of cylinder issues short of removal. 

[Alan Maurer]

With around 900 hours since new , compression checks with engine hot turns up compressions in the middle fifties. Boroscope did not show any particular damage

and I do not know where the air leaks out. In any event the engine develops full power on take off and runs very smoothly. my plan is just to recheck  in a month or two

as I am not at all anxious to think about a top overhaul. Exhaust valves looked good!

[DonMuncy]

9 hours ago, Alan Maurer said:

With around 900 hours since new , compression checks with engine hot turns up compressions in the middle fifties. Boroscope did not show any particular damage

and I do not know where the air leaks out. In any event the engine develops full power on take off and runs very smoothly. my plan is just to recheck  in a month or two

as I am not at all anxious to think about a top overhaul. Exhaust valves looked good!

If your A&P has a little time, and you have a little money, you might have him check after a few hours of flight. I have seen a couple of Continental cylinders in the 50s. Then and after a flight, those would be back to the 70s, and different one or two would be low. 

I think you are right to give it some time.

 

[Fly Boomer]

On 8/25/2022 at 5:07 PM, A64Pilot said:

But it’s common to have to top Conti’s mid time, especially if they are run hard habitually.

^^^this^^^

[Fly Boomer]

10 hours ago, Alan Maurer said:

plan is just to recheck  in a month or two

I'd say check after some number of hours, but you may fly more consistently than i do.

[A64Pilot]

I was an A&P before I was a pilot so what exactly a pilot can and can’t do I’m not sure about.

‘But I can see no logical reason why a pilot wouldn’t be allowed to do their own compression test. The equipment is simple and relatively inexpensive.

This is a good one with the master orifice at .040. To do the Conti test correctly you need a master orifice and it needs to be .040, not .060.

https://www.aircraftspruce.com/catalog/topages/atsdifferentialtesters_kit2.php?clickkey=4690

[Guest]

Continental SB03-3 and Lycoming SI1191A Continental uses a master orifice tool, or a compression tester with the orifice built in. Lycoming does not use the master orifice tool.