Top End Overhaul - Questions

[irishpilot]

No missing or broken rings. The #4 piston was the worst but all four have blow by. With the amount of work it takes to pull the top end apart, I don't feel that comfortable just throwing new rings in. It may get to TBO, it may not.

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[Yetti]

check the specs on valve guides and other things to determine way to proceed.    If you buy all new cylinders, you can send the old ones out for overhaul and have spares for next time.  There will be a next time.

[Shadrach]

On February 6, 2016 at 10:56 AM, MyNameIsNobody said:

Data Point: I bought a '66 that had 1,000 since overhaul...Not really.  It had 1,000 since an AD to inspect the crankshaft.  This was in 73 or 74.  I bought a plane with 1850 total time on airframe and engine.  At 1950 I Gupped the plane.  Elected to overhaul.  All accessories/hoses etc. at that time.  The cylinders had NOT EVER been overhauled.  I elected to oversize the cylinders vs. replacing.  I am now 14 years and 700ish hours post overhaul on those cylinders.  I am happy that I went the oversize vs. replace with new Lycoming route.

I hope you have success.  I would assume NOTHING on an overhaul.  Especially one that does NOT have detail in logs.  My logs on the engine overhaul are VERY detailed on what was replaced/re-built to include parts list with serial numbers.  I too had "none of that" on the first "overhaul" that WAS NOT.

I'm curious how your old engine looked inside. We opened ours in 99 at 1850 and 32 years and it looked fine. A broken exhaust valve had deminished confidence and in the engine.

[Shadrach]

2 hours ago, irishpilot said:

No missing or broken rings. The #4 piston was the worst but all four have blow by. With the amount of work it takes to pull the top end apart, I don't feel that comfortable just throwing new rings in. It may get to TBO, it may not.

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Yeah. If there's evidence of corrosion in the barrel, it's going to take more than rings. I would overhaul the cylinders at a minimum.

[MyNameIsNobody]

Just now, Shadrach said:

I'm curious how your old engine looked inside. We opened ours in 99 at 1850 and 32 years and it looked fine. A broken exhaust valve had deminished confidence and in the engine.

Dunno.  Poplar did Major.  There was case half separation that was causing oil on my windscreen.  Diagnosed as prop seal.  I paid to have two prop seals removed/reinstalled before diagnosis of case-half separation.  Before I bought the plane it flew about 15 hours in 20 years.....

Benign neglect had surely set in.  I was shall we say "Not a savvy" buyer.  I did not have Mooneyspace.

 

[M20F]

1 hour ago, Yetti said:

check the specs on valve guides and other things to determine way to proceed.    If you buy all new cylinders, you can send the old ones out for overhaul and have spares for next time.  There will be a next time.

I would second this or at minimum have the shop overhaul the best one of the four so you have a spare sitting around.

[irishpilot]

I'm curious how your old engine looked inside. We opened ours in 99 at 1850 and 32 years and it looked fine. A broken exhaust valve had deminished confidence and in the engine.

On initial inspection, the internals looked good. No issues on the inner case, crank, or cam. There is some slight wear on the cam lobes, but no pitting or corrosion. We are going to continue inspecting while we wait on the engine shop's cylinder assessment.

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[Shadrach]

1 hour ago, irishpilot said:

I'm curious how your old engine looked inside. We opened ours in 99 at 1850 and 32 years and it looked fine. A broken exhaust valve had deminished confidence and in the engine.

 

On initial inspection, the internals looked good. No issues on the inner case, crank, or cam. There is some slight wear on the cam lobes, but no pitting or corrosion. We are going to continue inspecting while we wait on the engine shop's cylinder assessment.

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This reinforces my theory about Lycoming metallurgy. New is not better. New is more often lousy. 

You have a Cam that is as near to 50 years old as makes no difference and has less than 1200hrs TT. That's an average of ~25hrs a year and I am betting that this sat for long periods with little to no activity.  The conventional wisdom is that your cam should have been a pitted, spalled through away item, yet it's perfectly serviceable with no pitting. Did the lifters show any evidence of pitting? I would expect to see a little.

 

When it's time to perform a major overhaul, you would be foolish to send this to the factory. Keep all of the internals you have and get it done locally.

 

Edited February 10, 2016 by Shadrach

[Yetti]

As much as certified tracking and paperwork and stuff and serial numbers.  You would think there is a good database for stuff like this.  Based on stories on MS it seems like the 1990s were the bad lycoming metallurgy years

[Andy95W]

4 hours ago, irishpilot said:

 I don't feel that comfortable just throwing new rings in.

FWIW, I never suggested just throwing new rings in.

IRAN (inspect and repair as necessary) can be as much or as little as you dictate.  Check and possibly replace valves and valve guides?  Absolutely.  Hone the cylinders? Absolutely.  Repaint?  Most shops will do that, too.

You pay extra to get the word "overhaul" on the 8130 airworthiness tags, even if they do the exact same work.  Since there is technically no such thing as a "Top Overhaul", I'm not sure what the point would be, especially if you plan to keep the airplane to TBO.

[irishpilot]

4 hours ago, irishpilot said:  I don't feel that comfortable just throwing new rings in.

FWIW, I never suggested just throwing new rings in.

IRAN (inspect and repair as necessary) can be as much or as little as you dictate.  Check and possibly replace valves and valve guides?  Absolutely.  Hone the cylinders? Absolutely.  Repaint?  Most shops will do that, too.

You pay extra to get the word "overhaul" on the 8130 airworthiness tags, even if they do the exact same work.  Since there is technically no such thing as a "Top Overhaul", I'm not sure what the point would be, especially if you plan to keep the airplane to TBO.

Thanks for the clarification. I do appreciate all the time everyone is taking to help me with this issue. Plane ownership is not for the faint of heart.

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[orionflt]

I saw what looked like some pitting on the skirt of the cylinder, that can be an indication of cam wear and lifter spalling.

Brian 

[jetdriven]

Pitting looks like from rust that forms on the cylinder wall.  Many times from the piston that stops with a valve open.  Scoring on the cylinder and piston Ive seen from cam wear, because it happened to us. Steel cam and lifter particles get embedded in the piston skirt then scores the wall and the piston.

[Shadrach]

5 hours ago, irishpilot said:

No missing or broken rings. The #4 piston was the worst but all four have blow by. With the amount of work it takes to pull the top end apart, I don't feel that comfortable just throwing new rings in. It may get to TBO, it may not.

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So the "ring debris" mentioned earlier was just carbon?  What's odd is that oil consumption jumped all at once after running it for several months. With cylinder corrosion, I would expect it "$#!t the bed" the first time it was run after being idle or gradually decline over the next 20hrs. Running fine for 30-50hrs and then having a spike in consumption surprises me.

[jetdriven]

29 minutes ago, Yetti said:

As much as certified tracking and paperwork and stuff and serial numbers.  You would think there is a good database for stuff like this.  Based on stories on MS it seems like the 1990s were the bad lycoming metallurgy years

my 2001 cam self destructed.  I think they were garbage from the early 90s right up until they changed to the roller cam to get away from it. Then the flat tappet cams they have sold since then are crap too. Aaronk25 is on his 3rd engine now in 4 years.

[irishpilot]

5 hours ago, irishpilot said: No missing or broken rings. The #4 piston was the worst but all four have blow by. With the amount of work it takes to pull the top end apart, I don't feel that comfortable just throwing new rings in. It may get to TBO, it may not.

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So the "ring debris" mentioned earlier was just carbon?  What's odd is that oil consumption jumped all at once after running it for several months. With cylinder corrosion, I would expect it "$#!t the bed" the first time it was run after being idle or gradually decline over the next 20hrs. Running fine for 30-50hrs and then having a spike in consumption surprises me.

Afirm, the ring debris turned out to be a lot of carbon. Yesterday I rechecked the debris and it was just a lot of carbon. The filter had a few small aluminum slivers. With the amount of scratches on the top of piston #4, we are pretty sure it was the source.

The oil consumption was a qt/3-4 hrs and within the last 7 hrs went to 1qt/1-2 hrs and the breather tube was pushing oil onto the belly. Plus it fouled plugs on the last flight. Definitely a noticeable change for me within the last 7 hrs. Any theories on the sudden jump?

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[bonal]

Been following this thread with great interest and thinking about my own engine it prompted me to sit down and really read my logs from day one. I have come to find that I have the original engine which has over 6000hrs it has made it to TBO with the help of some replaced cylinders. From what I have read still has same crank and cam. Currently at 700smo and producing high 70's on compression. Oil is around 1 for 4 but some of that is lost from leaks next oil change going to replace valve cover gaskets since this is apparently the source of the leakage. On one hand I'm thinking God this engine has really been run and is old and used on the other I'm thinking this engine has really proved itself as a trusty performer. I am a strong believer in if it ain't broke don't fix it but what's amazing is all the nuances that these airplanes have Its on its 4th OH and hopefully keep on running with the odd cylinder replaced as needed. I wonder if there is an easy way to determine valve stem size when I pull the covers I think I should be able to mike them at that time.

[Yetti]

It's pretty much dimensions and checking with micrometer at this point.  Your engine shop should let you know. Ask lots of questions cause you know we will :-)

Oh and get a cart to put all the pieces on.  Baggies and clean rags or blue rolls of "shop towels"   Being on the floor attracts dirt in all sorts of places.   Card board paper box tops make nice no scratch tool trays.

[irishpilot]

The shop came back and said that the putting on the cylinder walls is too much. They do not recommend a rebuild. The rings on the Pistons haven't been made in 30 years. They can sell refurbished cylinders for $1100 each, or new for $2200. They recommend refurbished unless I'm doing a full rebuild. Ya'll have any insight? Is it true an engine overhaul adds 25% to an aircraft value?

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[N601RX]

Call ECI and talk with them. They have the ability mate a new barrel to your existing cylinder head. I would not want used cylinders unles they could show me how much time was on them. 

[garytex]

Regarding ECI's demate-remate, thats a tricky operation that yielded a recent (you start to suspect you have been around the block maybe a few too many times when you start thinking 5 years ago is "recent") large AD on cylinders subjected to that process that were to be repetitavly checked closely for separation at the head barrel joint, and then thrown away after one overhaul run.  I had one of those demated cylinders not subject to the AD that started leaking at the joint.  This cyl came to me through an MOH by Custom Airmotive in Tulsa, and Mark, who runs the place had some stroke with ECI and I got good warrantee service through him back to my local mechanic.  Mark, and several other good shops in that area use a plater who turns out good work.  The plater grinds the cylinders oversize to knock out pitting and scoring, then plates back to nominal size.  Mark then does the rest of the OH service.  Valve guides, sources pistons etc.  Several shops here in Central Texas use his cylinder overhauls. If you like your cylinders check with Mark. He may be able to fix them.  But I agree with the above posters, if you do not have good cause to think that your cylinders have less than 4000 hours on them then the game gets much trickier.

Yes, those of us with unknown history rebuilt cyls are between a rock and a hard place when their time comes.  The angle valve cylinders are single source Lycoming so they hose us on price for new ones.  Therefore the overhaul pool of cylinders gets very little new blood, and there can be some really high hour cylinders being traded around.  This parallels the new vs OH situation that existed for all cylinders pre1995 before there were so many nice new cheap good PMA cylinders.  Re-using those high time cylinders resulted in short service life for overhauled cylinders.   Now, on most cylinders there are reasonably priced cylinders both from PMA and from Lyc and/or Continental.  So your chances of getting a reasonable exchange cylinder is much improved.  But not for us angle valve guys.

I had a couple cylinders fail the wobble test so last August I bought two new Lyc cylinder kits to replace them.  One of them ran hotter than a firecracker.  8 thousandths out of round, and then Lycoming kicked it back for warrantee. "Oh this cylinder is fine, you keep it."  I had since purchased a third cylinder to replace the OOR one, and it broke right in and ran cool as a cucumber. I called Lycoming and suggested that in this day and age of easy communication that kind of customer treatment would absolutely have results that were economically undesirable.  I mentioned Mooneyspace, and indicated that I would also be all over the Cardinal Flyers, and whatever the Arrow forum was, (these are the other users of IO360 engines), and that I would figure out which 6 cyl engines were angle valve engines, and which aircraft used those engines, and sound the alarm there too.  After about a week and a couple of polite but insistent phone calls Lyc indicated that they would honor the warrantee on the part, but not pay my mechanic for the R & R.  I haven't seen the refund yet, but they say it is coming.  

Even with this experience, (and i am now having to replace the other two cylinders) I have purchased two more new Lyc cyl kits, because I saw the results of aged cylinder overhauls prevalent back in the day before the overhaul pool received it's injection of new blood.  Old cast aluminum work hardens, fatigues, certainly cracks, and I think may somehow may move in a plastic sort of way, possibly explaining some valve train ills that seem more prevalant in high time cyls.  

I love the angle valve heads.  They make more power out of the fuel we pour into them than the parallel valve heads.  Maybe enough to offset the higher price over an overhaul run.  But in the instant case the pricing sucks.  Being subject to a single source supplier sucks.

An alternative theory would be replace with new, then your major would be cheaper when that time comes, as you could just overhaul YOUR known age cylinders.  Of course this doesn't work if your cam spalls and sends metal through the engine, trashing your new cylinder walls.  It's a toughie to know what to do.  Exchange cyls from a good overhauler seem to last around 1000 hrs.  If it's that long (or less) till you do the bottom maybe exchange cyls are the way to go.  That is the conventional wisdom.  I'm not sure either way.      

 

[irishpilot]

Thanks for the great post. The engine shop had a set of used cylinders that are in great shape. They overhauled them at good price and they stand by their work. I've got 850 til TBO so they should get me there. Buying new ones now didn't seem like the best option. I'll be putting them back on tomorrow and hopefully ready to be back in the air by Thursday

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[jetdriven]

How many hours are on these cylinders?  How long is the guarantee?

[ed]

BTW, you need to look at the valve lifter faces for any pitting (called spalling), very common on Lyc.  The second from rear  and second from front lobes are the worst as they operate two of the lifters so are very stressed.  Also run your finger over the cam lobe as you can feel any bad lobe easier than looking at it.

Also, be vary careful you get the rocker arm's back on correctly.  The exhaust rockers are "squirters" as they squirt oil onto the exhaust valve to cool it.

The intakes don't squirt oil (not drilled thru).  If you mix them up then you may suck oil in thru the intake valve guides and burn up the exhaust guides.

Believe me, I have seen A&P's screw this up.  I know its that way on all the parallel Lyc, so should be similar on the angle valve (200 HP) version.

[carusoam]

Welcome aboard Ed,

You have come to the right place.

Best regards,

-a-