O-360 Cylinders and Such

[rubixcube2k3]

So we’re into this year’s annual, and I have a cylinder (4) with a leaking at the exhaust valve 60/80 and it’s opposing partner (3) leaking at the intake valve 72/80. From my logs, these same two problem children were replaced in 2001 and 2000 respectively, so it seems they haven’t done too bad to make it nearly 13 years and 750hrs.  (although 1 and 2 are mid 70s and haven’t been touched since shortly after last major in ’89).  My IA and I are discussing the options, but basically at 1500hrs  and 25yrs, I’m weighing my decision pretty heavily.  Oil consumption Is pretty low – 1qt every 6-7 hours. 

 

That being said, topping the engine is a thought I’m having, but I’m curious to know if anyone can offer any insight with regard to the “Overhauled” cylinders I’m finding around the internet for around $350-$800each vs the “New” cylinders at $2300 each.  The OH’ed cylinders come with 8130, so I don’t think we’re talking about buying some grey market garbage.

 

My thought process would lead me to believe that if I had any thoughts of getting the latter cylinders, I would likely end up better getting one jug for now and a factory overhauled engine in the not so distant future. 

 

This is new territory to me, so I thought I’d solicit input accordingly .

 

Any thoughts , constructive input, or things otherwise to be aware of?

 

Thanks!

~Abe

[jetdriven]

I'd go fly it 30 mins at 75% power and recheck hot. 60 and 73% are within limits as long as the valves aren't leaking. Of it hasn't been ran in a while, or wasn't hot, or some random carbon is holding the valve open slightly it can skew the results.

Another thing about overhauled cylinders. They all come wih 8130s but they at not all the same. They can home it and cut the valve and seat with a stone and call it overhauled. It could have 2000 hours it could have 10k. You don't know.

We had a 182 last week, hadn't flown in a year and a couple cylinders were low. One was 37 and one was 45. After a 75% power run up for 5 mins they improved to the 70s. I'd just fly it 30 mins hard and rcheck before pulling them. Another thing the dental camera will show leaking valves really good, about 100hr before they actually burn.

[rubixcube2k3]

Thanks Jim! I lurk often, but try to stay hidden for the most part. ;-)

 

Byron,  the compression check was hot, and we did note this same cylinders exhaust valve leaking last year. We may press on and finish the rest of the annual, then fly and check once more after a short flight. I havent asked if we could do that, but I can't imagine him saying no. Obviously, I was more freaked out about the finding that he was. 

[mike_elliott]

Abe, You might consider getting some first run Nickel cylinders from someone like J&J out of Texas. I  would  pull #4 and check the cam and lifters really carefully. That might make a determination of what you do next. If you pull both 3 and 4, make sure you don't rotate the prop afterwards until you get it back togetheras there could be a chance of the rear main bearings rotating without torque on the thru bolts.

[cliffy]

#3 is still OK at 72. Not to worry, #4 is still OK at 60 but jetdriven has a good plan. Fly it and recheck. If it's still 60 you might think about lapping the valve, in place, in the cylinder. Can be done, is done all the time and it works. Takes about 2 hours shop time and can bring it back to the mid to high 70s. Just did one last week (56/80) and brought it to 76/80. 

 

If you decide to pull the jugs ( I don't think you really need to at this time), you might contact Pacific Continental Engines in L.A., Calif. for the cylinder work. They're fast and do good work.

 

Do you have any idea if your cylinders are first run, have thousands of hours on them (well used at the last overhaul) or if they are standard or ground oversize ? That info plays into your decision also. 

[carusoam]

Are you seeing temperature variations on an engine monitor?

The thoughts that come to mind...

M20C cooling is challenged more than other Mooneys. Just how much, can be displayed on an engine monitor.

I would expect exhaust valve issues are often caused by higher CHTs.

Modern technology since 60's:

- Cowl closure

- silicone seals around the dog house.

- camera that can fit down a spark plug hole

- digital engine monitors

- MooneySpace style communication

60's technology

- Rope Trick for sticking valves

Which ever way you decide to update the cylinders...

Try to identify if temperature distribution is a challenge

Sticking valves can cause them to bend

This is from my 65C experience.

No JPI + no cowl closure + no experience + idle plane = sticking valve

Carbon has a tendency to build in the valve guides. Carbon can stick a valve. A stuck valve can bend it's shaft.

A valve with a bent shaft leaks.

Franken Engine = various cylinder styles and a mix of oversize diameters are acceptable by FAA guidelines. Just not desired by anyone.

Check with your mechanic to verify any of these statements before using them...

Closing thoughts: depending on funds available

- get engine monitor

- check cooling system

- get replacement cylinders

- break them in, keeping them cool

- get to the next level...(factory reman, M20J, R......)

[cujet]

I'm a Director of Maintenance in a high end corporate flight department. However, I do get to play with little aircraft also. The above advice is generally very good. Run it hard, check again. Consider repairing your cylinders. Yellow tagged "overhauled" cylinders are very likely to be re-welded units from "who knows what or where" (yes it matters) and they often have a bad reputation for good reason. I'd avoid them, given the choice. 

 

Here is what we know. You have 2 very specific issues, and don't seem to have any others. It's very likely that repairing each specific issue will be easy. The above suggestion for "lapping them in place" is a good one if conditions warrant (I strongly suspect they do) . You may not find published procedures from the manufacturer on how to do this in situ. However, you could follow lapping procedures properly, without ever removing the cylinder. 

 

I'm taking a WILD guess here at internal conditions, but here goes: 

 

Note: You may want to operate the engine with some TCP to help remove lead deposits prior to maintenance. It does help, slightly...

 

1) Pull the plugs on the affected cylinders.

2) The one with the leaky ex valve, pull the exhaust pipe, likewise, the intake pipe for the other cylinder.

3) Remove the affected valve springs, consider replacing these 2 valve springs with new, as new will result in higher seat pressure and better heat transfer/sealing (they are very cheap) .

4) Pull the valve stem up the top spark plug hole and clean off the carbon by careful scraping and using maroon scotch brite. I do this using shop air flowing into the lower plug hole to prevent debris problems. THEN CAREFULLY INSPECT THE VALVE. Proceed if it looks OK. 

5) Run a properly sized valve guide reamer CAREFULLY through the guide, loaded with grease. This will remove carbon and allow the valve to center properly on the seat. DO NOT REMOVE METAL from the guide. (unless it's just a burr)

6) Use care to apply coarse valve grinding compound on the valve seat. Then lap the valve, using standard practices. Consider fine compound as a second round. I like using a battery drill, and rubber hose on the valve stem. Using both directions and regular valve lifting off the seat to allow the compound to flow a bit. This takes work. Don't be afraid of grinding too much. It's not very likely unless you spend 40 hours grinding. 

7) Clean off the compound like crazy, being sure not to allow grinding compound into the bore. Wipe off the valve seat and face. 

8) Reassemble and test for leaks. In fact, I might just run it hard and test afterwards. 

 

I'll bet you a dollar this fixes the problem and prevents future compression deterioration from these specific issues. 

[MB65E]

+10 for Pacific Contental Engines! Yes... Even for Lycomings!

Chris will take care of you!

But for now run the snot out of it!

-Matt

[cujet]

I neglected to mention that moving the valve around inside the cylinder is actually quite easy. From the bottom spark plug hole, use a forked rod to push up the valve. From the valve guide, use a strong, rare earth magnet tool. From the top, a flashlight or 2 prong mechanical fingers (the larger kind) 

 

It's really a non issue. 

[Andy95W]

I agree with cujet. If money is an issue, or if you are completely against the full major overhaul, then simply repairing what you have is the most cost effective way to go. Your cylinders do not need to be overhauled, just repaired (referred to as IRAN- Inspect and Repair As Necessary).

And if you want to Top Overhaul the engine, keep your own cylinders like cujet said and send them to a reputable shop. If yours are junk they will let you know.