High oil consumption and low compression on one cylinder. Rings?

Hi everyone,
Im looking to buy a cub but it has low compression and lots of oil consumption. We were told that it needs the ring replaced on cylinder #2. It is a narrow o320 150hp with 1000 smoh. Can this be done easily and is it worth it? I thought that it would be hard to seat the rings of one cylinder after the work, so would it be smarter to top all the cylinders? Help would be appreciated. Thanks!

If the fix is simple the seller should fix it. I wouldn’t buy it unless the engine was discounted as a core.

For sure. But that beiing said, the narrow isnt even counted as a core at overhaul time right? So it would be field overhaul or buy new engine + core fee.

Ington6 said:

For sure. But that beiing said, the narrow isnt even counted as a core at overhaul time right? So it would be field overhaul or buy new engine + core fee.

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Will be getting a 0-320 narrow deck 160 hp with log books with 400 hr new lycoming cylinders complete . Also has low hr leading edge exhaust and 82 41 prop 200 hrs reasonable priced

When would you be getting this? Know when the last OH was done? I dont need the prop but might be interested in the engine and exhaust.

This engine needs to have a cylender pulled for inspection. Being a Lycoming there is a big chance of Rustin the cylinders, the cam pitted and rust on the rods and basically in need of a total rebuild. If they won’t let you pull a cylinder they most likely already have. It’s a simple job and only takes a couple hours at the longest.

What is the oil consumption? What are the compressions and where is the air leaking? What does a borescope inspection show you? What does inside the valve covers look like? Lyconings don't normally need one cylinder reringed at mistime. A narrow deck was accepted as a core last I checked.

Ington6 said:

Hi everyone,
Im looking to buy a cub but it has low compression and lots of oil consumption. We were told that it needs the ring replaced on cylinder #2. It is a narrow o320 150hp with 1000 smoh. Can this be done easily and is it worth it? I thought that it would be hard to seat the rings of one cylinder after the work, so would it be smarter to top all the cylinders? Help would be appreciated. Thanks!

Click to expand...

Lotsa maybe’s
I cant imagine why you couldnt top one jug if low compression is limited to that cylinder and run hard with breakin oil for a bit to see if oil use stabilized
I would want a look at the cam. Will seller let you have a jug pulled??? Could be a simple fix or 10x a simple fix.
If not i would figure a steep discount to factor in a overhaul.



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Narrow deck... 1000 SMOH..... uses a lot of oil....low compression in one cylinder... originally had a TBO of 1200 hours until the exhaust valve diameters were changed..... Who or what company did the overhaul?.... How many times has it been overhauled? I doubt it came from Lycoming 1000 hours ago with a narrow deck.

If all else is good about the plane, figure what it would be worth to you with a fresh overhauled engine. Make allowances that the engine which is in it now is only worth whatever the current core values are.

The narrow decks had a tendency, unless modified to have crankcase fretting where the two halves rub together. Think $$$ for repairs including a major overhaul. Pulling one cylinder just replacing rings and looking around inside will not tell you about the crankcase fretting.

You may get a couple hundred more hours out of it. In any case with the issues you have described....that engine is talking to you. Best to bite the bullet now than to wonder about it for a while. Of course if you are only going to be flying over nicely mowed fields where you can always land safely .. give it a chance.