Thoughts on a Top vs Brand New Engine

[Alan Maurer]

Mooney People, My 2008 Ovation has almost 1000 original hours since factory new. Presently compressions are in the fifties and I burn some oil...maybe a quart every three hours.

So we spoke , ar Sarasota Avionics about a top or bite the bullet and order a factory new engine. At my age it would be the last engine I would every buy. 

Suggested that at 1000 hours the cam would not look  great if one could get a good look at it. Airplane runs great, smooth and fast. With STC done for Ovation. 3 , it really climbs fast.

Fair amount of Money for new engine but certainly tempting. So, Could just get the Six pack and top (Mike Busch says "Be Afraid" or  actually order and wait for new 

engine. Would love some opinions! Boroscope views of valves looked fine...probably cylinder walls wearing and rings. Don't know about cam.Oil analysis have been good.

Any Thoughts?

Thanks

Alan 

[GeeBee]

As long as they will sign it off on the compressions you got, I would fly it until you can't. Are the compressions in compliance with the Continental SB? If there is no metal in the oil there is no worry on the cam and cams do not fail catastrophically.  A quart every 3 hours is not great, but it is not terrible. 

[Fly Boomer]

8 hours ago, Alan Maurer said:

Mooney People, My 2008 Ovation has almost 1000 original hours since factory new. Presently compressions are in the fifties and I burn some oil...maybe a quart every three hours.

So we spoke , ar Sarasota Avionics about a top or bite the bullet and order a factory new engine. At my age it would be the last engine I would every buy. 

Suggested that at 1000 hours the cam would not look  great if one could get a good look at it. Airplane runs great, smooth and fast. With STC done for Ovation. 3 , it really climbs fast.

Fair amount of Money for new engine but certainly tempting. So, Could just get the Six pack and top (Mike Busch says "Be Afraid" or  actually order and wait for new 

engine. Would love some opinions! Boroscope views of valves looked fine...probably cylinder walls wearing and rings. Don't know about cam.Oil analysis have been good.

Any Thoughts?

Thanks

Alan 

If you want to know what's going on with the cam and lifters, compared to pulling jugs, pulling a rocker, push rod, push rod tube, and lifter is trivial.  With the right borescope, you can get a look at several cam lobes.

Also, see
https://youtu.be/VAnSnCPOAOU
https://savvyaviation.com/borescope-video
https://bit.ly/lapping-in-place
https://bit.ly/solvent-ring-flush
 

Or, if you are uncomfortable with any of that, order a new engine.

[LANCECASPER]

14 hours ago, Alan Maurer said:

Mooney People, My 2008 Ovation has almost 1000 original hours since factory new. Presently compressions are in the fifties and I burn some oil...maybe a quart every three hours.

So we spoke , ar Sarasota Avionics about a top or bite the bullet and order a factory new engine. At my age it would be the last engine I would every buy. 

Suggested that at 1000 hours the cam would not look  great if one could get a good look at it. Airplane runs great, smooth and fast. With STC done for Ovation. 3 , it really climbs fast.

Fair amount of Money for new engine but certainly tempting. So, Could just get the Six pack and top (Mike Busch says "Be Afraid" or  actually order and wait for new 

engine. Would love some opinions! Boroscope views of valves looked fine...probably cylinder walls wearing and rings. Don't know about cam.Oil analysis have been good.

Any Thoughts?

Thanks

Alan 

I wouldn’t be in a hurry to change out a 1000 hour Continental engine with compressions in the 50’s. Tell them you’ll think about it this next year and I would get it signed off and out of there.

On this engine if you measure the oil an hour after flying it will look like it used oil. If you measure it a few days later it might not. If you add oil after checking it soon after a flight you’ll overfill it and then it will blow out the next flight.  If it turns out there is real oil consumption and it bothers you I’d take it to an open-minded mechanic who would be willing to try a ring flush.

If every Continental that had compressions in the 50’s was grounded (which there is no reason to do) my guess is that would be half of the fleet.

[Fritz1]

in addition to the sound proposals stated supra, you may want to find somebody who is willing to lap the valves in place and check the wobble in the valve guides, if everything checks out, keep flying it, if money is of no concern order a factory reman that gets installed when all the required parts, hoses, engine mounts etc. are on the shelf which assures minimum downtime

[201Steve]

I can’t say for certain about Continental but I know Lycoming is a year and a half back ordered for new engines. If that’s also the case with conti, there’s your likely answer. 

[Utah20Gflyer]

3 hours ago, Fritz1 said:

in addition to the sound proposals stated supra, you may want to find somebody who is willing to lap the valves in place and check the wobble in the valve guides, if everything checks out, keep flying it, if money is of no concern order a factory reman that gets installed when all the required parts, hoses, engine mounts etc. are on the shelf which assures minimum downtime

I agree with this approach, but before you even do that repeat the compression test and note where the air is getting out of each cylinder. 
 

ring/cylinder problem = air coming out breather tube

Intake valve = air coming out intake

exhaust valve = air coming out exhaust 

cylinders where there are valve issues- lap the valves

cylinders with ring / cylinder wall issues try ring flush.  
 

You may find that with a mild amount of effort and money you can get your cylinders back to a place where you are content again.  
 

If it ends up still not being acceptable, your cylinders will at least be a good as they can be until new ones arrive, which could take a while.  
 

I wouldn’t do the bottom end on an engine that hasn’t shown any indication of cam or bearing issues.  

[Shadrach]

I would be skeptical of anyone suggesting that a Continental cam “won't look great” at 1000hrs.

[M20F]

Mike Busch Oil Consumption

[TGreen]

On 4/26/2024 at 11:30 AM, 201Steve said:

I can’t say for certain about Continental but I know Lycoming is a year and a half back ordered for new engines. If that’s also the case with conti, there’s your likely answer. 

For that matter, not clear when factory new cylinders for the IO-550-G will be available. 

[Pinecone]

On 4/26/2024 at 7:06 PM, Shadrach said:

I would be skeptical of anyone suggesting that a Continental cam “won't look great” at 1000hrs.

My thoughts exactly.

[dkkim73]

Alan, 

I recently had a bit of a scare where, shortly after annual (with some known older cylinders), a local mechanic suggested I replace all the cylinders at around 1450 hrs. There are some other factors to that story, BUT... 

There was audible leakage on the exhaust valves on two cylinders, low compression on one and "marginal" on another (24 and 40 at first mechanic, 34 and 60 at the 2nd opinion/treatment shop). Anyhow, after lapping and ring flush they came up, 70 and 64 cold and 74 and 70 hot. Seems the valve made a huge difference in the first case. Both cylinders have wear but the more conservative voices thought the situation was manageable with the more minimally-invasive, "Savvy" type approaches others above have mentioned. The 2nd local shop has a lot of experience with these techniques and say they often yield results. 

It seems to run well. We'll keep an eye on via borescope and periodic inspection. YMMV, but so far I am appreciative of this approach. 

David

[Niko182]

FWIW, the cam on my last IO550 made it to 2100 hours. It would’ve probably made it further, but that’s when I switched out the engine. From what I’ve read here, continentals don’t seem to run into the cam issues. Continentals have the cylinder issues. Lycoming has more of the cam issues. 
 

As for the shop, I don’t know them, but it might not hurt getting a second opinion. Recommending a new engine because of compressions being in the 50s and “the cam will probably look bad” isn’t a reason for a new engine. It’s a reason to investigate. As for the oil burn, try to figure out where it’s coming from. I’d bet good money that it’s most likely coming from the valve cover gaskets, the crank shaft seal, or the pushrod seals. If you don’t have the real valve gaskets, I’d recommend those too. A quart every 3 hours is high, but a slow drip from a couple of valve gaskets and a leaking seal can make the difference between 1 quart every 3 hours and 1 quart every 6 or 7. If you have oil leaks, you’ll definitely see a good amount on the belly. 
I’ll also add that if they’re recommending you buy a factory new engine instead of a top because the cams will probably look bad, without the shop actually having the knowledge that the cam is actually bad, this shop is probably taking advantage of you. That’s 75k vs 20k. 

[cliffy]

Lots to do and lots cheaper before you make a costly decision-

First, was the compression test done using a "Master Orifice'" compression tester as per Continental procedures?

If not find a mechanic that knows what he is doing in that regard

Secondly- follow Continental's procedures for tracking down compression leaks IF the cylinders are in fact low on compression

Any good A&P can tell you where the leakage is coming from.

IF its valve leakage do a "lap in place"  procedure  to try an fix the leakage without pulling cylinders. It does work many times. 

Just make sure you have them replace (with new) the valve rotators when they lap the valves.

Oil burning and ring compression leakage indicates time to try the ring flush procedure that Mike Bush promotes. 

Quite probably oil control rings seized

That too does work often enough to make the try worthwhile. 

What is Continental's max allowed oil consumption per hour? Are you below that? If so, not to worry- just fly it and put oil in. 

Just as a point of reference on my 4 cylinder Lycoming the max oil use allowed is near 3/4 qt per hour.  

If in fact the cylinders need work you might consider having your own first run cylinders overhauled BY A GOOD SHOP rather than waiting a year or more for new ones. Just follow Continental's book on reassembly using the proper specified tools. 

First run overhauls are usually a pretty good way to go in that you know what your cylinders have gone through. With a factory reman engine you have no idea how many hours are on the cylinders. Cylinder rework USED to be common place but for some reason now a days many shy away from such work. BTW, all A&Ps were taught how to overhaul cylinders in school! Reworking the overheads (valves and guides) was actually a shop bench job if the cylinder itself was within wear limits.  

Their is nothing dangerous about cylinder work if proper procedures are followed. 

You need more and correct information before you decide its time to spend lots of money.

You might consider signing up with Mike Bush for his help service.

I have no connection with him but I have spoken to him several times at seminars. 

Cam problems would be low on my worry list.

[jlunseth]

I'll just say this. It was more than a year from ordering before the new engine should up for my 231. It was supposed to be 8 months, but TCM spent several months disassembling and inspecting Cirrus engines due to the crankshaft AD. After the engine was installed it was several more months before all the gremlins were gone ... I hope. In retrospect, I should have had the old engine overhauled.

[DXB]

On 4/26/2024 at 1:55 AM, Alan Maurer said:

Mooney People, My 2008 Ovation has almost 1000 original hours since factory new. Presently compressions are in the fifties and I burn some oil...maybe a quart every three hours.

So we spoke , ar Sarasota Avionics about a top or bite the bullet and order a factory new engine. At my age it would be the last engine I would every buy. 

Suggested that at 1000 hours the cam would not look  great if one could get a good look at it. Airplane runs great, smooth and fast. With STC done for Ovation. 3 , it really climbs fast.

Fair amount of Money for new engine but certainly tempting. So, Could just get the Six pack and top (Mike Busch says "Be Afraid" or  actually order and wait for new 

engine. Would love some opinions! Boroscope views of valves looked fine...probably cylinder walls wearing and rings. Don't know about cam.Oil analysis have been good.

Any Thoughts?

Thanks

Alan 

Why not just work on individual cylinders as needed?  1000hrs and 16 years seems far too early to pull an engine where the bottom end is fine - unlike a new engine, it may be in the prime of life after making past infant mortality safely.  And I agree with Mike Busch that top overhauls are usually silly - I doubt all 6 are major contributors to the oil consumption; figuring out which ones may take some investigation....

[A64Pilot]

Concerns over top overhauls are over rated in my opinion, I’m sure some, possibly many A&P’s may have very little piston experience. I didn’t, but grew up as a motörhead so I didn’t have a lot to learn, but many mechanics didn’t grow up tearing everything apart and modifying it like I did so unless the book specifies a procedure they don’t follow one, assuming of course they read the book.

First if you have 6 new in box cylinders then you replace one as one is removed so the case half torque is never broken, but if your removing all 6 for overhaul then as each is removed any decent mechanic should stack a couple of fender washers on each stud and torque them, full torque isn’t required.

Lycoming has “special tools” which are plates that are installed and torqued as each cylinder is removed. I had intended to get condemned cylinders and band saw the bases off for torque plates but learned Lycoming beat me to it, I haven’t looked but would suspect such bases are available for Conti’s and if not band saw off 6 condemned cylinders. 

My advice is if you want factory new then put them on order and keep flying until they come in. Already have the shop picked out that’s going to exchange them, I’d use an engine shop. Be aware that many GOOD engine shops will take a brand new Conti cylinder and rework it before install, most aren’t crooks, Conti cylinders have “issues” and fixing those issues can add many hours of life to even new cylinders.

Talk to a good shop, it may be that overhauling the ones you have may be best.

Using a reputable engine shop that overhauls in house should keep the down time reasonable.

Everything is an opinion this is just mine,  but 1,000 hours on a bottom end shouldn’t be anywhere near its end of life.