Corona Engines Overhaul or Factory Overhaul (or just cylinder replacement)?

[Andy95W]

4 hours ago, ryoder said:

After I get to 1000 feet the CHT is primary for pitch   Unfortunately it does get up to 400 which is still in the green.  Also I fly with cowl flaps partially open to keep it below 380 or so when flying with more than 20 inches of MP or so.  I think the guppy mouth is a problem and I also think my doghouse could use some sealant.

I have had some weeks where I didn't fly at all.  Like right now I am having some minor procedures and won't fly until the stitches are removed.

Just MHO, but I think you're doing it right.  

I highly recommend the LASAR cowling closure.  Fairly inexpensive, seems to help lower CHTs a bit, and makes the nose look better.  On the 1965 and earlier, I think it makes it look a LOT better for very little money.

[oldn0tded]

As long as you're soliciting opinions....

I started flying in the mid eighties. I've been around internal combustion engines since before I was a teenager. I'm NOT an AI or an A&P, but I have always done my own wrenching, and do so now, on my plane, under the supervision of a local AI. Over the years I've seen a lot of different "kinds" of maintenance/repair/rebuild people/facilities in ALL areas i.e. marine, automotive, motorcycles, bicycles, and aviation. I'm not an expert, but I am experienced. 

So, here are my thoughts

Premise 1: I can safely say for every technician that really can DO the job, there are 20 that think they can.

Premise 2: There are no shortcuts. 

Premise 3: Pay attention to your instincts. Your "inner brain" talks to you all the time, be sharp enough to listen for the red flags.

First question

IMHO, I would not replace just the one cylinder, nor would I use overhauled/reconditioned/rebuilt cylinders. It's a false economy, in my opinion. New cylinders, and all four, no question. Keep in mind, a new top end could, theoretically, jerk the bottom out. 

Second question

Field overhaul or factory? The techs at Lycoming are not Supermen, they're just people with a LOT of very specific experience (and a warranty). As for the question of getting YOUR crank or YOUR cam back in your rebuild/overhaul, Do you really care? It's a part, that's all. If it specs out, what's the issue? I'm aware of the question over the quality of the steel, but has that ever been validated or is it another tale spun up at the hangar?  

As for the "field" overhaul, if I positively KNEW the tech was good, I wouldn't give it a second thought. For me, I'd have to be physically there before I could go there. 

Just some thoughts,

Old Knot Head

 

[jetdriven]

14 minutes ago, oldn0tded said:

. Keep in mind, a new top end could, theoretically, jerk the bottom out.

 

I generally agree with your post but this is perhaps the dumbest statement I have ever heard regarding airplanes since my first lesson 20 years ago. First place.  

[oldn0tded]

Well, somebody needs to get laid.. 

I'm guessing you have not had that happen?

I have....not with an airplane engine though, thus the THEORETICAL part....

 

[jetdriven]

15 minutes ago, oldn0tded said:

I get Well, somebody needs to get laid.. 

I'm guessing you have not had that happen?

I have....not with an airplane engine though, thus the THEORETICAL part....

 

I get plenty.  Theoretically I could go to sleep tonight and wake up tomorrow the winner of the Irish sweepstakes and be married to the playmate of the year.  But that is only a hundred times more likely than "the new top end jerking the bottom out". I really though you were kidding.

Instead of insulting my sexual prowess, perhaps explain how the new top end can "jerk the bottom out"?  Perhaps those new cylinders make so much extra horse power above and beyond 200 that the crank and rods can't handle it? Or something else? 

[oldn0tded]

"I get plenty"

Good, maybe you'll be more social. 

I think the bottom end in question is 2000 hours old, with a freshing up 4xx hours ago, and a prop strike. I'm reasonably certain that will increase the odds.

I stand by the original opinion. 

[jetdriven]

2 minutes ago, oldn0tded said:

"I get plenty"

Good, maybe you'll be more social. 

I think the bottom end in question is 2000 hours old, with a freshing up 4xx hours ago, and a prop strike. I'm reasonably certain that will increase the odds.

I stand by the original opinion. 

How can it increase the odds.   My lycoming factory overhaul is 2379 SNEW in the log book but it was overhauled at that time with an old crank, rods, and new cylinders.  How is that different than the scenario you described? 

 

Also, are you saying that new cylinders produce more stress on the crank and rods than a set of 1000 hour cylinders that all blow more than 60/80?  Show me one single shred that says a new set of cylinders can cause an an engine to fail because of over stress on the bottom end.  Just one.  Thanks. 

[oldn0tded]

Byron, 

It's not the crank, it's the bearings. Well, and maybe a crank. Let's think about it for a sec. 

Are you familiar with BMEP? I don't know the number for a Lycoming blowing 72/80, but just for the discussion, lets says it's 125. If the new cylinders bump it up to 135, then YES, there will be increased stress on the crank, but more specifically the BEARINGS. This crank is somewhat special due to the prop strike, that throws an unknown into the equation. Does anyone out there know how torsional vibrations affect the cranks in our motors? I don't but it's a question.

Finally, "a shed"? A shred of what? Its my opinion, based on prior experience. Do you have any "hands on" engine building experience? 

And you're welcome!

 

 

[Andy95W]

15 minutes ago, oldn0tded said:

Byron, 

It's not the crank, it's the bearings. Well, and maybe a crank. Let's think about it for a sec. 

Are you familiar with BMEP? I don't know the number for a Lycoming blowing 72/80, but just for the discussion, lets says it's 125. If the new cylinders bump it up to 135, then YES, there will be increased stress on the crank, but more specifically the BEARINGS. This crank is somewhat special due to the prop strike, that throws an unknown into the equation. Does anyone out there know how torsional vibrations affect the cranks in our motors? I don't but it's a question.

Finally, "a shed"? A shred of what? Its my opinion, based on prior experience. Do you have any "hands on" engine building experience? 

And you're welcome!

 

 

You've been asking a lot of questions and giving a lot of opinions, but very little factual evidence.  But everyone is entitled to their opinions, for sure.

But I'll stand by Byron/Jetdriven, who works in an aircraft maintenance shop, and my own 17 years of A&P experience, to say your opinions are not well founded in our experiences.

And if you tell me I need to get laid more, I'll agree.

[jetdriven]

If the crank and rods were magnafluxed as part of the prop strike inspection, they are placed back in the realm of "known". A magged crank is just as good as, and maybe better than s new crank because it has history.  My lycoming factory engine's crank may have had a prop strike but if it  was documented then it goes out the door in another engine. My previous engine went back to lycoming and it had a prop strike and the flange was hammer straightened from .004". Total time unknown.  it was turned to .006 under (thats .003 under limits, btw"  and it likely left the factory as a .009" under crank in a factory reman or overhaul engine. It was all in the logbook. 

I know BMEP.   I also know that an engine that's approved for 27" MP and 2200 RpM ROP can handle 3% more cylinder pressure because of new cylinders. Lycoming likes to cover their asses but yet no service bulletin saying caution, new cylinders may snap your crank.  I'm still waiting for a shred of evidence that new cylinders can  remotely cause engine failure.. C'mon, something. 

[oldn0tded]

.....and giving a lot of opinions, but very little factual evidence.  But everyone is.....

All I have is anecdotal evidence, what sort of factual evidence are you looking for? The OP was looking for opinions. Certainly, your experience gives your opinion more credibility than mine. If you say it's sound to put new cylinders on that bottom end, I would NOT say that was the dumbest thing I'd ever heard. 

Getting back to original question, If it were my plane, it would be a full rebuild with new cylinders. I could not use rebuilt cylinders, and I could not put new cylinders on a bottom end with that history.

As to factory or field, I'd get you to do it!!

 

 

 

 

[ArtVandelay]

BTW regarding factory overhaul and parts are just parts statement, Lycoming had issues with their metallurgy in 1999-2005 timeframe, I wouldn't want one of those parts.

[PTK]

This is getting good!! It is good ol' pop corn n' soda material!! Keep it coming...!!!

[Becca]

9 hours ago, jetdriven said:

I get plenty.  Theoretically I could go to sleep tonight and wake up tomorrow the winner of the Irish sweepstakes and be married to the playmate of the year.  But that is only a hundred times more likely than "the new top end jerking the bottom out". I really though you were kidding.

Instead of insulting my sexual prowess, perhaps explain how the new top end can "jerk the bottom out"?  Perhaps those new cylinders make so much extra horse power above and beyond 200 that the crank and rods can't handle it? Or something else? 

For what it's worth, his chances of getting laid declines every time his wife catches him trolling on mooney space.

[DrBill]

I'm in process of an overhaul too and as my mechanic pointed out.. New engines have some significant time dependent ADs. Where my 50 yr old crank and case do not .  So I'm  going the rebuild route.

Bill

 

[Andy95W]

53 minutes ago, Becca said:

For what it's worth, his chances of getting laid declines every time his wife catches him trolling on mooney space.

Hmmm....

This may explain my love life, as well...

[stevesm20b]

I had Corona Engines hone and install new rings on a couple of cylinders while I waited in their shop. I checked out their operation and watched how they work. They were very knowledgeable and do very good work. If my engine needed an overhaul that is where I would go.

[ArtVandelay]

I'm in process of an overhaul too and as my mechanic pointed out.. New engines have some significant time dependent ADs. Where my 50 yr old crank and case do not .  So I'm  going the rebuild route.

Bill

 

But I assume you don't have the history OPs engine does.

Prop strike, bottom o/h, top o/h, broken valve.....that's a lot of bad history.

[jetdriven]

Al those parts don't get thrown away, that prop strike crank, welded cases, spalled camshaft all go into someone else's engine who exhanged their old one because of "bad history".  The history just disappears when it goes through an overhaul shop.  

[ArtVandelay]

Al those parts don't get thrown away, that prop strike crank, welded cases, spalled camshaft all go into someone else's engine who exhanged their old one because of "bad history".  The history just disappears when it goes through an overhaul shop.  

Is that true for reman engines as well? It's higher standards I expect would result in newer or new parts with no bad history.

If you have a bad engine, at least with factory reman,overhaul you have a chance of getting a good one.

[M20F]

20 minutes ago, teejayevans said:

Is that true for reman engines as well? It's higher standards I expect would result in newer or new parts with no bad history.

If you have a bad engine, at least with factory reman,overhaul you have a chance of getting a good one.

 

http://www.avweb.com/news/maint/182826-1.html

Without seeing the OP's logbook and what parts went into the bottom nobody can really assess its condition.  My suspicion though is it was done properly to where you are going to take a bunch of 400hr parts and toss them in the trash or just look at them for no reason if you split the case. The fact you do the bottom and the top separate in no way makes a difference.  You just split up the cost but the work is the same.  If I had 4 good cylinders and needed a bottom I certainly wouldn't overhaul the cylinders just to write the word overhaul in the log book.  Likewise if I had a good bottom I wouldn't pull it for a snapped valve if I didn't need to.   

People get way too wrapped up in words like remanufacture, overhaul, TBO, etc.  My only concern in the OP's situation is getting all the valves replaced as 2000hrs and a lot of years is to long.  The fact all 4 cylinders were done at 1000hrs probably relates to somebody feeling it "needed to be done" as generally you don't just have 4 cylinders crap out all at once.  If there was abuse you would tend to see the cylinders all replaced at differing and shorter intervals.  

This is the biggest area where people just flush money down the toilet.  In the case of the OP he has a $5-8K option or a $25-$30K option.  The latter I don't think based on what he has shared does him anything other than lighten his bank account.