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Advice wanted - O-360 Major OH, teardown, new engine, or . . . . ?

R

Rick RV-4

Well Known Member
Patron
Looking for advice from those smarter than me. I'm certainly more of an operator than engine mechanic.

I have an older O-360 C2A installed on my RV-4. The engine was overhauled in 2002 and sat (but preserved) until 2009 when I first flew my RV-4. I do not know the total years in service on this engine or number of times it has been overhauled. Oil consumption has always been slightly high (1 quart per 5 hours), I'm guessing due to a less than stellar break-in by me. The perils of a newly OH'd engine and new plane test flight regime. I recently added an air/oil separator and the consumption is down to 1 quart per 8 hours.

I now have 600 hours SMOH and the engine is starting to tell me it's maybe time to take action. A few oil samples ago, the iron went up quite a bit, but has since worked itself most of the way back down to where it was historically, but not all of the way. Silicone was higher on the last sample as well. Compressions are fine (mid to high 70s) and the engine still runs well, and the performance has not dropped off at all. It is leaking oil a bit more than it used to but I have yet to determine where it is coming from. Guessing a few tablespoons per flight based on what I'm seeing on the belly. Not enough to see on the dipstick but annoying for cleanup. I fly the aircraft regularly - 2 or 3 times a week on average, if not more.

Any advice on what path to take? Here are my options: Of course it gets more expensive the further I go down the list but the safety factor goes up as well

- Continue to run it as is, and monitor with borescope inspections, compression checks, oils samples, etc.
- Pay for a teardown and then repair as required
- Suck it up and do a major overhaul
- Screw that old hunk of junk and go new.

I was leaning towards having a teardown done, and received a quote for just under $13,000. The provider of this quote thinks the total price to bring it back up to very good condition will be more once any required repairs are done. So that makes me think more about doing a major OH, but then with the unknown age or total time of the engine, would a major OH be a waste of money in the long run?

I did not put "top overhaul" on the list as I am not too concerened about the cylinders - more the bottom end. Not sure if that is a good thought process or not.

Thoughts?

Thanks,

Rick
 
Rick RV-4 said:
- Continue to run it as is, and monitor with borescope inspections, compression checks, oils samples, etc.
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I'm not smarter than you, but from everything I've read from people much smarter than both of us is to keep running it. Unless you have 40k burning a hole in your pocket and you want to stop flying for 9 months.

When you had excess iron, had you stopped flying for a week or more? From what I understand, iron is mostly related to corrosion of the cylinder walls, and possibly the cam. Cylinder wall corrosion is usually not a huge issue if it's a one-time thing, but if the cam is rusting, you will see more and more iron. And then a gradual degradation of performance. Not usually a sudden stop, so you will have time to make a decision then.
 
If Mike Busch were here he’d say to keep running it.
My opinion is the same. Personally I think all aircraft engines ought to be maintained “on condition” rather than some arbitrary schedule set forth mostly by lawyers based on a worst case scenario aircraft (sitting around, not getting flown, and living on the coast).
The exception to that would be magnetos. They should be inspected every 500hrs. They can’t be borescoped, or have oil analysis, or a filter checked like an engine. They have to be opened up to be looked at. And while it’s open, the “might as well while we’re here” philosophy applies.
I happen to know that Mike Busch had an “economical” overhaul done on both his engines back in the 90’s and has run them to 230% of TBO all the while taking extreme care to inspect them just about every way possible to ensure safety and reliability.

I want to make it clear that I have no “insider knowledge”. He writes and talks about this all the time.

There’s a lot of good data that shows there is a definite “bathtub curve” when it comes to engine reliability. Starts with high risk immediately after overhaul which then drops to low risk for an exceptionally long time (often way beyond TBO) and then slowly rises as time goes by.

I am of the opinion that an engine should only be overhauled under two conditions:

1: The engine can be determined beyond a shadow of a doubt by inspection and published data that it is no longer airworthy.

2: The owner can no longer sleep at night.

These are truly amazing airplanes and we should never lose sleep over being afraid to fly them.

Ultimately it is your airplane and pocket book. You should (and probably will) gather as much information as possible, weigh all the options and make the best decision you can based on the data you have available to you.
If you decide to go all the way to buying new, don’t let anyone tell you that you were wrong.
If you decide to continue and operate based on condition and have all the data and inspections to support that decision, don’t let anyone tell you you’re wrong.

Whatever makes you sleep better!

Cheers
 
I would continue to monitor with oil analysis and cylinder bore scoping. If you decided to do something then I would probably do a TDI/IRAN rather than a major overhaul, especially with 600 hours since major. The last TDI I did in 2019 was at a $8,200 flat rate with standard overhaul kit components (including gasket sets, oil filter, woodruff keys, bearings, O-rings and other types of single-use items) excluding thrust washers. Any extra work like machining or parts repair or replacement was extra. I went with 4 new cylinder assemblies at the time because I had the awful ECI Titan cylinders that caused the trouble in the first place. My case halves had to be machined due to fretting. The crank was lightly ground and the cam was polished. Governor was sent out to MT and P-mags were sent in to EMag Air for inspection just because. When it was all done my charges from the well-known engine shop was just over $13K. That price was pre-covid.
 
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Thanks all. I'm enjoying this conversation so far. As of now I'm leaning towards continuing to fly/monitor, or the TDI.
 
Rick, I dont know where you are located, but for oil analysis silicon is two sources - silicones (RTV) and actual silicon (sand grit). Silicon (grit) increase along with iron indicates some ingestion of dust and/or smoke from a forrest fire. I had that happen a couple of years ago and it took two oil changes to drift back lower. Consideration of when the Si and Fe occurred could indicate it is temporary. If Fe increased sharply but Si didn't, it could be a small amount of rust in the cylinders. That cause, and more frequent operation would reduce the Fe content. Hope this helps determine if the Fe change is temporary or longer term from cam/followers. The latter would (might be?) be cause for a deeper look.
 
Ditto. Fly it and monitor. Overhauling right now is not cost effective and you could have your plane down for a longer period than desired. If you need a part, it could be a Easter Egg hunt for it. See where the leak is coming from. It could be something very easy like the dipstick gasket at the case. I have had some luck with engines blowing/consuming oil by switching back to straight mineral oil and running the hell out of the engine for about 10 hours. Then when the oil blowing/consumption goes down, I went back to Phillips XC. Lycomings will let you know long before the blow up if there is a real problem.
 
Aden Rich said:
Ditto. Fly it and monitor. Overhauling right now is not cost effective and you could have your plane down for a longer period than desired. If you need a part, it could be a Easter Egg hunt for it. See where the leak is coming from. It could be something very easy like the dipstick gasket at the case. I have had some luck with engines blowing/consuming oil by switching back to straight mineral oil and running the hell out of the engine for about 10 hours. Then when the oil blowing/consumption goes down, I went back to Phillips XC. Lycomings will let you know long before the blow up if there is a real problem.
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Interesting . . . so the point of the mineral oil is what - to deglaze the cylinder walls?
 
Mineral oil is not a "slick" as oils with additives in it. It helps where down any micro asperities. It won't deglaze a cylinder. There are some good videos out there on how to do that with the cylinders on. Saavy Aviation has a lot of videos for working around cylinders on the airplane. Using mineral oil and running your engine hard to get some blowby or compressions back up from rings unseating is a relatively inexpensive and easy way to see if you can bring your cylinders up to snuff.
 
Rick RV-4 said:
Interesting . . . so the point of the mineral oil is what - to deglaze the cylinder walls?
Click to expand...
Mineral oil doesn't have the ashless dispersant blended (AD) in. The AD in detergent oil is designed to hold any wear materials in suspension so that they cannot be abrasive to the rest of the moving engine parts. Mineral doesn't have AD so these same wear materials are more free to contact the surfaces of the moving parts, where it is analogous to a lapping compound as the moving parts to wear against each other until they become finely machined together and matched. This is most important for new piston rings and cylinder walls as they lap themselves in together making an almost perfect seal. This is usually indicated by the CHTs where they start hot and then come down after the rings and cylinder walls have broken in together.

So switching back to mineral break-in oil is a way to encourage the engine parts to do a little more lapping of their surfaces together. It turns that same normally undesirable residue back into a desirable tool for a while before changing back to AD oil. While dubious, mineral oil combined with high power settings might help enough to avoid pulling, honing and re-ringing cylinders. One of those "worth a try" things.
 
jliltd said:
Mineral oil doesn't have the ashless dispersant blended (AD) in. The AD in detergent oil is designed to hold any wear materials in suspension so that they cannot be abrasive to the rest of the moving engine parts. Mineral doesn't have AD so these same wear materials are more free to contact the surfaces of the moving parts, where it is analogous to a lapping compound as the moving parts to wear against each other until they become finely machined together and matched. This is most important for new piston rings and cylinder walls as they lap themselves in together making an almost perfect seal. This is usually indicated by the CHTs where they start hot and then come down after the rings and cylinder walls have broken in together.

So switching back to mineral break-in oil is a way to encourage the engine parts to do a little more lapping of their surfaces together. It turns that same normally undesirable residue back into a desirable tool for a while before changing back to AD oil. While dubious, mineral oil combined with high power settings might help enough to avoid pulling, honing and re-ringing cylinders. One of those "worth a try" things.
Click to expand...

Thank you (and Aden). Great explanation(s)!
 
Ok, here's what I did, and it is of course different from what most posters above advise :devilish:
My ship made its first flight 20 years ago, in 2005, and has accumulated 2060 hours to date, increasing since I usually fly short of 400h/year. The engine totals 3942 hours, and has been rebuilt at least once, last in 2005. The engine was originally manufactured in 1977...
When I bought the aircraft, it had not flown for 2 years since the owner was still in hopes of getting his medical back... but I was assured that monthly run-ups were performed during this time (please no lecturing on the pros and cons of run-ups, dedicated threads are to be found elsewhere ;) ). So, assuming the engine O-360-A1A would not last long, I was able to get a discount on the price, and bought the machine. First oil analysis (after 10h) and subsequent ones until about 150h showed elevated iron values, no surprise.
But luckily, the engine has kept running reliably up to today during the 1726h I flew behind. Compressions are still in the 70's for all cylinders, and oil consumption is very good at 2qts/50h. Borescoping shows some glazing as well as some corrosion in the top of the jugs.

2 1/2 years ago I ordered a new engine thru Van's, and that superb looking TB arrived a month ago, and is awaiting installation during next Winter...
Why buy a new engine?

  • price. The price offered the Van's as an OEM is very good, even in today's $$$$$. I'm on the old continent, and the rate of exchange from the CHF is also quite favourable. A local rebuild would have shaved off +/- 7K$
  • upgrade. The new engine is a Thunderbolt. I hope for a smoother running engine, and who knows, with slightly more torque and power?
  • reliability. I've had one engine explode on me during an initial climb in a wooden Falco. This kind of experience is not really pleasant, and I sure would like to avoid performing a copycat. The reason for the engine to go was a ruptured small end of a conrod, due to fatigue.
  • resell value. The presently installed engine still runs nicely and reliably, and probably will for another hundreds of hours. It has already been sold to a scrounger builder.
  • work & downtime. As some of you know, is quite some work replacing an engine. I have an MT propeller which is due for overhaul (blade play, nicks in LE), and an engine mount (RV-7 gusset reinforced) showing 2 small cracks, and which I want repaired. Doing these 3 items at the same time should keep downtime to a minimum, MT quoting 6 weeks for an OH.
  • ancillaries. I will buy a new carb since the last rebuilt was 15 years ago. New hoses will be installed. Still debating about some other items, but my worn alternator belt sure needs replacement too.

There you have it, yet another point of view, though please keep in mind that being located on the other side of the pond, everything aviation is more expensive and complicated. Good luck with your decision (y)
 
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