O-300 Advice

VictorMike

VictorMike

Filing Flight Plan
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VictorMike
Well I finally took the plunge and bought a 172 to get back into GA after a couple of years- The big planes are becoming a job more and more. So I got myself a 172 with a O-300-D and coming from a lyc with my former K model the pricing for overhauls is a mystery to me. Obviously prices have gone up across the board but does anyone have some recent pricing experience overhauling an O-300 aside from the 41K I just got quoted with a good crank? The engine is right at TBO as it stands, compressions are good and I don't intend to jump right into an overhaul yet but I at least want an idea if it needs to be overhauled sooner rather than later. The airplane has consistently flown as well so I am not all that concerned about corrosion and it was topped with Millenniums recently. Some opinions would be great!

Thanks everyone
 
Recent Columbia Quote at $31.5 K. I’ve had good results with them.

Another guy I know is just way too busy.
 
Ditto for Columbia. They’re a good shop.
 
Anyone of the thought I should just run the engine out till something changes? As it stands it's healthy (knocking on wood) and I just hate fixing something that isn't broke right now. Again, my experience with the O-300s is limited. If it was my old o-320 I wouldn't hesitate.
 
If it were me, I would run it until it needed major work.

The O-300 is notorious for needing top end work every thousand hours or so, so you may be looking at an overhaul soon anyway.

Having said all of that, do what makes you feel most comfortable.
 
VictorMike said:
Anyone of the thought I should just run the engine out till something changes? As it stands it's healthy (knocking on wood) and I just hate fixing something that isn't broke right now. Again, my experience with the O-300s is limited. If it was my old o-320 I wouldn't hesitate.
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I'm definitely of the thought that you should run it until something changes, rather than spend a bunch of money (and assume the risk inherent with major maintenance) on an engine that seems to be working perfectly well. I got forced into an overhaul due to a camshaft issue. I went with LyCon, who seem to have done superb work. Base cost was $25k on an O-360-A4A, with options for various witchcraft taking it up to $33k. My own ended up being rather more expensive due to needing an entirely new camshaft and crankshaft.

All that said, my engine was running perfectly and I would have felt very comfortable flying behind it (even knowing the camshaft issue) until I saw a performance degradation or unsafe finding on inspection. Alas, I didn't have that option. Keep flying that engine!
 
VictorMike said:
Well I finally took the plunge and bought a 172 to get back into GA after a couple of years- The big planes are becoming a job more and more. So I got myself a 172 with a O-300-D and coming from a lyc with my former K model the pricing for overhauls is a mystery to me. Obviously prices have gone up across the board but does anyone have some recent pricing experience overhauling an O-300 aside from the 41K I just got quoted with a good crank? The engine is right at TBO as it stands, compressions are good and I don't intend to jump right into an overhaul yet but I at least want an idea if it needs to be overhauled sooner rather than later. The airplane has consistently flown as well so I am not all that concerned about corrosion and it was topped with Millenniums recently. Some opinions would be great!

Thanks everyone
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You got new jugs so just keep an eye on oil pressure. Drill baby Drill (holes in the sky)
 
sansoneservices said:
You got new jugs so just keep an eye on oil pressure. Drill baby Drill (holes in the sky)
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As I recall the idle oil pressure is really low any way. 5psi as I recall is the minimum. Especially with new cylinders I would run it until something changes.
Maybe look for an used engine or even an STC engine change, O-360 makes these a really nice airplane and easier to get engine parts. Could get used engine with some time left and just mount it when you need it or get it overhauled and have it ready to install when you need it.

Brian
 
I know of several that had new jugs and were flying another 1000 hrs or so

past TBO. Just monitor and you may add draining oil through a paint

strainer at changes.
 
Very subjective. Day VFR in the midwest? Fly it until it stops! (obviously don't do that but I would think the engine will tell you when it's ready). Add IFR, night, mountains, sprawling metropolis or any combination of those four and things get a little more complicated (at least for me)...
 
Your O-300-D is one of the types that has a harmonically balanced crankshaft, with 5th and 6th order crank dampeners. (all O-300's have them) This gives the bottom end much longer lifespan than the earlier engine without crank dampers, and makes the crank and cases pretty indestructible. It's extremely rare to hear of a catastrophic failure in the O-300 family. Cylinders and related components are a wear item, and they are replaceable pretty easy. I recommend replacement of wear components on condition. Mike Busch is the mathematician, and piston engine guru and he has long adopted the 'on condition' replacement of engine components.

The mfg TBO is a dartboard. For almost all piston engines, the lower unit will last double the repl time of the exhaust valve. Other wear components are somewhere in between. Busch has recognized a long mathematical engineering concept called the 'bathtub curve of failure'. Meaning, a component in an engine has a higher rate of failure in the first 50 hours, and concomitantly a higher rate of failure near end of life(for the specific component, crankshaft, exh valve, oil pump, etc). Meaning that once the component reaches around 50 hours, it's highly likely it will survive through the bottom of the bathtub curve and reach it's nominal end of life.

www.aopa.org

Opinion: Savvy Maintenance

Time between overhauls (TBO) is a strange concept. The FAA requires aircraft engine manufacturers to publish TBOs for their engines, but doesn’t require aircraft owners to abide by them.
www.aopa.org

So, based on the math and statistics, your 'new' jugs are a more likely place of failure than catastrophic failure of the lower end. The O-200/300 family do not have oil filters. The best investment you can make by far is an external filter which will trap metal media, and extend oil changes. I have them on each of my legacy Conti engines and I check the filter media each oil change. Oil analysis is also a great tool to verify component gradual and rapid failure.

Summary - go forth and fly past TBO. Put on a filter setup. Do oil analysis at each oil change and make a chart of metals in each report.
 
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Had a 300D in my 172B. Was a great engine if you weren't looking for a rocket ship. I would keep running it and do an oil analysis at oil changes. If you might keep the 300 later put a filter kit on it now too and cut the filter every change.

Mine would make carb ice at cruise power around 5k feet, not unique. I had a carb temp gauge and would add a touch of carb heat to keep the temp above freezing. That would also level all the egts very nicely. Never had the problem again.
 
Glad to hear this. I have a 172B my son is using for his private and then we hope to both use for instrument training. I hope we can finish our instrument ratings without investing in any engine work and get our kit plane done. Fingers crossed that MOSAIC results in increased demand for 172s about the time we sell it.

Our bottom end is past TBO but the engine runs great. A top overhaul wouldnt be devastating if it needs it.
 
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