TBO

John221us said:
Ok, on a related note. I have been chasing a running rough issue. The engine was last rebuilt in 1988 (24 years). It is an O-320 Lycoming. It has about 800 hours since overhaul. It accumulated about 500 hours from '88 until '99 and then about 50 hours until 2010, when I bought it (10 hour pilot in training). I have since put about 260 hours on it.
-it only runs rough between 2300 and 2450 RPM.
-It has been doing this for at least 200 hours (I was a new pilot, now I am less comfortable with this issue).
-I have rebuilt the carb, rebuilt and bench tested again, installed loaner carb.
-checked thoroughly for induction leaks (found a small one; didn't fix the problem).
-Checked mags, reversed ignition harness (per SB)
-EGT climbs during the rough running area. This is pronounced when throttling back for cruise. It smooths out at about 2300 and the EGT drops again. Runs smooth at 2,500 with no issues.
-Problem manifests equally on both Mags.
-I just had to put a new cylinder on it. (Compression drop). This did not affect the problem.
-Compressions are now good and I change oil regularly with oil analysis.

My A&P is out of ideas on how to fix the issue (a very respected local shop). Should I be looking at an overhaul, since this is a 24 year old engine?
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24 year old engine I would be looking at each cam lobe lift at the rocker, inspect for slack first.
 
Henning said:
24 year old engine I would be looking at each cam lobe lift at the rocker, inspect for slack first.
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A bad cam will effect the engine out put at all throttle settings.
 
Tom-D said:
Running LOP is how Ted got his engines to go to TBO.
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Negative. The 310 was acquired at TBO from a gentleman who ran ROP everywhere. He did it right, and had good reliability. We an additional 400 hours LOP with good reliability.
 
Ted DuPuis said:
Negative. The 310 was acquired at TBO from a gentleman who ran ROP everywhere. He did it right, and had good reliability. We an additional 400 hours LOP with good reliability.
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IO-470 ?
 
Tom-D said:
A bad cam will effect the engine out put at all throttle settings.
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Most people can only tell rough from smooth, they can't determine even 25% reduced output as long as it's smooth. A bad cam may only cause a vibration in a certain rpm range the smooth back out without quite making full power. Just sayin, if I was looking at a Lycoming that age I'd be suspicious of the camshaft condition.
 
Henning said:
Most people can only tell rough from smooth, they can't determine even 25% reduced output as long as it's smooth. A bad cam may only cause a vibration in a certain rpm range the smooth back out without quite making full power. Just sayin, if I was looking at a Lycoming that age I'd be suspicious of the camshaft condition.
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If that were true he would be talking about low horse power. not just a vib at certain RPM.
 
Tom-D said:
IO-470 ?
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IO-520-E - 300 HP @ 2850 RPM

He ran at about 16-17 gph per side at 25"/2500 RPM. Any leaner and it'd cook cylinders quickly. As it was, it still used cylinders now and then, but not regularly. I found with the engine monitor those power settings did about 400F CHT on hot days, which we know is not optimal.

We ran LOP, about 12 gph per side at 2300 RPM and 24" or WOT. Kept it below 380F on hottest head. Good compressions all around.
 
Ted DuPuis said:
IO-520-E - 300 HP @ 2850 RPM

He ran at about 16-17 gph per side at 25"/2500 RPM. Any leaner and it'd cook cylinders quickly. As it was, it still used cylinders now and then, but not regularly. I found with the engine monitor those power settings did about 400F CHT on hot days, which we know is not optimal.

We ran LOP, about 12 gph per side at 2300 RPM and 24" or WOT. Kept it below 380F on hottest head. Good compressions all around.
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You ran a much lower power setting, no wonder you got better life. he ran ROP and probably in the red box because he never went over the top to the lean side.
 
Tom-D said:
You ran a much lower power setting, no wonder you got better life. he ran ROP and probably in the red box because he never went over the top to the lean side.
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I did 65% LOP (so about 60% really), he did 75% ROP. He was about 150F ROP, so not in the red box, just warmer CHTs than would be optimal.

In 400 hours, I didn't change any cylinders, but he ran all of those cylinders before I did. So yes, we had better reliability, but his wasn't much worse. He was happy with his reliability and he wanted to go fast.

More than one way to skin a cat.
 
Tom-D said:
If that were true he would be talking about low horse power. not just a vib at certain RPM.
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Power is good at full throttle (excellent climb rate for a Cherokee, up to 1000 ft/min with just me in cool weather). I am sure there is no loss of power at full throttle. How do you inspect the cams on an o-320. I was told it was next to impossible. The EGT definately rises during this range and decends again, as you pass through. My mechanic was going to try the probe on a different cylinder, but I don't think he did, yet.
 
Jaybird180 said:
Ted, how long does it take you to fly 400hrs?
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In the context of the 310, we put the 400 hours on it over the course of about 24 months. In that time period, I personally flew 1,000 hours total. There were a number of other planes I flew, though.

Now, though, I'm expecting around 150 hours per year.
 
A much more civilized and gentlemanly number by any measure.

Ted DuPuis said:
In the context of the 310, we put the 400 hours on it over the course of about 24 months. In that time period, I personally flew 1,000 hours total. There were a number of other planes I flew, though.

Now, though, I'm expecting around 150 hours per year.
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wabower said:
A much more civilized and gentlemanly number by any measure.
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Are you accusing me of being civilized or gentlemanly? I thought you knew me better than that.

I am happier with the new number vs. the old number. Better still, I'm expecting more of those hours to be for personal travel.
 
Tom-D said:
This may be true, BUT , there is a far greater chance of the new parts list being a lot longer, and IF it does have a catastrophic failure it will ruin a lot more parts than you might have re-used at TBO.
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First off, let me say that I have been reading your posts and highly respect you for your knowledge and experience Tom.

I ran my Cherokee engine 3400 hrs, 1400 hrs past TBO. Two things if the engine is $14k then I saved $7 per hour by delaying the OH. So by the time the oh was performed the plane was 1400X$7=$9800. So I could afford a few more bad parts.

Second, the engine was disassembled this week and required no new parts other than clean, paint, recert. on cam/crank, grind hone case..... (obviously there will be new jugs, barrings, accessories and what is required to call it an Overhaul) but we found no failures. There was no additional wear. The IA who did the inspection told me that every part measured met serviceable spec and most met new spec.

That was no accident. We used MMO w/mogas, we did 100 hr oil change, filter screen checks, filter inspections and oil analysis, boroscope and compression checks annually and we bench-marked all oil temps/pressure so if something had gone wrong we would likely have seen it, maybe not everything but we were on the look out.

I look at it that I got $9800 free flying. You can discount that a tiny bit as I did rebuild all accessories except alternator which was more or a $1000 in a cherokee, I also remanned a couple of Jugs for $480 ea. It sure helped my cash flow as it was easier to spend $150 at a time to do the accessories and $500 a time to do the jugs than to have to come up with $14,000 plus labor to install.

Maybe it was just the Marvel Mystery oil used?
 
Tony_Scarpelli said:
First off, let me say that I have been reading your posts and highly respect you for your knowledge and experience Tom.

I ran my Cherokee engine 3400 hrs, 1400 hrs past TBO. Two things if the engine is $14k then I saved $7 per hour by delaying the OH. So by the time the oh was performed the plane was 1400X$7=$9800. So I could afford a few more bad parts.

Second, the engine was disassembled this week and required no new parts other than clean, paint, recert. on cam/crank, grind hone case..... (obviously there will be new jugs, barrings, accessories and what is required to call it an Overhaul) but we found no failures. There was no additional wear. The IA who did the inspection told me that every part measured met serviceable spec and most met new spec.

That was no accident. We used MMO w/mogas, we did 100 hr oil change, filter screen checks, filter inspections and oil analysis, boroscope and compression checks annually and we bench-marked all oil temps/pressure so if something had gone wrong we would likely have seen it, maybe not everything but we were on the look out.

I look at it that I got $9800 free flying. You can discount that a tiny bit as I did rebuild all accessories except alternator which was more or a $1000 in a cherokee, I also remanned a couple of Jugs for $480 ea. It sure helped my cash flow as it was easier to spend $150 at a time to do the accessories and $500 a time to do the jugs than to have to come up with $14,000 plus labor to install.

Maybe it was just the Marvel Mystery oil used?
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The MoGas probably had something to do with it, as did flying it frequently.

I'd say that your results are attainable, as I've seen other engines do the same. But Tom bases what he says on what he's seen over years and many, many engines. Because your engine did it doesn't mean that any other engine will necessarily do it, and that's why folks need to make their choices about what they do.

I'm in the school of thought that likes new-fandled devices. And so the 310 is equipped with a full Tanis system, JPI, and I think we're going to buy some engine dehydrators as well. We're hoping that with those, the new engines will make it longer than the 2100 hours we got out of the 1700 TBO IO-520s.
 
Our pawnee gets the snot run out of it for 3 weeks a year. Then it gets its annual oil change and is put away in the barn to sit for a year waiting on the next July to roll around. No picking, no dehydrators, nothing special except I have started adding camguard these last few years since it came out, but not the preceeding decade. Lycoming O-540 has about 3600 hours and 20-some years since overhaul. Runs like a champ.
 
JHW said:
Our pawnee gets the snot run out of it for 3 weeks a year. Then it gets its annual oil change and is put away in the barn to sit for a year waiting on the next July to roll around. No picking, no dehydrators, nothing special except I have started adding camguard these last few years since it came out, but not the preceeding decade. Lycoming O-540 has about 3600 hours and 20-some years since overhaul. Runs like a champ.
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Yeah, Lycomings will handle that sort of treatment pretty well. Plus Peoria isn't too challenging of a climate. Continentals are another story.
 
Ted DuPuis said:
Yeah, Lycomings will handle that sort of treatment pretty well. Plus Peoria isn't too challenging of a climate. Continentals are another story.
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i think its the other way around. lycoming cams go first
 
JHW said:
i think its the other way around. lycoming cams go first
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Correct, but Continentals seem to be more susceptible to corrosion otherwise. At least, that's what most mechs have told me.
 
Greg Bockelman said:
Yeah, but Ted MIGHT be a little biased. :wink2::D
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You're right, I am biased. That's why I'm selling the Lycoming-powered plane, keeping the Continental-powered one, and will not buy another Lycoming-powered aircraft again.

So tell me where my bias is? ;)
 
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