IO-520A pre-buy advice?

Hope this is not too far off topic, i am looking at a Navion to purchase that has been modified with an IO-520A engine. It is a run-out so I'm assuming we'll be changing out for a rebuilt in the near future. My question is, is there anything I need to be especially aware of in regards to this particular model engine? I am looking at couple different planes with different engines,(io-520BA, io-470H) but his one has most of the options etc I want. Just want to know what the reputation of this model engine is.
Thanks
Dave

Dave - just FYI, I moved your post from the other thread to start this one as I thought it was distinct enough to merit its own discussion.

Cheers -

Hal

Can't say I know any problems with the -A in Navions off the top of my head. You might try on yahoo groups in navion_aircraft_mail.

One thing to investigate (since it is run out) if this model is eligible for one of the "rebuild into an IO-550" mods.
Under what authority was it installed? I am only aware of authorizations for =B, -BA, and -BB.
What model Navion is it in?

I am looking at that option as well. This particular airplane has a one-time STC for the install. It is an "A" model that has the "beef-up kit" installed to allow for engines over 250 hp. It's just that if we go the upgrade to IO-550B route, the engine cost about 10K more, then its new tubular mount, fiberglass nosebowl and basket, new induction, exhaust, plus the STC, plus a lot of little things that add up to big$$$. So it would be much cheaper to stay with the same model. That's why I was hoping for input as to any particular weaknesses to the engine that would not be addressed in a "new" rebuilt IO-520A from Continental.
Any help is appreciated.

I had a T-34 A with a Cont O-470, leaked some oil, but ran and ran, not much maintenance. Not a lot of power, ok down low, hard to get much climb over 12,000 or so.
I now have Beech with a TSIO 520. Lot's of maintenance, often trouble with exhaust valves, overheating cylinders in climb. IO -550 seems some of the same, maybe a litttle less trouble. More power down low, still runs out of power if you need to go high.That is where the TSIO shines, I have been to about 19,000 with some more left.

The other problem is that the Russel Druett mount/cowl/STC kits are currently unavailable. Russell (Sr.) was killed in a car crash last year. His son hasn't quite figured out what to do with the business last I heard.

I've had an IO-550-B (on the Druett mount...which I have the world's record in turn around time getting delivered I believe). I've not had any problem with the engine other than the idiot starter drive adapter (finger pointing between Continental and Niagra).

I recently heard that Ryan Douthitt of Chino may have the STC or something very similar soon. Let's hope so.

IO-520 is a good engine. Take a good look for case cracking in the pre-buy as that will add about $10 grand to an overhaul if the case halves have to be replaced, they can be welded if not to bad and the early ones are known for cracking.

We change many more cylinders on our O-470,s than on the 520, and it make considerably more power than a O-470. When broken in properly, ours do not burn any oil and make TBO (we overhual at TBO). It will burn about two more gph than the O-470.

Thanks for the info. I'll report how the inspection goes.

I am not personally familiar with I 0 -520, but I know a lot about the TSIO 520, mine and friends. I have not heard of any of them making it past 1000 hours without some problem with exhaust valve leaking, burning. Of course Cont claims it is all the pilot's fault; just like Beech used to claim problems with the tails falling off V tails was all the pilot's fault. Now these same type pilots did not have tails falling off when they flew Mooneys, like mine, nor did they have compression problems or valve problems when flying Lycomimg.
I have heard that the non turbo, IO 520 or 550 is NOT free of such problems, may have a few less, may run a little cooler in climb.
I agree that Cont 520 s don't burn much oil, they just burn up the exhaust valves. Oil would be a lot cheaper.
For the reader who says his go to TBO, I'd like to hear details, what plane, where, who is the overhauler, what cylinders?
I forgot to mention case cracking. One very experienced shop told me that most of the cracks are around the area where the gear driven alternator mounts on the front right of the case. He says extra balancing of the alternator helps the problem. My plane had a cracked engine case for the previous owner, and i had one on another engine. Cont probably claims it is the pilots fault also, maybe we take off the cowling and jump up and down on the alternator.

As for as blaming pilots for factory or design problems, funny thing happened with V tail Bonanzas. Once the FAA, and Av Consumer magazine forced Beech to admit their really was a factory problem; and they issued an AD to check control cables, ruddervator balance and in some cases ad reinforcment, the problem of bad pilots or pilot error went away. I haven't heard of a V tail failure in years.
A better plane seemed to make all the pilots as smart as when they were flying Mooneys.

I operate one IO-520 on a Cessna 185 and nine O-470 on Cessna 180 (4)/182 (5)s. All professionally flown for natural resource work in the upper midwest. We rarely get above two thousand feet MSL and spend a lot of time at reduced power settings (15-20 inches,2000-2200 rpm), but when we do cruise we cruise hard (24/2400) to get where we are going. The aircraft are keep in a heated hanger (46 f) and never spend the night outside, they average 600 hours a year.

We are half way thru the third overhaul of the 520 and have yet to change a cylinder between overhauls, we could be just be very lucky, but I am very particular about how it is operated. I personally fly 99% of the hours on the 520 and am religous about cooling the engine for shutdown.

When I was first checked out in the 185, my former boss told me they were famous for warping exhaust valves (then burning them) and the secret was to get them as cool as you could and then to minimize the windmilling at actual shutdown (lowest rpm possible). I actually pull on the throttle when I am closing the mixture. We set idles at 500 rpm and I usually see 450 by pulling on the vernier throttle. They warp because they draft in cold air while windmilling just those few blades at shutdown, particularlly in winter.

Our overhauls are done at Popular Grove airmotive and we have had good luck with them. We did have several of our engines with the bad batch of cylinder, including the IO- 520. I put 395 hours on those cylinder without any problems and they were warrantied (had to come off at 400hrs.)

We did have the cases cracked at the last overhaul of the 520, but at the bases of the middle cylinders. We have a rear mounted belt driven alternator on it.

The O-470s seem to crack more cylinders than have bad valves problems.

Again, we could be very lucky,

Luke

Have you gone to the faa website and looked up AD's? Complying with ad's at overhaul can be expensive and most engine ads have to be cw at overhaul....just a thought

Sent from my DROIDX using Tapatalk

LLuke, that's great info. I think one of your secrets is that you spend most of your time at low power steady cruise, and a low altitude so that would be very easy on an engine; and is unlike what most of us probably fly.
For instance , I go back a forth from Aspen at 7800 feet to Denver at 5280 often, and I have to climb to 13,500 or 14,500 maybe higher enroute. The trip is less than an hour, but a climb and descent at ethier end. I have also flown to Texas, Phoenix, Santa Fe, and Oshkosh. I have done all of these in my T-34A (0-470)and Beech 36 TC. The 34 tends to run high oil temp in climb, and the 36 definitely tends to have high cly head temp in climb, right up to red line in the summer, even at 120 knots and full rich climb.

As for the valve troubles, none in the 0-470, but a lot in the TSIO -520 UB. I don't think it is related to valve warping or cooling. I have never heard of that before, and also it is standard to cool down the engine at 1000 rpm idle for 4 min to cool the turbo oil and bearings.
As far as everything that I have heard and seen and read the problem in not valves overcooling and warping; rather it is exhaust valves burning, seats burning, and leaking, from overheating. If cooling and warping was the issue it might also hit intake valves and we don't see any trouble with them.
Also running your engines in the 180 , 185 may offer more air flown and better cooling over the engine that the tightly cowled Bonanza.
Thanks a lot for your input.

To my knowledge the big Continental engines doesn't have much in the way of AD's. There are a few to make sure you don't have certain after market parks (certain Superior Air Parts cylinders, etc...).
The biggy is the crank controversy of the early-to-mid nineties but hopefully all that has been taken care of by now.

Quote:

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Originally Posted by Bill Greenwood

I am not personally familiar with I 0 -520, but I know a lot about the TSIO 520, mine and friends. I have not heard of any of them making it past 1000 hours without some problem with exhaust valve leaking, burning.

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Both TSIO-520-BB engines on my Cessna T310R made it to 1900 hours without a cylinder coming off. The engines are now at 2800 hours SMOH and 4700 hours SNEW, and I still have 9 out of the original 12 cylinders in service, only three had to be removed in 4700 hours. So I have to disagree with Bill's assessment. If you treat these engines right, they will treat you right.

I am not an A&P, but I have been shopping for a Navion for a while.
You might even be looking at the same aircraft that I have already looked at.
My mechanic advised me that there are two things on the IO-520A that might make an overhaul a less viable option than a factory reman, depending on the individual engine. Check these two things:
1. the light case was known to crack, so the particular case might be unusable.
2. the crank, if not a VAR crank, will not be usable.

In other words, if your aircraft has an unusable crank and case, then plan on a factory reman replacement, not an overhaul.

Again, these are specific to the engine in a particular aircraft, I am not saying all io-520a's are bad.
You might want to get the serial nbrs from the engine, and give them to somebody smart.


Bill

The "heavy case" may have helped lessen cracks, but did not stop them altogether, it still happens.

If you are looking at a Navion with a 520, be sure to check the paperwork. My friend bought a really nice looking Navion with a 520 engine, but turns out there is a question of the legality when the O-470 was replaced with the 520. The seller was working with the FAA to get full approval, but he passed away and not it is in limbo. He may get it resolved or may be able to fly in experimental category, don't know yet.
I guess most of the crank problems were resolved some years ago unless it is an older engine.

Mike, it's not "Bill.s assessment" that there are both exhaust valve problems and case cracking problems on Cont 520s, and to some extent 550s.
Check with any good oh shop, Aviation Consumer, and /or the Bonanza assoc or owners.
I don't know many people who fly 310s. It is possible that you have different cowlings and therefore better cooling in that engine installation. Also you may spend more time in level long distance cruise than others do, maybe even on IFR plans, and that may be easier on the engine. I would like to read your methods of operating that make your engines last so long.

Cont likes to make out like it is the pilot who is "not treating the engine right". Funny thing, when I flew a Mooney 201 with a Lycoming for 10 years all the way to TBO, same pilot, mostly same airports, same weather; I never had a case crack or an exhaust valve problem. I only got dumb when I got the Bonanza? Maybe if I wrote Lycoming on the engine it would last longer.

Kind of like some years back about 400 people were killed over the years in Bonanza v tail breakups. Of course, Beech did not want to admit that something might be wrong with their design. Therefore it must be the pilots fault. Nevermind that Mooneys were not coming apart in the air, even with less expericened pilots. Author Barry Schiff even wrote a puff piece on how good the Beech must be and therefore it must be the pilots fault.
Finally after many Aviation Consumer articles the FAA could not ignore it any longer,and they issued an AD to inspect the tails and to rebalance and in some cases reinforce the tail structure.
VIOLA! Virtually overnight the stupid pilots that had broken all those planes for years suddenly got so much smarter and nowadays tail failure and breakup is almost unheard of in a Bonanza.

Quote:

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Originally Posted by Bill Greenwood

...there are both exhaust valve problems and case cracking problems on Cont 520s, and to some extent 550s.

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Two different issues, Bill.

Case cracking is (and always has been) a known problem with big-bore Continental engines. I have never heard anyone suggest that pilot technique has anything to do with case cracking. Some models crack more than others. (Permold-case engines crack more than sandcast-case engines. Continental IO-360s crack more than any other model. Permold TSIO-520s crack more if they are red-lined at 325 or 335 HP than if they are red-lined at 285 HP. Etc.)

Exhaust valves are another issue. There have been periods of time (specifically the late 1990s and early 2000s) when TCM had problems with their cylinder manufacturing process, resulting in premature exhaust valve failure even in the face of perfect pilot technique. Those exact same factory cylinders when re-valved by a good cylinder shop (who post-reamed the guides and got the geometry right) would routinely make it to TBO with no valve issues. On the other hand, TCM cylinders manufactured in the 70s and 80s, and those manufactured after about 2005, do not have that problem so far as I've been able to tell.

Another problem is that tens of thousands of TCM cylinders have been pulled because of alleged exhaust valve problems that actually don't exist. Since 2003, TCM's guidance (SB03-3) states that the cylinder is airworthy unless the compression gets down to the 40s. Even if it gets down to the 40s or below, SB03-3 requires that the cylinder be borescoped to determine the true condition of the exhaust valve. If the valve looks normal under the borescope, then SB03-3 requires that the aircraft be flown for at least 45 minutes and then the compression re-tested.

Case in point: About two weeks ago, one of our Savvy-managed Cirrus SR22s went into annual inspection. The shop reported that one of the cylinders measured 38/80 with leakage past the exhaust valve. We had them borescope the cylinder and it looked normal. We dumped and analyzed the digital engine monitor data, and saw absolutely no evidence of exhaust valve leakage. We then directed the shop to complete the annual, sign it off as airworthy, then had the owner fly the airplane for an hour and bring it back to the shop, where they pulled the top cowl and re-tested the one cylinder. On the re-test, the cylinder measured 72/80.

Compression tests are highly unreliable and non-repeatable. No cylinder should ever be pulled based solely on a single compression test. The borescope is the gold standard for assessing cylinder airworthiness. The compression test is highly unreliable, primarily because it tests the cylinder under conditions that have no relationship whatsoever to the conditions that are present when the engine is running and making power. This is precisely why TCM wrote SB03-3 the way it did. IMHO, SB03-3 is the best guidance that has ever been written on the subject of when to pull a jug and when not to. On our professionally-managed Continental-powered aircraft, we always require that shops follow the guidance of SB03-3 to the letter. I can't count the number of unnecessary cylinder removals and valve replacements we've prevented by doing that.

Thanks for all the great advice. IF we buy it, will most likely take the Factory Reman option due to the Case/Crank issue.

Mike, as for the compression test, I have mine done when still warm, and I might see a variation of 10 lbs or so; but I would sure be surprised to find a 38lb test that did not indicate an actual problem,and was ok one flight later.
If the exhaust valves are actually leaking I have found that you can hear the compressed air coming out of the exhaust pipe.
In my case, I bought a 88 Be36 TC, with about 1200 hours, seemed to be in good shape. Frankly, since I had been flying a Mooney 201 for 10 years and it made it to TBO,and my T-34A had no real problems with the 0-470, I was not really aware and not as concerned with Cont engine problems as I might have been and my prebuy inspection may have missed something. The plane had already has one factory rebuilt engine for the previous owner due to case crack under warranty, so I sort of assumed the new engine to be good; and I also wanted the plane as equipped and as priced.
I flew it for awhile, then on the way back from Sun n Fun, I noticed a rougher idle and loss of power on climb; still had good mag checks.
When we got it home, one cylinder had NO, THAT IS ZERO, compression. Flying it another hour was not going to help; there was actually a pie shape piece missing out of the exhaust valve, just gone, so that I had about 315* of the original
360* face. I had never seen something that bad. A couple of other ones were low but had some compression.
The factory sold me some cylinders at cost. but I have still had some problems over the years, and had to buy a low time engine to replace that one due to a major case crack behind the alternator. By the way, my work back then was at an expert Beech shop, Pearce at Meadowlake.

I didn't know that Cont factory cylinders had good and bad years. Thanks for the info. As for as I know, down there in Alabama, the teach real good football, but not so much readin n ritin or engine building.

I may overhaul mine next year, am leaning toward Ram in Waco, and probably new ECI cylinders. I would appreciate your suggestion on this. Thanks

PS my friend has their flight school Cirrus 22 down right now and engine at Firewall for a case crack.

Quote:

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Originally Posted by Bill Greenwood

Mike, as for the compression test, I have mine done when still warm, and I might see a variation of 10 lbs or so; but I would sure be surprised to find a 38lb test that did not indicate an actual problem,and was ok one flight later.

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I think Mike's point about SB03-3 was that compression testing does not replicate engine running conditions and perhaps a slightly sticky valve guide during a "warm" compression test still might cause leakage that would not be present during engine running conditions (high temps and chamber pressures). This is all assuming that one follows the SB's guidance and takes a look-see with a borescope to rule out obvious damage before the one hour flight and re-check.

Quote:

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Originally Posted by Bill Greenwood

When we got it home, one cylinder had NO, THAT IS ZERO, compression. Flying it another hour was not going to help; there was actually a pie shape piece missing out of the exhaust valve, just gone, so that I had about 315* of the original
360* face. I had never seen something that bad. A couple of other ones were low but had some compression.

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The one hour flight would not be done in this case once the borescope inspection revealed the valve damage. The one hour flight is only done when the borescope inspection reveals no damage...

Drew, thanks. But you didn't include the part I wrote about being able to hear the air from the compression test leaking out the exhaust pipe. We could clearly hear that,even could feel it with my hand., and it was down on takeoff and climb power. So not counting any other check it was obvious that at least one exhaust valve was leaking a lot. I don't think intake valves leak as often since they run cooler, but if they did the air would go back into the intake. If the rings leaked, the air would go into the crankcase.
My point was how bad a Continental engine exhaust valve problem can be, such as to have an entire chunk missing on the valve head. I have never seen or heard of that on a Lycoming, certainly not the 3 I have owned. I have seen an Allison damaged by detonation when the line boy put jet fuel instead of avgas in, and it was spark plug damage, nothing like these valves.
And as for a "sticking valve", yes that can happen, but it is usually on a cold start up, "morning sickness" and frees up as the engine warms up. When I had the big problem first time was spring, after Sun N Fun, so not even cold weather.

I have looked up Mike's article about this, had even seen it before. I think the use of the borescope to see the color of the valve head is good. it seems to me that there are at least two kinds or qualities of borescope, I am not sure if most shops have the expensive one. I am going to talk to my a&p who is a Beech specialist in Boulder.

I am not at all convinced however that an engine with compression at 40 is going to produce full power. It is just not logical, that you can be leaking half the air out and have full power. Maybe if none of the leak is past the valves, and it is all going out the rings, the turbo can cover up a lot of that. I know that some older Lycoming engines can still run well for years even is showing some wear.
I am suspicious that what TCM has really done is just lower the standard on what is considered good. Maybe that is ok. And it is unlikely that is compression is at 40 that all leakage is just the rings. TCM engines don't burn much oil,don't seem to have that much problem with rings; or maybe it is just the the case cracks and exhaust valve failures occur first.
Other than that, I do like the plane, it is good for traveling. My Mooney 201 was a good plane also.

I am not an a&p, though am a graduate of Air Force mech school,and have been an owner and pilot for 32 years with experience with 5 different brand of engines, so I have some idea of engine issues.