C310N vs C310Q and compression drop mystery

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  • #84819

    I’m in market for a 310 and looking at an N and Q model. Am I going to find a big difference between the 2 models? Will parts be more difficult to track down for the N?

    The N has higher TTAF of over 600, and 500/1000SMOH engines, but it has flown 75-100hrs every year during its life.

    The Q has lower TTAF and engines (4000 and 600/600 engines), but it’s been sitting in a hangar since early 2000s. The Q has been annualed about every 18 months but not flown at all. I transcribed the compression for past 3 annuals and I see a huge drop in 2012. This is alarming. Why would compression drop so badly in an engine that is sitting in a hangar? Engine 2, cylinder 2 drops from 72 to 52 compression.

    ENGINE 1
    8/18/09
    78 76 77 65 79 78
    9/2/2011
    78 70 68 62 64 72
    12/15/2013
    71 72 71 68 62 72

    ENGINE 2
    8/18/209
    72 72 73 71 78 74
    9/2/2011
    70 64 60 68 66 64
    12/15/2013
    64 52 64 62 72 60

    I already got quotes for top overhaul and adding 12 cyl egt/cht on both engines, though I worry if this is just the beginning, not the end, of the problems. The Q was also involved in a low speed gear collapse accident in 98, but that just means it has nice new gears, right? I’m new to twins, much to learn.

    #103242

    I fly an N model and I haven’t found it difficult to find parts at all. The big difference for the Q is the hunchback cabin on the later models.

    Given those two planes, I would buy the N. A plane sitting in the hangar for 10+ years will absolutely have problems from sitting. Internal corrosion will occur on the engines. Planes need to fly. Our N has something around 8,000 TTAF. We’ve had some loose rivets, but nothing much for airframe issues from the age.

    Continental cylinders usually aren’t great on keeping compression anyway. The key is keeping CHTs low, regular flying, etc.

    Many people aren’t interested in Pre-Q (or Pre-R) 310s, which I think is doing themselves a disservice. The more I learn about 310s from the A through R, the more convinced I am that they represent great planes for different missions. If you don’t need the hunchback cabin or the long nose, an N represents a fun, sporty plane with good luggage capacity and reasonable efficiency.

    I do really like the Colemill conversion. If you can find one with it, I’d go for it.

    #103243

    Hangar queens can be a problem. Tanks dry out, engines corrode, rodents eat wiring, gauges go bad, ect. The rule is to go out and buy a very well maintained, good plane. Radios and high time engines are a known cost to cure. Look at the plane and see if it shows pride in ownership. The positive for a Q over an N would be a modern T panel and better autopilot. If you look at an N that has had those upgrades then it doesn’t matter. Just be careful in buying an older 310. A low price can be a major red herring. It is very easy to spend a 100k or more on a dog. Get a really good pre-buy.

    PS Before I changed out those cylinder, because of the compressions, I’d fly it 25-30 hours. Assuming that the cylinders aren’t rusted, compressions can easily go up with some use.

    #103244
    dburton
    Participant

      I looked for a 310 for a year. I would go with a late model with the lowest time, paint and interior you can live with and at least a gns430. I found an R model that had not flown much in 5 years but hangered with good paint, interior and radios for a great price. I like the back window in that it brightens up the cabin. The more you fly it the compression will come up and oil consumption will go down. They are very expensive to maintain and not a lot of pilots can fly them so the price is very low. Not very many pilots are looking for one. Good hunting!

      Don C310R

      #103294

      The R’s are almost twice the asking price of the Q. I haven’t sat in an R so I don’t know how much nicer the bigger window is. Are there any surveys on this forum about 310 operational/annual costs and recent sale prices to aid in my search? How about a checklist/guide on items to check before a pre-buy?
      Why is it that not many pilots can fly them?

      I have been doing research on twins and there’s no comparison to 310 in terms of usable load, speed, and economic fuel burn. The other light twins in that category are either slower, or burn more fuel, or both. ie:

      Aztek burns more fuel and flies much slower
      Baron 55 is fast but considerably more cramped cabin and usable load is not really meant for 6 adults, it’s more of a 4 adult plane.
      Seneca II I haven’t looked closely at yet.

      the 310N I am looking at is this one: http://www.ebay.com/itm/331118241350?ssPageName=STRK:MEWAX:IT&_trksid=p3984.m1423.l2649#viTabs_0

      has been flown 75-100hrs every year, kept in annual, and compressions on both engines are great.

      #103296

      The R’s truck-like handling I find makes it a negative vs. an N personally. The big nose is nice because it holds more baggage, but not nice because it’s harder to fit into a standard hangar. An R would not fit into my hangar, for instance.

      I think the “not many pilots can fly them” comes down to the fact that many hobbyist pilots can’t put the money in and don’t fly enough to be able to be safe and proficient in a twin.

      I had an Aztec for 4 years and 1000 hours. It burned less fuel than the 310 (21-24 GPH combined in the Aztec compared to 23-28 in the 310). It is way bigger, but it definitely can’t hold as much. I agree with you on the 310 being the best, which is why we kept the 310 and sold the Aztec. 🙂

      That N you linked has been for sale for a while. I don’t know how much the guy is realistically trying to get for it, but I think he had it listed at over $100k. Personally I think it’s probably worth $80-100k, but it certainly hasn’t been getting much activity. It looks like a nice plane.

      #103299
      dburton
      Participant

        I agree with Ted in that the 310R is a little heavier on the controls and just fits into my T-hanger(by 6ins. on nose and tail). I owned a 65 310J in the 70’s and loved it. The R seems to cruise at 180kts on 25 gph or you can pull it back to 20 gph and sight see. The Q has the back window after serial no. 200. At the low prices of these great 310’s, I would try to get the most plane for the money. Just my thoughts.

        Don 310R

        #103300
        quote TVYKRUTA1:

        I’m in market for a 310 and looking at an N and Q model. Am I going to find a big difference between the 2 models? Will parts be more difficult to track down for the N?

        The N has higher TTAF of over 600, and 500/1000SMOH engines, but it has flown 75-100hrs every year during its life.

        The Q has lower TTAF and engines (4000 and 600/600 engines), but it’s been sitting in a hangar since early 2000s. The Q has been annualed about every 18 months but not flown at all. I transcribed the compression for past 3 annuals and I see a huge drop in 2012. This is alarming. Why would compression drop so badly in an engine that is sitting in a hangar? Engine 2, cylinder 2 drops from 72 to 52 compression.

        I already got quotes for top overhaul and adding 12 cyl egt/cht on both engines, though I worry if this is just the beginning, not the end, of the problems. The Q was also involved in a low speed gear collapse accident in 98, but that just means it has nice new gears, right? I’m new to twins, much to learn.

        Usually cylinders will lose compression just sitting. What can happen is surface corrosion on the inside of the cylinder walls, and stuck rings, etc. As Ted pointed out, I would not replace any cylinder just bc of low compression – especially on an engine that has sat for awhile.

        One key things you want to do is a borescope looking at cylinder conditions (and exhaust valve). You probably will find some rust in one or more cylinders. Usually the ones with the exhaust valve cracked. It is always best to boroscope before the engines are started (after a prolonged time not running). Most likely though, the broker will present you with engines that just had their oil changed, and a quick run up prior to your inspection…. 🙂

        I think another critical task is pulling the pushrods on at least two cylinders and looking at the lifters/camshaft for corrosion. This is more important than the cylinders – bc the cylinders can be replaced but if the cam/lifters are damaged the engine needs to be overhauled.

        Since the early 2000’s is a long time. If I was the seller, I would seriously consider bringing it back to annual and hiring a pilot to fly it, or letting them build twin time for free. Of course, this is not what is typically done probably bc it would be expensive and not without financial risk.

        Much depends on the condition of storage – a humidity and temp controlled hanger would be ideal. More likely is a drafty hanger with no temp control. Near the coast or in wet climates greatly increase the risk of corrosion. The electronics don’t like swings in temp either, and in some areas it is almost raining in the cabin during temp swings.

        #103318

        If corrosion is found inside the cylinders walls and cam shafts, a top overhaul is not enough? Does the engine need complete rebuild?

        #103321

        I found corrosion on the wall cylinders at my first 340. They were 900 hours since new and 28 years old. We did a top overhaul. It was the smoothest engines I’ve ever flown. Sold it, and the new owner flew it to Germany and back.

        #103336
        quote TVYKRUTA1:

        If corrosion is found inside the cylinders walls and cam shafts, a top overhaul is not enough? Does the engine need complete rebuild?

        If the cylinders are lightly rusted or even a little corroded on the top land I would still run them. The rings are not going to be happy, oil consumption could be higher and compression might never be great – but the engine will still run fine with little additional catastrophic risk. It would be a good idea to check compression again after a long ground run and borescope.

        If the lifters only are damaged then they can be replaced. if the cam is damaged then the engine has to come out and be taken apart. You would not have to overhaul it, but you would be doing almost all the work of an overhaul.

        #103337

        If rust, lowered compression and excessive oil burn is not enough to warrant a top overhaul, what signs should I look for that would indicate one is needed? I am going to do prebuy soon so this info is very helpful. I suspect any shop I talk to will recommend an overhaul even if not absolutely necessary since it’s a $20,000 job for them.

        #103343

        The rust will go away with use, and light corrosion remaining is not the worst thing. if the valves are good and seating well, no evidence of cracks, overheating, etc then I would fly.

        When was the engine overhauled? Prolonged disuse dries out seals, rots fluid lines, etc.

        On the cylinders, I would check for cracks, valve issues, and the cylinder bases for cracked studs, smudged bases (dried out cylinder seal or torque lost). Also look carefully for case cracks.

        #103346

        You mentioned that the Baron is not a comfortable 6 place plane. Frankly, the 310 isn’t either. A 310 is roomier than the Baron, but the 5th and 6th seat is barely good for kids. I took mine out for more luggage room. If you really need to carry 6 adults comfortably, you will need a 414 or 421. Even with those planes you can’t fill the tanks and the seats.

        #103347
        quote SGERBER:

        You mentioned that the Baron is not a comfortable 6 place plane. Frankly, the 310 isn’t either. A 310 is roomier than the Baron, but the 5th and 6th seat is barely good for kids. I took mine out for more luggage room. If you really need to carry 6 adults comfortably, you will need a 414 or 421. Even with those planes you can’t fill the tanks and the seats.

        Good point. I put 6 people in the 310, but the rear two people are small and don’t enjoy it.

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