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Thread: O-290 conversion to O-320

  1. #1

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    O-290 conversion to O-320

    Have been seeing a number of these advertised lately. Anyone familiar with the conversion or have any experience with it. I have to admit that I don't even know enough about the differences between the O-290 case and the case for an O-320 to understand if this kind of conversion is even a good idea. All I can guess is that the crank and jugs must be changed out but I don't know if the bore changes, the stroke changes or all of the above (and then some).

    Brad

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    Re: O-290 conversion to O-320

    Quote Originally Posted by PA18project
    Have been seeing a number of these advertised lately. Anyone familiar with the conversion or have any experience with it. I have to admit that I don't even know enough about the differences between the O-290 case and the case for an O-320 to understand if this kind of conversion is even a good idea. All I can guess is that the crank and jugs must be changed out but I don't know if the bore changes, the stroke changes or all of the above (and then some).

    Brad
    You can do a "search" and find plenty of info

  3. #3
    Taledrger's Avatar
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    I think the conversion your referencing is a complete engine conversion. To my knowledge, which certainly is not much compared to a lot of these folks, an O-290 and an O-320 are different engines with no common parts. In other words you can't build a 320 out of a 290.
    Conversion of a O290 Cub to a O320 is pretty straight forward an as Josh mentioned the search will produce a great deal of info on the subject.
    Bob D

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    Thanks for the input. My understanding was that the two engines were completely different as well but I have been seeing a number of engines advertised lately that claim to be converted O-290's (for example, there is one on barnstormers right now from a guy named Gary Barber).
    My curiosity stems from the fact that I have quite a few low time O-290's available to me but I am leaning toward putting a 320 in my project (stretched pacer). The O-290's seem to be getting pricier to rebuild than 320's plus there seems to be little support for them these days. Just trying to tap the collective wisdom as to whether this was even an option. From what I am hearing it sounds like the "converted" O-290's are relatively unheard of which makes me think I will just go with the tried and true O-320 that started life as an O-320. Thanks again.

    Brad

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    Ruidoso Ron's Avatar
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    Brad,
    A good friend of mine just spent $17K, overhauling his O-290-D2 from his L-21B. I would think he could have bought a decent O-320 for the money.

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    FiftyNineSC's Avatar
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    Quote Originally Posted by Ruidoso Ron
    Brad,
    A good friend of mine just spent $17K, overhauling his O-290-D2 from his L-21B. I would think he could have bought a decent O-320 for the money.
    I think I know that guy!

  7. #7
    Ruidoso Ron's Avatar
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    [quote="N4653B
    I think I know that guy! [/quote]

    I'll bet you do! He's in your neighborhood.

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    17K overhauling an O-290. Yikes! I agree, he could have bought a fairly nice O-320 for that money and had money left over.
    Fortunately I don't have any intentions of putting a 290 in my plane and it seems like the converted versions I have been seeing are somewhat of an unknown quantity at best. There are far too many good 320's and 360's to be had to mess with a 290 or a converted 290 in my opinion. Although I hate the fact that I have a number of low time 290's available to me that I would have loved to looked into finding a use for. Now if I could only figure out how to use the continental O-470's that are also available in my stretched pacer
    Thanks again for all the help.

    Brad

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    kase's Avatar
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    Delete,

    I used the STC word on a exp thread, sorry.

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    Biggest issue on converting an O-290 to a narrow-deck O-320 appears to be boring the case out to accept the larger diameter cylinders.

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    Quote Originally Posted by JimC
    Biggest issue on converting an O-290 to a narrow-deck O-320 appears to be boring the case out to accept the larger diameter cylinders.
    ...Which can easily be accomplished by any half competent machine shop. A 480 can be created from a 435 in the same way. It is, after all, essentially a 290 with two more cylinders...

  12. #12

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    okay how about the engine mount? same mount for the 0-290, and the 0-320?
    ...he was so far behind the airplane, he wasn't even a good witness to the crash

  13. #13
    Ruidoso Ron's Avatar
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    Depends on whose STC you use. I used the Wag Aero, and was able to keep the same mount. I understand that there is an AD against one of the STC's that requires that you go to the -15 mount. Doesn't appear to apply to mine, and I don't know why.

  14. #14
    behindpropellers's Avatar
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    By the time you spend all of the money on modifying an 0-290 you will probably have spent just as much as a good 0-320 core.
    Piper J-5A C-90 N40877
    J-5 Project Pictures

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    STC... AD??? This is the "Experimental" section, is it not?

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    Quote Originally Posted by toobuilder
    STC... AD??? This is the "Experimental" section, is it not?
    Exactly what I wuz thinking. After being involved full-time in commercial aviation for, ugh! (boy, do I feel old!), almost thirty (30) years now there is NO WAY I would go the certified route ! With that said, I understand how/why some are more comfortable with certified ($!) aircraft . Well, to each his own.....and the poor buggers who are doing commercial work have no choice but to stick with certified aircraft ($!)

    Anyway, re: O-290s - Ross Racing Pistons in Calif has the proper size forgings - not for aircraft use of course - and will make the pistons cut for TotalSeal rings (or whatever brand one desires) for about $500/set of four. One could bump the compression ratio up 1/2 or so and go with O-320 valves, etc., etc......



    Tom

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    Quote Originally Posted by toobuilder
    STC... AD??? This is the "Experimental" section, is it not?
    Yeah, but....I know that if I were doing some sort of modification to an experimental which was similar to an STC'd modification, I think I'd take a pretty good look at any STCs. ADs too. Might be some interesting or useful information there. Just because you're legally entitled to ignore the AD's doesn't mean you're required to, or that it's wise to do so.

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    Quote Originally Posted by aalexander
    Quote Originally Posted by toobuilder
    STC... AD??? This is the "Experimental" section, is it not?
    Yeah, but....I know that if I were doing some sort of modification to an experimental which was similar to an STC'd modification, I think I'd take a pretty good look at any STCs. ADs too. Might be some interesting or useful information there. Just because you're legally entitled to ignore the AD's doesn't mean you're required to, or that it's wise to do so.
    Researching the design of a product that is available to the certified market is one thing, "USING" a STC on an experimental is quite another. It's not that you have the option of ignoring ADs and STCs on an experimental - they simply do not apply. There is no type certificate to supplement for an experimental. Just because a random selection of welded components resembles a Piper product does not make it one.

    I know people sometimes confuse the terms, but STCs and ADs are only paper, not parts. I'm sure that this is not news to anyone on this board, but there are those of us who are interested in non-production based solutions to problems and that is why we frequent the Experimental section. We're on our own, and that's just how some of us like it.

  19. #19
    Ruidoso Ron's Avatar
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    Quote Originally Posted by toobuilder
    I know people sometimes confuse the terms, but STCs and ADs are only paper, not parts. I'm sure that this is not news to anyone on this board, but there are those of us who are interested in non-production based solutions to problems and that is why we frequent the Experimental section. We're on our own, and that's just how some of us like it.
    True, but some of the AD's are actually based upon a history of component failures (such as the engine mount AD that I referenced above). Aren't these of interest to you?

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    Quote Originally Posted by Ruidoso Ron
    True, but some of the AD's are actually based upon a history of component failures (such as the engine mount AD that I referenced above). Aren't these of interest to you?
    Yes, my point exactly. If the AD was a result of the discovery that if you put engine X on mount Y, the mount would fail because of some unanticipated effect like harmonics, it might be something to pay attention to. Of course, one can take the attitude that "I'm experimental, that doesn't apply" but I think that would be cold comfort as you watch the engine sailing off in a different direction than your airplane, just like in the 3 accidents of certificated airplanes which precipitated the AD.

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    What AD or STC applies to a bunch of raw tubing that you fabricate into a mount? Or has homebuilding evolved into simply screwing together pre-manufactured parts? If it is the latter, by all means, follow the instructions on the STC.

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    Quote Originally Posted by toobuilder
    What AD or STC applies to a bunch of raw tubing that you fabricate into a mount?
    Sighhhh. None. Every single person on this thread agrees that this is true. Nobody is claiming different. Do you not grasp this or are you just playing dumb in order to create an argument that doesn't exist?

    However, if you do use a certificated engine mount in your experimental, (and some folks do) and there is an AD addressing that mount, you might be wise to understand the reasons and implications of that AD. That's all I've said here, and I'm not sure why you're trying to pick a fight by pretending differently.

  23. #23
    Ruidoso Ron's Avatar
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    Thank you aalexander! Ditto.

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    I'm not looking for a fight by any means. What we have here is a failure to communicate. This is typical of an Internet forum. My perspective from the "experimental world" views AD's and other such dealings with the "certified world" as secondary concern. Good info yes, but I build my own stuff wherever possible, so researching STC's is hardly my "default" position. In contrast, your post on the subject suggests that certified parts and the baggage that goes with them is fairly high on your list of considerations. I can see no right vs. wrong in either position, they're just different.

    Though you have a solid argument, I have seen plenty of remarks from others in this section concerning STCs on far more benign parts than structural components, so I should have just given you the benefit of the doubt and kept my mouth shut. I apologize for the miscommunication.

  25. #25

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    Glad we got that sorted out.

    It would certainly be prudent for anyone utilizing certified parts on their homebuilt/experimental to check the ADs. Safety of flight and all that. STCs are another matter, but there is good information in some of them.

    I think what threw some of us off was Ruidoso Ron's (Noisy Ron? How'd you come by that? BTW I really like your Deja Moo...) post
    Depends on whose STC you use. I used the Wag Aero, and was able to keep the same mount. I understand that there is an AD against one of the STC's that requires that you go to the -15 mount. Doesn't appear to apply to mine, and I don't know why.
    That sorta implied, to me anyway , that some think an STC is necessary for an experimental/homebuilt.

    Anyway, I always check ADs and SBs for any certified parts I use regardless of whether it's going into a certified or experimental and I recommend others do the same. The life it saves might be your own.

    Getting back to the O-290s. I have one that I'm looking to build up - plan is to utilize custom pistons as mentioned in my other post and have them cut for Total Seal rings. Most of the other stuff is pretty straight forward and jugs are cheap and fairly plentiful still....for now. Even so, I certainly plan to find out if an O-320 cylinder assy will truely fit without complications. That would be way cool!

    Tom

  26. #26
    Steve Pierce's Avatar
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    Last O-290 cylinders I got were $1100 each outright for overhauled ones. Do you know where some are for a good price?
    Steve Pierce

    Everybody is ignorant, only on different subjects.
    Will Rogers

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    Not to make you feel bad or anything, but a guy I know recently sold a complete O-290 for about the price you paid for two cylinders. I picked up a couple of jugs from another guy I know for a couple hundred $. Since nobody seems to want O-290s nowadays, good deals can be found if you're in the right place at the right time and just lucy .

    Tom

  28. #28
    Ruidoso Ron's Avatar
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    Check Six... Not sure whose STC that AD applied to, but think it was valid. It was brought to my attention by one of our members. (Are you out there?) When I researched it, I found out that it didn't apply to mine. I've had the O-320 for about 6 years, and recently reconditioned the mount. It looks perfect, but I do think the situation warranted investigation. If your engine mount fails, you should be sure that the cowling is in good enough shape to hold the engine on.

    Yes, Ruidoso means noisy. It wasn't reference to me, but to the Rio Ruidoso, after which the town near here was named. I suppose it could apply to me as well.

  29. #29

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    Quote Originally Posted by Check Six

    I think what threw some of us off was Ruidoso Ron's (Noisy Ron? How'd you come by that? BTW I really like your Deja Moo...) post
    Depends on whose STC you use. I used the Wag Aero, and was able to keep the same mount. I understand that there is an AD against one of the STC's that requires that you go to the -15 mount. Doesn't appear to apply to mine, and I don't know why.
    That sorta implied, to me anyway , that some think an STC is necessary for an experimental/homebuilt. Tom
    Nail on the head! While looking through this section, I imagine people with a torch in one hand and a saw in the other, building "cub-like" aircraft from raw stock. The thought that someone would simply purchase certified components and screw them together had not really crossed my mind. So when the question "What do you do about a mount?" was not answered with something about fabricating the correct thrustline or dynafocal angle, but instead, "Depends on the STC you use..." it seemed completely out of place. If we were in the "Modifications" area, then I could understand it. Perhaps I have misread the membership here as it is largely production based. It is unrealistic of me to expect all members to leave the certified world at the door when they come in, so once again - I promise to be more tolerant in the future.

    Quote Originally Posted by Check Six
    Getting back to the O-290s. I have one that I'm looking to build up... ...Even so, I certainly plan to find out if an O-320 cylinder assy will truely fit without complications. That would be way cool!

    Tom
    Fly cut the case for the bigger bore, and the 320 cylinders bolt up.

  30. #30
    Steve Pierce's Avatar
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    I think you will find a great cross section of people here. There are those building every single part from a bunch of tubing and sheet, there are those who are building kits, those who are finding bit a pieces here and there and building from them and there are some that are dreaming at the moment while they gather information. There are also a lot of certified builders and just pilots. I have been pleasantly surprised over the years at the interaction between the home builders and the certified crowd. For the most part I have seen cooperation from everyone and learned a lot from both sides.
    Steve Pierce

    Everybody is ignorant, only on different subjects.
    Will Rogers

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    Fly cut the case for the bigger bore, and the 320 cylinders bolt up.
    No worries about stud wall thickness, clearance issues, stroke, etc.? COOL!

    That'll be the best news I've had in awhile!

    Thanks.

    Tom

  32. #32

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    Quote Originally Posted by Check Six
    Fly cut the case for the bigger bore, and the 320 cylinders bolt up.
    No worries about stud wall thickness, clearance issues, stroke, etc.? COOL!


    Tom
    I'm not going to say "no worries" because I have not yet built one, but I do know the 290 and 320 share the same stroke (3.875) and cylinder bolt pattern. I'm planning the same mod to a 435 (which is a 290 with two added cylinders). If you look at a 320 case, the stud is much closer to the edge than the beefy 290 case. Did Lycoming completely redesign the case to accommodate this change, or did they simply remove material from an overbuilt early case? Logic tells me that they were thinking ahead, and designed enough meat in the 290 to go oversize. I'd certainly do some investigating If I were you, however.

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    sounds like it's time for somebody (volunteers ?) to call an expert. ken @lycon engines, visalia,ca. i'm sure he'd know. he builds some neat @$#^ .
    ...he was so far behind the airplane, he wasn't even a good witness to the crash

  34. #34
    Steve Pierce's Avatar
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    I have to talk to Ken today on about an engine. I will ask him.
    Steve Pierce

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    Will Rogers

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    Quote Originally Posted by Steve Pierce
    I have to talk to Ken today on about an engine. I will ask him.
    Did you find out anything?
    Lorne

  36. #36
    Steve Pierce's Avatar
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    Talked to him for over an hour about a couple of other things and forgot about this. He is supposed to call me back so I will see what he says.
    Steve Pierce

    Everybody is ignorant, only on different subjects.
    Will Rogers

  37. #37
    Steve Pierce's Avatar
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    Ken didn't know for sure but said if the bolt pattern was the same it should work. They do it all the time to make a 580 out of a 540. Might be worth looking into for an STC with no new O-290 cylinders out there.
    Steve Pierce

    Everybody is ignorant, only on different subjects.
    Will Rogers

  38. #38

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    Quote Originally Posted by Steve Pierce
    Ken didn't know for sure but said if the bolt pattern was the same it should work. They do it all the time to make a 580 out of a 540. Might be worth looking into for an STC with no new O-290 cylinders out there.
    Did he mean a 480 out of a 435? A 540 shares the same bore and stroke with the 360. What bigger jugs are available to increase the size of the 540... the 390, perhaps? That makes a 585.

  39. #39
    Steve Pierce's Avatar
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    Lycoming is building a 580 by putting a bigger bore on the 540. Not sure what the equivalent 360 is. Ken machines the 540 and 360 case to except the bigger bore cylinders.
    Steve Pierce

    Everybody is ignorant, only on different subjects.
    Will Rogers

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    I've heard that an O-360 crank (and jugs of course) can be installed in an O-320 to convert it to 360. Any truth to that? If true, could a 290 also be taken to 360?

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