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O-290 conversion to O-320

P

PA18project

Registered User
Missoula MT
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
 
PA18project said:
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
Click to expand...

You can do a "search" and find plenty of info :D
 
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.
 
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
 
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.
 
Ruidoso Ron said:
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.
Click to expand...

I think I know that guy! :eek:
 
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 :wink:
Thanks again for all the help.

Brad
 
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.
 
JimC said:
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.
Click to expand...

...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...
 
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.
 
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.
 
toobuilder said:
STC... AD??? This is the "Experimental" section, is it not?
Click to expand...

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 :evil:! With that said, I understand how/why some are more comfortable with certified ($!) :bad-words: aircraft :crazyeyes:. Well, to each his own.....and the poor buggers :cry: who are doing commercial work have no choice but to stick with certified aircraft ($!) :bad-words:

Anyway, re: O-290s - Ross Racing Pistons in Calif has the proper size forgings - not for aircraft use of course :wink: - 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......

:peeper

Tom
 
toobuilder said:
STC... AD??? This is the "Experimental" section, is it not?
Click to expand...

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.
 
aalexander said:
toobuilder said:
STC... AD??? This is the "Experimental" section, is it not?
Click to expand...

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.
Click to expand...

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.
 
toobuilder said:
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.
Click to expand...

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?
 
Ruidoso Ron said:
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?
Click to expand...

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.
 
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.
 
toobuilder said:
What AD or STC applies to a bunch of raw tubing that you fabricate into a mount?
Click to expand...

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.
 
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.
 
:D Glad we got that sorted out.:cheers

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.
Click to expand...
That sorta implied, to me anyway :stupid , 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 :bad-words: or experimental :love: 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! :up

Tom
 
Last O-290 cylinders I got were $1100 each outright for overhauled ones. Do you know where some are for a good price?
 
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 :D .

Tom
 
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. :pty:
 
Check Six said:
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.
Click to expand...
That sorta implied, to me anyway :stupid , that some think an STC is necessary for an experimental/homebuilt. Tom
Click to expand...

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.

Check Six said:
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! :up

Tom
Click to expand...

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