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Thread: O235-C to O320 upgrade

  1. #1

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    O235-C to O320 upgrade

    Hi, I'm sure there must be threads on doing this conversion (particularly in a 12) but I've tried a load of different search terms and haven't found one!! Can anyone point me at one (them?) please? Basically I'm looking to see how difficult, how much and far reaching this upgrade would be and whether it makes sense versus having (at this point unspecified!!) work done on my O235-C. From the angle (see what I did there?!!) of climb performance, sitting behind an O320 is a no brainer

    Thank you!!!

    P

  2. #2

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    I'd guess most -12's went from 0-235 to 0-295 to 0-320....

    That's what mine did (the 235 - 295 being before my ownership), so not sure if there's many threads on direct 0-235 -0320.

    I believe, here in the States, that almost all the STC's for a -320 conversion require PA-18 tailfeathers....not a big change and if that is all the requirement imposed over in the UK, it's certainly worth it.

    One will want to evaluate the engine mount and the impact on W&B and so forth. While my size tends to mitigate the finer points of W&B, in days gone by, for handling if not for staying in the W&B envelope, if flying by myself, it was beneficial to throw a small backpack all the way to the back of the extended baggage. Obviously, this will vary depending on the aircraft and the engine mount selected.

    Compared to stock, IMO, the best mods are: 0-320 (with PA-18 tailfeathers), flaps, and -18 gear (I think that's as much personal preference as anything).

    The more mods, the more work, weight, and cost (i.e. fuel burn) a -12 is to fly...just something to keep in mind.

    FWIW, in my -12, being a mediocre pilot, nevertheless, if I were light and on my game, I could land the -12 (via slipping, etc) as short with the 0-295 as I can with the big flaps it now has. With the flaps, I can be heavier and still make the short landings. Takeoff (even when the 295 was the starting point) is where the real benefit of the bigger engine shows up. Add flaps and it's even more so.
    Back In Alaska
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  3. #3

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    Quote Originally Posted by pa12drvr View Post
    I'd guess most -12's went from 0-235 to 0-295 to 0-320....

    That's what mine did (the 235 - 295 being before my ownership), so not sure if there's many threads on direct 0-235 -0320.

    I believe, here in the States, that almost all the STC's for a -320 conversion require PA-18 tailfeathers....not a big change and if that is all the requirement imposed over in the UK, it's certainly worth it.

    One will want to evaluate the engine mount and the impact on W&B and so forth. While my size tends to mitigate the finer points of W&B, in days gone by, for handling if not for staying in the W&B envelope, if flying by myself, it was beneficial to throw a small backpack all the way to the back of the extended baggage. Obviously, this will vary depending on the aircraft and the engine mount selected.

    Compared to stock, IMO, the best mods are: 0-320 (with PA-18 tailfeathers), flaps, and -18 gear (I think that's as much personal preference as anything).

    The more mods, the more work, weight, and cost (i.e. fuel burn) a -12 is to fly...just something to keep in mind.

    FWIW, in my -12, being a mediocre pilot, nevertheless, if I were light and on my game, I could land the -12 (via slipping, etc) as short with the 0-295 as I can with the big flaps it now has. With the flaps, I can be heavier and still make the short landings. Takeoff (even when the 295 was the starting point) is where the real benefit of the bigger engine shows up. Add flaps and it's even more so.
    Is the O295 some sort of update to an O290? I haven't heard of this engine, but I do know (have heard) that O290 spares are difficult to get hold of, if not, the 130/140 HP would have been very interesting, as it's obviously not far short of the 150/160 of a 320.

    Do the PA-18 tailfeathers include an enlarged fin, or are they a new rudder, horizontal stabiliser and elevators?

    And 100% yes on the slipping approaches. When I first flew the PA-12 I was constantly floating long on landing, now I land it 100% with a slip (takes me back to my Pitts S-1S!!) and now I can pretty much land it where I choose
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  4. #4

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    For starters, I meant "0-290"....sitting here with an old Garmin 295 on my desk so my fingers made the easy connection and didn't type what I should have....

    The 290 is what was in my -12 when I bought it. It had a few hours on it, but still, the difference (primarily in getup and go) when I switched from the 0-290 (130-ish hp) to the (160 hp) 0320 was very noticeable.

    As I recall, IIRC, my tailfeathers change was horizontal stabs and elevators only (plus reburbishing some of the associated trim and tubing, but that was due to "crap, look how bad that is" vs. required by the STC). No records in front of me, but I don't recall touching the vertical stabilize or rudder when adding the horizontal stuff.
    Back In Alaska
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  5. #5

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    Quote Originally Posted by pa12drvr View Post
    For starters, I meant "0-290"....sitting here with an old Garmin 295 on my desk so my fingers made the easy connection and didn't type what I should have....

    The 290 is what was in my -12 when I bought it. It had a few hours on it, but still, the difference (primarily in getup and go) when I switched from the 0-290 (130-ish hp) to the (160 hp) 0320 was very noticeable.

    As I recall, IIRC, my tailfeathers change was horizontal stabs and elevators only (plus reburbishing some of the associated trim and tubing, but that was due to "crap, look how bad that is" vs. required by the STC). No records in front of me, but I don't recall touching the vertical stabilize or rudder when adding the horizontal stuff.
    Shame it's not a Garmin 295 upgrade route, would be a lot less than the Lycoming route

    Wow, if 130 to 160 HP is very noticeable, something less than 100 to 150/160 is going to be a step change!!!!!!

    And thanks on the tailfeathers info. I've done a lot on the back end, on the trim system and rigging wires, so further upgrade work can build on this

    I think I'm right in saying that the O235/290 engine mount can also take an appropriate O320? and also the fuel flow tests from my (repaired) fuel tanks is PLENTY to cope with the GPH I've seen quoted for a 320!!
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  6. #6

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    With due regard to the different regulatory regimes, I think all the STC's that I looked at required a specific mount to go the -320 route...the mount varied based on the STC, but my fading recollection was that I would have had to purchase a new mount to go from my 290 to a 320...but again, no paperwork in front of me and I'm not sure how the UK handles these type of changes.

    On the "noticeability", my 290 was probably worn out (struggled to get passable compression #'s at the previous annual or two) and at the time of switching, all I did was replace the engine (with a newly OH'd 320) and the mount (plus tailfeathers). So...same old fuselage, wings, tires/wheels, tailwheel, etc. but with some 20 - 30 extra ponies (i.e. minimal weight addition to go with the 20%+ hp increase)

    After that switch, I'm not sure which was the bigger adjustment: a) "Holy cow, I'm flying NOW" or b) when I pull back on the stick, stuff HAPPENS. In the original-to-me configuration, I had to make a very positive input to get flare....when I did that after the new tailfeathers, I managed to get at least 2 touchdowns per landing on few landings.
    Back In Alaska
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  7. #7

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    Went from o235 to o320 on my cub.clone. best change is climb above 7000. Take off alittle shorter, speed alittle faster, fuel burn 3 gph more.

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    I have a early J-5A which was upgraded before I got it with a O-235 C1 engine and PA-12 wings and cowling - the undercarriage is PA-18. Tailfeathers were the same as J-3 which I think are the same as PA-12. She flew nicely but lacked nose up elevator authority at low speed. Due to a parted rudder cable under braking, which led to a locked brake, she ended up on her nose and the engine people wanted a lot to repair the engine.

    I consulted Charly Centre at Crosswinds and fitted a O-320 B1B with 81/43 Borer, Stoddard engine mount ( a short mount) and the larger PA-18 tailplane and elevators - I bought the prop, exhaust, baffles and engine mount from Charly ( very knowledgeable and helpful guy).

    The result is a quite light aircraft (1010 lbs empty) which gets off the ground very quickly indeed and cruises at 115 mph at 2400 with 21Ē tyres. The nose heaviness is gone, I think mainly due to the Stoddard mount and larger elevator area. Charly makes a swing out mount to order which eases access to the rear of the engine, but I didnít buy that.

    I liked the plane before, now I love it - Iím with pa12dvr in the ďHoly CowĒ department!


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    Click image for larger version. 

Name:	Image1568077903.077093.jpg 
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ID:	44392Just adding a picture of the J-5/PA-12 hybrid - the new cowling was professionally color matched, but thatís another story


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    O235-C to O320 upgrade

    If youíre going to upgrade, why stop at an O-320? Go straight to the O-360 with the Crosswinds STOL STC. There is no substitute for displacement.
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  11. #11

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    Quote Originally Posted by windy View Post
    If youíre going to upgrade, why stop at an O-320? Go straight to the O-360 with the Crosswinds STOL STC. There is no substitute for displacement.
    Can't disagree with a thing here.....but (and perhaps I made a mistake in only having two data points) when I evaluated the 320 / 360 160 /180, I flew two -12's with the 360: 1 even had a constant speed prop.

    What put me off of the big engine was the shaking that happened on shutdown (and a slightly lesser degree on startup). Just couldn't get my head to accept it. I'm sure it would have been fine (especially since I subsequently had a frame up overhaul of the whole plane) but went with the -320 in the end.
    Back In Alaska
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  12. #12
    skywagon8a's Avatar
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    Quote Originally Posted by pa12drvr View Post
    .... I flew two -12's with the 360: 1 even had a constant speed prop.

    What put me off of the big engine was the shaking that happened on shutdown ......
    This is a shutdown procedure issue which is called for on the 0-360 which I have described in other threads.
    N1PA

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    Quote Originally Posted by skywagon8a View Post
    This is a shutdown procedure issue which is called for on the 0-360 which I have described in other threads.
    I’ve missed it in other threads. What’s the cliff note version of the 360 shutdown procedure?

  14. #14
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    Run engine at a little over 1000 rpm.
    Pull mixture to idle cut off.
    AFTER the little explosions inside the cylinders stop making noise and before the rpm starts slowing.
    CLOSE and HOLD the throttle closed until the propeller stops.


    If you are experimental and are able to install an electronic ignition system which automatically retards the timing, you can pull the mixture to idle cutoff with the engine running at idle rpm with no shake.
    N1PA
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  15. #15

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    As you go up in horsepower, you obviously go up in weight, and your PA-12 becomes less of the nimble dancer it once was. If you're not interested in backcountry performance, I'd suggest you stick with the 0-235. Flew mine for years with that engine---very reliable, bullet proof, easy to hand-prop, and no need for Super Cub tail feathers. But I was interested in bush performance and upgraded to the 0-320/150 hp/Stoddard STC and then upgraded again to the 0320/160 hp/Borer prop---which I think is a good combination unless routinely flying heavy or at high altitude.
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    Maybe I’m missing something with the 0-360 shutdown with Borer prop. I pull throttle closed idle to 500 or so and pull mixture. I don’t think it shakes at all or just to us to it notice?�� never seemed to be noticeable or excessive.

    Doug

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    A friend of mine has a 320-powered 12, his uses the stock mount but it has some of the tubes beefed up--
    I believe you split a larger tube & weld it in place around the stock tubing.

    BTW the clichť is "no replacement for displacement"--
    it just doesn't pop without the rhyming.
    "No substitute for cubic inches" is another one.
    Cessna Skywagon-- accept no substitute!

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    skywagon8a's Avatar
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    Quote Originally Posted by Colorguns View Post
    Maybe I’m missing something with the 0-360 shutdown with Borer prop. I pull throttle closed idle to 500 or so and pull mixture. I don’t think it shakes at all or just to us to it notice?�� never seemed to be noticeable or excessive.

    Doug
    You are one of the fortunate few. Perhaps it can be attributed to a long propeller giving a better flywheel action? Which prop do you have, as the Borer prop is named after the STC holder Roger Borer and is installed on 0-320 engines.
    N1PA

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    Quote Originally Posted by skywagon8a View Post
    You are one of the fortunate few. Perhaps it can be attributed to a long propeller giving a better flywheel action? Which prop do you have, as the Borer prop is named after the STC holder Roger Borer and is installed on 0-320 engines.
    0-360a2a. Borer 8242 even at an idle of 500 or less, yes can see shake on the exhaust stacks at 500-, probable worse of it, but I was use to dads 185 with seaplane prop. That shook!

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    I hadnít really considered going straight to an O360, as jumping from probably <100 to 180 hp seems a huge jump, but having said that Iíve got maybe 50 hours behind a 360 (carb) in a PA-18 when glider towing and to be honest, even without a glider on the back, it never felt over powered.

    Iíve also got around 100 hours behind a 360 (injection) in a Pitts S-1S and even that didnít feel THAT over powered!!

    In the Pitts particularly, the 360 felt soooooo smooth and in both aircraft, I donít recollect any shaking on shutdown, is it something to do with resonance or the engine mounts? And on the mounts topic, Iím guessing a 235 to 360 swop would need a new mount?


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    I just went from a YO-233 (essentially a lightweight O-235) to a Titan O-340 on my Super Legend Cub. Although I would do it again, it has not been all upside. The airplane is not as light on the controls. It was a really great flying airplane with good performance for the horsepower before. Now it is about 10 knots faster, shorter on TO, and much better on climb. Pitch is heavier, not terrible but heavier.

    So the real question is what are you using the PA 12 for? If it is just fun flying by yourself, you may want to think twice before spending the money on the upgrade. For carrying a load and hitting higher elevations, the bigger engine is a no brainer.

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    Quote Originally Posted by Brandsman View Post
    Click image for larger version. 

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    skywagon8a's Avatar
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    Quote Originally Posted by Lasater View Post
    It was a really great flying airplane with good performance for the horsepower before. Now it is about 10 knots faster, shorter on TO, and much better on climb. Pitch is heavier, not terrible but heavier.
    What is your new empty CG? Likely it moved forward. Place some ballast at the tail post to move the CG back to where it was before you made the engine change. See if that pitch feel lightens up.
    N1PA
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    There was a pretty good article in Vintage Airplane magazine years ago about the flying qualities of up-emgined Luscombes.
    The author owned a 320 powered Luscombe and liked it, but said "it no longer flew like a Luscombe".
    Cessna Skywagon-- accept no substitute!

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    Quote Originally Posted by skywagon8a View Post
    What is your new empty CG? Likely it moved forward. Place some ballast at the tail post to move the CG back to where it was before you made the engine change. See if that pitch feel lightens up.
    With my 0360 in my -12 I needed weight in tail and tools in ext baggage. Now flies with very little nose up trimming. Great balanced plane now that I did this adjustment.
    Doug
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