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Thread: PA-12 Long or Short Engine Mount

  1. #1

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    PA-12 Long or Short Engine Mount

    Hi Folks,
    I am the new happy owner of a Pa-12. Bought it 2 months ago and loving it.
    It has 160hp and am looking at ordering the Leading Edge (now Power Flow) exhaust for extra hp on floats.
    Has anyone experienced it on a PA-12?
    Anyone tried their RMW version (Revised Muffler Weldment)?
    How do I know if my mount is the short or the long one if I don't have the original O320 STC installation paperwork?
    Thanks All!

  2. #2
    Gordon Misch's Avatar
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    Personal opinion only, from a -12 owner. Long mount looks graceful; short mount (which I now have) looks stubby.
    Gordon

    N4328M KTDO
    My SPOT: tinyurl.com/N4328M (case sensitive)
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  3. #3
    windy's Avatar
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    If you have the original PA-12 cowling, have a ton of space between the back of the engine and the firewall, and it feels nose heavy on landing, you have the long mount. If there’s hardly any room behind the engine, like an oil cooler would barely fit without being really close to the firewall, then you have the short mount.

    I had the Leading Edge exhaust on my PA-12 with the short mount and an O-320 150hp engine. I couldn’t tell any difference in power from the exhaust. The aircraft weight and CG location make a lot bigger difference in performance and is a lot cheaper than the LE exhaust. I did not like the LE exhaust because the muffler was behind the engine and it radiated a lot of heat into the cockpit. In the summer, it was uncomfortably hot. I sold the LE exhaust when I upgraded to an O-360 engine. The guy I sold it to put it on his Pacer & flew with both exhausts on the same day and couldn’t tell the difference.


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  4. #4

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    Leading Edge exhaust is heavy. More weight is the last thing a -12 needs on its nose.
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  5. #5
    TurboBeaver's Avatar
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    Windy and Kevin are giving you good advice, that exhaust is Not going to fix your problem.......... you would be ALOT happier with the results from maybe a set of 160 pistons, vortex generators? Rerig your wings and get rid of a bunch of washout? Ditch some weight? Do you have a lite weight starter, alternator, oil cooler???? EarthX battery? How much pitch in your prop?
    What is the AOI between your floats and bottom of your wing? So many things that are going to net you way better performance than the exhaust line of thinking.
    A 84/35 Catto would breath new life into your 12 and help your CG in a big way, legality is another issue.
    you bought a great airplane, have fun with it.
    e
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  6. #6
    Steve Pierce's Avatar
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    Sutton exhaust will give you more rpm and save weight and get away from the exhaust AD and gets the muffler and the heat off the firewall.
    Steve Pierce

    Everybody is ignorant, only on different subjects.
    Will Rogers
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  7. #7

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    How does your mechanic sign off your annual without logs that include STC or other major modifications?
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  8. #8
    akavidflyer's Avatar
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    If you can lift the tail with 2 fingers you have the long mount. With said mount be very careful lifting the tail above your waist or you will be trying to rope the tail and pull it back down as it stands on its nose.

  9. #9

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    If you have a short mount you likely have a PA-18 exhaust. Replace the muffler with an Atlee Dodge Hotrod muffler and you'll recognize some added performance. A 160hp short mount PA-12 on EDO 2000s is a really fun combo. Even with the short mount you'll appreciate some weight aft when on floats.

    Fond memories.
    Attached Thumbnails Attached Thumbnails Click image for larger version. 

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    Last edited by stewartb; 08-04-2021 at 03:34 PM.
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  10. #10
    TurboBeaver's Avatar
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    https://www.dropbox.com/sh/n8v3r70kr...TSLd3bSza?dl=0
    Folks shouldn't forget a long mount has advantages when loaded heavy aft, like anytime you haul 3 adults. The short mount is advantage ALONE, lite,CG wise. BUT a long mount combined with a lightweight starter/alt, cooler moved to back, and a composite prop will net around the same CG as the short mount does.
    Should perform like this Cruiser, with 1/4 tanks and two hind quarters of a bull moose on board.???????
    That big Catto prop wrapping up 2500 plus as it makes the turn?
    PA12's rigged up correctly are dam fine floatplanes! Time it, up onto the step; with around 350lbs moose meat in the back, Here is the actual spot. Click image for larger version. 

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    Not alot of floatplane traffic in or out of that location.Click image for larger version. 

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    Attached Thumbnails Attached Thumbnails Click image for larger version. 

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    Last edited by TurboBeaver; 08-08-2021 at 06:51 PM.
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