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Thread: -12 or -32? was Carb Differences

  1. #1
    ceweaver's Avatar
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    Default -12 or -32? was Carb Differences

    Evening Group,

    For those who read my intro post a few weeks ago, my thumb is healing nicely (will require surgery to remove the remaining nailbed and reshape a little...but that's the price of making a less than intelligent maneuver) and I have about 4 hours in my Tri-Pacer now. The plane has an O-320-A2B in it and we're (IA and most everybody at airport and carb shops my IA has called) fairly certain that I have a problem with my accelerator pump (at a minimum). My IA couldn't get the full number off the carb but could see 10-3678-?2 (the "?"appears to have been restamped). I have access to a carb off a O-320-E3D for a test flight, but the TCDS for that engine lists a 10-5009 as the carb. I have seen that the 10-5009 is also listed on the O-320-A2B (on the Kelly Aerospace website) but it is not listed on the PA-22 TCDS. What are the differences between these carbs? Can the 10-5009 be used on the plane since it isn't listed on the PA-22 TCDS? Also what's the difference between the -32 and -12? I'd like to get this resolved before Labor Day so my family and I can fly down to the beach for the weekend so I'll probably just order a carb from either Chief or Aircraft Spruce...their prices are fixed and the same as the shops my IA has called.

    Also, am I making too much out of the differences since they all are listed for the O-320-A2B in various places?

    Thanks in advance,
    Chad "Peanub" Weaver

  2. #2
    Administrator Steve Pierce's Avatar
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    Default Re: Carb Differences

    The -12 runs leaner than the -32. Not sure on the other number you posted but when I talked to the Kelly tech guy a few weeks ago he gave me a similar number that had a better atomizing nozzle. I will look up my notes and part numbers at the shop. The just is you are really not legal with a carb not called out in the TCDS however I have used data like the engine TCDS which calls out the other carburetor part number as data to get a field approval. Did it on a PA11 which calls for a Stromberg carb but the airplane had a Marvel Schebler and the TCDS on the C90 allowed it. Field approval was no problem but that was a year or so ago.

  3. #3

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    Default Re: Carb Differences

    The 10-5009 should work for a test flight. The big difference is that these carbs have a smaller main jet opening than the 10-3678-32 -- about 10% smaller. (My guess is that you have the -32 carb which seem to be more common than the -12.) The 5009s also lack an economizer feature present in the -32, but losing this is no big deal.

    If you try the 5009, one thing to watch is the cylinder head temps during long climbs due to less fuel flow and therefore leaner operation. I believe the 5009 was created for the Cessna 172s which have much better cooing systems than our old Pipers.

    There are two versions of the 5009. If the part number is 10-5009N, then it has been modified in the field with an improved main discharge nozzle which provides better fuel atomization for more equal fuel distribution among the cylinders. (Lycoming Service Instruction 1305C deals with this. It is a worthwhile mod.)

    I fly my experimental Pacer with an O-320 A2B running a 10-5217 carb, which is a later version of the basic 5009N design and uses the same improved nozzle. I like the carb, but I found I had to open up the main jet to get more fuel flow to keep the cylinder head temps under 400 in climbs.

    Steve Pierce has a good point about the legal issues, but from an operational perspective, I would have no problems in doing a test flight with the 5009. I just wouldn't engage in long climbs. I would keep the full power climb to maybe 1500 feet then go to a more relaxed on route climb to the test altitude.

    Bob

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    ceweaver's Avatar
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    Default -12 or -32? was Carb Differences

    Steve and Bob,

    Thanks for the information. Is there a desired carb for the 150hp PA-22? Was the -12 intended for planes based and flown in higher areas of the country? Sorry for all the questions. I ordered a -32 before pulling my carb because I had to fly the plane to Lynchburg (LYH) for radio work yesterday. We're planning a trip to Myrtle Beach the weekend after Labor Day to spend with my parents and I'm trying to make sure we have everything in time for me to put a couple of hours on the plane before starting out.

    Y'all are a big help to a new Shortwinger.

    Thanks,
    Chad

  5. #5

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    Default Re: -12 or -32? was Carb Differences

    G'Day Chad,

    I have a copy of a PA22 Overhaul manual on CD that I ordered on Ebay(somewhere in the 'States but can't remember where). It has a parts manual for PA22 plus overhaul and parts manuals for 0215, 0290 and 0320. Also has overhaul manuals for every starter, generator and carby ever fitted to a '22. Good value for, I think, $US35.

    It lists seven different carby assemblies depending on which model engine was fitted:
    OEM Carb. No. -- Carb. No. -- Model No.
    61547 -- A10-3103-1 -- MA3A
    69250 -- A103678-12 -- MA.4SPA
    72394 -- A103678-32 -- MA.4SPA
    71098 -- A103878 -- MA-4-5
    71710 -- A10-4164-1 -- MA-4-5
    72920 -- A10-4401-1 -- MA-6AAA
    72740 -- A10-4404 -- MA-4-5

    I am sure Steve P or JW will also have the same information and can steer you in the right direction.

    Curly

  6. #6

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    Default Re: -12 or -32? was Carb Differences

    i dont think your supposed to put a -32 on the same sump as a -12 one has a tapered throat sump one is straight dats what the carb guru at bulducs in mpls told me although you can get a conversion kit for it which is 180.00

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    taildraggerpilot's Avatar
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    Default Carb Replacement

    What is the better alternative or your recommendation?

    I have the wrong carb (10-3678-32) installed on my engine (O-320-B2A). To retain the -32 carb, I need to install Lycoming kit 71186 per Lycomign SB258. This kit installs a sleeve and retainer pin to improve the flow of the -32 carb.

    I could also exchange my newly rebuilt carb for a 10-3678-12 carb and not modify the oil sump. Which is the better alternative?

    What is the typical fuel burn of a -32 carb with the sleeve installed? Would installing the sleeve improve fuel consumption? Or should I bite the bullet and exchange the carb.

    The kit costs about $80
    An exchanged carb is about $700

    On the surface installing the kit is cheaper, but would the additional fuel savings make buying a -12 carb advantageous?

    Thanks,

  8. #8
    Gilbert Pierce's Avatar
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    Default

    It is hard to say what the typical fuel burn it as the fuel burn vs rpm transfer curve is really vertical in the cruise range. Small change in RPM makes a big change in fuel burn. I lean aggressively. At 2450 rpm and leaned I burn about 8.8 gph. Pull it back to 2350 and I see 7.5 plus or minus. At 2550 it's about 9.5 to 9.8 gph. I occasionally fly with a T-P owner who told me he had a -32 carb. He would be burning 10 gph while I was burning slightly less then nine. When we got to the fuel pumps it was evident.
    Ask folks their fuel burn and it is all over the map. I have an EI FP5L fuel computer and can now see why. Just small changes in the mixture or throttle or altitude all effect fuel burn. Based on flying with others and fueling up at the same time I am comfortable that my fuel burn is less then most. Part of it is the -12 carb, part of is aggressive leaning with my EI UBG16 engine analyzer.

  9. #9
    Administrator Steve Pierce's Avatar
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    Default

    Ben, I have a sleeve you could borrow to rest. It is tapered and would be captured between the carburetor and the small diameter of the sump. The STC to install the 160 hp engine on a Super Cub requires a -32 carburetor but the TCDS on the 160 hp Tri-Pacer allows a -11, -12 or -32. Have consistently seen less fuel burn with the -12 and was confirmed by a carburetor OH facility. That being said I know 160 HP SC drivers w/-32 carbs with a similar fuel burn to the my Dad is posting. If you want to do some testing I could loan you the sleeve.

  10. #10
    andya's Avatar
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    I have an A2B, 150hp with the -32 carb. I typically cruise between 8000-9000, lean to about 80-100 rich of peak with the throttle backed off just enough to not have the enrichment valve working. Seems to consistently do about 8.8-9.0 gph and TAS of 108 knots with a 60" pitch prop and turning about 2500+ at those altitudes and pwr settings. I have the one piece venturi that was installed by an old timer and it seems to work well.
    "Progress is our most important problem"

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