Ma3-SPA carb orientation


A KR-2 Builder started a little internet tempest by asking a discussion group what was the ‘right’ way for his MA3 carb to face on his plane. This came complete with the insinuation that I advise people to mount them ‘backwards’, and speculative responses about it never working, terrible risk, etc. All the great answers you would expect asking a question on a discussion group where most of the people have mystery email names and very few answers come from people who have ever flown the combination.



Above is the MA3, freshly overhauled by D&G Supply in Niles MI, (269)-684-4440. This is the FAA fuel system repair station that is run by Russ Romey. We have been sending builders there for 12 years. He is an excellent source of rebuilt MA3’s and Stromberg NAS-3s. You can read the story here: MA3-spa carb pictures, Wagabond notes. I have an entire section of my website devoted to carbs here: Carburetor Reference page. It has  been there for two an a half years. Because I have good tracking on my page, I can tell that not one single person read it this last week, because it is much more fun to ask internet strangers for answers than do a little reading.


The originator of the question, later sent me a note asking the same question, never mentioning that he had previously asked it on the open net. His question included a picture of his carb linkage spaced out by an An3 bolt with 2″ of washers on it, asking if it was OK to do this. He also mentioned getting advice on this from his local expert who was qualified because he was an A & P and a Tech Councilor.


I will try to keep this short: If you want to know something about your Corvair, ask Myself or Dan Weseman  first, not after you go to the internet and imply I tell people to do things wrong. Second, I have used the term ‘Local Expert’ in a negative sense in countless stories like this: “Local Expert” convinces builder to use cast pistons. I don’t care if your ‘expert’ has an A&P or is a tech councilor. Real A&P’s know never to give advice on any model of plane they haven’t been trained on…Realize also that about 100 experimentals crashed on their first flight last year, and I am going to say that Tech Councilors looked at 80% of them and never spotted the item that caused the issue. (neither did the FAA) And last, if you need to kill yourself, putting the throttle linkage on 2″ of washers on an airframe with poor survivability, will do the job. (Before sending hate mail please read: Steel tube fuselages, “Safe” planes and 250mph accidents)   But I kindly ask that those bent on self destruction please use another tool besides a Corvair powered plane, as I already know plenty of people in the FAA and NTSB, Read Comments on aircraft accidents.



The carb we use is a 10-4894 from an O-200 in a Cessna 150.


In that plane, the data tag faces the prop. It works fine.


In tricycle geared Zenith aircraft, we put the carb on with the data tag facing the firewall for clearance reasons. There are more than 100 planes flying just like this, It works fine, and any internet joker who says it does not has no credibility. We have been flying them that way for more than a decade: 12 years of Zenith’s powered by FlyCorvair Conversions.. It works fine.


On planes were nose gear clearance is not an issue, We install the carb with the data tag facing the prop. We have done this on many airframes, including our 601XL. It works fine.


I have also made a one of a kind installation where the carb was sideways. It worked fine.


When I put a linkage on a carb arm, It either has a fork end, or an AN3 spherical rod end right next to the arm, with an area washer outboard of it, and the bolt always has a cotter pin in it. If done this way it works fine.


If you want to kill yourself, stacking 2″ of an 3 washers on a skinny bolt and putting the throttle linkage on the outboard end of this will do the job It works fine.*

*Just imagine the new pilot on his first flight, suddenly aware on final that his plane doesn’t glide well at the speed he is used to approaching, is startled, and jams the throttle in for power, except the long skinny bolt bends, and the throttle stays shut, and his glide path leads to a point 100 feet short of the threshold. His nose gear breaks off in the soft dirt, the bottom cowl digs in,  breaks the 5/8″ x 5/8″ wood  longerons, fractures the fiberglass header tank, and his IFR panel wiring provides the ignition source.  Right after they put out the fire, The A&P / Tech Councilor will say “It was that God Dammed Corvair motor that killed him, I told him to get an O-200”. 


The 20 minutes it took to write this was probably a waste of my life.



17 Replies to “Ma3-SPA carb orientation”

  1. It’s not a waste William. In Aviation, as in many other activities that can result in fatal events, the Darwin rules continue to be applied. Just as you’ve said many times and correctly so, physics, chemistry, and gravity are all laws that if broken can and often do result the participants death.
    What amuses me is that these very same folks harping about the MA3-SPA “not working” in any other orientation than one are the very same that will INSIST that an automotive electronic fuel injection system right off the automobile is “far safer” than any carburetor.
    Today I started a fresh overhaul Corvair engine. In it is a new Otto OT-10 cam with the loose thrust washer from Clarks Corvairs.

    Because in my opinion you ARE the authority on Corvair engines converted for experimental aviation, I am now very comfortable with the cam operating in my 65 Monza car!

    Our flight Corvair engines will use the cam with the thrust washer tight as designed. We who insist on the best possible powerplant for the money invested are listening closely to you William.

    You are a man of integrity and not many in this world deserve the respect you do. To be born a gentleman is an pass on as a gentleman is an accomplishment. We met once for a short time in person and even then your humbleness in teaching was evident.

    1. Not for one nano second do i question the experience ,wisdom,knowledge etc,possessed by W.W. BUT! [isn’t there always] i for one find the delivery of the valuable information he imparts to be imperious and undiplomatic.As a proclaimed college instructor i would hope he could develop a demeanor in keeping with professorial dignity and still kick ass.

      1. Lee,
        I say things pretty diplomatically the first half dozen times, but only a small percentage listen. Any time I may sound sharp, I can easily point out I have hit the same point, from many diplomatic angles, many times before, but less than half of the builders pay attention. How diplomatic should I remain if the guy is going to hurt himself but he still isn’t listening? I don’t have a set answer for that, but it is the recurring vital question.-ww.

      2. As a one time army drill instructor i can fully empathize with your predicament.

  2. I might ask a local A&P to pass review on my Safety Wiring or Tubing Flaring but they are far from qualified to pass judgement on most homebuilt engine installation details. They are trained to maintain certified aircraft in accordance with the approved repair manuals using best practices. The engineers long ago decided which way the carb should be oriented or how to set up the throttle and mixture control arms so the A&P just keeps it that way. And just because an A&P is a Tech Counsler does not make them qualified for those judgments, it just means that they are willing to work with homebuilders and provide the benefit of that training.

    Saying all that I am constantly amazed at the questions that new comers ask on the Internet knowing that the answer is spelled out in the readily available conversion manuals. I have to wonder are they too lazy to read or too lost to have the bible of successful Corvair conversion on hand as they undertake their own conversion.

  3. Sorry William, your words aren’t wasted on this guy! I look forward to your writings. If anybody agrees that you wasted your time…… well, therein lies the problem…… with them, not you!

  4. For what it’s worth, if anyone happens to be standing around the nose of my 601, please don’t mention that the MA3 is “backwards.” After 391 hours I don’t want my plane to get a funny ideas.


  5. The reality of how humans operate in this world today is the “waste of time”. You bringing that fact to clarity William, is not! Many good lessons in this writing.

  6. I have both the earlier and later manuals, the Chevy service manual and the early Corvair tech/engineering reports. Then of course we have William’s presentations here. Outside of such sourcing it is amazing to observe what people will say about the Corvair. I even had a person once ask if I was using the 4 or 6 cylinder Corvair. It took about five minutes just to establish that it was always a 6 cylinder engine. Go figure.


  7. Gus posted this and of course I read it and I can hear your voice as I do and I just love hearing it like being in the hanger with all of you so many years ago. You are the best!

  8. William, I would like to redeem the 20 minutes of your life you believe you wasted on that article to let you know I did read it, I did enjoy reading and feel I learned something as well! So see! You hit a grand slam in my book! 🙂 thanks for the investment in my future.

  9. Your post on Carb was not a waste. It just shows how common sense has gone out the door these days.
    Remember everybody the devil is in the details and the little details are the things that will kill you.

    Just my two cents, Build them safe!


    []Timothy Shupert
    CADD Technician
    Ayres Associates
    3433 Oakwood Hills Parkway • Eau Claire, WI 54701-7698
    T: 715.831.7642 •

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