Inexpensive carb testing

Builders,

Inexpensive carbs, the testing of the day. Dan Weseman had been looking at an adaptation of a specialized carb for a while. Today was the day we ran it for a long time and ran a lot of flow and hot start tests. It worked pretty good. It is made in America and costs about $400 new.

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Above, the carb feeding a 2700cc Corvair on my run stand outside the SPA/Panther factory.

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Above, The carb and adaptor to our standard Corvair manifold.  The carb is aimed at 200 cid industrial forklift engines. It is not approved for aircraft use by the manufacturer, so if you need support from their tech department, it has to asked in a way that doesn’t threaten the job and livelihood of the guy answering your questions. For people who have a hard time reading between the lines: Don’t call nor email the manufacturer.

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The 1/2″ thick aluminum adaptor was drawn by Dan at is desk, sent to his CNC machine, I tapped the holes, and it was on the run stand start to finish in 60 minutes. Note the carb mounting holes are recessed below the gasket line.As Dan said, some days it is fun to be at work.

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Above, the carb in action. On the same engine, under the same conditions, it gave up less than 40 rpm to a perfectly tuned MA3-SPA. This is the stuff you learn testing. Visually, you can see from the adaptor above, the carb has a much smaller throat diameter than the MA3.  If I show an internet discussion group the smaller carb, 90 percent of the people would state that it would be a terrible power loss. Testing proves that it isn’t. This is why talk is cheap, testing costs money, and being ignorant costs a fortune.

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-ww.

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About William Wynne
I have been continuously building, testing and flying Corvair engines since 1989. Information, parts and components that we developed and tested are now flying on several hundred Corvair powered aircraft. I earned a Bachelor of Science in Professional Aeronautics and an A&P license from Embry-Riddle Aeronautical University, and have a proven 20 year track record of effectively teaching homebuilders how to create and fly their own Corvair powered planes. Much of this is chronicled at www.FlyCorvair.com and in more than 50 magazine articles.

11 Responses to Inexpensive carb testing

  1. Dave Hoehn says:

    William,
    I’m curious about this. I would not expect a forklift engine carb to have provisions for mixture control that could easily be adapted to use in an aircraft. That implies that you and Dan are envisioning this carb only for those aircraft that are never flown at density altitudes of 5000′ and higher (a significant portion, and possibly even a majority, of corvair-powered planes); or possibly you are envisioning it being installed downstream from a normalizing turbo and thus might not need a mixture control for most common flight conditions. As I said, I’m curious; any comments?

  2. Greg Ocker says:

    A lot of older farm equipment used Zenith carbs.
    Might be a source for used carbs.

  3. feregas says:

    Mr. Wynne,

    Would this carb work on a low wing aircraft or only on gravity fed installations?

    Thank you

  4. John Klemin says:

    Just came across this thread and am wondering if the name and model of this carb is going to be revealed someday? Sounds alot like the stromberg. Am still looking for a carb for my corvair which is still aways from being ready for a carb but it seems that boththe Marvel and Stromberg are getting scarce. At least the model number indicated. Is the MA4 not adaptable to use?

    • John, The carb was a particular model of Zenith. For now, if you are looking for a good carb, look at a Stromberg NAS-3 there are plenty of them a MA-4 is way too big.

      • John Klemin says:

        Thanks for the reply. I knew the MA4 was too big but I thought maybe the venturi could be changed to a smaller one and the jets reduced. It’s hard to find good info on these carbs. Plus i have a MA4.( found it in the swap meet at the turkey run this year).I hope the NA S3A stromberg is better than the old 97’s I am used to dealing with. I’ll see ya’ll at one of the colleges this year.

      • NAS-3 is from the aircraft division, it is a different world than a 97.

  5. John Klemin says:

    While surfing the net about carbs, I came across an article on icing. It said that adding ‘EGME’ ethylene glycol monoethyl ether .015% would prevent carb icing. It was named ‘Prist PF 205 low-flow. Have you heard of this? John

  6. John Klemin says:

    Do you have a model number for the stromberg? According to bendix/stromberg they had several different NA S3A1’s depending on the engine it was to go on.

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