Ed and Bill,

        Just some ponderings as I progress along my way of understanding
        different carb developments.
                 I notice with a slide carb ( round on round opening) you get         more of a straight line function of air to fuel ratio as it
        progressively opens.
        With a flat slide on round opening you get 'diminishing returns'
        ( my term) as you get past half way.
                 I notice that some carbs have eggs shaped openings, I guess
        that's to even out the percentage of fuel/air mix to percentage
        of opening and to compensate for the enrichening at higher RPM
        i.e. more air to fuel at higher rpm at the fatter end (top).
                 I was wondering what was wrong with a square carb - not
        completely square mind you, but with some roundness to corners
        say 1/2 diameter.
        Wouldn't this provide for a more linier opening to fuel/ air
        ratio mix OR does this pose other problems such as air flow and
        drag/ turbulence?                  George (down under)

    Typing your subject line a bit fast there George?
    Actually Ford tried a completely square opening just prior to going
    to FI. The attempt was to make the carb throat into a supersonic
    nozzle. It had a square, or rather a rectangular opening with a
    specially shaped ramp on one side that moved. It was electronically
    controlled. That was suposed to be it's weak point the electronics
    would faill and the nozzle wouldn't work. Then it was just a crappy
    wierd looking carb! Hard to beat the two circles system. Many have
    tried and many have failed. If your making a new carb, just go round
    and save yourself some trouble. You need the linear change in
    opening to keep everything working properly. You can do it other
    ways, (the Predator carb uses two barn door type flaps that open
    into the throat, leaving a square opening), but EXPECT to have a
    BUNCH of development time in it to get it to work.
    Bill Jepson

         Bill,
    Thanks Bud - I'm hearing you. I won't attempt the degree of
    complexity you are mentioning - but it's all very interesting!
         I thought about an electrically controlled needle that moved up and
    down that was governed by an O2 sensor reading, but it would require
    very fine adjustments, probably a small servo motor - beyond my
    capacity. Until I win Lotto that is!
         Marvelous how the mind probes the different concepts. As soon as I
    sent the last e-mail I realised a completely square carb would have
    too much opening at the lower end - hence the egg shape that has
    been used.
         I'm now thing half round at the bottom ( to centre) and then square
    sides at the top half.
    It's worth looking at - but blending the shapes i.e. carb to round
    inlet tube might be a neat trick.
    George ( down under)