Carb angle help please.

Discussion in 'Inboards' started by sean-nós, Aug 21, 2012.

  1. jonr
    Joined: Sep 2008
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    jonr Senior Member

    Stick a wide band O2 meter on the exhaust and you will know exactly what the mixture is. Then unscrew it and use it elsewhere.
     
  2. WestVanHan
    Joined: Aug 2009
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    WestVanHan Not a Senior Member

    So does that mean the tilt is mainly a concern mostly at idle?:confused::confused:

    I know my runabout idles very rarely.
     
  3. Submarine Tom

    Submarine Tom Previous Member

    You mentioned it ran fine on angle in the previous installation so why fix it if it ain't broke?
     
  4. WestVanHan
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    WestVanHan Not a Senior Member

    I think Jonr has the right idea-I'd be interested to see the results of running it at this angle and testing the exhaust.

    Then putting in the angle plate (with no adjustments) and testing it again to see what the difference is.
     
  5. sean-nós
    Joined: May 2010
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    sean-nós Senior Member


    The last owner had changed the engine and put in an auto engine with an auto carb so I don't know what the original setup was like.
    I did test the new engine with the old carb and it ran fine, now I have a new marine carb for it and I just want to set it up right. "I'm a total newbie to V8":D
     
  6. WestVanHan
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    WestVanHan Not a Senior Member

    ...sounds healthy.

    Once you get her going,please post a video on a good run,gps if you have it!!

    Great looking boat

    Thanks
     
  7. CDK
    Joined: Aug 2007
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    CDK retired engineer

    If that is your conclusion I didn't express myself well enough.

    A tilted carb causes the air/fuel ratio to change: richer if the float is on the high side, leaner if it is on the lower side. A richer mixture has little impact on engine performance, only on your wallet because you pay for fuel wasted. A leaner mixture shows itself by harder starting and decreased engine performance.
    Only if the tilt angle reaches a value where gas flows freely from the main jets, idle running is impaired.
     
  8. tunnels

    tunnels Previous Member

    Has the bowl got a sight glass on the side usually has a spot in the middle if it has thats the fuel height !! use and try and if you find a wedge then use it :D.
     
  9. 7228sedan
    Joined: Nov 2009
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    7228sedan Senior Member

    Pretty sure you'll have no issues at 12 degrees. I've seen quite a few ski boats set up that way with no wedge. Run it as is, and if a problem install a wedge... just my .02 :)
     
  10. Frosty

    Frosty Previous Member

    This is rediculous conversation . Carbs are desigend to run at these angles or cars would not go up hill. Boats dont even go up hill.

    Ever heard of a hill climb where cars go up to 45 degrees and more uphill.

    The carb bowl is as small as it can be and the float is designed so that at any angle the center of the fuel bowl is the same.

    If you took a small perspex box with water in it no matter what you did the level of water in the middle would remain the same.

    It a very small space, all the fuel does not flow to one side. !!!

    Oil pick ups normally need attention before carb angles do.
     
  11. CDK
    Joined: Aug 2007
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    CDK retired engineer

    Nobody said the engine won't work; without a wedge you're wasting fuel because there is not enough oxygen for combustion of the rich mixture.

    I copied a picture from "Automotive Principles & Service" and drew the approximate fuel level through both the original and the 12 degrees rotated one.
    With the fuel level raised almost to the tip of the tube, the air/fuel ratio changes significantly. And so does the fuel bill!
     

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  12. jonr
    Joined: Sep 2008
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    jonr Senior Member

    IMO, set up the carb for a perfect mixture at whatever angle you typically run at (not sitting at the dock) and call it good enough.
     
  13. Frosty

    Frosty Previous Member

    Thats just a line drawing Most single fuel bowl carbs have the bowl on the rear of the throat. I only know of the big 600CFM Holley that has two and I don't think fuel consumption was a priority in its design.

    That particualr down drafty carb is an antiquated carb anyway Either a Zenith or Stromberg not used for 40 years.

    Some of the Brit Su had a seperate fuel bowl not even part of the carb

    The main jet pick up is always at the bottom of the bowl body or picked up from the bottom with an emulsion tube..

    Primary jet does nothing for acceleration but is only idle. Once the butterfly is cracked open transfer or accelerator jets feed fuel in and then the main.
     
  14. CDK
    Joined: Aug 2007
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    CDK retired engineer

    Frosty, look at the picture in post #1. It is a Rochester or lookalike with the bowl on the high side. The simplified line drawing just shows the principle.
     

  15. Bglad
    Joined: May 2010
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    Bglad Senior Member

    I noticed in the video the transmission output flange was turning while the enigne was running and spun up when the engine was revved. If it was in gear now worries. If it was in neutral it could indicate the transmission plates are damaged. If the rotation cannot be easily stopped by hand then I suspect a problem.
     
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