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Fuel retention in carb

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  • Fuel retention in carb

    I am having a small problem with fuel being dumped from the carb into the intake after the engine is turned off. My car is a '56 Power Hawk with a Carter 4-bbl. After cutting off the engine, I can hear a noticable gurgling sound. If I try to start up the engine in the next day or so, I can't do so until I pour a few ounces of gas into the carb. Turns over just fine then. A weak fuel pump may be contributing to the problem when starting, but once she kicks over (w/ gas added) she seems to run fine. What's wrong w/ my carb?? Perhaps I missed something during the rebuild.

    Thanks, Dan

  • #2
    Sounds like two different issues. The sound amy just be the modern gasoline boiling off, but the car should start even with a dry carb. The accelerator pump should squirt fresh gas in on a restart. It is possible that you have a weak fuel pump, but I'd check to make sure the accelrator pump is squirting when you pomp the throttle.

    Studebaker On The Net http://stude.com
    64 R2 4 speed Challenger (Plain Wrapper)
    63 R2 4 speed GT Hawk
    55 Speedster
    50 2R 10 truck
    JDP Maryland

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    • #3
      Thanks John

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      • #4
        quote:Originally posted by PwrHawk

        I am having a small problem with fuel being dumped from the carb into the intake after the engine is turned off. My car is a '56 Power Hawk with a Carter 4-bbl. After cutting off the engine, I can hear a noticable gurgling sound. If I try to start up the engine in the next day or so, I can't do so until I pour a few ounces of gas into the carb. Turns over just fine then. A weak fuel pump may be contributing to the problem when starting, but once she kicks over (w/ gas added) she seems to run fine. What's wrong w/ my carb?? Perhaps I missed something during the rebuild.

        Thanks, Dan
        I would guess the "gurgling sound" is water in the jacket and radiator moving a little as it heats and or cools. Most cars do this. I doubt if it is gas going into the intake manifold. If it was, it would not start again a few minutes after turning it off since it would be flooded.

        Most carbs on older cars have been rebuilt several times. Dunking them in the carb cleaning solvent eventually removes the sealant in the float bowl. The gas then evaporates out of the bowl over the next few days. To solve this you can do what you are doing (prime it with a little gas), install an electric fuel pump and pre-fill the float bowl before engaging the starter, or have a speciality shop rebuild the carb and recoat with the proper sealant.

        -Dick-
        Dick Steinkamp
        Bellingham, WA

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        • #5
          Sounds much more like what's going on. Obviously, I can't tell from inside the car whether the gurgling is from the carb or the radiator. Gas has definately evaported out of the bowl though. Can anyone recommend a good carb rebuilder in/around eastern NC? Meanwhile I'll also try a related suggestion from a seperate post (thicker gasket between carb and intake to minimize heat transfer).

          Thanks, Dan

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          • #6
            I thought the carbs had a vent and sent the gas down the side of the carb/block if pressure was high in the carb's fuel line after shut down.

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            • #7
              My 2 cents are,

              I talked to a chemical engineer about gas boiling point and here is what I learned. Todays gas is highly refined using a cracking type refinery. What this does is it allows high sulfur crude to be broken appart to remove the extra sulfur and results in single chain hydrocarbons. These have a low boiling point, old style gasoline was distilled from sweet crude which by nature has low sulfur content, distilled fuel has groups of Hydrocarbon chains, which burn too easy but have a higher boiling point so they added lead to the fuel to increase the burning point which raises the octane. Almost all fuels sold in the US today also contain alcohol which is an oxygenate intended to help ensure enough oxygen to burn all the hydrocarbons. All of this equates into gas that boils at a much lower point than our old cars were designed for. I asked how we could raise the boiling point and the solution is diesel fuel, which contains multilinked hydrocarbon chains which have a much higher boiling point. This will work well for all low compression engines like the Commander 6 and early Champ and V-8's. Mix no more than 25% diesel, infact the best way is to try several variations until the boiling problem subsides. This will also eliminate vapor lock. ONE must not add too much diesel or performance will suffer.

              Other than diesel add an electric fuel pump nearest to the gas tank and plumb a second line and tee in between the mechanical pump and the carburetor, add a one way check valve between the mech fuel pump and the tee, this way if your mechanical pump dies the electric will keep you running, otherwise the electric will pump your crankcase full of gasoline. I've added an electric to my 1949 Commander and it fixed the vapor lock and makes the car idle smoother when its warmed up.

              Restore it, don't replace it.Keep the Studebaker reproduction industry going

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              • #8
                quote:Originally posted by 1949commander

                My 2 cents are,

                I talked to a chemical engineer about gas boiling point and here is what I learned. Todays gas is highly refined using a cracking type refinery. What this does is it allows high sulfur crude to be broken appart to remove the extra sulfur and results in single chain hydrocarbons. These have a low boiling point, old style gasoline was distilled from sweet crude which by nature has low sulfur content, distilled fuel has groups of Hydrocarbon chains, which burn too easy but have a higher boiling point so they added lead to the fuel to increase the burning point which raises the octane. Almost all fuels sold in the US today also contain alcohol which is an oxygenate intended to help ensure enough oxygen to burn all the hydrocarbons. All of this equates into gas that boils at a much lower point than our old cars were designed for. I asked how we could raise the boiling point and the solution is diesel fuel, which contains multilinked hydrocarbon chains which have a much higher boiling point. This will work well for all low compression engines like the Commander 6 and early Champ and V-8's. Mix no more than 25% diesel, infact the best way is to try several variations until the boiling problem subsides. This will also eliminate vapor lock. ONE must not add too much diesel or performance will suffer.

                Other than diesel add an electric fuel pump nearest to the gas tank and plumb a second line and tee in between the mechanical pump and the carburetor, add a one way check valve between the mech fuel pump and the tee, this way if your mechanical pump dies the electric will keep you running, otherwise the electric will pump your crankcase full of gasoline. I've added an electric to my 1949 Commander and it fixed the vapor lock and makes the car idle smoother when its warmed up.

                Restore it, don't replace it.Keep the Studebaker reproduction industry going
                Well I'll be darned! Thanks '49commander! I knew from just my own experiences that "old" and "new" gasoline is completely different, I just didn't know exactly why. This is a problem that's not gonna go away. In fact, no tellin' what's in store for us old car folks regarding fuels, especially if the world moves further towards fuels like ethanol and hydrogen. I guess all we can do is try to keep up with the changes.

                So far it's an easy fix, add a little diesel, mebbe an electric pump, and hopefully that'll get us through for a long time. I think that the diesel additive trick does a lot of good for our old engines, even more than reducing heat related problems. I know that it's worked for me!

                Thanks again for the simple answer Brian!

                Sonny
                http://RacingStudebakers.com
                Sonny
                http://RacingStudebakers.com

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