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Thread: Anyone else out there run a Vacuum Gauge, or know how to use one?

  1. #1
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    Anyone else out there run a Vacuum Gauge, or know how to use one?

    I've always liked having a vacuum gauge, and it can tell you countless things about what is going on with your engine. You can watch in real time the negative pressure changes in the intake system, and try and figure out what it is telling you, and what the carburetor is sensing . You can see things like when your power valve opens, throttle position, engine load etc. I'm going to install one in my 55 on a LS engine. It's more fun to watch than the temp gauge going up and down. https://www.motor.com/magazine-summa...a-vacuum-gauge

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    Last edited by 55 Rescue Dog; 02-25-2021 at 02:06 PM.

  2. #2
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    I have one permanetly mounted in a Camaro drag car, you cannot set a Holley up without one.

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    Yes, and I use it when setting the idle mixture screws. A hand-held gauge works better for under hood checks though. I've been using this one for 45 years.
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    Last edited by 55 Rescue Dog; 02-25-2021 at 03:11 PM.

  4. #4
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    Quote Originally Posted by 55 Rescue Dog View Post
    Yes, and I use it when setting the idle mixture screws. A hand-held gauge works better for under hood checks though. I've been using this one for 45 years.
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    That is the way Iíve always done it. Once it is all set up i would have no need for one mounted in the car. The OP states itís something to watch. Entertainment is the only reason I could see one permanent mounted on the dash. The grandsonís might get a kick out of it as the needle bounced around. Not like a oil pressure or temperature gauge that indicates low or no oil pressure or too high a running temperature. Those would require some sort of action if out of range.
    An amp or volt gage keeps operation limits in view too. Even a fuel gage can require a response.

    But the vacuum reading is all extremes on the dial and changes with throttle movement. What does that tell ya other than just something unusual under the dash? Canít see it when under the hood setting up a Holley, so a separate vacuum gauge is still necessary. An air/fuel would be of more use.

    Iím not saying donít put one in, if that is what you want, but why?

  5. #5
    Registered Member BamaNomad's Avatar
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    Some older (sixties?) GM cars had factory installed 'vacuum gauges'. (Pontiacs? maybe firebirds?)... and was recommended for attempting to maximize fuel mileage...

    (just come off the gas when the gauge begins to drop?)...

    Here's one for sale...
    https://www.ebay.com/itm/18467854909...BoCAZIQAvD_BwE

    s-l1600.jpg
    Last edited by BamaNomad; 02-28-2021 at 06:53 PM.

  6. #6
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    I will never forget those Pontiac vacuum gauges. If you know the tricks on using a vacuum gauge you can pick up a lot of fuel mileage. It is no different the instant MPG monitors that are on most modern cars. The higher you can keep the vacuum the better is all it is about, and trying to keep the power valve from kicking in at around 6-8 inches, adding more fuel. You can even see when it happens on the gauge at light throttle when it passes that point.
    Last edited by 55 Rescue Dog; 03-01-2021 at 07:12 AM.

  7. #7
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    yup, i have one under the dash. i use the car alot for kinda short trips, like 200 miles one way. i try to watch the gauge, for something to do. i find myself trying to let off the gas to get better mileage. i know, stupid.

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    My Dad had a vacuum gauge in a 63 Olds station wagon. I remember it having different colors in the arc of the gauge, guess that showed various degree of optimum operation? I had a 65 Impala SS 300/327 4 peed and was lucky enough to have a factory tach in the dash, another option for that gauge position was a vacuum gauge or a clock. I was happy with the tach, no needle set but seem to remember it being a 6,000 RPM tach, redline at 5,500. Wish I had never sold that Impala, what a dumb*** mistake that was.

  9. #9
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    and, i like to try to set up the idle mixture by listening/watching the engine respond. then i use the gauge, just to see how close i get first.

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