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  • gordr
    Vacuum is measured in inches, not pounds, the number being the height of a column of mercury that a given degree of vacuum will support. At sea level, a complete vacuum will support a 30" column of mercury.

    A gasoline engine will typically run between 12 and 20 inches of vacuum in the intake manifold at idle or cruise. It can go over 20 descending a hill with closed throttle, and it can go well under 12 at wide-open throttle under load. You might be able to pull 6 to 10" of vacuum by lung power, but it would be hard work to suck enough air out of the vacuum booster reservoir to make it work. (that purple thing in the mirror is your face, LOL)

    Shop vac moves a lot of air, but I don't know what the static vacuum would be if you used it. Definitely not too much for the booster to handle.

    If you can get Oscar close to another vehicle, just run a length of vacuum hose from a convenient port on the engine of the other car. You can also get hand-operated vacuum pumps, like the Mity-Vac.

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  • kmac530
    started a topic Brakes: Vacum


    I have completed my install of a 2 pot Corvette style MC and 7" 2 diaphram mini booster under my truck. I will be bleeding the brakes today to see if I can get Oscar back stoppable again...yeah.

    My question is about vacum. I do not have a motor in him right now, but I would like to test out the vacum booster. Does anyone know a way that I can synthesize the vacum required to activate the booster?

    How many pounds of vacum does a V8 make? Isn't it low, like 4-7 lbs of vacum?

    Could I use a y on my compressor hose and cause a suction or syphon effect like a spray uses?

    Stick a hose in my mouth and suck {hahaha NO jokes} like a straw and make a few pounds of vacum just long enough to push the brakes a few times and see how the booster works?

    I dont need vacum to bleed the brakes, but once that is done, I just want to test it.

    HMMM, I just thought about a shop vac. When I was cleaning out small spaces on my truck I stuck a long funnel like a trans funnel with my shop vac hose stuck inside of it and used the skinny end to get into nooks and crannies. Worked great, I just hop it is not TOO much suction.
    What do you guys think?
    Sorry, Gals Too.