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just for my general carb info

Discussion in 'The Garage' started by k20, Aug 6, 2003.

  1. k20

    k20 3/4 ton status

    Sep 9, 2001
    Likes Received:
    Mineral Springs, NC
    Ok, I dont know much about carbs so figure what the heck might as well learn something right. Anyway...
    1.)What is different in a double pumper and say a regular 4 barrel?
    2.)Mechanical vs Vacuum secondaries...I assume with vacuum it waits till the engine is needing the fuel to open the secondaries, whereas with mechanical, they open when you put it on the floor? correct?
    3.)Does the carb (ok now this sounds REALLY newbish) just more or less drip the fuel down the bore and let it mix with the air or what? I know FI it sprays fuel and it comes out of the injector pre-atomized. Never really wrenched on a carb so dont know.

    Ok, theres the extreme newb questions, but since at the moment it appears i may (if no one will burn a chip at a reasonable price [$800 isnt reasonable]) end up carbing the 496. We'll see and thanks for the answers.
  2. bigblock44k5

    bigblock44k5 1/2 ton status

    Jun 8, 2003
    Likes Received:
    Hurlburt Field, FL
    1. Double pumper means you have two set of accelerator pumps instead of one. (The things that squirt fuel into the carb when you push the gas pedal, running or not.)
    2. You are on the right track with vacuum vs. mechanical secondaries. Vacuum secondaries basically wait to open the secondary throttle plates untill your motor is pulling enough air to need the extra fuel. (ie. High RPM'S)
    3. Carbs also spray fuel somewhat like fuel injection. The difference is, the fuel spray is sucked into the engine instead of being pressurized like FI. To make it simple, the vacuum going through the carb sucks the fuel out of the float bowls through the metering blocks and jets and into the engine. This is why you change jet sizes to get the right amount of fuel going into the engine. I think that about covers the basics, I'm sure there is plenty of info on the internet to explain in detail. Such as the Venturi effect that actually makes the fuel suck into the engine. /forums/images/graemlins/deal.gif

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