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Demon carbs offraod ?

Discussion in 'The Garage' started by Dunc03, Jun 3, 2004.

  1. Dunc03

    Dunc03 1/2 ton status

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    Anyone running a demon carb, or know how that stck up on angles. I'm thinking about running one on my crate engine, cuz the q-jet is not cutting it, and I'm not enough of a carb tuner to make it woek right. Actually my biggest problem is GM stopped producting the power valve spring I need. Thank in advance for the info.
     
  2. pauly383

    pauly383 Daddy383 Staff Member Moderator

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    Power Valve spring ?? No power valves in a Quadrajet. There are springs on the secondary door, the APT, the accelerator pump, the inlet filter, the linkage, but no power valve. Edelbrock makes new Quadrajets , many others rebuild them . There are parts available from those avenues. I swear by my Quadrajet , poor mans injection. /forums/images/graemlins/k5.gif
     
  3. Dunc03

    Dunc03 1/2 ton status

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    I'm pretty sure all quadrajets have a spring that sits under the power valve. It is the spring that makes your main system operate. At idle vacuum holds the spring down, and then when you accelerate( less vacuum) the spring begins to rise which increases the fuel flow by raising the rods out of the main jets, or at least thats the way that mine works. Anyways the spring I would need would be a spring that actuates at about 14 mm Hg. The highest you can find from edelbrock is 10 mm Hg. Anyways I can't find the right spring, so I'm looking at a demon carb that is calibrated for my engine. I'm really just wondering how demon function offroad compared to the q-jet. Thanks for the help though.
     
  4. 84_Chevy_K10

    84_Chevy_K10 Banned

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    If a Q jet is not cutting it and is functioning correctly, you need to convert to EFI. No Holley, Demon, Barry Grant, or otherwise is going to satisfy you if a Q-jet won't do what you want.

    Welcome to EFI swap land. /forums/images/graemlins/thumb.gif
     
  5. Dunc03

    Dunc03 1/2 ton status

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    It is not functioning properly, and I lack the parts to correct the issue. I would love to convert to MPFI, but it will be around 2 grand to convert because I have vortec heads. Can't really pony up that kind of dough right now. If I could get the q-jet to act right on the motor then I would keep it, because it never gives me problems in the dirt, it just sucks on the streets in traffic were response matters. My motor supposed to produce 330HP and becaseu of air/fuel ratio problems, I'm seeing maybe 270 and getting 10 mpg. THis motor will never get great gas milage, but with 3.42 and a .70 overdrive ratio it should be better than 10.
     
  6. 84_Chevy_K10

    84_Chevy_K10 Banned

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    With those airplane gears and that overdrive, depending on tire size I'll bet you're realling lugging the engine. 3.42 and O/D would be horrible for mileage unless your tires were 28" tall or so.

    Gears aren't, "if more is better" all the time. A higher raio (lower number) will only help fuel mileage until you start lugging the engine down at which time it will start costing you.
     
  7. Dunc03

    Dunc03 1/2 ton status

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    so what should i be running with 33's
     
  8. Hossbaby50

    Hossbaby50 3/4 ton status

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    Just don't use OD unless you are cruising on the highway above 60mph or so. You tranny will be much happier with you too since it won't heat up as much and will be locked up more often.
     
  9. pauly383

    pauly383 Daddy383 Staff Member Moderator

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    [ QUOTE ]
    I'm pretty sure all quadrajets have a spring that sits under the power valve. It is the spring that makes your main system operate.

    [/ QUOTE ]

    Oh, thats the APT ( adjustable part throttle ). You can adjust it so your rods sit higher or lower in the jets. MY carb from I-5 has been drilled and tapped for a plug on the airhorn. They replace the factory style with one that can be adjusted from outside the carb with a phillips head screwdriver. I know some of the springs are not available, but springs can be found from non-automotive sources and easily used on a carb. Have you tried different rods with any of the springs that are available? Perhaps a different jet or rod with the spring you have will allow the proper mix for the spring(s) you have /forums/images/graemlins/k5.gif

    Good Read, shows some mods that may help
     

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