625cfm street demon

Fuel and Air Systems

  1. Mike 340

    Mike 340 Well-Known Member

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    Hey everyone, I am new to this forum just wanted to know if anyone has tried the street demon 625cfm carb?
    I just put one on my 340 and I have found that it seems lean. My engine is a 68 block with 71 J heads and tq intake with 71 340 exhaust manifolds and a comp cam 268xe . Any input or information would be great.
    It's just a cruiser 5500 rpm . Already have the calibration kit.
     
  2. Coronet 500

    Coronet 500 Well-Known Member

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    318, XE 256, Ed Performer, 3.55 gear, manual, in a truck, found it just right.
     
  3. nm9stheham

    nm9stheham Well-Known Member

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    What are you basing the 'lean' conclusion upon?
     
  4. Mike 340

    Mike 340 Well-Known Member

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    Mine is in a 67 dart gt 727 auto with 3:55 gears and MP performance ignition with the orange box. Car seems to be very responsive, but doesn't leave alot of wheel spin .
    215 r 14 tires.
     
  5. Mike 340

    Mike 340 Well-Known Member

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    White spark plugs
     
  6. TrailBeast

    TrailBeast Slightly Twisted Member

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    Running real gas or coolaid like we have.
    It's hard to read plugs running coolaid as they always look lean.
     
  7. Mike 340

    Mike 340 Well-Known Member

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    94 octane. It's the best I can get. Most around here is 92. There is a airport that will sell me av gas but I don't think that I should.
     
  8. RustyRatRod

    RustyRatRod 30 Degrees Outta Whack FABO Gold Member

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    How does it RUN? Does it pull good and want to keep pulling, or does it lay down at high RPM?

    If all you are basing your opinion on is spark plug color, throw that out the window, because as already stated, you cannot read plugs on modern gas.
     
  9. Mike 340

    Mike 340 Well-Known Member

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    The "fatter "I jet it the harder it pulls and the better it idles. The plugs are starting to get a light tan color now. I think I am going the right direction.
     
  10. dart4forte

    dart4forte FABO Gold Member FABO Gold Member

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    If it's like the Edelbrock it should have a step up rod chart. I would first find a back country road for doing the tuning. Start out with making a full throttle pass and while coming to a stop shut the motor off. Don't let the engine idle. Now pull a couple of plugs and see how they are burning. If they are looking a little white in color I would say you are a little lean. If that's the case go by the step up rod chart to see which rod you should use. You may get to the point based on the chart where you may have to change jets.

    If your plugs look a medium to dark tan then you are in the ball park. If the plugs are black or even wet you are too rich

    Of course everything else with the engine should be up to speed.
     
  11. 67dodgedartconv

    67dodgedartconv Well-Known Member

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    A little off topic but did you have to use the demon carb throttle stud or did the one from your previous carb work? I ordered same carb a couple of days ago but don't know if I need to order the stud also while I am waiting for delivery.
     
  12. Mike 340

    Mike 340 Well-Known Member

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    Yes you need the throttle stud and you need to split the carb to put it on. I found out the hard way and had to take it back off the engine.
     
  13. 67dodgedartconv

    67dodgedartconv Well-Known Member

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    Never would have figured you had to take carb apart to attach stud. Thanks, will go ahead and order one.
     
  14. d1970

    d1970 TODAY IS A GOOD DAY TO HAVE A GOOD DAY

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    Check this video out, a Street Demon 625 carb on a Dart, it will show how to install the Chrysler linkage at 3:26 of the video
     
    • Thanks! Thanks! x 1
    • 67dodgedartconv

      67dodgedartconv Well-Known Member

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      Thanks, d1970! That cleared things up a lot. Saved me a lot of trouble and some money too.
       
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