street demon or dp?

Mopar Racers Forum

  1. rbkt65

    rbkt65 Well-Known Member

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    getting ready to drop 440 into dart/duster. eng is .030,10.0/1 comp,bullet cam that is 271 adv and 242 at .050 with .548 lift. has open plenum intake. trying to decide between demon 625/750 or holley 650 dp. carb charts say approx 670 cfm. any thoughts? i don't have any experience with street demon carbs. thanks in advance.
     
  2. dano

    dano Evil Handy Man FABO Gold Member

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    What is the intended use of the car/motor combo? Auto or manual? Gear? Stall?
     
  3. Oldmanmopar

    Oldmanmopar Going left turning right FABO Gold Member

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    With that cam, If you want response I would use a 4 corner idle circuit carb. You want to idle off the secondaries so not to be into the primary transfer ports. Square the primaries over the transfer ports and leave it there. Use the secondaries to adjust the idle.

    On a iron head 340 I never had smaller then a 750. The 340 in my Duster has a 1050 and the EGT's were perfect and the response was right there. Nailing the throttle off a foot brake would lift the wheels. I have a 318 bone stock 2bbl motor. I put a 600 AFB on it. I cannot believe how crisp it is.

    Most guys read plugs as i did in the past. Using EGT gauges on each bank will tell you the true air fuel and where it needs to be. Exhaust effects carb choice in many ways. That 318 with the 600 has a 2 1/2 exhaust with 1 5/8 primaries. The 340 with the 1050 has 3 1/2 exhaust with 2 inch primaries. 1971 340's came with a 800 from the factory.

    The gold Demon we just finish got a 800 quick fuel 4 corner idle circuit. The car is 4 spd. and will break the tires loose on a roll in third gear. I just had that car out for a ride last week.

    Now if your after economy get a 600 or a 500 2bbl. That is the same as a fat guy like me trying to suck a milk shake down through a coffee straw. In the past six pack's were used on bone stock motors the ones that I owned did not seem over carbureted.

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    • roccodart440

      roccodart440 Well-Known Member

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      If those are the only choices (which I don't like any of them), the 750 demon.

      If it were mine I'd run a 950HP Holley on it, maybe a QF.
       
    • 318willrun

      318willrun Stomper 4x4... we kept energizer in business

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      agree with the above statements. Though the carbs you listed will "run good", you are leaving a lot of performance on the table.
       
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      • Walker434

        Walker434 Well-Known Member

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        I also agree with above. If you are looking for a lot of performance that 440 will be choking on a 750 carb. I'd go Holley HP 850 or possibly 950 depending how tight (RPMs) you are going to twist it.
         
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        • roccodart440

          roccodart440 Well-Known Member

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          My 950 combo peaks at 5800 and 6200 through the traps. It's very crisp.
           
        • RustyRatRod

          RustyRatRod 30 Degrees Outta Whack FABO Gold Member

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          Two 750 Street Demons on a tunnel ram.
           
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          • AJ/FormS

            AJ/FormS 68 B'cuda fb, Form S clone ... 367/A833/3.55s FABO Gold Member

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            625 is way too small.
            A 600choked my 367.The 750DP on it now seems adequate; It liked the 850TQ it once wore.
            Your 440 is about 20% bigger than my 367.
             
          • rbkt65

            rbkt65 Well-Known Member

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            here is rest of the combo-3400 lb car,18.5x33 mt et streets,3500 conv. 3.73 or 4.10 gear, ladder bar,a/c, rev pattern cheeta vb. sorry bout not giving you all the paul harvey rest of the story details.
             
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            • furrystump

              furrystump Well-Known Member

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              Street or strip? Intended use? If you are chasing every hp and it will spend its life at WOT, you need a good bit over 800 CFM. Street car about 750-800 cfm will give very nice throttle response, but not kill it at rpm.
               
            • flyfish

              flyfish C8H18+N2O = :-D

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              None of the carbs listed would be anywhere near optimal. I would go with a Holley 950dp.....if you are using one of the ones listed because that it what you have on hand, I would take the 650dp and put a 750 Proform main body in it (not ideal, but it would work pretty well).
               
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              • MikeD

                MikeD Well-Known Member

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                If it's a street car and you want economy, run the 750,if it's good performance you're after, go with a HP 950, the 950 has very good shift recovery because of the small base.
                 
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