Speed demon carb

Fuel and Air Systems

  1. muscle72

    muscle72 Well-Known Member

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    Is a 850 speed demon good for a big block either a 383 or 440 with a 292 high extreme energy comp cam. Is the 850 to much carb? would a 750 speed demon be better?
     
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    • Aron Gleason

      Aron Gleason Well-Known Member

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      I would get a hold of Dominic thumper on Facebook. He's the go to carburetor guy. He's well known for how good his carburetors perform.
       
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      • beanhead

        beanhead Well-Known Member

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        Use the shiny one.
         
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        • muscle72

          muscle72 Well-Known Member

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          The shiny one? Not talkin about the one that's my profile pic.talkin about another l have
           
          Last edited: Sep 15, 2021
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          • beanhead

            beanhead Well-Known Member

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            What type of driving are you building for? Compression, heads/flow, intake, exhaust and engine size kinda need to be known for a real recommendation..
             
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            • muscle72

              muscle72 Well-Known Member

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              Probably stock 906 heads with bigger intake and exhaust valves.either a 383 the cam is goin in or another 440 close to 10:1 compression or stock compression a 68 383 hp makes
               
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              • vintage chromoly

                vintage chromoly Well-Known Member

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                An 850 is fine for a warmed up 440.
                 
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                • BSB67

                  BSB67 Well-Known Member

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                  Hard to pick a carb when you dont know the motor it is going on.
                   
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                  • blue69runner

                    blue69runner Well-Known Member

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                    650-700 cfm four barrel Holley is fine on a 383. 9.8 to 1 is what I am running. Plenty of pep. Running 80 jet's in it now it had 74 jetting on primary and 80 jetting metering plate. Changed to 80 jet's on primary and it work's fine now. Just my two cent's.
                     
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                    • RJRENTON

                      RJRENTON FBBO Gold Member FBBO Gold Member

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                      Who is "Dominic thumper" and what are his credentials. I'm a "carb guy" as well and I'm sure he's not heard of me either and I'm not on Facebook. Is he a self proclaimed expert too? Just curious....perhaps we can exchange some tuning "secrets".
                      BOB RENTON
                       
                    • Aron Gleason

                      Aron Gleason Well-Known Member

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                      He doesn't claim to know everything, but he's well known. He's working with Shane Studley at precision cylinder head.
                       
                    • Aron Gleason

                      Aron Gleason Well-Known Member

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                      If you want to you can give him a call. 760-900-3895
                       
                    • moparedtn

                      moparedtn Ed on the Ridge FBBO Gold Member

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                    • muscle72

                      muscle72 Well-Known Member

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                      What l thought for a 383 if l put a radical cam thinkin might have put a 750 on it. I have a 292 high extreme energy comp cam for it.im running a 600 Carter afb now on it.engine is stock basically with aluminum intake and headers.
                       
                      Last edited: Sep 21, 2021 at 2:27 PM
                    • RemCharger

                      RemCharger Well-Known Member

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                      Ever been on Moparts? He's well known there.
                       
                    • muscle72

                      muscle72 Well-Known Member

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                      Yep l have
                       
                    • PRHeads

                      PRHeads Well-Known Member

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                      “Extreme Energy 292”??

                      There are:
                      292H
                      XE294H
                      XE295HL

                      I don’t know if the recommendations are still the same for the Speed Demon line since Holley took them over, but they used to be recommended for use with cams that were under 240@.040.

                      My experience with them has been that they were a little miserable down low when the duration started approaching that 240@.050 figure.
                       
                    • RJRENTON

                      RJRENTON FBBO Gold Member FBBO Gold Member

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                      What is he "well known there" for? I do not do facebook at all, or any of the "trendy" social media venues. I prefer to do my own do dilligance rather than taking someone elses opinion. I re-ask the question....who is "Dominic thumper" and what are his credentials? ....just because he has a face book listings does not qualify as an authoritative source. Nor do I know Shane Studley at Precision Cylinder Head.....does he own the business or just works there or does he design cylinder heads using computer modeling or ???? Perhaps, I could benefit from sharing knowledge....or not....
                      BOB RENTON
                       
                    • beanhead

                      beanhead Well-Known Member

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                      Dom builds and preps carbs for mainly the race-oriented crowd, and while his business isn't necessarily to the level of notoriety of say Braswell, Dickey, Mike & Bo Laws....he has a solid customer following. Why he doesn't have a full-blown marketing campaign and fancy website, who knows...maybe he prefers word-of-mouth advertising and keeping a lower profile.
                       
                    • 747mopar

                      747mopar FBBO Gold Member FBBO Gold Member

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                      Just my personal opinion not knowing much about your build, 750. I've tinkered with an 870, 850 and 2 750's on my 456", all worked fine but driveability on the 850 & 870 for city driving just wasn't there. The 750 I have now is crisp everywhere under any situation.
                       
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