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Is 850 cfm too much for warmed over 440?

Engine Issues

  1. djais1801

    djais1801 Well-Known Member

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    stock iron heads (port/polish) by Keith Black. Torker II intake, Hughes cam, headers, 3" exhaust, dana 60 3.54 gears 4spd 18 spline hemi trans
     
    Last edited: Feb 2, 2020
  2. DetMatt1

    DetMatt1 Well-Known Member

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    Cam specs?
     
  3. 44070dart

    44070dart Well-Known Member

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    Probably.. You will lose some bottom end with that carb.. It would be crisper response with a smaller carb. We all tend to over carb. IMHO.
     
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  4. fasjac

    fasjac Well-Known Member

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    Is it manual or auto? I tend to think it’s a bit much but, with a stick you can get away with it. The cam is tell tell though.
    If not over .509 lift, you’d probably like a 750 or 780 w vac secondaries. IMO
     
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  5. djais1801

    djais1801 Well-Known Member

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    IMG_0268.JPG
     
  6. djais1801

    djais1801 Well-Known Member

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    It's a 4spd... I attached the cam card
     
  7. fasjac

    fasjac Well-Known Member

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    I see, nice! I know that sounds great. Personally I think it handles the 850 just fine. Are you feeling a lull or bog on the lower end?
     
  8. djais1801

    djais1801 Well-Known Member

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    Not really... it was running rich...plugs weren't gapped properly and timing was off...but the front bowls are filling up even after adjusting. Gonna replace the needle/seat and see how it does. It has a Holley "Brawler"
     
  9. djais1801

    djais1801 Well-Known Member

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  10. fasjac

    fasjac Well-Known Member

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    D, man it sounds really good. I’d go through the fine tuning stuff and rock on!!
    IMO
     
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  11. Chryco Psycho

    Chryco Psycho Well-Known Member

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    I have always used 2x the ci as rule of thumb , tuning is key but for reference the 71 up 340 used an 800 cfm TQ carb , ,I never run less than 850 on a 440 & yours has a better cam , ported heads & 3" exhaust so 850 is what I would be using for sure , I prefer Proform or Quickfuel carbs with replaceble air bleeds , 4 corner mixture screws & mechanical secondaries
     
    Last edited: Feb 3, 2020
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  12. R4Sedan

    R4Sedan Well-Known Member

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    Healthy cam and 4-speed nice.
     
  13. 44070dart

    44070dart Well-Known Member

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    Use what you like.. but this formula has been around for a while. It may run well with an 850 , probably better with a 750/780 .. and although you didn't ask, a 3" exhaust is over kill on that engine. IMHO


    How to calculate Carburetor CFM
    The formula for calculating how much CFM (cubic feet per minute) your engine requires is: CFM = Cubic Inches x RPM x Volumetric Efficiency ÷ 3456.

    Any ordinary stock engine will have a volumetric efficiency of about 80%. Most rebuilt street engines with average bolt-ons have a volumetric efficiency of about 85%, while race engines can range from 95% up to 110%.

    Example: Using a 355 CID engine x 5,500 max rpm = 1,952,500
    Take 1,952,500 x .85 = 1,659,625
    Then 1,659,625 ÷ 3456 = 480 CFM


    Even with about a 10% cushion, a 500 CFM carburetor will handle this engine great. If you try this formula yourself, be honest with how much rpm the engine will see. You’d be better off with a carb smaller than needed rather than something oversized that can lead to poor drivability and performance.
     
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  14. djais1801

    djais1801 Well-Known Member

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    I appreciate all comments/suggestions.
    The headers/exhaust were on there when I bought the car...I may look for exhaust manifolds to go back to stock looking...That depends on what money is left after working all the bugs/surprises out of her.
     
  15. Chryco Psycho

    Chryco Psycho Well-Known Member

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    Back in the real world where the carb flow is real #s & a 750 may barely flow 600 cfm I continually prove the formula wrong on the dyno or the track , 750 is for a 340/360 , Mopar used the 800 CFM TQ , you will be down on power at less than 2x the CI . I have tried this on the dyno using multiple carbs & engines , power increases with CFM , even Mopar rated the 440+6 20 hp higher with more airflow , the TQ carb was used across the board from 71 up , 650 CFM Carters were not cutting it . With my race car the ET dropped & the MPH picked up with every increase in carb size , I started with an 850 moved to a 950 & ended up using a 1050 on a 440 CI engine , not stroked . using 516 ported heads & variety of intakes & headers of course .
    The formula depends on real cfm air flow through the carb & aircleaner which is generally lower than the rating of the carb .
    You can do what you want but in the real world more CFM = More power , you might as well get as much as possible from the engine you spent so much to build .
     
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  16. Racer Dave

    Racer Dave Member

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    How you drive it will make a difference, especially if it never sees any RPM, in which case smaller will be more responsive (due to greater air speed through smaller venturiis though - not because of less max. CFM) . My experience has been a lot like Chryco's - no problem with an 850 on a healthy 440, and running a 1050 Dominator on a 440+.030 (not stroked) as well. After all, Chrysler didn't feel shy about 1,200 CFM on a 6-pack :D Of course around town the 500 CFM center carb does all the work....but when you stand on it, hold on! And those motors didn't have anywhere near the cam or breathing you do.

    Anyway, your richness problem is most likely carb tuning (those needle/seats sound suspect to me as well). Sort that stuff and happiness will follow.
     
  17. Dodgeboy

    Dodgeboy Well-Known Member

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    I run a 383 with a smaller cam then what you got, I switched from a 750 to a 850 carb 2 years ago and I love it.
     
  18. Mastertech

    Mastertech Member

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    The big question is this for mainly street or track. If for street always go with vacuum secondary's. You can then fine tune the opening to prevent any bog. With mechanical secondary's you are pretty much flushing a toilet with gallons of unused fuel to cover a bog on the street. This will wash down the cylinder walls and thin out your oil. The key to the Carter T-Q was the ability to adjust the rate of the air valve opening so that the engine could draw only as much air and fuel as it needed.
    Also the little 340 cylinder heads way outflowed the 350 chevy and mopar rated the horse power at 5000 rpm to keep the insurance companies happy but neglected to mention that at 6000 rpm it was actually about 30 hp higher. The Camaro guys never did figure this out!
     
  19. djais1801

    djais1801 Well-Known Member

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    It is mechanical secondaries...There does seem to be an issue with the needle/seat and the front float.
    I have ordered those parts from holley. I am not mechanically inclined whatsoever and going off what my mechanic is talking about. But on face value, would putting smaller jets in help it perform better?
    forgive my ignorance... worse comes to worse I will just swap to an edelbrock 650 or 700 w/ electric choke.
     
  20. Racer Dave

    Racer Dave Member

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    Main jets only affect the fuel mixture, and unless you are getting black smoke or the spark plugs are black I'd say don't go there yet. What's more likely in your case is a power valve that's too high since your cam is healthy and intake vacuum may be low at idle.

    Warm it up with a vacuum gauge on an intake manifold vacuum port and read the vacuum at idle. Divide by two to find the correct power valve. The Brawler comes stock with a 65 (which means 6.5" vacuum) so if you have anything less than 13" vac. at idle a change might be in order.

    There's lots of knobs to twist and buttons to push on a Holley and many give up and bolt on an Eddy, but my 2 cents is once the Holley is dialed in it will be a great carb. There's lots of great carb tuning info on the Holley site.

    I am curious about your answer to Mastertech's question about use.... what percent street and what percent track? Because if it's never - or very rarely - going to the track perhaps a carb change might be in order.
     
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