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Thread: is a 750 holley to much carb for a 350
          
   
   

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  1. #1
    frankgomez65 is offline CHR Member Visit my Photo Gallery
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    is a 750 holley to much carb for a 350

     



    I have a 350 bored 30 over With 302 dur fireball street/strip crane cam, with flat top pistons, With 64cc chamber with 2.02 valves.1.6 rockers, headers flowmaster 3". And a performer elbrock intake. It seem like at full throttle it is running out of gas, or do i have a fuel pump problem, stock fuel pump.

  2. #2
    frankgomez65 is offline CHR Member Visit my Photo Gallery
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    i think its a 3/8 stock steel fuel line with a 3/8 fuel hose.
    ya i need to get a fuel pressure gauge and check it.
    is 750 holley to much carb for my motor

  3. #3
    gassersrule_196's Avatar
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    i use a 750 dbl pumper on my 283 so it musnt be to much for a 350 :O

  4. #4
    like2gofast is offline CHR Member Visit my Photo Gallery
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    Post formula

     



    Is't it displacement x's peak rpm and then 80% of that for VE for carberation?
    Maybe you could check your filter as well. Too big and you'll get vapor lock ,too small (starvation)sounds like a probable cause in your case.
    Also I would consider at least a 95 gph pump.You're probably at around 350 HP?
    Anymore questions I'll be in the study with an iron pipe.

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    Last edited by like2gofast; 09-24-2008 at 02:10 AM.

  5. #5
    techinspector1's Avatar
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    Quote Originally Posted by gassersrule_196
    i use a 750 dbl pumper on my 283 so it musnt be to much for a 350 :O
    You rock Scooter.
    After playing around on my new DynoSim, I have observed that there really isn't any such thing as going too big on the carb from a power standpoint. I have been taught for many years that you don't want to over-carb a motor, but the software tells me a different story.
    Some time back, Denny suggested a formula of CID times 2. I think that formula is valid and may even be a minimum, as in your case. (CID times 2.48).
    Playing with a 283 last night, I observed increased power the larger I went on the carb, all the way up to 1000 CFM.
    Last edited by techinspector1; 09-24-2008 at 10:10 AM.
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  6. #6
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    This may be true at wide open throttle but I think practical limits apply in terms of throttle response and good fuel atomization when you go too big

    -Chris
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  7. #7
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    Quote Originally Posted by skids72
    This may be true at wide open throttle but I think practical limits apply in terms of throttle response and good fuel atomization when you go too big

    -Chris
    I think you're right.
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  8. #8
    firebird77clone's Avatar
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    CID X 2 will usually keep you streetable.
    .
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  9. #9
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    Curious ?

     



    At what RPM is the power dropping off at? based on the cam and heads you are running your intake may be part of your problem,a Performer RPM or Weiand Stealth would be a better choice than the Performer you have which is making its power from off idle to 5500 RPM.The standard Performer works well with a cam of lesser duration to improve mileage and low end torque.As for the fuel pump SBC performance pumps are priced reasonable so changing it would not be a bad investment anyway.

  10. #10
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    C9x
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    Bless you TechInspector.

    I've been arguing this point for years and I usually get the old carb-size with VE tossed at me.

    For street use, Skids72 comment on good atomization probably applies, but perhaps not.

    I run a single 750 Edelbrock on a 462" and at part throttle - meaning light throttle in the 2400# Deuce roadster - and subjectively viewed, vaporization is probably doing ok.

    Over at "GoFastNews" I think they have an upcoming article on running a huge by large carb and initial reports are it's doing ok.
    Not sure if it's strictly for racing or street running as well.

    Little brother runs a pair of 1100 cfm Dominators on his 500 cid DRCE engine and the car has good manners at part throttle operation - which means he's pretty much running on the idle circuits.
    The car, an about 2500# Henry J tube framed drag racer.

    Going the other way I've run a 600 cfm smog Holley on the 32 with the 462" Buick engine and it ran well.

    Interestingly, mileage was about the same.
    C9

  11. #11
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    i built a 525 air boat engine it left my shop with a 750 new in a box to go along with the build the air boat came back with a 950 holley i told them for the rpm of the engine were i built it to make max power it and lower rpm use it was to big of a carb well after washing the walls down and just not working it came back and i put a HP 750 back on it works great now .alot of times your better with a smaller carb for street use as for some thing light with a stall you can go up on the cfm. i run a 1150 on a 468 that work great with some stall and gear this car had a 850 1050 but the 1150 9377 list just work good i used the same 1150 on my 632 donovan it works ok had two 1150s 9377on my 573 that work good as much as i could tell use to pull up the front wheels in the shop parking lot now the carbs are on a big chief 565 that i did the machine work on they seam to do good with them ? if your running hi rpm and not low speed in a light car then you can run abit bigger carb. i may do it all wrong but i look at rpm and the cid and weight ? no formula just what i know what has work in the past
    Last edited by pat mccarthy; 09-25-2008 at 09:24 AM.
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  12. #12
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    I'm thinking that the old quadrajets GM used on factory engines were actually rated at about 750, so I wouldn't think it's too big. Probably just a tuning issue.

    Hey Techinspector, what Dynosim software are you using?
    I ain't dumb, I just ain't been showed a whole lot!

  13. #13
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    Quote Originally Posted by Sinister
    I'm thinking that the old quadrajets GM used on factory engines were actually rated at about 750, so I wouldn't think it's too big. Probably just a tuning issue.

    Hey Techinspector, what Dynosim software are you using?
    DynoSim Pro Tools 4.20
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  14. #14
    417strokers is offline CHR Member Visit my Photo Gallery
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    A small carb will run better for all around street use but I hve never seen a small carb go faster on a drag strip than a big one .

  15. #15
    BigTruckDriver is offline CHR Member/Contributor Visit my Photo Gallery
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    Quote Originally Posted by 417strokers
    A small carb will run better for all around street use but I hve never seen a small carb go faster on a drag strip than a big one .
    true
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