Help me pick my next Carburetor please!

Discussion in 'Engine Topic' started by Vortec80, Mar 4, 2019.

What Carb should I use out of these?

  1. Holley 670 street avenger

    6.3%
  2. Holley 750

    68.8%
  3. My current Holley 600

    0 vote(s)
    0.0%
  4. Other...Please drop other suggestions in the thread

    31.3%
Multiple votes are allowed.
  1. Vortec80

    Vortec80 Camaro project is a go

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    Hey guys!
    I have a holley 600 right now with vacuum secondaries. Single feed. Looking to go bigger possibly. Unfortunately I cant afford to test them all. I have read a ton of threads but havent found a build just like mine to make a choice. I apologize.

    I have a vortec 350 with a high rise dual plane intake, 2.02, 1.94 valves and valve job. Lt4 hotcam and long tube headers. Roller rockers as well. Making A little over 400hp. Th350 trans

    I'm looking either to go 670 or 750 for another carb. I'm looking at Holley 670 or Holley 750. I know holley may not be liked by all but I am a fan.

    Let me know what you guys think!
     
  2. jeff swisher

    jeff swisher Veteran Member

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    On my 350 chevy engines I have ran all kinds of carburetors with small 260H and large solid flat tappet cams 252@ .050.
    many people say the small carb has better driveability I call BS I have never noticed any huge differences ..very tiny difference on some. I am not talking stock 250HP stuff I am talking 375+ HP sbc.

    If you can tune the Holley and like them get an old 3310 or 4779 and get after it.
    Or step up to one with the no choke tower if you are bucks up.

    Would I run a 670 cfm rated carb. NO I would not unless rules dictated it.
    I like my 3310 and 4779 but I did not like them in stock form..they just did not have the upper end pull 5000+ rpm that the AFB or Q jet had in the same 750 cfm rating.

    I thinned/slabbed the throttle shafts in the old Holleys and made my screw heads smaller in the throttle blades..Yea I could have got new smaller head screws. I ported the air horns down and polished and slightly enlarged the venturies and polished and thinned the boosters a bit and Then they had the upper end pull of the other brand carbs.

    Jetting was optimized in each carb.
    I have not regretted my used Holley purchases on the 750 cfm ones.
    MY tweaked 4779 the way I like to finish the used carbs out.
    Yea it is dirty and has been on 3 different engines and still going strong many thousands of miles later.
    JB weld of course.
    4779 001.JPG
     
  3. RS1979

    RS1979 Veteran Member Lifetime Gold Member

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    I went from a 650DP to a 3310 750 vac secondary and noticed a huge power increase. I've got an engine similar to yours and it really likes it
     
  4. Vortec80

    Vortec80 Camaro project is a go

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    Thanks for the feedback guys! I am leaning towards the 750. Just trying to move past all the people telling me around town that a 750 is too much carb for my engine and a waste of gas.

    What makes that the general consensus? My buddy runs a 750 on a 302 and it loves it!

    Rs1979, what's your build if you dont mind?
     
  5. jeff swisher

    jeff swisher Veteran Member

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    Friend of mine with a 357" with flat tops and Edelbrock Estreet heads and XE268H just recently pulled off his 600 edelbrock after many weeks or tuning it just right and stuck on an out of the box 750 edelbrock and said it is much more tire spinny out of the hole now and pulls way harder everywhere.
    I have a 1407 edelbrock on one of my 350's and a 4779 Holley in the above pic on my Vortec head 357"

    Usually if I need more than an 800 cfm carb I go dual 4 with a Tall tunnel-ram you can't match the power with a single 4.
     
    Vortec80 likes this.
  6. biker

    biker Veteran Member

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    Have a look at the Holley street demon 625. Seems to be marketed right at combos like yours. I have the 750 version on my 383 and it is awesome. Not the Demon that people typically think of. This one is similar in design to a thermoquad. Easy to tune and easy to drop on and run.
     
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  7. Vortec80

    Vortec80 Camaro project is a go

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    I've read on the 625 on their website. With the 600 (1850s) I'm running now it just feels like the engine is being held back a little. It's like its pulling for more but it's not getting it
     
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  8. RS1979

    RS1979 Veteran Member Lifetime Gold Member

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    350ci 9.5 compression, AFR Eliminator 65 cc 180 heads, Elgin Pro Stock cam. 510 lift 310 duration 244 @50. 3500 stall 3.73 gears
     
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  9. G72Zed

    G72Zed Veteran Member

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    Looking at your combo with 400hp, I would suggest looking at the Holley 3310 750 VS. Very versatile, and if your dual plane does not have a "notched or cut down" divider, all the more reason to use the 750 VS as the engine is only seeing 300CFM of your current 600cfm Holley right now. After all, the 302 Z/28 and the 70-72 Z's used a Holley 780 VS on a dual plane for a reason.

    A quick test would be to hook up a vacuum gauge with a long vacuum line to the manifold vacuum port, and see the reading at WOT, you may be up there.

    Generally you will move/use 1.3 to 1.4 CFM per observed HP. Must also include VE% if known (or a good guess) and I also incorporate a correction factor for a true dual plane.

    As far as "advertised" CFM ratings go for Holley's, I had 4 on the bench a few days ago prior to testing, the stock (w/choke tower) 4777-2 650 flowed 667 (wet), and the 3 other HP (no choke) 650's (all the same spec's) flowed 694,706, & 721 (wet). All 3 650 HP carbs I built were tuned on the same 350 SBC, made 565hp, used/moved 735 CFM (=1.3).

    Hope this helps.
     
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  10. Vortec80

    Vortec80 Camaro project is a go

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    Thanks for the feedback! That's great.


    Guys, Would a 750 holley 4160 part# 0-80508S be a solid carb? I can get a new one for 300$ . It looks like it's the same as the 3310 but with an electric choke. I have a manual choke carb now but have no cable for it
    Carb shopping at the parts store right now
     
    Last edited: Mar 4, 2019

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