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is my 850cfm Q-jet too big for my 350?

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by Silver84k5, Feb 14, 2002.

  1. Silver84k5

    Silver84k5 1/2 ton status

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    i keep hearing it is too big, is this carb that is on my 350 interchangeable with a 454? thx for help

    If you dont make it the first time, Drink another beer, and press a little harder on the gas
     
  2. KRAZIE87K5

    KRAZIE87K5 1/2 ton status

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    It is a bit oversized! Anyhow, YES - you can install it on a 454 too.

    <font color=red>GOT MUD???</font color=red>
    <a target="_blank" href=http://home.attbi.com/~netwrite>Midwest Caravan</a>
    454/TH400/NP205 - 14BFF/D60/w/ 4.10s - 36" TSLs
     
  3. 86K5TrailBlazer

    86K5TrailBlazer 1/2 ton status

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    nah! its just fine. It wont flow 850cfm if your engine wont take it but it can if it can, hehe. Anyway whatever you do its fine. Unless you got big big hp

    <a target="_blank" href=http://www.myk5.com/gallery/>SoCal Big Dawgs</a>
     
  4. 6.2L Jimmy

    6.2L Jimmy 1/2 ton status

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    A 355 c.i. engine with 100% volumetric efficency (full race) calls for 632 cfm ,so I would stick on a 650 cfm and be done with it.I had a 355 c.i. with 85% v.e and a 650 worked great, Hope this helped

    Mike

    1989 GMC Jimmy 6.2L 4x4,1969 Camaro Z/28 502 C.I. B.B.C.
    BLOOD,SWEAT AND GEARS!
     
  5. 6.2L Jimmy

    6.2L Jimmy 1/2 ton status

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    A 355 c.i. engine with 100% volumetric efficency (full race) calls for 632 cfm ,so I would stick on a 650 cfm and be done with it.I had a 355 c.i. with 85% v.e and a 650 worked great, Hope this helped. My opinion an 850 is way over carbed, it is made for a big block really.

    Mike

    1989 GMC Jimmy 6.2L 4x4,1969 Camaro Z/28 502 C.I. B.B.C.
    BLOOD,SWEAT AND GEARS!
     
  6. jc71355

    jc71355 1/2 ton status

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    i had an origional q-get on my 355, not sure on size but i put on a holley 650 and lost almost all of my low end power. Made good Hp but it wasn't worth the sacrifice in low end power. I ended up putting a 750 edelbrock and gained some back but nothing like it used to be. Just thought i would tell my experience.

    James

    <font color=blue>91K5 350 2.5in Suspension lift 33/12.5
    If It's a JEEP thing why is your engine and tranny the same as my K5[​IMG]</font color=blue>
     
  7. Twiz

    Twiz 1/2 ton status

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    You can't really over-carb an engine with a Q-jet.

    The Air-valve door on the secondaries will only let in as much air as the engine needs. So, if the engine only needs to flow 650 cfm, then the Air-valve door will only partaly open enough to flow 650 cfm.

    By-The-Way. You can modifie a Q-Jet to flow over 1000 cfm, and still have good low RPM power too! - [​IMG]


    <font color=white>.</font color=white>Eric
    <font color=white>.</font color=white>Twizted
    <P ID="edit"><FONT class="small">Edited by Twiztid on 02/15/02 07:18 AM.</FONT></P>
     
  8. Grim-Reaper

    Grim-Reaper 3/4 ton status Author

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    Quit listening to the hogly folks. Quads adjust to the engines needs. you may need to tighten the vac flap over the secondaires so they don't come on so strong or you might ned to put smaller main jets in that carb but it can run fine on that engine.
    Get "Tunning rochester carbs" book at your local parts store and it will tell you everyting you need to know.

    Women dig dents and flat paint!
    coloradok5.com/gallery/Grim
    75 Jimmy, Dollar
    Grim-Reaper
     
  9. RootBreaker

    RootBreaker 3/4 ton status Premium Member

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    nahhhh... it wont work so .... I wil buy it from ya...
    just kidding... I like q-jet better.. . I have both and like my q-jet....

    <a target="_blank" href=http://community.webshots.com/user/rootbreaker>Pics of buildup</a>78 Chevy 3/4 - 14" on 40"x17x16.5 Ground Hawgs
     
  10. KRAZIE87K5

    KRAZIE87K5 1/2 ton status

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    All I have to say is that my Holley still sucks (like always)! [​IMG] And I can't wait to put on the Q-Jet I have on the bench! I just have to figure out how to put it back together! [​IMG]

    It's good to know that the Q-Jet has a way to "adjust" is CFM based on what the engine requires, vs. what the carb forces (like my Holley)...

    Thanks Twizted and Grim!

    <font color=red>GOT MUD???</font color=red>
    <a target="_blank" href=http://home.attbi.com/~netwrite>Midwest Caravan</a>
    454/TH400/NP205 - 14BFF/D60/w/ 4.10s - 36" TSLs
     
  11. dyeager535

    dyeager535 1 ton status Premium Member

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    The problem with the 850 is that more than likely (unless Edelbrock seriously changed the casting) you are dealing with even larger primaries, with the same size secondaries. Not good for gas mileage, but not going to eliminate it either : )

    The larger you go on the primareis, the less velocity you are going to have, which isn't good if you don't really rev the engine.

    The "only flows what it needs" applies...the primary rods are governed by vacuum, as are the secondaries, but you are *still* going to lose velocity at lower RPM's with a larger primary venturi, like the 800's vs the 750, and likely the 850 vs either of those carbs.

    I'd run it and not worry, but had I bought a new carb, I'd have purchased the 750 for the small primaries....better economy/theoretically better throttle response too I suppose.

    Dorian
    My tech/links page: <a target="_blank" href=http://www.dorianyeager.com/index2.html>www.dorianyeager.com/index2.html</a>
    Why insist on counting when the ring gear has the tooth counts stamped in?
     
  12. 84_Chevy_K10

    84_Chevy_K10 Banned

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    I doubt they'd enlarge Q-Jet primaries. That would defeat the purpose of having a Q-jet.

    Tim
    '84 Chevy K10, lifted, loud, fast, and 3/4 ton axles
     
  13. dyeager535

    dyeager535 1 ton status Premium Member

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    Difference between a 750 and 800 was always on the primary side, I can't imagine enlarging the secondaries even further, that would require moving a lot of stuff like secondary hangars, the secondary rod orifices, etc.

    Wouldn't be as much material removed from the secondaries as the primaries to achieve 50 more CFM, but I guess someone would have to ask Edelbrock how they did it.

    Dorian
    My tech/links page: <a target="_blank" href=http://www.dorianyeager.com/index2.html>www.dorianyeager.com/index2.html</a>
    Why insist on counting when the ring gear has the tooth counts stamped in?
     
  14. Silver84k5

    Silver84k5 1/2 ton status

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    Thx all, sorry it took so long for a thank you but i been gone ;]

    If you dont make it the first time, Drink another beer, and press a little harder on the gas
     

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