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q-jet cfm?

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by weisel, Feb 13, 2002.

  1. weisel

    weisel 1/2 ton status

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    just curious with all of this q-jet talk, but how many cfms dose a q-jet have?

    No, thats not a dent in my body. I call it my armor.
     
  2. Jeff427

    Jeff427 1/2 ton status

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    There were a few odd balls, but generally they came in either 750 cfm, or 795 cfm (which is usually rounded to 800). The neat thing about them is they automaticly adjust their airflow to match you engine, so you can put a 750 cfm Q-jet on a 6 cylinder and it will only flow what the motor can handle, just FYI [​IMG].

    <font color=purple>Jeff427</font color=purple>

    <a target="_blank" href=http://lyonsdesign.bizhosting.com>Lyons Design</a>
     
  3. Greg72

    Greg72 "Might As Well..." Staff Member Super Moderator

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    I think Jeff's got it right.....from what I've been able to learn, it seems like the CFM is achieved by simply re-jetting. There are no signinficant changes in the base casting or throttle bores themselves. The only exception might be the 850CFM....but I don't know for sure.

    Here's a link on DYeager's site that will help you determine the 750's from the 800's:

    See it here: </font color=blue><a target="_blank" href=http://coloradok5.com/gallery/albun38>http://coloradok5.com/gallery/albun38
     
  4. dyeager535

    dyeager535 1 ton status Premium Member

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    CFM is actually changed by the castings. It's the fuel bowl casting (the center of the 3 pieces) that is different between 750 and 800's. Primary CFM difference is *roughly* 250 vs 300CFM for the 750 vs 800 CFM carbs.

    Most carbs from the 70's on, perhaps even earlier, were limited on the secondary side, secondary air valve shaft has a tang on the passenger side, for around 500-600CFM. Cut it.

    Nice Link! : )

    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?
     
  5. Greg72

    Greg72 "Might As Well..." Staff Member Super Moderator

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    Yep....I "baited you" to come out and answer on this one! [​IMG]

    I bookmarked your site a while ago, and I go to it often. I'll admit I don't understand everything that's there yet.

    It's hard when you're first learning because even the "best" information can simply be "too much, too soon". Once I get a better base of knowledge and I go back to re-read that stuff.....it suddenly makes a lot more sense!!!

    Thanks for going to all that trouble to put the info there.....I know it's going to help me a lot in the future.




    -Greg72

    '72 K5 Blazer - 427BB/TH350/NP205/6" Lift/35x12.50's
    <font color=blue>See it here: </font color=blue><a target="_blank" href=http://coloradok5.com/gallery/albun38>http://coloradok5.com/gallery/albun38</a>
     

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