Dismiss Notice

Welcome To CK5!

Registering is free and easy! Hope to see you on the forums soon.

Score a FREE t-shirt and membership sticker when you sign up for a Premium Membership and choose the recurring plan.

650 cfm or 750?

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by wheelin247, Feb 8, 2001.

  1. wheelin247

    wheelin247 1/2 ton status

    Joined:
    Aug 29, 2000
    Posts:
    178
    Likes Received:
    0
    Location:
    hayward,ca
    i have a basically stock 350 but its got a racing cam and drag headers what cfm should i get 650 or 750 need help soon as possible thanks ....
     
  2. angelglo

    angelglo 1/2 ton status

    Joined:
    Aug 4, 2000
    Posts:
    105
    Likes Received:
    0
    Location:
    S.F. bay area
    do this. mulitiply your cubic inches x the maximum RPM's you will be using. divide that number by 3456. then mulitply that number by your VE%.. that is the volumetric efficiency percentage. this is the amount of air that your motor will be breating in. race engines go to 100%. 1/4 mile cars go way above 100%. with intake, headers and cam, try using about 95%. after all is done, you will get the MINIMUM cfm's you should use. i hope this helps.
     
  3. SuperUnknown

    SuperUnknown 1/2 ton status

    Joined:
    Feb 8, 2001
    Posts:
    165
    Likes Received:
    0
    Location:
    Prince George, British Columbia, Canada
    I would go with the smaller one.
    750 is probably too big for you enging.
     
  4. bablazer73

    bablazer73 1/2 ton status

    Joined:
    Apr 4, 2000
    Posts:
    3,363
    Likes Received:
    0
    Location:
    upstate ny
    650. 750 is way to big for a mild small block. max rpm will depict cfm requirment.

    your right. I don't understand the jeep thing!
     
  5. nyyef

    nyyef 1/2 ton status

    Joined:
    May 16, 2000
    Posts:
    479
    Likes Received:
    0
    Location:
    Saudi Arabia
    even though the stock carb is about 750 or 780cfm (something like that), a 650 will give you better driveability and throttle response which would be much better for a truck.

    Knife.
    knife.coloradok5.com
     
  6. dyeager535

    dyeager535 1 ton status Premium Member

    Joined:
    Dec 13, 2000
    Posts:
    26,979
    Likes Received:
    189
    Location:
    Roy WA
    You've got to figure in the primary side for driveability and economy...a Q-jet has small primaries..right around 250 CFM for the 750CFM model. Just read an interesting article by David Vizard, and they actually got better performance with 1000CFM carb, (I think it was a SBC) and before everyone goes saying that is way too much, I agreed too. But the guy knows what he is talking about, and the article explained it. The URl is now dead, but looks lik eit may come back, if someone wants to read it in the future... http://www.dorianyeager.com/index2.html
     

Share This Page