Flow numbers

Discussion in 'Race 400/430/455' started by Buickrat1, Feb 24, 2019.

  1. Buickrat1

    Buickrat1 Well-Known Member

    What flow numbers have you guys seen on Stage 1 iron heads with 2.13 intake 1.75 exhaust 11/32 or 3/8 stem?
  2. Stevem

    Stevem Well-Known Member

    What flow numbers are you looking for?
    On a well built race motor with at least 11 to 1 compression every 4 cfm of Intake flow@28" per cylinder will make you 1 hp.
    Note that this is Intake flow with the Carb and Manifold bolted on, not just the bare head!

    With over 12.5 comp on a well thought out motor every 3.8 cfm of flow will get you 1 hp per cylinder.
  3. hugger

    hugger Well-Known Member

    Most I've ever heard is 295, Dave knows how to make hp, I'm betting he has a badass set In The works
  4. Rob Ross

    Rob Ross Well-Known Member

    These are my Gessler heads,

    Lift Ex In
    0.100 59 71
    0.200 125 150
    0.300 168 227
    0.400 192 284
    0.450 195 303
    0.500 197 305
    0.550 199 303
    0.600 200 300

    I've heard of other heads going 320-330 but have never seen the data yet. The above data was from AMPs flow bench 2.13/1.77. At one time I had 2.16 intakes and moving back to the stock size helped the mid lifts.
    Last edited: Feb 25, 2019
    kenny t likes this.
  5. Buickrat1

    Buickrat1 Well-Known Member

    These are good numbers thanks for the information. I picked up a set of heads from a garage sale. I saw that they were ported so I put them on the flow bench and they match your numbers but only to .400 lift. After that they stay the same through .600 lift. same with the exhaust.
  6. Stevem

    Stevem Well-Known Member

    Dont go looking / grinding for more high lift flow above .400" lift at the expense of that real nice & fat 227 cfm @ .300" lift as that's what you want as opposed to yanking 310 cfm @ .600" lift or more!!!

    If you want to grind more for bigger numbers above .400" lift while keeping that flow level at .300" then get custom made 2.15" valves and open up the Throat diameter of the valve bowl to the same ratio you have now with the 2.13" valve and then open up the window at the crown of the short turn that same amount .
    This assumes a port wall sonic check out before firing up the grinder!
    Last edited: Feb 26, 2019
  7. Rob Ross

    Rob Ross Well-Known Member

    You're welcome, what a great find!
  8. HotRodRivi

    HotRodRivi Tomahawks sighted overseas

    No kidding, thats one cool garage sale.
  9. Buickrat1

    Buickrat1 Well-Known Member

    Update, when I initially flowed the heads they were all dirty and the ports had oil in them from loose guides. I have taken them a part and cleaned them up. I am going to put a 11/32 stem stainless valve in them and do some clean up work in the bowl are and work on the short side to see what kind of air I can pick up.
    billiegoat, Rob Ross and Julian like this.
  10. Stevem

    Stevem Well-Known Member

    There's not much to be gained by cleaning up the Intake bowl other then cutting back the web / support on the Exh bowl side of the Intake valve guide.

    You first need to pin down where the actual restriction is which if done only by eye can lead to a loss of flow once ground on or excess port volume and a loss of throttle responce.

    Post up some pictures of your ports for a review and some suggestions if you would.

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