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weird stuff at end of track

Discussion in 'The Hokey Ass Message Board' started by tylerb, Jul 18, 2008.

  1. tylerb
    Joined: Oct 25, 2006
    Posts: 75

    tylerb
    Member

    Hello,
    I have a '65 Galaxie. The drive train consists of a bored and stroked 406, Holman Moody Ha-B camshaft, Hooker headers, a tri-power setup, and a C6. I launc the car around 2,500 with no problems and i am shifting at about 5500. When I shift into second the car is fine and runs strong, but when i shift the car into 3rd at 5500 it begins to lurch almost like a lean surge. When this happens it's like the car has hit a brick wall. I figured it has to be a fuel problem. Just for kicks and giggles I tried shifting it at 4500 and it stopped lurching and I ran my best time of the night, a 14.2 @96mph, whereas before while shifting at 5500 i was running 15.5 if that shows you how bad it gets if I rev it to 5500. Something isn't right i should be able to shift the thing at 5000 or 5500. I will say that it was 90 degrees and very humid that night so that could contribute to the problem. I currently have a fuel pressure regulator running at 6.5psi. I'm pretty sure that this is enough fuel pressure, but I just wanted to get some other thoughts. Maybe it is getting starved for fuel at higher rpms?
    Thank guys,
    Tyler
     
  2. RacerRick
    Joined: May 16, 2005
    Posts: 2,753

    RacerRick
    Member

    Look at fuel volume to start with...you can have adequet pressure but still empty the fuel bowls.
     
  3. Shifty Shifterton
    Joined: Oct 1, 2006
    Posts: 4,964

    Shifty Shifterton
    Member

    You've just perfectly described, and apparently self-troubleshot, a fuel delivery problem.

    Time to evaluate your pump, line size, condition of the soft lines (collapse risk), and cleanliness of your tank pickup.

    Do it before any more full throttle lean-outs. They're not good for longevity.

    Consider a fuel pressure gauge in the car that's coming from a sender near the carb inlet. Even it's only temporary for a month or two til it's sorted out. It's necessary to evaluate how fixy your fixes are, and protect the engine in the meanwhile.

    good luck
     
  4. hoarder1212
    Joined: Jun 1, 2007
    Posts: 156

    hoarder1212
    Member

    What size fuel line do you have?
     

  5. Von Rigg Fink
    Joined: Jun 11, 2007
    Posts: 13,426

    Von Rigg Fink
    Member
    from Garage

    he beat me to this question..maybe its not "pressure" but volume?
     
  6. gas pumper
    Joined: Aug 13, 2007
    Posts: 2,956

    gas pumper
    Member

    Can you put a gauge fitting right at the entrance to the carb? and run a flex line to the edge of the hood. so you can watch the pressure drop at the big end?
    You can probably test on the highway with this setup. I found the right fuel level I had to run in my tank by this method.

    Frank
     
  7. tylerb
    Joined: Oct 25, 2006
    Posts: 75

    tylerb
    Member

    I have 3/8 fuel line on it right now....i have a pressure gauge on the line right before the fuel enters the fuel log and it reads a 6.5 psi i did at one point put a temporary gauge inside the car and watched the pressure when i was a full throttle and it stayed a steady 6.5
     
  8. Ramblur
    Joined: Jun 15, 2005
    Posts: 2,101

    Ramblur
    Member

    I believe its running out of fuel also. Had the same thing with my 327/57
    Chevy back in the 70's. Some guys at the track talked me into putting a
    "cool can" on it(half-gallon sized canister with coiled fuel line running
    through it). Fill it with ice and I instantly picked up .8/sec.:eek:. I was only
    16 or 17 but to this day that was probably the best $10 I ever spent.

    Back to now, I haven't seen a cool can on a car in ages but it still speaks
    to a fuel delivery problem.
     
  9. tylerb
    Joined: Oct 25, 2006
    Posts: 75

    tylerb
    Member

    hmm thats sounds like a good idea.....i have seen them at summit but not sure how much they cost
     
  10. liljgoneman
    Joined: Dec 31, 2006
    Posts: 160

    liljgoneman
    BANNED

    empty bowls is a good bet, that's not a great volume of fuel to start with and when you get her spinnin up top, it's very likely that while pressure remains good the motor is askin for all the pump's got and then some. feed her more and i'll bet she rewards ya! starve her and she'll punish you though. just don't push her too hard through the lights 'til you get the problem corrected.
     
  11. BigChief
    Joined: Jan 14, 2003
    Posts: 2,084

    BigChief
    Member

    Check the float levels in the carbs to make sure they're set correctly and also make sure the inlet needles on all three carbs are functioning properly. 6.5psi and a 3/8" line is plenty of fuel for this combination. Make sure any in-carb/inlet type filters are removed and that you have a good in-line filter ahead of the carbs.

    If you find that the carbs are OK and getting plenty of fuel (temporarily install an air-fuel meter in one of the header collectors/head pipes) then check for possible valve float. The cylinder heads need to be dialed in to the cam and valve spring specs....if the spring pressures and/or rocker geometry are off you could get early valve float. That solid lifter 406 should be able to rev much higher than 5500, especially with the shorter stroke.

    -Bigchief.
     

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