fuel problem!!! ( think)

Discussion in 'High Performance Modifications' started by CB63SK, Sep 26, 2011.

  1. CB63SK

    CB63SK New Member

    Messages:
    24
    Likes Received:
    0
    Joined:
    May 21, 2006
    Location:
    GARLAND (where the cops beat you) TX
    heres what i have....

    1978 z28 camaro. 400+ hp 400 SB. 4 Sp trans.
    1970 ls6 BB q-jet.
    stock style fuel pump
    stock style distributor

    heres what is does...
    ST gear (shift about 5000 to 5200) no prob.
    ND gear about 3000 to 4000 (rpm's) she falls flat on her face. if i let up for a few seconds we are back in the back seat.

    a few buddy's of mine say it's a fuel problem. but i;m not sure.

    i have a aftermarket holly fuels pump (12-834). but it does not have a nipple to hook up the return line.

    any ideas on a new aftermarket fuel pump???? i want to stay with the mechanical.

    could it be something Else????

    any input will be helpfully!!!!!
     
  2. Damon

    Damon Veteran Member

    Messages:
    12,939
    Likes Received:
    23
    Joined:
    Nov 16, 2000
    Location:
    Philly area
    Yeah, sounds like a fuel starvation problem. Before you change anything get a gague hooked up to it that you can actually SEE WHILE YOU ARE DRIVING. Fuel pressure sitting still is nearly meaningless. You have to see what it's doing under WOT conditions pulling through the gears. I have a cheap remote-mount fuel pressure gague setup that I duck-tape to the outside of the windshield (temporarily!) to get an idea what's going on during a run. If it's right, fuel pressure won't deviate more than ~1 PSI anywhere in the run.

    If you're outrunning the fuel system it will be obvious. Fuel pressure will nose-dive and then the engine will nose-dive shortly after that. You won't have to guess if it's a problem- it will be as plain as the nose on your face.

    The pump itself is only one possible source of the problem. It can be the stock lines, the "sock" in the tank, an inadequately sized fuel filter or any one of a million little things that cause the fuel system not to keep up.

    If you want to try a good pump the Carter 6 PSI street pump (110 GPH) is hard to beat for volume and reliability (mine is probably 10+ years old with zero issues). The more recent Holley pumps are Carter pumps, by the way. The old Holley "chrome" pumps are well known for having "issues".

    Lack of a return line doesn't matter. That's primarily there to address vapor lock issues in stock applications. Has nothing to do with what's going on when you're wide open hauling a$$ down the track.
     
    Last edited: Sep 26, 2011
  3. CB63SK

    CB63SK New Member

    Messages:
    24
    Likes Received:
    0
    Joined:
    May 21, 2006
    Location:
    GARLAND (where the cops beat you) TX
    cool. i will check into that. where do i hook up the fuel pressure gauge? ( my biggest down fall is carbs. i can't tune one to save my life.)
     
  4. markw

    markw Veteran Member

    Messages:
    819
    Likes Received:
    2
    Joined:
    Jun 6, 2009
    Location:
    Illinois
    Whatever you do DO NOT put a fuel pressure gage INSIDE the car! Keep it outside the car, taped to the windshield as noted. Just 'T' into the line feeding the carb. Often an inline fuel filter can be removed and replaced with a 'T' fitting temporarily. Keep it safe, leak free, and securely mounted away from the fan belt.
     
  5. captaincog

    captaincog New Member

    Messages:
    14
    Likes Received:
    0
    Joined:
    Sep 5, 2009
    Location:
    Rialto, Ca
    YOu could have a line that is collapsing internally. If it continues to get worse I would also look for this. Try putting the fuel pressure guage as close to the carb inlet as possible. You can get aftermarket fuel pressure guages that will go inside the car for a permanent mount. The fuel line goes to a mechanical sender that sits in the engine compartment and the guage is then actuated by a separate non-flammable fluid line that runs to the guage. It is a lot of work, but once you have a fuel pressure guage you will not want to go back.
     
  6. Kjdavis93

    Kjdavis93 Veteran Member

    Messages:
    112
    Likes Received:
    0
    Joined:
    Jun 11, 2005
    Location:
    Columbus, Ohio, United States
    Maybe try tuning the carb with a vacuum gauge, there are videos on you tube. Basicaly you hook the vacuum gauge to the base of the carb and adjust the mixture screws until you get highest vacuum reading and you will have to go around it back and fourth until you the most out of both sides. Should put you in the ball park. Im sure someone can give you a more scientific explanation. Also make sure you Accelerator pump is adjusted correctly.
     

Share This Page