Engine wont rev in the 1/4 mile

Discussion in 'Engine Topic' started by Domobomb, Sep 14, 2017.

  1. Domobomb

    Domobomb Veteran Member

    193
    1
    Nov 10, 2009
    Windsor, Ontario
    Hello guys.

    I took my car to the strip and made about 7ish passes.

    The car seems to bog down/hesitate and wont rev past 3500-4000rpm, at least in third.

    I was letting the transmission shift for me which was about 4000rpm in 1st and 2nd.

    I thought my plug gaps were too wide at .045", so I dropped them to 0.030" with no change at all.

    I'm thinking it's running out of fuel. I don't have an O2 sensor so I cant check AFR.

    I was going to try replacing the fuel pump and fuel filter.

    What do you guys think?

    Here is a typical timeslip with street tires...

    60' 2.248
    330 6.275
    1/8 9.617
    MPH 72.30
    1000 12.633
    1/4 15.308
    MPH 82.72

    Engine Specs:

    Carb: Holley 600
    Intake: Edelbrock Performer RPM
    Heads: Dart SHP 180 64cc, 2.02/1.6" valves
    Cam: Lunati 10120703 - 268/276 duration, Lift .489/.504"
    Exhaust: 1 5/8" Long tube headers w/ 2.5" pipes and flow master mufflers
    Compression: ~9.5:1
    Ignition: Stock HEI with MSD cap and high voltage coil.
    Stock GM rotating assembly.
    Stock mechanical fuel pump.

    Also has a TH350 with 2400 stall and 3.42 rear gear.
     
  2. snowcone

    snowcone Veteran Member

    416
    0
    Aug 4, 2011
    Colorado
    Sounds like your motor is starving for fuel. Could be secondary jetting is too small, fuel pump is not pushing enough fuel (will want to find out your "free flow rating" of the pump), clogged fuel filter, could be a clogged pick up in the tank (little sock that goes on the pick up tube). Could even be a clogged passage way in the carb.

    You will also want to verify your total timing and at what engine rpm the timing is all in at, this can be changed by the little springs in the distributor. Here is a good guide to becoming familiar with that - http://outintheshop.com/faq/hei.htm
     
  3. GoldenOne7710

    GoldenOne7710 Veteran Member Lifetime Gold Member

    4,230
    178
    Jun 23, 2004
    Athens, GA
    I see you've upgraded the coil and cap...with an otherwise stock HEI? The module is what keeps the coil saturated with spark. If you're still running the stock ignition module...well they tend to lose a bit of energy above 3800 RPM. Especially done by 5000.

    It could also be lack of fuel....and it may very well be a combination of both issues.
     
  4. tom3

    tom3 Veteran Member

    10,761
    77
    Aug 1, 1999
    ohio
    How old are those heads? Probably not, but weak valve springs will cause problems like this with a radical camshaft. Weak fuel supply will sometimes cause the engine to pretty much shut off, then catch, repeat. Lean in the secondaries might actually cause this type of hesitation too, let off the gas just a bit and it runs better sometimes.
     
  5. Green hornet

    Green hornet Veteran Member

    1,074
    142
    Oct 11, 2015
    North Bay, CA
    Check the float levels. If they are set to low the engine is going to be starved for fuel at the higher RPM. Check all the basics first before you go crazy. Just my .02 cents
     
  6. muscl car

    muscl car Veteran Member Lifetime Gold Member

    With a 60' of 2.248 I suspect gearing is the issue at hand here . Do you know the rpm you were pulling crossing the stripe at the big end
     
    71 rs BBC likes this.
  7. cadillac_al

    cadillac_al Veteran Member

    552
    35
    Apr 22, 2015
    Maine
    Man, that car is laying down, only gained 10 mph from the 1/8th to the 1/4. It must be fuel. The 1/8th mile time isn't bad, especially with the slow 60 ft time, but it isn't doing much after that.
     
  8. Mwilson

    Mwilson Veteran Member

    what is your total timing set at out of curiosity? 36-38? too bad you dont have a visible fuel pressure gage. Is the carb fairly new? Are you shifting manually or letting the tranny shift itself?
     
  9. COPO

    COPO Veteran Member Lifetime Gold Member

    16,050
    201
    Sep 15, 1999
    Ontario, Canada
    I once tried a 600 Holley on my LT1 and it ran out of air/fuel at 5000 rpm.
     
  10. mrdragster1970

    mrdragster1970 Veteran Member Lifetime Gold Member

    .


    Can you hear the ignition popping, or is it still semi smooth, just losing power???


    .
     

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