Sbc 350 gas in oil.

Discussion in 'Troubleshooting & Diagnosis' started by Beaber89, Jan 14, 2018.

  1. Beaber89

    Beaber89 New Member

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    Feb 3, 2017
    I have gas finding it's way in to the motor oil, I'm sure there are threads of this already. Here are my details . Sbc 350, just over 500 mile rebuild . New everything . Yesterday I went from an Edelbrock 1411 to a Holly demon 1901. 750 cfm to 625. The 750 ran okay but I definitely needed something smaller. The demon is brand new out of the box. Running rich off of my Afr gauge 10.5 and bumping in to 9 off idle. Exhaust is running black . I read posts already with most saying the fuel pump but since I just changed this carb then it may be more likely the carb. Something to point out, with the 750 carb the fuel filter would not hold full of gas. With the 625 the fuel filter does hold full gas. Suggestions before I buy a different fuel pump are appreciated .
     
    Last edited: Jan 14, 2018
  2. Lowend

    Lowend Administrator. .a car, a man, a maraca. Staff Member Lifetime Gold Member

    14,242
    207
    Mar 25, 1999
    San Jose, CA, USA
    I'm not sure what you're asking here:

    Is there gasoline in the fuel and you're wondering why?
    Is the car running rich and you're wondering how to fix that.

    Both?
     
  3. Beaber89

    Beaber89 New Member

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    Feb 3, 2017
    There is Gas in the motor oil.
     
  4. CorkyE

    CorkyE Veteran Member Lifetime Gold Member

    9,053
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    Nov 4, 2004
    Ringgold, GA
    A carburetor running rich doesn't dump fuel into the oil, there has to be a mechanical issue where fuel is going into the engine.

    One day old for the install, take another look at what you did.
     
  5. Lowend

    Lowend Administrator. .a car, a man, a maraca. Staff Member Lifetime Gold Member

    14,242
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    Mar 25, 1999
    San Jose, CA, USA
    One a motor that new, I'd tend to think the rings didn't seat
     
  6. Beaber89

    Beaber89 New Member

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    Feb 3, 2017
    A possibility. I didn't have this problem or notice to have this problem before yesterday. I've been running this motor every week for the past year. Maybe it's just the mech fuel pump diaphram going out in coincidence. So suggestions, change the oil and see what happens?
     
  7. jimrr

    jimrr Veteran Member

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    189
    Jun 12, 2016
    sarasota
    Bad rings......the fuel is washing by the rings into the pan. Or.......More than likely too much fuel pressure pushing the fuel past your float's and washing down the cylinder walls.
     
  8. Beaber89

    Beaber89 New Member

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    0
    Feb 3, 2017
    Thanks for the input. I'll check pressure and reference recommend pressure.
     
  9. czizza

    czizza Veteran Member

    821
    14
    Jan 8, 2004
    N. Massapequa, NY, USA
    You are running too rich ... If it is the same issue I had all you need to do is lean it out. When you are too rich you wind up washing fluid down the cylinder. Try changing the jets you want to be around 13.5 for cruise and light throttle and 12.5 for power runs.

    Those numbers are just a suggestion your engine will tell you where but you should be close to the above numbers.

    https://ls1tech.com/forums/general-maintenance-repairs/1465683-running-rich-gas-oil-help.html
     
  10. COPO

    COPO Veteran Member Lifetime Gold Member

    16,055
    201
    Sep 15, 1999
    Ontario, Canada
    Check your vacuum reading at idle and swap out the power valves to 1/2 you’re idle vacuum reading. Sounds like your dumping more fuel than what the engine needs.
     

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