Fuel boiling over into carb

Discussion in 'Engine Topic' started by snowcone, Mar 10, 2016.

  1. muscl car

    muscl car Veteran Member Lifetime Gold Member

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    Check your fuel line routing and make sure it's not in contact with exh or engine heat . What I've done to mine is wrap my #8AN fuel lines with household foam pipe wrap to protect copper pipe . I wrap my fuel lines with this then sleeve it with 1500 deg heat sleeving to further protect from heat soak
     
  2. Damon

    Damon Veteran Member

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    Yeah, anything you can do to fashion (or buy- they have them pre-made for Holleys) some sort of heat shield could do nothing but help. Also, if the only gasket between the carb and intake is a single "thin" (1/16") gasket, try stacking up 2 or 3 more on top of that. Not just too open up a little room, but more gaskets also equals more insulation from heat conducting up from the intake through the carb body.

    And, of course, anything you can do to keep engine and underhood temps down is going to help as well. 160* thermostat, not 195*. Got adequate airflow in/around the engine? Get headers ceramic coated (helps a lot more than you might think).

    This is rarely a game you win in one move.
     
  3. 450bench

    450bench Veteran Member

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    May be a heat soak issue but I've seen vented gas caps blow 2 feet off when taken off because they don't function properly. I had it happen most recently on my 69. I noticed gas leaking into the intake floor from the carb. You could hear it. The pressure over-rode the floats. Took off the gas cap, which was supposed to vented, and it shot off releasing big time pressure. Drilled a very small hole in it. Problem solved.
    Just a thought.
     
  4. onovakind67

    onovakind67 Veteran Member

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    If your running fuel pressure is 7psi and the carburetor will shut off the fuel as a part of normal operation, how much pressure would you have to have in your gas tank to overcome the needle/seat? Would your gas tank change shape dramatically with this much pressure inside?
     
  5. Twisted_Metal

    Twisted_Metal Administrator Staff Member Lifetime Gold Member

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    My Son's Camaro did this too.

    He could beat my car in two back-to-back 1/8 mile passes but a third pass would have his fuel boiling and I could take the win. :)

    A phenolic spacer took care of the problem for him.
     
  6. snowcone

    snowcone Veteran Member

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    I went ahead and got a phenolic spacer to try and the carburetor stays much cooler, works pretty well. Ill have to wait for a hot day to make sure all fuel bowling is over with but so far so good.
    went with this unit here.
    http://www.summitracing.com/parts/edl-8723/overview/

    The problem I'm having is after I installed it and took it for a quick drive to get it up to temp, I hooked up my vacuum gauge and it fluctuates at idle between 14-16 which it did not before. Should I be worried about a vacuum leak? It seemed to run great and I didn't notice any difference in the way it ran. What I'm worried about is driving it like this and creating a lean condition form the vacuum leak.

    Could it be leaking around the base? My manifold is open with a line through the middle and the spacer is 4 hole so i used a gasket that matched my intake on the bottom side.


    [​IMG]]



    Also for those with stock hoods I was able to fit a 1/2in spacer under the carb with a drop base air cleaner and it clears the hood.
     
  7. snowcone

    snowcone Veteran Member

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    There is one area I found along the frame rail that is relatively close so I will try this trick on that area great idea.
     
  8. Orange71

    Orange71 Veteran Member Lifetime Gold Member

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  9. COPO

    COPO Veteran Member Lifetime Gold Member

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    Heat shields work great.
    [​IMG]
     

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