Fuel leaning issue

Discussion in 'Small Block Tech' started by Christos, Jan 27, 2013.

  1. Christos

    Christos Member

    Hello all, I have a 68 Buick skylark 4 door that was a 2 barrel converted to a four barrel. It currently has a 750 cfm Edelbrock with an electric choke sitting on it. Stock internals. I have a glass fuel filter on it in between the fuel pump and carb. The issue i am having is that when i start the car, i have 5 psi of fuel pressure and the glass filter fills up with gas. as the car runs, the fuel pressure drops to 4 psi but the fuel in the filter leans out to almost nothing. if i romp on it the car bogs and backfires. if i slowly accelerate the car functions fine. I recently timed the car following the service manuals instructions by warming the car up, putting it in gear, pulling off the vac advance hose on the point distributor and plugging the hose (Did leave the vac advance in the distributor open though) and set timing to 0. but the fuel leaning appears to be my problem. checked venting but appears to be alright. I don't think the fuel is boiling so any suggestions?
  2. gsgtx

    gsgtx Silver Level contributor

    try putting the timing at 8* also watch to see if the timing advances when you rev the engine up.
  3. Christos

    Christos Member

    the timing is definitely advancing, i checked that.
  4. gsgtx

    gsgtx Silver Level contributor

    i would try it at 8-10* justto see if it makes a diference, damper might have slipped,if not your must be right with the fuel issue. also check a spark plug see if there fouled. how about the accelerater pump can you see it squirt
  5. LARRY70GS

    LARRY70GS a.k.a. "THE WIZARD" Staff Member

    It is normal for the filter to not appear full when the engine is running. I would get that glass filter off, it is a fire hazard, not all the time, but often enough. Fuel pressure sounds low. You can do a volume test, but if the fuel pump is old, I'd replace it, they are cheap enough.

    Stock initial timing only applies if the engine is completely stock, including the distributor. It has been 44-45 years since that car left the factory. Unless you are the original owner, and know it's history, lots of parts get changed in that time. The original distributor part number for the 1968 350 engine is 1111330. See if that is what you have.

    In any case, have a look at my Power Timing thread, and set the total timing to 32*(vacuum advance disconnected). Getting the mechanical advance all in at 2500 RPM, and limiting the vacuum advance will give you a seat of the pants performance increase, along with a cooler running engine, and better economy. http://www.v8buick.com/showthread.php?63475-Power-Timing-your-Buick-V8
  6. sean Buick 76

    sean Buick 76 Buick Nut Staff Member

    Sounds like a fuel supply issue to me. I would remove the line to the carb and run it into a bucket then turn over the engine to see how much fuel supply you are getting. It sounds like one of three things is your issue:

    1. Clogged sock at the fuel tank
    2. Cracked or collapsing rubber lines between fuel tank and fuel lines or at the fuel pump
    3. bad fuel pump

    Furthermore like Larry says, those glass filters are dangerous as they can crack and cause an engine fire. As long as your carb has an inlet filter then the there is no need for a filter between the carb and the fuel pump.

    Also just so you know the Edelbrock carb never will get close to as good of fuel mileage as the factory Q jet carb. I have never heard of anyone being happy with bolting on a E-brock carb onto a Buick 350, all I hear is stories about lack of power, lack of fuel mileage, and then success stories when they switch to a Q jet carb designed for the engine.

    GM spent a ton of time and money to calibrate the Q jets for each application so the best bet for a drop on carb that will work great without any mods is a Q jet made for a Buick 350. Sure an aftermarket carb can be made to work however it will normally take internal mods to make it work even close to as good as the stock Q jet.

    Others will come on and say I am wrong, but you can make up your own mind based on the info we give.
  7. Christos

    Christos Member

    holy crap what a difference:shock: Set the timing in about 8/10 degrees and what a difference. I oringinaly tried to put a quadrajet on the car but i stripped one the screw holes so i used the squarebore holes, plus the electric choke hookup was easier. The car has a poston s divider manifold on it. This car is kinda my crash course in learning about cars. next i need to learn how to set points (dwell) and the advance cut off. that was mentioned.

    I am happy the way things are now.

    I have a 73 buick engine in the garage that is the goal. the 350 is just so i can enjoy the car.

    The next step though is to get a th400 cause the st300 is peeing fluid all over the place.
  8. gsgtx

    gsgtx Silver Level contributor

    now you need to set points[dwell] that might be why your timing is off. then go back and set total timing the way Larry says how to do it.

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