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  1. #1
    Join Date
    Jan 2003
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    PRESTON, LANCASHIRE, ENGLAND.
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    62
    Posts
    136

    car running rough

    hi guys
    I have a 350 sbc fitted with a 600cfm edelbrock carb. I have been running this set up for yrs without any probs. recently though when I floor it in any gear it coughs, and backfires through carb and only when I take my foot of the accelerator and reapply slowly does it run ok, it ticks over no probs. I have being trying allsorts to remedy and have even fit new ali heads that I have been planning on doing for a while anyway. I have fit new metering needles but not jets cus roadcraft had no stock of one of them and new accelerator pump and gaskets. Other than fit a new carb I do not know what else I can do. Compression on all cylinders is around 150. The only thing I havnt touched is the HEI module or capacitor. What fuel pressure should I be running, I have a holly red top fuel pump and filter king fuel pressure regulator. HELP please anyone
    regards graham

  2. #2
    Join Date
    Apr 2004
    Location
    on the edge...almost falling off
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    Posts
    8,367
    Fuel filter??
    BIG TONE


    Mercedes SL owner, definitely NOT a kitcar owner like you lot!


  3. #3
    Join Date
    Jan 2003
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    PRESTON, LANCASHIRE, ENGLAND.
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    62
    Posts
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    what do you mean big tone, dirty filter and not allowing enough fuel into carb
    graham

  4. #4
    Join Date
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    on the edge...almost falling off
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    It's a possibility Graham, especially if you're asking for a lot of fuel all at once like when you're accelerating?

  5. #5
    Join Date
    Jan 2003
    Location
    PRESTON, LANCASHIRE, ENGLAND.
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    62
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    I can understand your theory tony but why would it backfire when I ask for more fuel, it doesn't backfire when ticking over or accelerating at a reasonable pace, only when I floor it
    graham

  6. #6
    Join Date
    Mar 2006
    Location
    Oxfordshire
    Age
    66
    Posts
    1,303
    Spitting back through the carb is probably due either to a very weak mixture (blacked fuel filter as Tony suggested, blocked main jet(s), major inlet manifold/carb vacuum leak) or an ignition issue - timing too advanced (dizzy might have moved due to loose clamp), bad or fouled spark plug(s), ignition leads crossfiring or shorting, pitted/badly adjusted points or bad capacitor (if you have points rather than breakerless ignition) or other poor/intermittent connection on the LT side.

    Plenty of things there for you to check if you haven't done so already!
    Alan

    CRC Thames Valley Regional Rep
    UK Rep for European Cobra Club
    Dax Tojeiro DeDion - Huddart SBC 383

  7. #7
    Join Date
    Jan 2003
    Location
    PRESTON, LANCASHIRE, ENGLAND.
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    62
    Posts
    136
    don't know how or why but I think the spring in the filter king regulator has been put in wrong. I think the spring goes inside the filter and attaches to the underside of the filter king top. mine was under the filter pushing the filter up when tightening the glass bowl into place so I think it was fuel starvation. not been for a run in it yet but am hoping I have solved it. think its been like that for ages
    graham

  8. #8
    Join Date
    Jan 2003
    Location
    PRESTON, LANCASHIRE, ENGLAND.
    Age
    62
    Posts
    136
    ignore previous message, just found out spring is/was in correct place between base of filter and bottom of glass bowl,
    graham

  9. #9
    Join Date
    Mar 2006
    Location
    Oxfordshire
    Age
    66
    Posts
    1,303
    Graham,

    I suggest you replace the glass fuel filter with a plastic or metal one - if the glass shatters, spraying fuel and hot exhaust headers make a dangerous under-bonnet combination!
    Alan

    CRC Thames Valley Regional Rep
    UK Rep for European Cobra Club
    Dax Tojeiro DeDion - Huddart SBC 383

  10. #10
    Join Date
    Sep 2010
    Location
    Nova Scotia
    Posts
    643
    Sounds like the ignition has become to weak to fire the plugs under heavy load. A lot of things can cause this, but I'd check the plugs and in particular do the "midnight" test on the wires. Open the hood in the dark and with the engine running, look (and listen) for external arcing.

    Looks like this was mentioned before (post #6). As for a fuel issue, I'd check the accelerator pump squirt. With engine off, pear into the carb and give the throttle (at the carb where you can reach) a quick twist.
    John

    my world... my universe... my garage.

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