Fuel pressure/mixture adjustment?
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  1. #1
    Compulsive chicken choker English Impala's Avatar
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    Fuel pressure/mixture adjustment?

    Just fired up the Chevy after a two week hibernation & its running as rich as it ever has! Black smoke, stinking of petrol, sluggish, the car's just the same... .

    Fuel pressure gauge shows 8 psi on tickover. Carb is an Edlebrock 600 4-barrel.

    The carb is off Andy (58 Delray's) 58 which has a 350, so I guess it might want the mixture tweaking for my 305? Fuel pressure, is 8 too high? I asked a similar question a while ago on the NSRA but can't find the bloody thing!

    Regarding setting the mixture, how? Many moons ago I had a special clear spark plug & you set the mixture until the right colour spark could be seen in the plug. I no longer have that & it wouldn't fit anyway! So, whats the best rule-of-thumb/basic set up for an Edlebrock as they are different to the Holley that I used to use?

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    I'm a grown up drunk! chevy2's Avatar
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    i'm guessing 8psi is too high,
    try starting on 5-6psi,
    to get the mixture right you'll need to get the motor up to operating temp,
    only then can you set the mixtures correctly,
    start off with the 2 mixture screws wound out about 2 turns each,
    once the motors fully warm, gradually wind the screws in 1 at a time to lean it out,
    once the idle drops off wind each screw out 1/4 of a turn,
    you should be fairly close.

    or use a vacuum guage using direct vacuum from the base of the carb,
    adjust the 2 mixture screws trying to get the highest reading at idle.

  4. #3
    Compulsive chicken choker English Impala's Avatar
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    Thanks, just tried to adjust the pressure regulator & my metric allen keys don't fit! I'll buy an imperial set & try what you've said.

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    Off the Xmas card list kapri's Avatar
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    Yup, agreed. I wouldn't be looking at more than 5 -6 psi as well otherwise it can start pushing the floats up and dripping fuel in .

    Don't forget to recheck your float levels and you have got a filter inline i take it ? Dry tank can soon loosen particles when fuels added and stick the floats up.

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    Exceeded sell by date Plumpcars's Avatar
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    Be wary of your pressure gauge when it's hot as well. On many of them the pressure on the gauge drops when the engine bay warms up. Checked mine the other day and it shows 1 !

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    Quote Originally Posted by Plumpcars View Post
    Be wary of your pressure gauge when it's hot as well. On many of them the pressure on the gauge drops when the engine bay warms up. Checked mine the other day and it shows 1 !
    I bet it ran OK Steve, a lot of old carbs used to run at 1lb. If you don't have new needles and seats 4lb would be a good start.
    If some's good, more's better and too much is just enough

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    Exceeded sell by date Plumpcars's Avatar
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    Runs fine Roger but I know that some of these gauges are known to be inaccurate when warm. I do think that people overestimate how much fuel pressure they actually need to run fine on a street car though.

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    Anorak
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    Quote Originally Posted by Plumpcars View Post
    Be wary of your pressure gauge when it's hot as well. On many of them the pressure on the gauge drops when the engine bay warms up. Checked mine the other day and it shows 1 !
    OK I am guessing here as I don't know what type of gauge you have.

    But IF

    It is a liquid filled one, moon or similar and the reading goes wobbly on you, before you start swapping pumps etc there is a rubber plug on the side. It is a kind of blanking grommit. Pull it out and a bit of the magic juice that is in there will ooze out and all will be good.

    If your gauge is not that type then ignore what i said.

    G

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    Compulsive chicken choker English Impala's Avatar
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    Pressure wound down to 4 psi, new filter fitted, sorted! Thankyou.

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    Official RnS Addict bigyellataxi's Avatar
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    Cool, can I carry on washing up now???

    Do you want that blokes number re the bonnet???





    Quote Originally Posted by English Impala View Post
    Pressure wound down to 4 psi, new filter fitted, sorted! Thankyou.

    Fueled by Jim and Luckies.
    Still doing all the shit I used to ;-)

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