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Thread: Fuel pressure and flooding. Aaargh!

  1. #1

    Fuel pressure and flooding. Aaargh!

    Has anyone else had trouble with Edelbrock carbs flooding?
    I suffered with fuel starvation on the Rocket running the original mech fuel pump. This improved with a facet electric pump, but the pressure on them is around 8psi. Edelbrock carbs should be around 5psi. So, fitted a Filter king that I had kept for just such a problem. This helped with higher rpm, but still floods up at idle or after a fast run.No real grunge in the filters thankfully. Ive also fitted a phenolic insulator spacer to stop heat sink. The 303 is a big chunk of engine on a hot day.
    I checked pressure with a gauge connected into the pipe directly, not a tee piece. Even with pressure backed down to 4psi it is
    still flooding. I 've checked the float heights. The Needle valves don't look bad and seem to seal when blown through, but not 100% happy with them.Its a float related problem.
    My thought is the viton tipped needle valves play up with modern fuel (got some new heavier duty sprung off road ones on order..)
    running out of ideas other than that. 8mpg just rubs it in . Anyone got any thoughts? Thanks, Jim

    Ooops, should be in Tech discussion , sorry.
    Last edited by Jim The Sweep; 01-08-19 at 03:54 PM. Reason: wrong place

  2. #2
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    8 mpg???? Unless it's a monster of a performance engine it sounds like you need a good tune up, or lighten the foot! An AFR meter is a good start and at 8mpg could be paid for in no time!

    The Edelbrock floats are pretty delicate things and in my mind are all too easily damaged which is an issue as they require bending of tangs to adjust float heights - doing this incorrectly and things can be go wrong quickly. This might have happened up against the needle valve which might also explain things? The floats need to be able to move freely with no binding too.

    Chris
    Bumper sticker - This is an historic vehicle and only has three speeds....... if you don't like this one you sure as hell won't like the others.

  3. #3
    NSRA member kapri's Avatar
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    If all else if set up correctly it's generally the fuel that's the issue. Ethanol is the cuplrit and if an engine isn't run regulalrly it will evapourate leaving stickiness on float needles that can cause it to flood up.
    Galations 6:7

  4. #4
    Thanks for the replies. No, it isnt a monster performance engine, its a stock 49 Rocket 88 with twin pipes and a 4bbl edelbrock carb. Cheers for your input, jim

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    What size carb is it , and have you jetted it to suit the engine .

  6. #6
    NSRA member razor's Avatar
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    Where abouts are you ?
    I can highly recommend ATSPEED in Raleigh in Essex.
    I just had my rod with a 350 sbc and 600 Edelbrock carb tuned by them on their rolling road . and wow what a difference . I had similar problems to yours.
    They stock all the parts needed to for Edelbrocks
    Good luck anyway
    Dave

  7. #7
    Thanks for the recommendation, Im in Norfolk so that is quite possible. Will try the new needle valves first but a proper rolling road tune up is the answer.

  8. #8
    a bit big, 600cfm . It is a 1406, and I havent touched the jets.First problem is the flooding.

  9. #9
    Is the carb new or used? if used, I will personally go through and check that everything is clean, specially the air bleeds and while there check the jet size so that you have a starting point to tune it later.
    Did you set the float at 7/16?
    Did you set the idle with a vacuum gauge? if yes, how much vacuum? any changes in vacuum reading while adjusting the idle screws?

  10. #10
    The carb was on the car when bought, it looks newish.i've had the jets out and cleaned everything as normal, and also set the float heights as per spec. Couldnt see sizes on the jets but they look pretty big holes!
    I did try setting idle with Vac gauge, but to be honest the flooding makes that a bit irrelevant for now. Suspect it is a bit rich but until the float side of things is sorted, everything else is secondary.
    If the mechanical pump was a bit easier to get hold of id fit a new one of them too .It has to be rebuilt by a firm in the USA which puts me off a bit. It aint a Chevy..
    Do appreciate the advice, cheers.

  11. #11
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    The primary jets will look large but they get partially filled with the metering rods.

    If the pump is pumping and the pressure is in spec then I'd not necessarily be looking there tbh. Could try lowering the pressure further?

    More likely floats / needles as you've suggested, but what have you got the idle screws at? The initial setting is something like fully in (gently) then 2 turns out.

    Edelbrocks have a tendency to work rather well straight out of the box! Have you got the instructions? They're available online. Includes of tuning / troubleshooting.

    The primary circuit shouldn't be in play at idle and when engine vac is high the metering rods are pulled down to restrict fuel flow. Guessing here but if the engine vac was low (or there was a leak) and / or the springs on the metering rods too heavy you could be getting more fuel in than is required too early on.

    Chris
    Bumper sticker - This is an historic vehicle and only has three speeds....... if you don't like this one you sure as hell won't like the others.

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  13. #13
    Thanks everyone, off on holiday so can have a think about it. Cheers for the replies, Jim

  14. #14
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    IMHO ,the carbs too big . i had the same thing with a 302 in a 1967 mustang i bought a couple of years ago ,
    previous owner had put a brand 650 cfm edelbrock on it , was terrible after a short run even ,
    Next day i bought a new 500 cfm edelbrock set the mixture screws on the bench bolted it on , problem solved , ran like a new car with a stock pump and did 28mpg ,
    there was nothing wrong with the 650cfm carb on it just too big . other option is to change all the jets and needles in your 600 to the ones they fit in the 500 not perfect but will be a lot better
    .

  15. #15
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    Edelbrock carb, you might find it is not flooding, but dribbling fuel from the primary booster, due to a blockage in a tiny little breather hole in the brass booster jet thing. Can you see it dribbling out of the very centre of one of the primaries onnthe carb?

    I had the same, stripped and cleaned, and swapped needle valves side to side etc, and finally google pointed out a tiny air hole that has to be free, or fuel pours in from one of the jets for some reason.

    I had to run a tiny drill through when I eventually found the blockage, the ethanol fuel ****e had dried up and set as hard as powder coating.
    Polygamy is having more wives than you really need.
    Monogamy is essentially much the same thing.

  16. #16
    I have a 1406 on my 302, just overhauled the carb for this same reason, mine was spewing fuel into the intake and when you switched the engine off it continued to do so. The pump is pushing 6 psi, the floats in mine were all over the place, a full refurb and set up as per the documentation has solved the problem and it now runs sweet..

  17. #17
    Thanks, I finally got some time to fit the offroad needle valves id ordered. These seem to help, no more flooding.Next step is to up the pressure to about 5psi from the 4 that im running at the moment.Idles well but starves under prolongued acceleration.
    And I thought carbs were simple! been spoilt on EFI Volvos for years...

  18. #18
    One thing to bear in mind about fuel starvation. It's not all about pressure but volume plays a major part. Many people wind the pressure up to overcome a perceived shortage when in fact what may be needed is a larger volume through using a change in feed pipe bore size etc.

  19. #19
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    When you see how small the needle jets sizes are, compared to the fuel line, pressure is sometimes the only way to stop fuel starvation.
    Polygamy is having more wives than you really need.
    Monogamy is essentially much the same thing.

  20. #20
    Quote Originally Posted by Paul B View Post
    When you see how small the needle jets sizes are, compared to the fuel line, pressure is sometimes the only way to stop fuel starvation.
    Or bigger jets

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