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  1. #1
    Join Date
    May 2005
    Location
    Rolla, MO
    Posts
    301

    Edelbrock Carb problem

    I am having problems with my Edelbrock 750 carb and don't know where else to look. I have had to jet richer on the primaries by quite a bit to get it to run a good AFR.

    A few weeks back I was doing hard braking and the car died and was difficult to restart, but it did.

    I tried it again a few days ago and it died and would not start. After towing it home, I finally got it started by cranking the timing as far advanced as it would go. I hooked up a vaccuum gauage and am pulling 7 inches or so and before it was over 15 at idle. The car won't idle down and can't tolerate any load. Above 2 K the motor seems to do okay. I thought I might have flooded it but it never smelled like gas.

    I checked the float settings and they were a little off, but even after correcting them no change. I noticed some silt in the bottom of the bowls and was wondering if something could have gotten clogged.

    I have removed every vaccuum hose and plugged them with no change. I have removed the EGR and plugged the ports in the manifold with no change.

    I am thinking something is worng with the carb and I can't figure it out. I thought the Edelbrocks were supposed to be simple and if nothing else utterly reliable. The carb has run me well up until the last little bit. Before the big problem it would surge slightly at low load cruising.

    Yesterday it seemed like the idle circuit was not giving it any fuel. If I pump the carb it will run for a few seconds and then want to die as if it is running out of fuel.

    I have tried to track down a spare carb to bolt on to see if it is the car but can't. I am tempted to hi Autozone and buy a new one but hate to waste money if there is a simple fix.



  2. #2
    Join Date
    May 2005
    Location
    Rolla, MO
    Posts
    301
    I put on a new fuel filter and PCV today. No change. I put on a new Edelbrock 600 CFM carb (750 originally). Once I got it started I was able to at least drive it. The AFR was showing max rich at low engine speed. Once the car got going, it actually ran fairly well, just not much vaccuum although it got better the longer I drove it.

    For the most part the AFR was very rich throughout all situations which struck me as odd as the carb was much smaller than what it replaced. At least with the smaller carb the AFR would come off of max rich.

  3. #3
    Join Date
    May 2005
    Location
    Rolla, MO
    Posts
    301
    Would a cracked exhaust crossover on the bottom of the intake be the source of a vaccuum leak? The crack that I can see if over 2 inches long. The intake is an EGR intake if that matters.

  4. #4
    Join Date
    Jan 2007
    Posts
    54
    What size motor? Is there adn spacers on your carb? also try to go with around 5 to 5.5 fuel pressure. Edelbrocks seem to like lower pressure.I had a similar problem on a 350 and lowered the size of the carb and removed the spacer. As far as the crack they are never good. try to JB weld to see if any changes.

  5. #5
    Join Date
    Sep 2006
    Location
    Southern Indiana
    Posts
    4,687
    Country Flag: United States
    Double check that one of your metering rod pistons didnt stick or that you havent bent one of the metering rods or had a tip break off.
    Once in a while you will get a metering rod tip that breaks for some reason. Give all the fule passages a good blow through.
    Also if some trash got into a passage it may give you fits.
    If you want someone to work on the carb PM me and we can talk it over if you find a back up carb to run.
    I build carbs for fun and a little money on the side. Most time I am either at my regular job or working on my monza or building race engines.
    Carbs are fun diversion for me.
    Lee Abel
    AFTERMARKET PERFORMANCE

  6. #6
    Join Date
    Feb 2007
    Location
    East Freetown, MA
    Posts
    515
    Wouldn't have that problem with a Holley..........Two seconds to fix a float or jet!

  7. #7
    Join Date
    Oct 2004
    Location
    Tucson Arizona
    Posts
    310
    Country Flag: United States
    Sounds like a dirty main jet. Mine has done the same thing. I pull the top off, blow through the jets and put it back on problem gone.

    No that crack, there a big problem there and it will cause an internal vacume leak. Since you have an EGR manifold I am going to guess it's a cast iron intake. It is quite common for them to crack in this very place at the exhaust cross over and into the plenum and cause problems.

    If you can see the crack you will have to remove the intake and replace it. before replacing it I would verify it is a crack and have the splash shield removed from the bottom, have it cleaned and magged to make sure. Then go aftermarket to solve the problem.

    Joe
    "If you can leave black marks on a straight from the time you exit a corner till the time you brake for the next turn.......
    Then, you have enough horsepower."
    -Mark Donahue

  8. #8
    Join Date
    Mar 2002
    Location
    North California
    Posts
    671
    I would think that it would be the accelerator pump Edelbrock
    Part #1470 and sells for around $ 10.00 A picture and link are
    below.

    http://www.jegs.com/webapp/wcs/store...10002_11498_-1

    I just replaced one for a friend who was having a similar
    problem like yours.The part is simple to replace,and might
    be the fix!

    Hope this helps!


    -Jim

  9. #9
    Join Date
    Sep 2006
    Location
    Southern Indiana
    Posts
    4,687
    Country Flag: United States
    pump wont make vacuum problem, just drivability

  10. #10
    Join Date
    May 2005
    Location
    Rolla, MO
    Posts
    301
    I wasn't a carb problem. The timing chain had hopped a tooth or two and the cam was 20 degrees or so retarded from the crank.

    I did swap from the 750 to a 600 after getting the motor back together and it has totally changed my motor. It is more responsive and the car revs much better. The 750 was just too big.

  11. #11
    Join Date
    Sep 2004
    Posts
    72
    That timing chain would have never jumped if you would have had a holley.