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New carb time to tune, holley, stumbles when I stomp

Discussion in 'The Garage' started by sled_dog, Jun 1, 2003.

  1. sled_dog

    sled_dog 1 ton status

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    I pulled the QJet finally this afternoon. WEnt and got one of those Spectre Holley to QJet manifold adaptors and put a Holley 600 with electric choke and vaccum secondaries on my motor. Plugged all the vaccum lines that can no longer be used, removed my EGR and made my own block off plate for it and hooked up the carb. Alright so it idles good though a few hundred rpms too high(idling at like 1000-1100 I think). So when I go and step on the gas it stumbles. I pulled 1 plug and it was almost white so I figured i was running way too lean. So I turned the choke thing towards richer and realized I had a vaccum port not plugged on teh carb so I plugged that. After that it got better but I didn't check the plugs(was out for a test run and about to go home and check when I got a speeding ticket YAY, let me off big time though). If I really really ease into the throttle it doesn't happen but it still happens in third and fourth when it lugs a little. It runs like my QJet did when the motor wasn't warmed up yet. I have no knowledge of holley tuning so any help would be greatly appreciated. It runs like a bat out of hell after it lugs alittle, has quite a bit more power than that old Qjet was feeding it.
     
  2. bryguy00b

    bryguy00b 3/4 ton status

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    yeap same thing hear..mine runs great besides that hesitation thing..worse when its cold but not to bad. of course i know i have a vacum leak but i cant find it i can hear a sucking when i floor it..and it does that make sure you put a fual filter in it to..holley dont have the internal one like the quads do and the PO of mine didnt even have a fuel filter on it put an inline one on it right befor the carb..seemed to help when its cold..i dont have to let it warm up as much..
     
  3. sled_dog

    sled_dog 1 ton status

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    I put a fuel filter on right away. I think probably have a vaccum leak somewhere. Gonna do the can of carb cleaner and spray the hoses tomorrow afternoon.
     
  4. bryguy00b

    bryguy00b 3/4 ton status

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    yea mine revs when i spray the cleaner in it..
     
  5. big pappa b

    big pappa b 3/4 ton status

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    All aftermarket carbs unfortunately aren't setup to run at optimal performance for EVERY motor. You said when you step on the gas it stumbles. Are you saying when you stomp on thye gas or just giving it enought o accelerate? If it's when you stomp the gas it sounds like the accelerator pump could be adjusted. They make a kit that has a few different pump cams and springs to go inside the accelerator pump for tuning. Kits are fairly cheap and it has easy to follow instructions
     
  6. SUBFAN

    SUBFAN 1/2 ton status

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    I believe Holley puts a small brass screen inside their carbs. I put in an inline filter and remove that screen.

    Your Carbs need a bigger/faster squirt of gas from the accelerator pump. Either adjust the cam for this or get a bigger acc. pump.

    Now Ya'll need to buy a book on tuning a Holley carb, because sooner or later you will want to swap in different jets, adjust the floats etc. Good luck....
     
  7. bryguy00b

    bryguy00b 3/4 ton status

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    is the acc. pump on the carb someplace or what? sounds like something i would be interested in upgrading..
     
  8. SUBFAN

    SUBFAN 1/2 ton status

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    Pull on the linkage, and watch the pass. side. You should be able to see where/how it kind of works....
     
  9. big pappa b

    big pappa b 3/4 ton status

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    EDIT>>>MAJOR EDIT!!!!

    OOPS!! Nevermind.. both covers are square. Dumb mistake on my part..So it's been a few years since I worked on carbs /forums/images/graemlins/confused.gif
     
  10. SUBFAN

    SUBFAN 1/2 ton status

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    What you are describing with your pic is for the vacuum secondaries.

    The accelerator pump is located under the front float bowl.

    Pull up some more pics of the real thing....
     
  11. m j

    m j 1/2 ton status

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    the acc pump is big enough, they only come 2 sizes for all holleys, 30cc or 50cc

    IIRC usually the discharge nozzles are used to tune the accell circuit.

    there is a check ball type thing under the discharge nozzle, be sure it is not siezed.
    that carb should run really well 'out of the box' on your engine
     
  12. sled_dog

    sled_dog 1 ton status

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    I asked a friend who runs a Holley on his 350 in his 84 he said he cleaned his floats and it fixed right up. It was pretty cold this morning and after I fought it and got it running I had to work the throttle extremely carefully to get it to not stall out. This carb really needs a good cleaning I think cause well it was dirty when I got it and I never cleaned it /forums/images/graemlins/crazy.gif. When we took it out of the box that the guy gave it to us in(came with my dad's new race car) I turned it over and stale gas just poured out of the fuel inlet so that told me the bowl isn't so clean.
     
  13. Ryan B.

    Ryan B. 3/4 ton status GMOTM Winner

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    If you have an electric fuel pump you can adjust the float bowl levels by just running the fuel pump and not having to have the engine running... With a mechanical fuel pump you have to start up the engine.
    Unscrew and Pull out the sight plug out of the side of the float bowl. If gas rushes out then your float level is too high. For street, Adjust it so gas just barely runs out of sight plug hole when you shake the vechicle from side to side...
    If you go off road on steep hills and inclines set the float level ~ 1/4" lower than the sight plug hole so that no fuel will run out of that hole unless you really shake the truck.
    From time to time you might get a little junk maybe just a grain of sand plugging up the needle and seat valve causing fuel to leak into the carb and run way rich. With the fuel pump off now, unscrew the screw, and back off the 5/8" nut on the top of the float bowl and take out the needle and seat, blow it out make sure its clean.
    Then re-install it and set the float level by turning the 5/8" wrench (which raises or lowers the needle and seat), then lock it down with the screw.
    Best to set it too low to begin with so gas isn't coming outta the sight plug, then raise the float level to the correct setting.

    The accelerator pump would be a problem if it a bog right of idle, like when you first hit the gas it stumbles and then comes back... Like mentioned earlier, they make an assortment of accelerator pump cams which are easy to swap in and out to tune it.

    If the stumble is more like on the mid or top end it would either be the vaccuum secondaries or possibly the jetting. Our 327 was stumbling bad at about 4000-4500 rpms, bogging down for a second and then overcoming it like you mentioned. I changed the vaccuum secondary spring from the stock normal colored spring to the weakest "short yellow" spring and it fixed the problem so the secondaries will open as fast as possible now. They make a quick change vacuum secondary spring housing you can replace it with, otherwise you have to take the side of the carb apart with the choke everytime you swap springs.

    I'd say adjust the float levels and get them perfect most of the time it will be that isn't set at the right level. I seem to have to re adjust it every few months of driving every day because a little junk will get in there and clog the needle and seat from closing fully..
    Good luck! /forums/images/graemlins/thumb.gif /forums/images/graemlins/k5.gif
     
  14. sled_dog

    sled_dog 1 ton status

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    Well I think its my accel pump cause there is wet fuel around the base of the bowl where the pump bolts on. Guess I need a new gasket for the accel pump, time to go see if Auto Zone has a rebuild kit for me.
     
  15. Rusty68

    Rusty68 1/2 ton status

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