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High Idle w/ Edelbrock 1406 WTF?

Discussion in 'The Garage' started by mofugly13, Sep 12, 2004.

  1. mofugly13

    mofugly13 1 ton bucket of rust Premium Member

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    I bought my K5 with the Edelbrock 1406 already installed, and after cheching it out initially, I didn't realize that the idle was too high, 1100-1200 rpm. When I killed the old engine and got the new crate 350 in and put together with the used 1406 and brand new performer intake. So I got it all fired up and went to tune the carb, and could not get the idle down below 1200rpm. The idle screw is backed all the way out (not even touching the throttle lever). I have taken all the vacuum lines off and plugged them and checked everywhere for vacuum leaks, but to no avail. I read a post on here once that said that something with the throttle plates and/or where they seat on the carb 'body' may be worn, thus allowing some airflow and causing the high idle. This might make sense to me because when I first got the K5 the idle was WAY high, like 1600rpm. The truck would try to take off as soon as I let my foot off the gas at stoplights and stopsigns. I remedied this by adding TWO more throttle return springs to hold the butterfly's closed. Because of all the springs, it makes for a very stiff skinny pedal. So, armed with this info, what should I do about the high idle? What if the butterfly's are, in fact, not seating completely when the throttle is closed?
     
  2. big83chevy4x4

    big83chevy4x4 3/4 ton status

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    1406..elec choke? can't remember
    i had the same problem with my qjet, the choke was not adjusted corectly, it was holding the plate open just a hair.
     
  3. mofugly13

    mofugly13 1 ton bucket of rust Premium Member

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    It's actually a 1405 with the elec choke kit installed, and I've checked all that. /forums/images/graemlins/dunno.gif I'm befuddled.
     
  4. 84_Chevy_K10

    84_Chevy_K10 Banned

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    Vacuum leak?
     
  5. mofugly13

    mofugly13 1 ton bucket of rust Premium Member

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    From my original post...
    [ QUOTE ]
    I have taken all the vacuum lines off and plugged them and checked everywhere for vacuum leaks

    [/ QUOTE ]
     
  6. sickquad

    sickquad 1/2 ton status

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    Sometimes the best solution for a carb problem is to buy a new carb. Not that much money considering you already sprung for a new intake and motor. Summit sells the remanufactured Edelbrocks for $200. Have you hooked up a Vacuum gauge to the carb to find out what it's doing?


    -Chris
     
  7. NerdBoy

    NerdBoy 1/2 ton status

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    This may be a dumb question, but you mentioned that you backed the idle air flow adjustment screw out, but, did you adjust the idle air mixture screws? I didn't see you mention that. They are the two screws on the front of the carburetor.

    In case you haven't seen it, you can find the idle adjustment instructions here.
     
  8. diesel4me

    diesel4me 1 ton status Premium Member

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    It only took me a day to make my 1405 edelbrock *(Adapt-O-Brock) linkage to work on my 79 C10's "new"305 I installed--the same problem as yours,after getting a V8 accelerator cable (mine was a six cylinder)and installing it--I couldnt get it to return to idle--I had to remove the bracket that holds the cable and file the holes out making them more like slots,and pused it closer to the carb,allowing the throttle to close completely--I had only about a 1/16 of an inch to spare,I had to use one of the closer holes in the throttle lever to make it work.I had one of those tiwan cable holders for the detent and accelerator cables, but I couldnt use it because the bolt that holds it to the carb is the outer rear bolt.which has no bolt in it because my carb is on the quadrajet manifold with an adaptor,and it uses the inner bolts to hold the carb on,and you cant put a bolt in that outer hole--the intake is in the way.I spent more time hooking up those cables than it took to install the motor /forums/images/graemlins/angryfire.gif--ended up using a hose clamp with a 3/16 bolt brazed to it to hold the detent cable,and I had to put a light helper spring on it to help it return to the normal position.I hate messing with throttle linkages and detent cables--if you jerry rig it too badly,your life is at stake if it sticks wide open,and its dangerous to pull over on the highway around here to fiddle with stuff like that--its the number one reason I dont like aftermarket carbs,they NEVER fit the original linkage correctly,you always need to make adapters,remove EGR valves that are in the way,and engineer a new linkage and detent cable hookup--and why is it they never give you those damm "ball joint" things that snap onto the cable and go in the throttle lever--I was using the end of an old sparkplug as a substitute til I coul get to the boneyard(10 bucks at a speed shop--they can keep them!).
    You may want to be sure the secondary butterflies arent sticking open,they might be rubbing on the base gasket,or the adapter,if you are using one--the choke also has a fast idle cam that could be sticking,or choke not opening all the way,the accelerator pump can make the throttle want to stay open if its sticking in its bore also.I wouldnt run too stiff a return spring,because that will tend to "egg"out the throttle shaft bushings. Hope this helps you some--I know I was ready to go buy a quadrajet at the boneyard and ditch the edelbrock carb--I was pretty frustrated by the time I re-engineered the linkage and cables--and had a very sore back from bending over it all day----. /forums/images/graemlins/crazy.gif
     
  9. sickquad

    sickquad 1/2 ton status

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    It shouldn't take more than an hour to tune the carb and setup the linkage. The stock throttle cable and bracket worked perfect for me and my edelbrock intake and carb.

    -Chris
     
  10. mofugly13

    mofugly13 1 ton bucket of rust Premium Member

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    [ QUOTE ]
    This may be a dumb question, but you mentioned that you backed the idle air flow adjustment screw out, but, did you adjust the idle air mixture screws? I didn't see you mention that. They are the two screws on the front of the carburetor.

    In case you haven't seen it, you can find the idle adjustment instructions here.

    [/ QUOTE ]

    Yes, I have adjusted the idle air mixture screws using a vacuum guage in order to get the max vacuum. I got the idle down as low as I could before I messed witht the screws, and I followed the manual to a 't'.
     
  11. 1-ton

    1-ton 1/2 ton status Premium Member

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    What you could do is remove the throttle cable, but not the return spring, and then start your truck. If the idle is normal, then you know the throttle cable is causing the problem. If the engine is still idling high, with the throttle disconnected, then the throttle cable is not the problem.

    Then you could try spraying some carb cleaner at the base of the carburetor where the throttle shaft is. If the idle goes higher, then the throttle shaft is worn out. When a throttle shaft wears out from age, it causes two problems (1) the throttle plates get out of alignment and hang up, (2) a vacuum leak is created at the throttle shaft; so you end up with two different things causing the engine to idle high.
     
  12. diesel4me

    diesel4me 1 ton status Premium Member

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    I agree it SHOULDN"T take more than an hour--but it always does,because they dont give the small parts you need like the "ball joint" fittings for the throttle linkage,nor do they tell you you might need an adapter,your stock air cleaner wont fit(without another adaper,and possibly the "banjo"type fuel fitting),on and on--I think yours went right together because --
    A--you were lucky~
    B--you used an edelbrock manifold(its always nice to be able to have everything the same brand,designed to work together)--adapt one to a stock GM quadrajet intake,and see how long it takes to put an edelbrock on,and make it driveable with detent and accelerator cables working properly--
    C--your not me!(My luck sucks! /forums/images/graemlins/ignore.gif)!
    D--I probably had too much to drink,due to the frustration and my aching back! /forums/images/graemlins/grin.gif /forums/images/graemlins/crazy.gif
    Another thing that might have caused the fast idle problem--if he put manifold vacuum to the vacuum advance(assuming it has one)it would advance the timing slightly,that will incease the idle speed some--but maybe not all the way up to 1600 rpm though-- /forums/images/graemlins/thinking.gif /forums/images/graemlins/confused.gif
     
  13. RingMaster4x4

    RingMaster4x4 1/2 ton status Premium Member

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    How many CFM is that carb?
     
  14. 454k30

    454k30 1/2 ton status GMOTM Winner

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    The 1406 also comes with an electric choke, I have one, no disrespect intended. It is a 600cfm carb as well. My buddies 305 had the same idle problem and it was that with the linkage all the forward the plates were still not closing completly. Same as above we had to adjust the bracket holding the cable forward enough to get them closed. It was also sticking a little after that so we cleaned a lubed all the linkage really well and 600rpm followed. Hope this helps, I hate carbs but hey for the price they are much more available for us working class
     

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