Rio24

Triple webers DCOE 40

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    First off i want to thank everyone that has helped me with my project 240.   So it starts!!  Now trying to tune and sync the carbs.  Having trouble with a super high idle aroung 1300rpm with timing set advanced around 12 degrees,  any lower and the car diesels and backfires.   the engine revs smooth unless you blip the throttle , in which case it bogs for a sec and climbs.   i have not driven it yet(still need work on suspension and brakes).  any other guys with webers have any input on this?  as far as timing? what dizzy to go with?    also,  the lights flickers and ammeter goes nuts in car.  does not happen all the time, it does smooth out and when it goes crazy, there is a slight squealing noise in engine bay.  All and any input is greatly appreciated 

     

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    Get the electrical then valve lash, and timing set first then focus on the carbs.

    First some questions:

    Do you have a sync tool?

    Is the manifold and linkage in good shape and solid with equal length push rods?

    What is type and serial number of each of the 3 carbs?

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    Thanks for the help,  I checked and adjusted valves but when the engine was cold.   The linkage is all new and equal length.   They are Dcoe 40.  On the top they each read   Dcoe 40 18 and 9m

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    Can you write the full tipo and no for each carb like below?

     

     

    40dcoe107.JPG

     

     

    For your fast idle issue, set the timing at 15 degrees at idle, disconnect the push rod to each carb then start closing each throttle plate using the idle stop screw on each carb and see if you can get idle down. (this is a quick check). 

     

    For next step: You will need to report idle jets and set idle enrichment screws our same amount then measure air flow in each throat.

    btw is your engine stock 2.4 with stock cam?

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    Timing is set to 15 ,  all push rod even and idle set screws are all the way out(no contact with linkage)   idle still high.  Mixture screws are even at 3/4 a turn.  Stock cam.   I think...   air flow are as even as I can get  #1 carb vary in flow,  5 on cylinder #1 and 7 cylinder # 2

    Cylinder 3 and 4 carb is even at 5 

    Last carb is same as the first one.   I thought different flow was because of pcv on #2 intake runner and brake booster fitting on #6 runner.

    All carbs are the same as picture below

    IMAG0948.jpg

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    Thanks. Great info. 

    Can you disconnect the push rods to make sure the throttle plates are at full stop?  This could be the issue.

    Once you get the carbs air balanced and a nice idle, then you can attach the push rods to verify the same air flow( i.e. the push rods are not pushing at idle).

     

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     No, thank you for talking it out with me and taking the time.  I have disconnected the push rods, they are completely closed.   I'm confused how the engine still runs with plates closed.   Is there a seperate opening for idle circuit?  Excuse my ignorance 

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    OH.. i see what your problem is in the picture: it says: "Made in Italy"   :pow:   sorry couldn't help myself.. (I HATE italian junk!!)   eh but seriously.. if the valves are closed in your carbs, there must be some other air intake.. also known as leaks... ;-)

    • Haha 1

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    7 hours ago, Rio24 said:

     No, thank you for talking it out with me and taking the time.  I have disconnected the push rods, they are completely closed.   I'm confused how the engine still runs with plates closed.   Is there a seperate opening for idle circuit?  Excuse my ignorance 

    image.jpeg

     

     

    At idle, the only places for air to pass to the cylinders are:

     

    On Carbs:

    1.  Idle enrichment screws.  If these are open too much or if the idle jets are too large (have too much air and fuel passing through large drillings)

    2. Throttle plate air bypass (built into 40DCOE 151 and 45DCOE152 carbs). Early carbs like your 40DCOE 18's may have holes drilled in throttle plates.

    3. Twisted throttle shafts (one plate closed but the other is partially open...usually on early carbs with brass rods).

     

    On Intake:

    1. Poor sealing between carb and manifold (loose hardware where softmount grommets/thackery washers are located).

    2. Poor sealing between head and manifold.

    3. Air leak from brake booster.

    4. Other (such as you PCV fitting).

     

     

    What are your idle jet sizes?

     

    For a next step, I would recommend that you check for all of the manifold leaks then if no leak is found:

    Keep push rods off and, with engine running, start turning in idle enrichment screws in to full stop then back out to 1/2 turn (gentle pressure at full stop is fine).  For early DCOE's like yours, the taper on the idle enrichment is rather abrupt so a small turn lets a lot of air and fuel pass.  Most early carbs work between 1/2 to 3/4 turn out.   Yours at 3/4 are way out there.

     

    Read this if you want your head to hurt: http://240260280.com/Tech/Carbs/Weber/DCOE Theory Operation and Tuning.html  :)

     

     

    Edited by 240260280
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    It's finally a nice day in Chicago, so I can't wait to get in the garage.  Thanks again    I'll get back to ya

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    OK....no found leaks.  I fixed the electrical problem(bad voltage reg) and notice the engine oil was fuel saturated from me trying to start the engine for 3 days until I realized carbs were so far out of sync.  I changes oil and filter and voltage reg, and now it's idling around 1000.   It actually surges from 700 - 1100     it's getting better!   I messed with idle mix screws and that's best I can get it.  Timing is at about 15.   Idle jets is f9 .45 and main jets f11  115.  It's getting there.    I really appreciate your help!!

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