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Discussion Starter · #1 ·
Okay, I cleaned and rebuilt the 40 DCOE 27 Carburetors, now what do I do?

1. I have been reading some various instructions on tuning, adjustment, aligning throttle valves, idle, but it is still a bit confusing. I will read around the posts, but where is the best explanation for this?

2. I will put on the floats, top gaskets, before the cover-plate. There were some left over gaskets, but some are probably for the fuel line and others for later model carbs.
 

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Not quite sure what you are asking. Are the float levels set? This is done with the top gasket in place. After assembly, but without chokes installed, check to see butterflies close completely by holding up to a bright light.
After installation on the car, watching the CENTER connecting linkage, adjust until the carb without the idle adjustment also has butterflies closed by watching the link for motion while acting on the adjustment screw on the connector link. Then tighten the idle adjustment screw while watching the center link. BOTH butterfly bars should begin to move at the same time. If not, readjust the connector link. This gives you a rough adjustment of everything completely closed and beginning to open at the same time.
Set the air correction (4) needle valves about 3/4 turn off the seat (closed position) DO NOT force tighten these screws. Attach the throttle link to the bell crank. Adjust the idle screw so you see the link just start to move. Screw in 1/2 to 3/4 turn further, and start the car.
From there on, balance and adjustments are a matter of either experience, or various tools. After 45 years of setting these up, my only tool is a screwdriver and experience. Final idle speed should be 500 to 1000 rpm depending on cams and engine condition.
 

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Discussion Starter · #3 ·
Balance and adjustments on mixture screws

Set the air correction (4) needle valves about 3/4 turn off the seat (closed position).
From there on, balance and adjustments are a matter of either experience, or various tools. After 45 years of setting these up, my only tool is a screwdriver and experience. Final idle speed should be 500 to 1000 rpm depending on cams and engine condition.
Is it okay if there was a hair-line amount of light (hardly perceptible) coming through the butterflies?

All Mixture screws are set at 3/4 from the seat. It runs fairly decent, but not fully smooth. I put a tube from my ear to each venturi. I could hear the valves and a different wind noise. I was told one should try to make each sound the same. Do you have any more detail on this:confused:
 

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In the picture above, the carb cover gaskets need to be put in place before you install the floats in the cover, assuming you're putting together and not still taking apart. Probably you know this, but I didn't see them pictured...

Andrew
 

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Lorencew,
The hair line of light is OK, IF-- it is even on both butterflies of the same Weber. If not, it indicates possibly one butterfly loosened and not properly reset, (minor problem) a twisted butterfly bar, (more major problem) or a notched bore in the Weber body (Major problem) . Adjusting these perfectly has taken me quite a while to master. I always suggest this area of Weber work be left to one familiar with the potential problems. Damaged components here can run into money to correct.
As to the "whistling tube". I do not use this technique myself having done both the balance and air correction needles by feel. If balance is off the engine will twist with its normal shake. If the air correction is off, screwing one needle in or out should increase engine speed. Correctly set all needles will be adjusted for the highest engine speed. We should only be talking about a 25 Rpm or so variance here along with smoothness. Both attained by moving back and fourth between the air correction needles and balance link between the Webers, using the idle adjustment screw ONLY to keep the engine slow, 800 Rpm or less.
The engine should be warm to hot before attempting these fine tuning adjustments. All ignition components must have been 100% as well. No fine tuning will overcome bad points, wires or plugs. For that matter, engine mechanical condition is also important. If compression is not even on all four cylinders, Weber tuning won't help much. How did the engine run before you worked on the Webers? {Rule #1 of the rough running Alfa is "Don't fool with the Webers!" If they WERE fine, chances are they ARE fine. The problem is usually ignition. Webers seldom suddenly go bad other than with bad fuel. They loose their fine tune edge gradually, or by someone "adjusting" them.}
I hope this helps.
 

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Discussion Starter · #6 ·
Any idea what this noise is?

The engine runs strong with throttle open.

There is, however an occasional "hick-up" during idle. The engine makes the noise and nearly quits. Any idea what this noise is?:confused:

It can be temporarily cured by depressing the accelerator. Does this mean that the idle screw is set too low?
 

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Four cylinder Alfa engines with Weber carburetors do what I refer to as "hunt" at idle. Engineers might say it is because of the firing order, while other manufacturers have use a spinning counter balance shaft in the block to smooth out idle.
An increase of the idle speed might help, with race engines of days past, we used very high idle speeds because severe cam overlap prevented any sort of true idle. You might find by slightly increasing idle and readjusting the air correction screws, you can find a "sweet spot" where the idle is not too high, and is reasonably smooth. All this assumes that all other systems are functioning perfectly. Ignition, valve timing and clearances and compression as well as balance between Weber #1 and #2!
In short, fiddle with it some more.
 

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I put a tube from my ear to each venturi. I could hear the valves and a different wind noise. I was told one should try to make each sound the same. Do you have any more detail on this:confused:
Not sure of your question - the balance screw should be adjusted until the volume of the sound coming from each carb's intake is the same. If they are out of balance, one will be louder than the other. Of course, you need a length of hose held close to your ear (not in your ear) to hear this.

As Gordon writes, it takes some fiddling to get a smooth idle, and good transition from the idle to main nets. Are you confident that your carbs are jetted correctly?

Search the BB archives - a bunch has been written on Weber jetting and tuning. There are some "how-to" guides available on the net - one that is very good is at: Weber DCOE for Triumphs
 

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Jay, as usual is dead on with this. I had NOT read the DCOE tuning for Triumphs until someone asked me something about the discussion, so I did read it and it was GOOD! This is an excellent introduction.
 
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