Weber DCOE Tune after restoration - Page 3 - Alfa Romeo Bulletin Board & Forums
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post #31 of 37 (permalink) Old 11-12-2018, 10:10 AM
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Yikes. You got me on that one!
I'll search around to see if I can find anything. Perhaps someone else knows? The cars that I've worked on here in the States, and what I've used, is 'standard' black rubber vacuum hose from an autoparts store. Like the same stuff as the big rubber hose from the cam cover to the air cleaner only it's a bit smaller than the diameter of a sparkplug wire.

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post #32 of 37 (permalink) Old 11-12-2018, 10:22 AM
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Exactly, Jim. Black, single layer rubber hose.

R.I.P. Alfa Romeo 1910 - 1986. 1987---> Badge engineering since then.
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post #33 of 37 (permalink) Old 11-15-2018, 06:13 PM
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As you pointed out you changed the compression ration, so jetting may have to be found through experimentation. Some will argue that you don't touch the extra emission screws, but I found I needed to get my Nuova Super to idle properly. I also use the factory mercury manometer ….. don't see how you can make these things work without it …….. but others will disagree.

But here is a little of my research when I did my first emission control carbs about 2 years ago.

Instruction from “Emission Control Weber Carburetor Tuning Manual” page 54-57:
• Set idle mixture.
o Establish an idle at prescribed value for vehicle (e.g. 900 RPM)
o Working on one “idle mixture adjustment screw” at a time, obtain the highest RPM, most stable running as possible
o After all idle mixture screw adjustments complete reset idle RPM to prescribed value.
• Re-check vacuum balance with vacuum gauge.

The following is provided by others and has not been verified:
• Opinion #1: Emission style needle tipped air correction screws normally will adjust somewhere around 6 turns off the seat.
• Opinion #2: 6 would be unusual, 3-4 is normal.
• Opinion #3: if you start with the needles over the barrels closed, all adjustment with the fine rear needles, you can end up with them 6 turns off the seat. Yes, I know that's not the way you are "supposed to do it", but many prefer to forget the perfectly clean idle with different cams or in racing, and begin with the forward needles closed, using the fine rear needles only.
• Addition comment by #3: If your forward needles are seated, then yes, 5-6 turns off the seat is Ok. The CORRECT adjustment with these is to close the rear needles, and get a rough adjustment with those over the barrels first. This is usually much like single adjustment classic (old) Webers, 3/4 turn off the seat. Then locking those down, get a fine adjustment with the rear fine needles, often in the four turn off the seat.
That aside, most users don't bother and leave those coarse needles closed, doing all adjustment with the fine needles.
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post #34 of 37 (permalink) Old 11-15-2018, 07:50 PM
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Carl, you are correct, BUT there were at least 4 different types of needles used ion DCOE's. 2 are common, one less so and one very odd. I've pictures of them all, and will try to illustrate here. Oldest (non-emission, Italian) 3/4 turn off the seat. Next a medium taper, used on Italian non-emission and emission Webers, 4 turns off the seat. Finally non-serial numbered emission Webers, with the FINE long taper needle is 6 turns off the seat. These 3/4, 4 and 6 are starting points for adjustment. A 6 turn very fine needle may run correctly as closed as 3.5/4 turns or 7 or 8.
The odd needle is brass, not steel, and was on an odd pre-emission 40DCOE107A and some other Webers.
This needle has an "O" ring seal up top. I set these at 3-4 turns out to start.
I'll try finding pictures...


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post #35 of 37 (permalink) Old 11-15-2018, 08:15 PM
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Couldn't find my old pictures so I took new ones. Note that these needles are NOT interchangeable in the Webers that used different needles. The holes into the body throats are different sizes, and the internal needle seats are in different positions. Further, needles must NOT be over tightened on the seat as it is possible to displace the aluminum that forms the seat, and push the needle itself further through the hole into the body throat, damaging the body.
First is the oldest style blunt needle. I've seen some on very old Webers that have even a less pointed tip. These also start off 3/4 turn off the seat. Second is the longer taper mentioned above. Third is the emission very fine needle, and finally is the brass pre emission 107 style needle with "O" ring.
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post #36 of 37 (permalink) Old 11-16-2018, 07:21 AM
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Needles

Gordon - nice picture, I had not seen the 4th type. My 1976 Nuova Super's 40 DCOE 44 + 45 had something like the 3rd one. Note the "cupped washer" (the O-rings were hard as rocks).
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post #37 of 37 (permalink) Old 11-17-2018, 10:03 AM
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I've restored a lot of Webers over the years, and seen or worked on most all the DCOE variations.
Some rare ones required re-creation of original parts to replace non-restorable components. Many assume that currently available parts will "fit" all DCOE's. While many components are interchangeable, the DCOE Italian Webers changed over time, and one needs to know how they were set up new at that point in time to be able to have them restored correctly. These variations make this interesting work!


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