Re: Weber question

[Simon Favre <simon@xxxxxxxxxx>]

I think the 28s would be way too small. I assume this is the '71 Spider 
in your sig we're talking about, right?  Is it a 1750 or 2000? Since
these cars did get a lot of updating and swapping around, you should
always specify. Since the US spec 71s did not come with Webers, we do
know the car has been modified. What follows worked on a 1750 with
32 mm venturis and 40DCOE27 carbs the last time it had to go thru
California emissions testing (now exempt).

What worked for me was a very careful adjustment of the F/R balance,
idle mixture, idle speed and ignition timing. If the Webers on your
car have the little brass inspection screws above the progression
holes, you can use them to align the F/R balance between carbs. With
the engine off, and all the brass plugs removed, crank the idle speed
screw in until you can see the butterflies thru the progression holes.
Adjust the F/R balance screw until the butterflies are aligned. (This
does not work on later Webers that have the holes sealed.) Crank the
idle speed screw back where it was.

I set the timing to 2 degrees retarded from the factory spec. You can
fix it later (nudge, nudge, wink, wink). I would do this before the
final idle adjustments, which follow:

I adjust the idle mixture using the lean-drop method. Crank the idle
mixture screw out until you get to max RPM. Crank it in until the idle
drops significantly. Screw it back out 1/8 turn. You may need to blip
the throttle occasionally to get the engine to "digest" the change in
mixture. It also helps to set the idle speed a little high so the
differences are more obvious.

Adjust the idle speed to just below the max allowed for idle in your 
state's emission test. The higher the RPM at idle, the less HC. You
should probably use a digital tach to confirm the settings. Make sure
the car idles below the limit after a good drive.

Usual disclaimers apply, YMMV, caveat emptor, E. Pluribus Unum. It
worked for me.

Kevin wrote:

>I have recently had to start emisions testing my Alfa, and this has
>caused some problems.  I was wondering if anyone has tried using very
>small venturis to help clean up the idle?  I am currently running 34s,
>but I have a set of 28s.  Would this increase the velocity through the
>idle circuit to make a differance.  They only check us at idle, and at
>3000 Rpm.  at 3000 I am clean, but at idle I am right at the limit on
>hydrocarbons.  Experince and best guesses welcome.  Kevin

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