Solex 42 tuning

[Bart]

Gentlemen,

Referring to the interesting thread on carburetors I would like to add following question:

Can every happy owner of a fulvia 1600 fitted with standard 42DDHF solexes make a picture of a mixing tube? These can be found attached to the air correction jet, which are the middle two jets when you open the little hatch in the top of the carb. Unscrew the jet and you will see a brass tube, 3.5 or 4mm outside diameter and with a pattern of holes in it. It’s the holes that are of most interest.

I have two different sets of air correction jets/mixing tubes. On the one set (A), the tube is drilled with 4 holes at different heights, and the bottom of the tube is open. The second tube (B) is drilled with four holes at one level, at square angles to each other. In addition, a 0.85mm hole is drilled somewhat higher. The bottom of the tube is closed. Both sets are said to be fulvia 1600, however give completely different engine characteristics. (I tried to add a picture of my tubes but don’t know how to; mails, pictures and correspondence can be sent to my address franschman@hotmail.com)

Set A gave acceptable idling and excellent pick up of power. However at rpm over 4000 the mixture seems to be too lean. Plugs get whitish and engine doesn’t pull well.
Set B gave good idling and also good high speed performance, however at the cost of a huge dead spot if you suddenly open the throttle. Plugs remain light brownish.

So probably none of the versions are as Lancia intended them to be. According to a little book on Solex tuning I’ve got, mixing tubes were made in endless varieties and I know the previous owners of my engine tried to ‘improve’ performance by changing jets and tubes…

I would like to know what Lancia intended it to be (as this is most likely the best setting…)

For the sake of improving our common knowledge on this great car,

Bart Boosman