Old Solex carb/emulsion tubes/choke diameter

t35ct35c Member Posts: 1
edited July 2014 in Bugatti


I am new here and hope my post is in the right place.

I have several questions about Solex carbs.

I have a Bugatti T35c. For those not familiar with old cars, It is a 2 liter supercharged inline 8. max. rev 6000 rpm. boost power of the blower is about 6 psi (1,4 atm.). It is equiped with a single 48 mm updraught Solex carb. Venturi 36,5 mm Main jet 240/1000.

I have been brouwsing the internet and found not much. What I could find is the following:
for a supercharged engine the carb size is;

0,41. square root ( cylinder volume . max.rpm/1000 . number of cylinders . pressure of blower (bar))

in this case 0.41. squr (250 . 6 . 8 .1,4) = 44,5 mm
I also found venturi should be 80% of needen carb size. in this case 35,6 mm

main jet size for given choke 190-205 thousands. Aux. jet 50-60 thousands.

At the moment I am running a 240/1000 jet and aux. jet 125/1000. With smaller jets, engine is running too lean, but sparkplugs are fouling. Warmer types do not seem to cure this.

Another problm is the main jet. This is in fact an emulsion tube. A drawing can be found here: http://www.hells-confetti.com/Technical data/Solex/Solex main jet.pdf
From lean to rich it is 44,41,43,42

I do not understand how it works. Could someone explain what happens inside the emulsion tube when airflow increases?

There is also a 51-59 series and a 60 series, but I cannot find data.

Other qustions: has the choke size to be 80% of the carb bore size?

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