I agree..... in daily driving i guess the 70% of the time the caqrb is working in the range of the "transition slot".
A lot of people start to tune the carb changing the main jet..... but this is the last thing to do.
First of all it is VERY important the right idle tuning (you will need a vacuum gauge)
This is what I do:
1) fix an idle speed..... let say 800 RPM
2) with the vacuum gauge connected to the manifold, start to adjust the idle screws in the direction where the RPM increase.... and, consequentely, even the vacuum.
3) after this first step, let say you have some 1000 RPM idle...... close butterflys to restore the previous 800 RPM
4) keep working in this manner until you will reach the highest vacuum with the wanted idle speed.
After this operation you should have a very small portion of the transfer slot facing out from below the butterflys (some 0.020-0.030").
If you have a lot more slot opened..... your idle air bleed or you idle restrictor are of the wrong size!!!!!!
If you are in this balpark..... you can go on!
Normally, at this point, I disconnect the secondaires, in order to be able to open folly the primaires without any opening on the secondaries.
Now you can start to evaluate how your "first two holes" are working..... and if you accelerator pump is working.
If you don't have a wide band O2 sensor..... is a matter of "feeling" and you can only hope to be right.
Now let assume your primaries are ok...
Reconnect the secondaries and try to avaluate if the timing of the vacuum sacondaries is correct:
A small "puff" of black smoke when a quick WOT is operated should be ok!!!!
If you have too much black smoke, may the your secondaries are opening too slowny
If you notice a bog..... they are opening too quickly.
In my opinion the most important tuning area is the transition...... from idle to some 3000 RPM under light load.....
just my 2 cents....
