Chevrolet Repair: 1979 Vette not down shifting, screw driver, plastic button

Question
I recently bought a 1979 Vette automatic with a small block 350.  I installed a new 600cfm 4 bbl carb and the engine runs ok. I have a charging problem to address first.  When I am driving the car and step on the gas, I can feel the the carb kick in (all 4 barells) but he car does no down shift. I can manually down shift and the car will really go.  Is there something I need to adjust?

Answer
Hi Dan Good,

Try adjusting the Throttle Valve cable.  That is attached to your linkage at the carb.  You should see a plastic button, shaped like a square with one side being an arch.  You have the car off.  You use a screw driver to press that button in.  The part with the teeth should shoot back.  If not, push it back.  Then release the button.  Then operate the carb throttle to WOT.  Then release.  This should have pulled the part with the teeth back out.  You are adjusted.

If this is confusing, write again and I will try to be more clear.

C J S