@Popsachbum... Thank you so much. It's apparent I'm missing some kind of return spring. Do you believe the setup pictured is accurate for your year? I only ask because the two 4100 carbs I have are slightly different from each other in regards to the primary pivot. I assume neither were original to the 65 TBird. One appears to have a tang with a hole for a spring but also has a completely useless bracket pivoting on the same shaft. The spare (w/an earlier accelerator pump) is closest to yours as pictured.
