[PeteF]

The adjustment for the secondary throttle plate idle is on the right side, accessible from underneath the base. If you look closely, you can see the threads protruding up through the base. Depending on your intake manifold, you may be able to insert a small Allen wrench with the carb installed. I can do this on my 351W. It is much easier with the carb off, where you can easily adjust it . The factory setting is normally 1/4 turn from full closed. You could try increments of an additional 1/4 turn to see if you get better results. With more secondary opening, you will have to reduce your primary screw to keep the same idle speed. Good luck.