Reply to "New Carb recommendation"

Vacuum secondaries are closed when the primary throttle blades close by a link from the primary throttle shafts to the secondary throttle shaft.

Vacuum secondaries open not from manifold vacuum but rather the vacuum created in the primary venturies as the air speed through them increases, thus the higher the primary airflow the more the secondaries open.

Vacuum secondaries have no accel pump as they open slowly and in a controlled fashion that does not lower manifold vacuum as they open, this negates the need for fuel enrichment from a acceleration pump as a stable manifold vacuum will prevent fuel from dropping out of suspension.