1970 Chevy Corvette Vacuum (I beleive)

Find avacuum schematic from a Vette-resto shop and see if you have any check valves missing. It sounds like a vacuum surge when started, which shouldnt happen. There is a resevoir to keep any sharp changes in vacuum from messing with the operation of those systems, otherwise the headlights would drop and the wiper cowl would fall every time you gave it hard throttle