i never had a problem getting vacuum secondaries to open.....I have found by using them at the race track that the VS carbs are about a good tenth slower then a same size double pumper...
I must be a 1%..........
Quick Fuel Carburetor Secondary Covers 63-12QFT
Quick Fuel Adjustable Vacuum Secondary Kits 63-1QFT
I used the more expensive billet one since I am a 1%...........