pvc plumbing question!

[maxwedge528]

i recently installed power brakes on my 67 stepside with a 454 and TH400 transmission. i also have a dash mounted vacuum gauge and a MSD ignition system with centrifical advance. i also have a street demon carburetor. i use the large port at the rear of the carb for the power brake booster...the large port on the intake runner is plumbed to the TH400...one very small port on the carb is plumbed to the vacuum gauge....and i have one additional very small port capped. where do i get the vacuum for the pvc valve? the one available capped port is maybe 1/8 or 3/16 which does not seem large enough for the pvc valve.. i did use the search function and did not find the answer...maybe it was there...and i misunderstood! thanks in advance for the answer..