If I am correct in asumeing your talking about the large port that is at the back of the carb,at the base, then one line runs to the power brake booster, and as on mine there's a tee withe a 1/4 inch line that runs to the modulator on the transmission.
![[Linked Image]](http://i270.photobucket.com/albums/jj110/plmcrzy67/524391_12.jpg)
