You can get a nipple to thread into that hole & hook a hose to your gauge. Anything below the throttle plate is manifold vacuum, that's what you want to be checking for tuning & driving economy. The only vacuum port on the 'B' is above the throttle for the vacuum advance, will have little or no vacuume at idle & increase as you come off idle.
Last edited by BC59; 07/30/2012 2:11 AM.
