Quote Originally Posted by firebird77clone View Post
You might also check the vacuum source the line comes off. Best bet is to use a source directly off the intake. If you are using a source off the carb base, it may or may not have vacuum at idle. The carb nipple which has vacuum at idle is the one you want, and is referred to as 'ported'.
firebird, your theory is correct, but you have the incorrect term. Ported or "timed" vacuum ports are above the throttle plates and have no vacuum at idle.