87 b150 slant 6, I was doing the basic tuneup stuff the other day and noticed the vac. advance on the distributor was taped off. I know its supposed to go to the carb but there are no open ports or capped off ports on the carb. I have the Haynes manual and it is no help.

 

There was no vacuum advance for your engine, only mechanical advance. The distributor was probably changed by a previous owner who couldn't find the exact replacement.

 

Well, I checked into getting the correct one and all the parts stores that I visited showed me that the manual transmissions had them (vac. port)and automatics didn't. I have a manual trans. so if it isn't for advancing the timing what is it for?

 

If you feel it should be connected then just cut a tee into one of the existing ported vacuum lines and hook it up. By ported I mean there should be no vacuum at idle and vacuum gets stronger as you open the throttle more and more. You do not want to hook it up to a constant source of vacuum.