Distributor, what's the tube at the base of the distributor called my new didn't come with it

 

What is this dist for?
Model, size engine, year are all important , unless you can post a picture.

 

78,f150, 300 inline 6

 

It's on a 78 f150, 300 inline 6

 

Without a pix, not sure.
Is this the vacuum advance unit that is held on to the side of the dist?

 

Yes,it is

 

OK, then all you need to do is, remove the clip that holds the arm from the vacuum advance unit,, then remove the 2 screws that hold it onto the dist and now install that unit on the new dist.
3 steps, install 2 screws, connect the arm to the pin , install the retainer clip , and you are good to go.

Did you mark anything so you get the dist in correctly ? If not, unless you know EXACTLY what to do, you could get into deep waah- noo na !

That dist tells the plug when to fire and if that is not set correctly on installation , the wrong plugs could get the spark to fire at the wrong time and the engine may not even start and could backfire out the intake or exhaust.