It's possible there is only a mechanical advance or even an electronic one if you are using one of the newer ignition systems, but most carburated engines do use vaccuum advance as well as mechanical advance. The vaccuum advance unit will look like two miniature pie plates stuck together along their edges ~2-3" in diameter attached to the side of the distributor on edge. there will be a small hose or metal line attaced in the center of the face furthest away from the dist. A metal tube or rubber hose will run from it to a vaccuum port on the engine, usually on the base of the carb but sometimes to a fitting on the intake manifold.

 

I guess i only have mech advance then, no pie plates or anything like that at all. Thank you.

 

What engine is in your truck? Is it a stock or aftermarket distributor?

 

I have a 302, stock all around to my knowledge, basically, the whole trucks a mess, I dont have a clue what half the parts are out of...but I do think its a Motorcraft, or at least stock distributor. The whole thing doesnt look 40 years old, like the rest of the engine before i cleaned and painted it

 

Flathead?
OK, I've seen plenty of them, but never worked on them.

 

Can you throw up a gallery? I'm really curious to see your distributor. I run a 302 (1972) in my truck, so I'm familiar with the block. However, I've never seen a distributor without a vacuum advance (at least, not on a 302). I've heard they exist, but never seen one.

Also, I've never done timing with the Vac Advance disconnected. I always time it to start (I don't have a light).