Tight or slack?

Generally speaking slack wire advance.

It's easy enough to check. Take the points cover off and look at which way the points are rotating when you turn the engine over. (the heel that rubs on the cam should be trailing the pivot point. If it's being 'pushed' round you have the wrong points)

Anyway, the timing is fully ADVANCED when the cam ring is rotated as far as it will go in the OPPOSITE direction to the points. So if the points are rotating clockwise (which I think they are on a domi) the cam ring needs to be rotated anticlockwise.

Whip the cap off and pull the advance and retard lever about and you'll see the cam ring moving.

When you take the end cap off, just make sure the cam ring does not fall out and disappear into the further recesses of the shed as you manipulate the advance/retard lever. It can happen!