How should the weight, flap and coil spring be positioned when being put together?

 

If it's cold, they should be put together so the valve is shut. As it gets warm it should open up. That is not a ordinary coil spring, that is a bi-metallic spring. It moves when it gets hot. If you have a propane torch you can try it out.

I do like the vacuum operated ones better.

 

Thanks for the help. I found a book with what I was looking for.