what size it the Schrader valve i want to hook up a fuel pressure gauge and dont know the size of the fitting

 

The fitting is a -4. Be sure to remove the schrader valve first, if you are going to connect a -4 line to the fitting.

 

remove the little pin on the in side of the valve

 

Does anyone know where to get a replacement? When I got my nitrous kit off my friends car I had to give him the valve that goes in the fitting. They look the same as a tire valve, but dont know if the seals on that would break down because of the fuel.

 

just get a 4an cap if you can't get the correct insert.