That would make it the proportioning valve.
RwP
BTW, I don't know how a "valve" with only two fittings could proportion anything. I can see it restricting flow, or acting as a check valve, but to actually proportion anything, it would require three fittings, with connections to both the front and rear brakes.
Doug, I'm seeing F4SZ 2B091 B in the parts catalogue that I can access, but I'm guessing that it is likely obsolete from Ford. Referred to as a "brake pressure control valve".
cheers
Ed
Guessing from looking at your pictures, The red and clear markings have something to do with the orifice size. Kind of like jetting a carb. Different models, different orifice, same body. Saves manufacturing costs. Did you try to take it apart and change the o-ring?
Alan
DLF, are you fabricating your own SS brake lines? If not, who is doing it for you?
I need new ones for mine.
Thanks
Mark