Is there anyway to test a porportion valve before installing I was given it when I bought the disc frontend for a swap "upgrade" and it's been sitting in the shop for years and I was thinking of tearing it apart and clean it and rebuild it but if there is a way to test it and see if it works right then on she'll go.

 

The only thing that can be tested is whether or not the brake warning switch is grounded... if it is grounded, then the internal piston has defaulted to one side of the valve.

It is not serviceable and Ford doesn't offer a rebuild (seals and o-rings) kit. However, there is an FTE member (alchemist1) in the Dentside forum who took it apart and is attempting to rebuild it. He's waiting for an o-ring kit at the moment and is keeping us in the loop on his progress.

Here is the thread: https://www.ford-trucks.com/forums/1...ing-valve.html