28920 are all before 1970. What are the date codes on the valve bodies? It's basically a rhetorical question, I already know what you're going to find...71-77 or thereabouts...different cases tho. Some early bb 727s had provision for the ptk vb tho; might've come from a bb. But who knows if this is the problem? I never take that chance anymore...trying to track down a problem all because of mismatched parts...or it could be internal...I'd get a newer case.
