Compressor question, optimax 150, 2004

[Pecos23]

Same set up on my rails. Port side, top valve is fuel and side one is air.
The brass Schrader fuel valve assembly is held into the rail by a stainless steel bracket held in with two Allen head bolts. The brass insert that is the lower part of the Schrader valve assembly spins in the rail. Wish I had taken a picture. This insert is about 1/2 in in diameter and is what allows the Schrader valve to mount into the rail. This is all below the threaded portion of the valve, and not the core inside the valve.

[EuropeanAM]

Suggest you replace those o-rings when you are done (normally not going to easily spin around, unless the o-rings are oil-coated, or the o-rings are compromised in some fashion).