Wow, I'm really struggling with this. I pulled the flare seat from the rear port of my '69 #309 Master Cylinder ... and there is no check valve. So I looked at my other #309 Master, and again no check valve.
So I called the placed that sleeved my master (Ron Karp's) ... and he's telling me that they really never had a check valve in the master cylinder. GM mis-wrote the Service Manuals, and the check valve is somehow incorporated with the Metering Valve.
Can some of you confirm, or deny this?
I'm thinking more like my master was "rebuild" by an AutoZone type place along the line ... and they did a hap-hazard job leaving the valve out. But both of my master's ... and the one I have apart doesn't even appear to be machined for the little valve/spring?
What's the scoop?