73 Valiant R12 AC system pressures

Needs a little more if it still has bubbles. I use 50/250 as a guideline but the sight glass will tell you when it gets full and the duct temp will tell you if it's working properly. Many things effect pressures. Many variables. Ambient temperature being a big one. Plugged condenser or bad air flow is another. I don't have a service manual to look up capacity. Are there any underhood stickers with system capacity marked on them? You're at 2.25#. Another 1/4 to half pound might be what you need.