G E's tool will hook on the bottom flange and screw tight against fitting and open the vlave and on the other end of the tool will be a 1/4 flare to hook up your gages but for the most part just add your own access valve and leave that one alone

Have you seen one of those adapters for the GE port?

you could have a floating restriction how many ozs does it hold? if its low that will show up right away what freon did you use? what are the pressures? did you replace the drier? did you pull a vacuum before recharging it? you could have air in the system.did you flush it good with nitrogen? you can add thawzone to it. lots a stuff it could be

When I replace a compressor or do a sealed system this is what I do after I recover freon I flush system with nitrogen both hi and lo sides. I always replace the drier as it could have a restriction in it I get one with a hi side valve so that when I am done with the plumbing. I can pressure it up and check for leaks then I put a vacuum pump on both valves and pull in a vac for min of 30 minutes the longer the better pull it in a deep vacuum. Then let it sit for awhile to see if my pressure on my gages rise which would tell med it's leaking. after that I charge it if its working properly my drier will be warm and on r-12 my hi side may be 150 or better and my low will be 3-4 lbs. When a system is low it will run in a vacuum anywhere between 1 inch and 20 inch if it goes in a deeper vac than that it's restricted

The nitrogen is just air wich gets rid of any freon trapped and moisture etc. Don't think I've ever seen aluminum drier I know they used steel with a lot of nickle in it. Some of the old stuff is hard to work with tho