I'm not experienced with the old A/C systems and just bought a 72 Scamp with a 318 and tried to charge it with 134. I put in 2 lbs and looked for bubbles in the sight glass and didn't see any. I put in another 1/2 pound and no change.The compressor stays on but the low side is at 0 and the high side is at 100. The only place that gets at all cold is by the valve by the firewall but not inside. To my knowledge the low side hose should get cold up to the evap core. I am looking for help with the low pressures and wondering what the original capacity was. Any help would be appreciated. Thanks Craig