evap could be freezing up. Vent temps should not be in the 30's. If you have a temp control, back it off a little.

It's possible your TXV is not exactly the same as the Chevelle. Disconnect the blower motor and note the PSi on the POA. Do the same for the Chevelle. Is the condenser the same size on both vehicles? Are you using the same compressor? What about air flow across the condenser? Did you try misting the...

One thing to remember is the heat of the air inside a vehicle can influence your AC performance. If the ambient air in the vehicle is hot, it will make the Ac seem not cold enough. Sometimes your vehicle must run for 20 to 30 minutes before the vent temps come down. This is because the Ac system tak...

the hose that goes to the condenser is the high side

Also make sure the drier is connected in the correct flow position.

If you were low on refrigerant, you'd see flashing (bubbles) in the sight glass. To measure the line temps, use of a gun type thermometer is not accurate. The tubing has a reflectivity that will throw the temps off. I use a clamp on type thermometer (you can use a K-type that converts to a voltage o...

Are you using R 12? Sight glass clear? Disconnect the blower motor and the low side should be at 28 PSi. I used to be happy if those older systems were at 48*. You can check the TXV by removing the sensing bulb, holding the bulb in your hand for a minute or two, see if the readings change. Then plac...

Have to know which refrigerant you are using. Maker of unit? Is there a sight glass on the drier?

Your input and output of the evap should be about the same temp. This will tell you the evap is fully flooded. The output can be a few degrees colder. Gm used to state that to do a partial charge to fill system until both of these lines are the same temp and then add a few more oz of refrigerant.