I'm going to remove engine for bay glean and paint. Does the air comp. need any special attention? There is only a little pressure left.Do I need to seal all openings? Also what do I have to do in rechargeing in spring? 74 duster, 318 2 bbl THANKS

Sealing all the openings will prevent dust and extra moisture from entering and oil from spilling. As a minimum it will need evacuated and re-charged next spring with a new receiver/dryer highly recommended.

Beyond that it depends on what condition its in now. Is it still R12? Good time to plan an upgrade if needed.

WHAT WILL IT TAKE TO UPGRADE TO 134?

Lots of ways to do the upgrade. If the current compressor is OK it can work with 134. The minimum upgrade would be a new expansion valve, new receiver/dryer and new pressure/safety switch. New hoses recommended. Classic Auto Air or Bouchillon or possibly a local shop can fix you up with the parts.

A new (much) lighter, more efficient Sanden compressor would run around $250 with brackets. A new high efficiency condensor to go in front of the radiator would help and be a couple hundred more. If you go that far, might as well get a complete "cab forward" kit from Bouchillon or Classic.

The basic process is to use compressed air and AC cleaning solvent to flush debris and old oil out of the system (except compressor). Install the new parts, add the correct oil, evacuate and re-charge.

If you re-use the old compressor, you dump or drain as much of the old oil as possible and then go ahead and use it.