good battery on c4 93 vette does not stay charge after 2 days

Something is draining power when the car is off like stereo, amp, light, etc. Take off the negative battery terminal and use a multi-meter and select current (amps) at teh highest range. If it you connect one lead to the negative battery cable and the other lead to a good ground (unpainted, metal surface) there should be a small (10mA or less) to very . If you get a higher reading, something parasitic is draining power. If there are wires connected to the positive side of the battery terminal, disconnect those first and check with the multi- meter again. Its a process of elimination. A test light is also a cheaper alternative to the multi-meter, if you do not have one. Check for plugged in phone chargers, GPS, etc. Disconnect and test again.

Do you have a bluetooth in the car? There has been issues with the GMC Terrains draining power from the batteries if the car is shut off before the bluetooth is turned off. Have you checked to make sure there is not a bad cell in the battery? There also has been a rash of bad batteries brought over across the ocean. Make sure the battery connections are tight and clean of corrosion. Check the positive cable for cuts or exposed wire that may be shorting out and draining the battery. Check the connection to the starter also. First, bluetooth, second battery check, third cable connections and clean connections, fourth cable serviceability .