I have a 1984 z28 that we were working on, worked fine drove it home, next morning the key will go into the lock cylinder but will not move ( secondary note the switch for the trunk and door locks not working either ). Someone outside told me that maybe I have the Ignition " Locked out" . and that it is a security measure that the key and other will not move.
Reading in the forum as well said maybe a fried lock cylinder... any suggestions?

 

Does your car have an automatic trans? The later year cars have a cable that prevents the key from being turned unless the trans shifter is in "park". Not sure if your 84 has the same setup.