Just asking on behalf of a friend who has a 91 V6 firebird, its been struggling to start for a while, like the starter not kicking in properly sometimes, so hes fitted a brand new starter and its still doing the same thing.

He said it just makes like a clunk noise and wont turn over sometimes, maybe after 5 or 6 attempts it will then fire up

 

Sounds like possibly a dead cell or two in the battery. Could be caused by a dying alternator not charging the battery. He should get both checked out. Another thing to check for would be for corrosion and/or loose connections.