LAX immigration is pretty unpredictable. It is worse in summer than during wintertime. As a non US citizen it usualy takes between 30 and 60 minutes between landing and exiting thru customs, but it has taken me over 90 min a few times.
It all depends of what happens when you miss you next flight. If you are on the last flight of the day on a nonrefundable non changeable seperate ticket i would least 150 min, possibly even more If you are on one ticket or have a flexible tickets and there are later flights you have a good chance to make a 80-90 min connection.