Tach Problem

[dowguard]

When I am driving my 1988 Camaro the Tach is reading quite high. It sometimes hits the stop before it shifts and I know that its not running 7k rpm. At idle it stays at 3500 rpm. How can I fix this? Thanks for any help.

[RS3SDL2MG]

my 67 has the same problem and for some reason it seams worse in cold weather ?? mine will idle and show 3K when cold but after it run's a while it will go back down to normal ,,,,