The 583 in my 89 mach 1 has been bored .020 over. What should i change the jets to? It takes forever to warm up but runs fine after that. I know it needs bigger pilots, maybe smaller mains, but i dont know how big/small to go.
thanks

I would use 1 size larger then stock on the mains. Keep the pilots the same and see what happens. If you can not get the idle rich enough you may have to bump the pilots up 1 size. You not warming up may be a stuck open thermostat.

What does the plugs look like?

Leave the mains stock if they are. The 89 Mach's were rich from the factory. Try turning in your air screws to richen up the idle.

I think its going to take a little more than turning the air screws, i have to keep using the primer for 5-10 minutes until it will idle on its own. i'll see what the air screws do though.
thanks for the help

Go ahead and up the pilots one size, and see what happens. Make sure you don't have any air leaks.