i have a 1991 camaro 3.1 and i recently put a new head gasket in it and a new cap and rotor but its running really rich and i dont know why. what could be causing this?
Ignition timing retarded too much maybe? There should be a test plug on the firewall and this should be grounded when checking and adjusting the timing.
What’s it doing, belching black smoke? Sooting spark plugs up?
High fuel pressure perhaps. Did you notice rich running before the headgasket work? have you inspected the fuel pressure regulator and the vacuum line too it?
Look at it this way. It’s ready for that supercharger now 
(Kidding. It’s not. Don’t do it.)
I’d go with ok440’s suggestion and check the timing first. If you don’t have a timing light, oftentimes you can find an auto parts store that will rent you one. Otherwise, you can get a decent one for around 60 bucks.