I recently purchased an 84 Z28 with the high output 305. I took it to get smogged with failing results. It passed most of the test except for the hydrocarbons portion. Usually this mean a lean mixture and fuel not being burned completely. The engine burns oil initially from idle to about 1200 rpms. When I start it up after sitting overnight, the idle is so rough to the point it shuts down unless i give it gas. I know my choke is to blame for this.
How would I go about troubleshooting and fixing these problems?

 

A good place to start on the choke problem would be to check the pull-off diaphragm, or the adjustment of its linkage. When the engine is running the vacuum should operate it and it should open the choke blade about ¼", which you can check by hand.

High HCs are as you stated the result of unburned fuel, or oil. However, your diagnosis is incorrect: a lean mixture cannot cause that. High HCs in conjuction with normal CO usually indicates a misfire (occasional cylinders spilling raw fuel into the exhaust, mixture OK otherwise). Check the plugs, plug wires, cap, rotor, etc.

 

i just replaced the plugs and the wires. Cap and rotor i havent checked yet. Could it be because the plugs are not gapped right? To my knowledge they were pregapped. Could the cat have something to do with this?
Also whats the cause of burning oil?