Emissions fail - any advice

[jlolson]

I've failed emissions twice on my '71 C20 5.7L.

Prior to first test:
Vehicle was not running when I bought it. Fresh oil/filter, new plug wires, new gas tank, flushed fuel lines, new carburetor, timing adjusted, idle screw adjusted but left idle fuel mixture screws alone (new Edelbrock carb, thought it would be dialed in).

Pollutant: Reading/Standard - Result
Loaded Hydrocarbons (HC) in PPM: 132/450 - PASS
Loaded Carbon Monoxide (CO) in %: 3.54/3.75 - PASS
Idle Hydrocarbons (HC) in PPM: 379/450 - PASS
Idle Carbon Monoxide (CO) in %: 8.94/5.0 - FAIL

Prior to second test:
Idle fuel mixture screws dialed down as low as possible without stalling, Idle set precisely 550RPM in drive, replaced PCV valve, new spark plugs, burned one can of "guaranteed to pass" emissions formula, filled up with 91 octane, added 1 can of octane booster, drove for about 20 minutes on the freeway to get it hot as hell prior to testing.

Pollutant: Reading/Standard - Result
Loaded Hydrocarbons (HC) in PPM: 149/450 - PASS
Loaded Carbon Monoxide (CO) in %: 5.68/3.75 - FAIL
Idle Hydrocarbons (HC) in PPM: 119/450 - PASS
Idle Carbon Monoxide (CO) in %: 1.88/5.0 - PASS

I'm going to give this one last try prior to taking it to a shop. I may have screwed up the "guaranteed to pass" emissions formula by not running the tank completely empty (looked empty but when I filled up it only took 15G). I'm going to run it empty again and put more fresh high octane. I also plan on changing the oil again, the engine was likely all sludgey after sitting for 4 years and 2 oil changes won't hurt.

I'd really appreciate any suggestions because I'm out of ideas. I've already spent a small fortune on this thing and can't get it licensed. I really don't need to start dealing with a mechanic on this truck, I bought it so I could do the work myself. Any tips/tricks/repairs before I go again???????