Long story short, What causes an engine to have high Hydrocarbon (HC) readings on an emissions test?

Engine info as follows
350
Edelbrock Performer Intake and 750 Carb
Comp Cams Magnum ~280 duration, 480 lift
World Product Sportsman II Heads

I'm in Alaska and it failed the tailpipe emissions test. The tester said it appeared to be a problem on the passenger side since the HC numbers were 542 ppm on the drivers side and 1089 ppm on the passenger side, which ultimately caused it to fail. There isn't really any emission equip. on it, no catalytic converter etc.

Any ideas what would cause this?

What were the rest of the test results.
HCs are unburnt fuel.
You have an engine miss more than likely.

mixture screw turned farther out and/or the float level is higher on the pass side. Jake may also be on to something, a missfiring plug would sent the HC reading through the roof. A quick compression test, a new set of plugs, wires, cap and rotor, as well as a carb rebuild and proper setup will go a long way to passing that test.

What were the rest of the test results.
HCs are unburnt fuel.
You have an engine miss more than likely.

Drivers Side - HC=542 CO=2.2% CO2=5.4% O2=11.7%
Pass Side - HC= 1089 CO=1.77% CO2=4.5% O2=13.4%

It does seem to have a little miss but at the time I had recently put new plugs and wires on. I do have a new 600 cfm Edelbrock carb to put on.

Thanks for the replies,