CO on your Chevy is way to high. Forget all other emissions components and
focus on the carburetor. If you plan on doing this work yourself you'll be
needing a tool to measure CO output from the tail pipe while you may
adjustments to the carb. At the smog station they use the smog machine set
to "manual 5 gas analyzer". Engine performance shops sometimes have smog
machines, but most often use a self contained 5 gas analyzer. This repair
can not be done without a tool indicating how your adjustments are effecting
emissions, unless you want to run back and forth to the smog station with
every correction you make, which is not feasible.
Let me explain the smog test results... (both idle and 2500rpm are based on
the same principle) 9.03 Carbon Monoxide (CO) is a direct indication the
carburetor is dumping too much fuel into the engine. As a result the
hydrocarbons (HC) have increased. HC is basically the raw fuel which the
engine was unable to burn at all, and CO is the fuel that was partially
burned. Very simple, not brain surgery.
I think the engine in your Chevy is sound... You only need to get the carb
perfectly tuned (I mention tuned and not rebuilt - since it's already
rebuilt, right?) and that will get you to pass the smog check. Most vehicle
owners think when they purchase or rebuild a carburetor it comes tuned or
gets tuned during the rebuild. Problem is every car, truck, SUV, van and
motorhome has it's unique thirst for fuel, and the rebuild shop or
manufacturer knowing this, make only major adjustments to the part, leaving
minor/fine adjustments to the installer. Though minuet, one size does not
fit all, and 99% of the time you'll need to fine tune a rebuilt carburetor
after the installation, and with an emissions measuring tool.
