Hey.
Most of you dont have to worry about emissions, but for those in places like I live, this could be a helpful post.
I installed a slightly more aggressive than stock 1968 HP 440 in my 74 challenger.
The initial emission testing game back like this:
HC: 5298 PPM Limit: 1200 ppm
CO: 9.37% Limit: 9.00%
CO2: 3.54% Limit: None
So, because I figured it was running way rich (high HC, low CO2 denote incomplete combustion), my first test was to drain the tank and fill it with E85. ethanol both runs cleaner (for CO and HC) and you need more fuel to get the same energy, so I figured that should take car of a great deal. The second thing was to significantly advance the timing. Remember, E85 has an octane number of around 110. I advanced the timing about 10degrees before I got any ping or dieseling. Lastly, i tuned the carb with a vacuum gauge to get it running well.
So after taking it down to the DMV today; I passed and the numbers look like this:
HC: 119 PPM Limit 1200 ppm
CO: 0.73% Limit 9.00
CO2: 12.32% Limit NA
Now, some of you may say E85 is terrible for the fuel lines etc. And you are right, long term they will corrode, but for a couple days you should be fine before switching back, although with the high Octane, you may want to just change it over if you live near an e85 station.
Hope this helps a few of you.
