From the same page:
“Question: 1983 Toyota Tercel 3A mileage: 150k+. I live in Flagstaff, Arizona, Elevation 7000 feet. First question: The car gets poor fuel mileage and I believe is running very rich (strong exhaust smell). The spark plugs are always fowling. I have been told it needs to be Altitude Adjusted. Would that help and how would I do that? Second question: In the winter the water temperature never gets warm enough for the heater to work. Do I need to install a different thermostat and what kind?”
Wow, so rich that he can smell the unburnt gasoline, yet it’s running too cold!. Even if the article is correct, it still doesn’t support your theory. How many people in this thread have had their car running rich without overheating the engine? Consistent with the information contained in the posed question, I drove my Shelby to the same place described above with 72 jets. The car was running so rich that it was difficult to keep running. Just like the car mentioned above, it ran cold.
This wouldn’t be the first time that I’ve seen the writings of magazine editors defy the basic laws of physics. If you haven’t figured it out yet, it doesn’t take an engineering or any other degree to write for a magazine.
With regard to the fuel continuing to burn in the exhaust ports, it is true that an air pump is commonly used to oxidize the remaining unburnt hydrocarbons. They don’t, however, reignite and burn. Even if the remainder were to reignite, the surface area in an exhaust port is less than that of the cylinder and the velocity is higher, so there would be less transfer of heat, even if the temperatures were the same, which they are not. With regard to your theory that the cylinder pressures would be too too high, that’s absolutely absurd, at part throttle, the cylinders are under filled, not over filled.
A rich mixture would indeed cause an engine to run hotter, providing that it was rich enough to hydraulic the cylinder and crack the block, otherwise, a richer mixture will nearly always cause an engine to run cooler. Ever adjust a natural gas heater? The leaner the mixture, the more blue the flame becomes, the richer the mixture, the more orange the flame. The wavelength of the light is inversely proportional to the molecular energy, or heat, of the combustion.
With regard to your motorcycle running hot, the engine will run hotter because the density of air at high elevations is lower, it therefore has less heat capacity. On moving-air cooled systems, this will make little difference since the thermal time constant of heat conduction limits the transfer of heat. On a motorcycle, where there is little or no airflow, the cooling is dependent only on the density of the air and emissive transfer. Higher altitudes typically also have lower humidity, which further lowers the heat capacity and therefore lowers the cooling efficiency of the air. Cause and effect, see how that works ?
With regard to the particular engine in question, I have a few questions: Was the carb originally used on an EGR equipped vehicle? If so, it will run rich without the EGR. On an Edelbroch or Carter carburetor, the power valve is integrated into the needle and seat. The needles occasionally stick, and when they do, it’s almost always in the high-flow position. A leak between cylinders could also force the piston used to modulate the needles too far into its bore.
You do have a great deal of technical knowledge.
