Thanks to Mar-Ktech and Hot Rod Lincoln for giving us the idea of adding an O2 sensor in the exhaust stream. This sensor is really valuable in that it will tell you right away if you are running too lean or too rich.
I added mine just below the manifold using a weld-on bung that I got at Summit Racing. The O2 Sensor is a Standard Motor Products SG5 for $20. It takes awhile (10 minutes at idle) for it to warm up enough to start sending valuable data. There are O2 sensors with warmers that give the result right away, but I am not in a hurry.
Its a simple install. Drill a 7/8" hole in a place that doesnt interfere with anything with the sensor sticking out about 6 inches near the manifold. Weld in the bung and then screw in the sensor. Dont forget to put the flange ahead of the bung before welding.
To read it is even simpler. Using a voltmeter that reads in millivolts, plug the + lead of the voltmeter into the sensor wire, the - lead to engine ground. The center of the sensors universe is .5 volts. .5 volts represents a perfect oxygen to fuel ratio of 14.7:1. Less than .5 volts represents too lean and more than .5 represents too rich. It produces as much as 1 volt.
Through some initial testing, I am finding on a stovebolt engine that was designed long before O2 sensors were even a thought, the proper way to fix a WAY TOO LEAN or WAY TOO RICH condition would be changing the Carb Jet. If you are getting around .25 to .65 I wouldn't worry about it.
Another way to adjust for optimum is the fuel mixture screw on the carb, however, that goes hand in hand with your timing and engine performance, so that may not be the best choice. If your plugs are gray, you are good to go without an O2 sensor, but I found it quite interesting to actually see the soot on the spark plugs without even taking them out! It is an indicator, nothing more, but an interesting one.
Anyone have other experiences with this? I am learning as I go.
