It's easy to install a "narrow band" 1-wire O2 sensor and read it using a voltmeter, very inexpensive. Standard brand SG-12; The reason it's called narrow is because it basically revolves around stoichiometric (14.7 parts air to 1 part fuel by weight) and "rich" and "lean" conditions on either side of that in a narrow range. While "stoich" AFR is theoretically perfect, in practice it isn't seen very often.

http://www.bob2000.com/carb.htm

What you want in my opinion for tuning is a wideband O2 sensor and display, don't really need a data logger and graphing programs and all that. Not for carbed engines probably. It will also convert the voltages to actual AFR for you, and adjust AFR display for different fuel types -E10 for example as well. I think the problem with the narrowband setups is they won't display down to 12.5 - 13.0 AFR (full throttle) nor up to 15 - 16 AFR (lean cruise); I'm sure a narrowband could be made to work and is far better than nothing, but the prices have come down quite a bit on the wideband kits. The fuel savings alone after a roadtrip, it will pay for itself. EFI modern engines run as high as 18 to 1 on the highway, don't try this at home kids! But if you really want to get a carb dialed in it's the way to go. Plugs don't "color" the same since leaded gas went away.

Idle mixture doesn't really matter too much. (Though it does if you have to pass a smog check) What happens is the most efficient burning of fuel skews the NOX emissions very high relative to CO and HC. That's a whole different deal there, and probably not what you're concerned with.

While the idle mixture setting does affect the overall AFR in the other circuits - transition, cruise, power, etc, it's like pissing alongside a firehose. Adjust it where it idles good, slightly lean. If it's too rich it will tend to load up the plugs after a few minutes and the idle will suffer, and also contribute to fouling.

Where the wideband makes your money is in determining optimum cruise jetting. A carbureted engine in good shape will cruise on level ground around 15.5 to 16.0 AFR or so, this requires experimenting. The trick is to then monitor the WOT AFR, it will likely need adjusting after jetting down. In many carbs this is a little tough to do, as the power valve channel restrictors are basically jets, but they are fixed in size. Simply going with a different power valve will change when the extra fuel comes in, but not how much, it is limited by the PVCRs. The key thing is never go too lean on power. It's OK to lean it out quite a bit when cruising, but never under load or acceleration. I bought an Innovate LM2 kit, it works slick I gotta say. It allows you to see exactly what's going on in real time. The stock Y Block isn't a performance engine but I don't need to have a fuel tanker follow me around anymore. It is truly amazing how much fuel can be wasted out the tailpipe with no noticeable change in performance.

The LM-2 is a little spendy, but not that bad. Should be able to pick up the basic kit under $200 if you dig around. I don't remember what I paid, just under a couple hundred. Used units pop up now and then too. The LM-1, the earlier basic unit works just as well for what you want to do, these used units are up for auction now and then, I just got impatient. Snag one if you can.



That is exactly where O2 sensors shine. Everybody seems to think they are only for EFI but they will really help dial in a carbureted engine. I would suggest getting one that has a numerical display of AFR. Innovate has the gauge and wideband sensor under 200 bones. I think that's all you need.

I'm not sure you can "get there from here" with a 1 wire O2 sensor is the problem. Maybe....

Find out what the total range of voltage output is with the SG-12 for example, and convert these to the AFR numbers. If a 1-wire narrow band sensor actually has an equivalent range of say, 12 to 16 AFR, you can make it work (I think) just fine. You'll just have to convert voltage numbers on the fly to AFR is all, no biggie.

Get the jetting dialed in and plug fouling is a distant memory, plenty of power when needed etc, and should see a significant fuel economy increase, at least on the highway. Your vacuum gauge is also useful here. Make certain if the carb has a Holley type power valve that it is closed when cruising or measuring AFR at cruise, otherwise correct jet selection will be impossible. That's the lesson O2 sensors teach, each carburetor circuit is tuned separately, they all work together but each has to be measured and adjusted in isolation, if that makes sense. Short version: lean it out till it sqeeks on the highway, fatten it up on the acceleration & power, done.

One thing - the ignition system has to be in top condition to properly tune, it's easier to light off a rich fuel mixture. Also, if your engine has an intermittent misfire - the gauge will show lean, not rich, as one might expect. These sensors measure oxygen only, if the plug isn't firing, the fuel isn't being burned... but neither is the oxygen. So make sure the ignition timing and distributor bushings and secondary voltage and everything is 100% first before tuning the carb.

I shoot for about 15.5 to 1 at steady level cruise on the highway and WOT is 12.5 to 1 Mileage about doubled. Hope this helps, let us know what you find.

Wait. For $179, it doesn't include the O2 sensor itself?? That sounds nuts.