I added one after seeing RV6's in his 67 coupe at the Bash last year. We both have the AEM 30-4110. I welded bungs on both exhaust pipes just after the long tube header collector flange, and on a couple of the individual header tubes. I mounted the gauge in a dual gauge pod in the console ash tray.

Last edited by rpm (8/12/2018 1:39 AM)

I can't take credit for the idea.  I got it from this video on youtube.  Its a good video and worth watching all the way through.

MS wrote:

Has anyone used it to rejet and tune their carburetor successfully?

That was the reason why I added mine. I believe I was successful, I do know it runs much better throughout the throttle position. During the drive down elevation thru Colorado and into Texas with RV6 (Gary), he would occasionally talk about his air/fuel ratio. He changed jets in Amarillo as he started his trip at 8,000 ft. This caught my curiosity. On my post trip car inspection I found the carb was way too rich, even though I averaged 16.7mpg for the entire 5k mile trip. So I called Gary for his take on the O2 sensor and gauge.

Since you get o2 readings from idle thru WOT, you're able to change the primary and secondary jets to get to your goal settings. In addition to the exhaust pipes, I installed a bung on the leanest and richest (based on plug readings) individual header runner. When the jets are changed you get immediate results shown on the gauge. It certainly helped me tune the carb, and would recommend it. There are many air/fuel ratio charts online that are pretty close.






 

MS wrote:

I ordered an AEM gauge.

 
Wide band I hope! Best for carb tuning.

The AFR gauge was a last ditch effort at tuning the carb. I had a couple of hiccups and did not know if it was lean or rich condition causing the problems. The AFR dialed me in.

After changing jets twice on the way to the bash last year and driving all the way home with the "Florida Jets" in the car I changed the jets to the "Amarillo Jets" and have driven all summer with them installed. I have always fought a cruise to slight addition of power (like a small hill) lean condition (>16 AFR). I have been slowly bumping the main jet size while bringing down the power valve opening. This seems to be a high altitude (house is 8500') problem as even though I was running lean in Florida I had no stumbles anywhere in the power band. Lots of get up and go too!

So even with the AFR gauge it is still a trial and error scenario to tune a carb, but at least I can see the results and adjust accordingly. 

RPM, how much difference do you see between the right and left banks? 

Went to Summit and got an Autometer wideband. Installed it (bung on pass. side). Set fast idle with vac gauge and timing light.
Read slightly lean at idle. Ohhh, so it's best to tune at wide open throttle. I went to an SCCA autocross where wide open throttle would be common. Oooops, hit so many cones when I looked down to read AFR gauge. Still don't know for sure, but car doesn't stink like raw exhaust after a long cruise. 
More info later after I stop hitting cones. Maybe a long stretch of country road, pulling hard in second and third... cell phone camera mounted to roll bar aimed at gauge... or something like that.
Paul