Air/Fuel Mixture Gauge

June 2002

Background | Installation | Cost | Postscript

Background

After replacing my carb, I didn't really do any tuning on it. When I went to get a SMOG check, I failed with to much O2 which can mean I am running too rich. I decided to install an O2 sensor and a fuel/air mixture gauge to help me tune the carb. I suspect that my jets are too large for this engine.

Installation

The first step was to get the O2 sensor bung welded in. I took it to a local muffler shop and they did it for $20. That seemed a little steep, but I didn't feel like driving all over town to find a cheaper place. Once that was done, it was just a matter of wiring it up. I already had one gauge below my dash, so I just bought a 2-place bracket and put them together. I used a switched power source so the gauge and sensor heater would only be on when the engine was running.

Cost

02 Sensor w/ weld-on bung $50
Summit Racing fuel/air gauge $30
Welding labor $20
Total $100

Postscript

Once it was in and working, I was able to really see what my carb was doing during all phases of driving. I proceeded through the steps to get it all correct. When I was done, it passed smog easily and was cleaner than it had ever been. It ran much better, too.

  • Idle - Adjust for 850 RPM
  • Air bleeds - Adjust for stable RPMs and correct mixture at idle (slightly rich)
  • Jets - Decrease size until mixture at cruise was correct
  • Power Valve - Change to allow PV to kick in much earlier to avoid excessively lean mixture during acceleration. ( I used a vacuum gauge to help determine the correct one.)