82 SC mixture and timing

SUperman and others have helped me get ready for these adjustments, but I have a couple questions to make sure I get everything just right:

Is it preferable to adjust the mixture or the timing first? Or just go back and forth to re-check everything?

I understand the technique of using a dwell meter through the test connection, but the label in my engine compartment describes using the exhaust gas analyzer to get .6 CO2 before the catalyst after disconnecting the Oxygen Sensor. Do you have to disconnect the sensor for the dwell meter method? If it matters, my car has not had a catalytic converter since I've owned it.

Is the CO2 method more accurate? If so, where does one get an analyzer?

I'm also having trouble finding a digital dwell meter. Sears and the auto stores all have analog ones only.

Thanks,

Olivier
82 SC

The "four gas analyzers" are expensive, so you would need to take the car to a shop for that. This adjusts the mixture according to emissions and is very accurate. I still like the dwell meter method though, and believe it is also highly accurate.

I adjust with the O2 sensor hooked up and the engine fully warm. This means at least 20 minutes of driving for my car. If you do the dwell meter mixture procedure, you will see the O2 sensor "duty cycle" modulate back and forth about ten degrees (like between 40 and 50 on you meter, centering in 45. I believe that this means the O2 sensor is working, which is nice to be able to verify. If you unhook the O2 sensor, or if it is not working, the duty cycle will not modulate. it will hold steady. It also holds steady during warmup.

and the timing gets set first. And the valves get adjusted first, if you're doing valves also. And change filters first if you're doing that as well. Mixture is last on the list.

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'83 SC

Thanks, Super. You said you got the digital dwell meter at Sears? THe lcal Sears Hardware doesn't have one, maybe I'll check a main Sears store.

Olivier