Recommendation for a 4-gas analyzer

I looked for one of these several years back to get my 1992 C4 through Emissions testing. They were either $2,500 new or around $1,000 used. The problem with the used ones was accuracy. I ended up getting an Air/Fuel ratio wideband O2 sensor and gauge then installed it. Did the same thing on my carbureted 454s on my boat. That allowed me to dial in the Holley carbs on the boat and make sure the fuel injection was working properly on the Vette. In the Vette's case, I ended up changing the ECM to a FAST XFI so that it was more reliable and tunable. The only additional item I needed to figure out was the NO emissions which were controlled by the EGR valve on the C4 and didn't matter to the boat. Not a huge deal but it took three tries at the Emissions station to get that dialed in so that it would pass.

If you are dealing with carb systems......a wideband O2 sensor and gauge will probably get you 95% of what you are shooting for. They make one now that is handheld but you still need to install an O2 bung on one of the exhaust pipes.



https://www.amazon.com/Innovate-Motorsports-BASIC-Digital-Wideband/dp/B001S7W836/ref=sr_1_2?dchild=1&keywords=Exhaust+Gas+Analyzer&qid=1612624813&sr=8-2

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Analyzers need to be calibrated regularly. An old used unit probably will need it. This could be quite expensive.

 

No, O2 sensors work by comparative measurement of free oxygen in the exhaust stream versus free oxygen in ambient air, which also has the effect of making them self compensating for altitude.

The rear of the sensor needs ambient air.


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This is what I used and it is easy to install. Drill a hole and clamp it on. If you are just dialing the fuel system in.....then you can remove the O2 sensor and put in a plug. In any case you want to make sure the wire to the gauge/handheld you are using is long enough to reach the inside of the car. That way you now have a rolling dyno to see what is going on with the air/fuel ratio.

The first step is to set the idle circuit. On most carbs once the engine is warmed up, the idle circuit can be tuned. Personally.....anything close to 14 is good since 14.7 is optimum for the idle circuit. If the engine is cold .....fuel enrichment will kick in that will push the numbers to the 12 (rich) range. Depending on the fuel system (jets or needles) they can be tuned for cruise and wide open throttle.

That's what we used when we dyno tested marine engines since the air/fuel ratio impacted performance more so than recirculating emission exhaust gases.

https://www.amazon.com/GlowShift-Clamp-Wideband-Oxygen-Adapter/dp/B07KY1TJ6B

There are a number of decent YouTube videos on the subject.


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Definitely sounds like a small vacuum leak on the affected Bank. The leak becomes less relevant as the rpms are advanced. Monitoring the A/F ratio will hopefully help track it down.

 

It could also be a difference in cam timing between the two banks causing the idle issue.

 

For an old fashioned car what about colortune transparent spark plugs? These are not suitable to EFI tuning, but for CO adjustment and idle jet selection they do work perfectly. I am even using it to individually adjust the injectors of my K-JET MFI.

The only annoyance is the requirement to work in a slightly dark area (i.e late in the afternoon if you work outside).

https://www.gunson.co.uk/product/G4074

 

I have to say ..never seen that and not sure how accurate they can be but that is so cool

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They are damn accurate as you can see the combustion inside the chamber: white combustion is too lean, orange is too reach, blue is perfect.

The plug are not perfectly transparent, so it's difficult in direct sunlight to distinguish between white and blue. Orange is super easy to see, so I usually start from rich and then lean the mixture until combustion is not orange anymore. Which gives me slightly rich. If I need to pass emission control, I perform the adjustment at night in order to reach the perfect combustion color.

Being a "glass plug" that's a fragile plug, so not to be used under load. High rev should be avoided, so cannot be used for main jets or EFI tuning.

They are so cheap that I have bought two sets in order to check cylinders in parallel.