Chassis dyno .. ?

A/F mixture , a sensor in the headpipe vs. a tailpipe sniffer?

I'm think a sensor in the headpipe will give accurate readings vs. one in the tailpipe?

I've found the difference is very little between the two if both are accurate.

My in-the-car display reading from an 02 in the collector is within .1 a/f of the chassis dyno sniffer... but that is only for WOT

sniffer works great as long as you have no exhaust leaks

Putting a bung in the headpipe is the best option. You have to weld one in though. You can plug it with a short bolt after dyno.

I suggest you also "read" the spark plugs.

Thanks guys , this is for another board member , he called a local place to get his carb dialed in and they said they have a tail pipe sniffer , should be good enough for what he needs .