I have a 1981 B21A 244DL, with a Zenith-Stromberg Carburetor. Regardless, this can apply to any car, aeroplane, etc.

I used a hose clamp to fasten a temperature probe to #1 Exhaust Manifold down pipe, approximately 2" down from the mounting bolts. The meter will measure up to 1400 deg Fahrenheit.

I leaned/enriched the mixture, ever so slightly, to find the peak Exhaust Gas Temperature transferred to the cast iron downpipe. It turned out to be 521 deg F.

Ideally, it would be preferrable to install a probe into the exhaust gas flow just above the Flange, where all the down pipes are collected into one. That would yield an average temperature.

Theoretically, that should yield the stoichiometric mixture 14.7 : 1 Air to Fuel Ratio.

The downside is that one cylinder could run hotter.

Anyway, the engine runs well and smoothly.

I will be curious to know the mileage.