I'm holding out on getting one of these, too cheap I guess. I rely on plug readings. I use both edelbrock and holley carbs and have a good baseline for both setups and what the engine likes, the benefit of the AFR is not really worth it. More likely answer is I probably don't know what I'm missing but as long as I get reasonable gas mileage, good power and smooth operation I'm good. good luck with that thermoquad, it may just run well right off the bat with some light tuning if its been worked.
My 470" ran great cruising at 11.8-12:1 and achieved reasonable economy while doing it, which most owners would never realize unless they killed the ignition and coasted off the highway to read plugs. Initially, the Holley Ultra XP was so
fat OOTB, it was running 10.5:1 AFR while at cruise (again, average owner wouldn't realize this) but was actually very lean at WOT and had another lean-spike during the initial tip-in. That 12:1 AFR at cruise, was the best I could achieve with what (most) owners would do, by making simple jet changes.
Squirter, pump-cam, jets, power valve, and air-bleed tuning were required to get an
acceptable tune. There is no easy way to tune these 'race oriented' carburetors without a Wideband on a street car. Potential engine damage vs. $150 Wideband, easy choice with this application.
I agree however, that with most street applications, the carburetors are tuned
very close OOTB. My 600 Holley (4160) on our SBM required a small jet change in the primaries and a lighter vacuum secondary spring, that's it. 14:1 AFR Idle / 15:1 AFR Cruise / 12:1 AFR WOT.
