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Old 04-24-2013, 10:19 PM
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A NB is very accurate at showing the 14.7:1 cross point. And manipulating the PCV air flow by hand while watching the gauge will show you where you are at.at various above idle rpm/throttle points.. Thats what you need to know.
is it richer than or leaner than//.Stoichiometric....?

You do not need to know the exact AFR. Off idle transition AFR leaner than say 15.5 is too lean (drivability)
richer than 12.8:1 is too rich.
Just get it close to 14.7:1. There is no ideal ratio. close to 14.7:1 is good enough thru the idle transition.
But first set the curb idle for best idle using a vacuum gauge and get the throttles position correct.
The AFR gauge will be richer than 14.7:1 at idle, when the idle is set correctly. usually 12.5 to 13.8:1 ratio @ idle.
Idle quality and manifold vaccuum is the priority , not curb idle AFR.
Play with the pri and sec throttles idle position and idle base timing .

You don't need a wide band for any of this tuning.

Same with WOT power main jet tuning. You don;t need to know the exact AFR.
You just need to know if the jet change you just made up or down in jet size made you go faster or slower.
and wether your jet changes are getting you way too lean @ WOT.

It is a lot friggin easier to just find a different PCV valve air flow rate to correct a simple slight off idle/transiton lean spot
than to start drilling blind. You very rarely ever need to drill a carb. EVER.

Do ALL this FIRST.... You can tune the whole carb 99% using a low cost NB and a tach and a vacuum gauge
and some drive testing. You can build you own portable 12volt powered NB heated AFR gauge tool for under $100.
I did, you can too. 3 wire 4 wire NB replacement O2 sensor EG NTK 21006, summit/auto meter NB afr gauge, (or a DVOM) 4 wire trailer brake light extension wire harness with flat plug. 12v car cig lighter plug.

Last edited by F-BIRD'88; 04-24-2013 at 10:45 PM.
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