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Wide band AF. Holley carb adjusting?

2K views 7 replies 5 participants last post by  Andy79Z28 
#1 ·
The '34 Roadster works pretty well. Ignition is adjusted. It's easy to start, pulls evenly and good, no stumbling. The idle is maybe a little high, even with the adjusting screw all the way out, but all in all the engine works well.

But the AF ratio is way too rich. Crusing around 12-1500 rpm shows 12-12,5:1.

QFT Super Street (Holley based) 650 CFM DP carb.
Engine is a Chevy small block mainly standard except air gap intake, headers and 2 x 2,5" exhaust, straight thru mufflers.
6 speed trans.

What do you suggest? Lean down the primary jets a bit?
If so, how much? 3 steps?
 
#2 ·
first lean down your idle until it stumbles at transition, then go back just a hair to cure the stumble. then lean your primaries, but only go 1 step at a time. for cruise 15:1 is about ideal, but sometimes its needs to run richer with a carb to compensate for uneven distribution.
 
#4 ·
i put a $20 narrow 02 gauge, and an old spare 02 sensor I had laying around in my car... best $23 I ever spent (forgot the $3 for the 02 bung)

I had to go down something like 6 or 8 jet sizes to get my holley 650 (vac secondary, dual feed) to run 14.7-ish:1 at cruise.

1200-1500 rpm cruise seems a tad low.. what ground speed are you doing that at? 55mph with an o.d that wouldn't surprise me much :>
 
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