Tweaking jets on a Holley...

[Restomod Z28]

Can I get some feedback on how everyone arrives at their jetting for a street car? I'm referring to actual test & tune on the street (not the track or dyno). I have a full Holley jet kit...

Should I disconnect the secondaries and tune the primaries for best performance first? Then, once the primaries are properly tuned, allow the secondaries to kick in and tune them?

In case it matters, here is a little background. My current tune (IIRC) is 74/84 jets. This is a 10:1 CR 383 sbc with a 230/236 @0.050" cam. This new carb seems to be jetted fat and the car feels a bit sluggish across the RPM range (as compared to my previous setup). I have NO stumbles or bogs. The mechancial secondaries open smoothly. My fuel pressure, mixture, floats, and timing are set correctly.

Any advice is appreciated... I'm learning as I go. Thanks!

[fishtail8]

Throw a fresh set of plugs in it and drive it for a day or two, then pull a couple out and see how they look. If they're blacker than black you could probably pull some fuel out. If they're tan-ish I'd leave it alone.

[eldogg]

I street tune with an Innovate wideband O2 sensor. Without a wideband just read the plugs. Fishtail is right, start with fresh plugs.

[Pro Stock]

Throw a fresh set of plugs in it and drive it for a day or two, then pull a couple out and see how they look. If they're blacker than black you could probably pull some fuel out. If they're tan-ish I'd leave it alone.

This is good advice, when you start leaning the carb I would probably start with the secondary, the 10 number spread from front to rear is probably to much, if the engine is as rich as you say I would take about three numbers of jet out of the secondary to start with and work from there, You would save yourself alot of time and frustration if you could put the car on a chassis dyno where they can tune for max power and fuel ratio with an O2.

Dale

[Skip Fix]

"Should I disconnect the secondaries and tune the primaries for best performance first? Then, once the primaries are properly tuned, allow the secondaries to kick in and tune them?"

That is the best way to tell if you have a wide band. Tuning primary acceleration and accelerator pump circuit and cruise. The add in secondaries at WOT.

Otherwise trial and error on how plugs look and how responsive motor feels. A wide band can sure pay for itself in time though!

[MonzaRacer]

I tune primaries air bleeds and power valve for best driving/cruising perfromance. Then keep richening till car slows down. honestly had more cars tuned this way. Hard part is getting air bleeds and transitions circuits down perfect,,,,I also recommend the Innovative wide band.

[Restomod Z28]

Hard part is getting air bleeds and transitions circuits down perfect,,,,I also recommend the Innovative wide band.

Can somebody explain how to tune the idle to primary transition? My car goes lean (stumble and pop - off the chart lean on my narrow band O2) as I gently apply the accelerator off of cruise speeds.

It seems that some people say go with a larger discharge nozel and play with the pump cams as needed. Others say to focus on the transition slots (even widening them). Any thoughts here?

The air bleeds control the richness of the mixture at idle, right? As I understand this, the mixture screws control the flow of this mixture at idle vacuum. So, I would tune the idle mixture by enlarging/reducing the air bleeds to get the correct A/F ratio? Right?

Sorry for all the basic noob questions... I see the value in the wide band O2. I'm looking for a gently used unit.