tuning with an a/f gauge

[westcoastgalaxie]

Just installed a innovate a/f gauge but now I need to learn how to tune with this thing. What are some good resources that I can use to educate myself?

For those that have experience with FEs and this tuning, anything unique I should be aware of?

[jmlay]

Innovate has been in several articles where carbs were tuned.:

http://www.innovatemotorsports.com/resources/carb-central.php

[jayb]

What I've done is to turn on the datalogging feature, go out for a five minute drive with a couple of acceleration bursts, and then come back, download the data, and tune from there.  I've often seen a lean spike on hard acceleration, meaning that some accelerator pump tuning is required.  Also at idle and low RPM cruise you can adjust the idle mixture screws to change the A/F around, and over 2500 RPM or so if you are running rich or lean you can change out the main jets to adjust the values.

For  idle and standard cruise, just driving down the road, you want to shoot for an A/F of 14.7:1.  Under hard acceleration you'd like to have more like 12.5:1 or 13:1.  Hope that helps - Jay

[westcoastgalaxie]

Thanks that gets me in the ballpark for now. I will read up for the fine tuning of it.

[westcoastgalaxie]

Got my a/f gauge running and boy talk about a great tool, problem is buying all the parts to have a wide selection to tune with (carb parts) gets expensive quick so I could use some help with getting in the ballpark.

1.) There is a lean spike off idle, ~17.5 ish, should I increase the pump shot size or mess with the cam? Currently has a pink and 31 std. If which to what value? I am thinking a 35-37 on the shot and leaving the cam alone.
2.) Vacuum in gear is around 8-9" some cruise conditions see around 6-8", 5" ish mild acceleration. Normal steady throttle holding at 2k is around 15". Current power valve is 6.5, do I need to drop it down to a 5.5?

This is my interpretation of what I am seeing on the gauges, but I am a newb so maybe I am wrong. I can post video if needed. Maybe y'all can see something I am missing. Its a lot of data for me to process. Thanks

[Barry_R]

I would work with the A/F numbers to get a nice grip on WOT and cruise - still use seat of the pants and plug readings to verify the results.  Remember that you are averaging a full bank's O2 readings in the collector - easy to have one cylinder richer or leaner than the others & get you into trouble since it won't show up clearly in the data. 

I consider the transient behavior - tip in, part throttle crowd, etc. - to be much more of a driveability & feel thing than any O2 data is going to provide.  You can use it as a reference "it feels really shaky as it gets beyond 13:1" - but don't try to chase a number 'cuz it'll probably fool you by wanting something different than the gauge would indicate.

[jayb]

When you see the lean spike on acceleration do you get any hesitation?  If not, I'd leave that one for last.  When you do get around to tuning it remember that increasing the shooter size will shorten the time that the pump shot takes.  I can't say I've ever followed a set procedure for accelerator pump tuning, but in a lot of cases a cam change is all that is required.

I think you do need a power valve, probably a 3.5 or 4.5.  You don't want to be too close to the power valve coming in under cruise.