I've been fine tuning my setup for about a month now thanks to the help of an AEM wideband but have come upon a problem. I started off with the stock settings which was pig rich and had worked on getting closer to ideal and ended up with 14.3 at 3000 but was still rich down low at 12.5 and still went rich again at 3400 to 12.5 to 13.0. I tweeked the IAB from .068" to .071" (specs say it should be .070" stock) and reajusted the idle screws with really no change down low but got up to 14.7 to 15.0 at 3000 and it still goes to 12.5 to 13.0 at around 3400.
I'm kind of stumped on what to do next as any changes I feel will change the good crewsing numbers that I have right now.

Current set up
pri 69
sec 76
IAM .071"
vac yellow spring

Its on a 400 +.030 9.5 to 1
452's ported stock valves
stock intake and exhaust manifolds
Voodoo 303 cam .494/.513 226/234
timing set at 10/36
in a 73 Roadrunner

The speed demon doesn't have changable IAB or IFR so I'm hesitant to play with these much and how much smaller can I go with jets, I never fiured they get down that low?

Anybody got ideas where to go next?

""14.7 to 15.0 at 3000"" (Tuning in this range should be the IAB's, metering screws, and the IFR's). This might be the transition circuit.
Note: you can change the A/F readings quite a bit with just the metering screws at idle or cruise. But since the IFR's are not adjustable, you may not find a happy medium.

""12.5 to 13.0 at around 3400"" (Tuning in this range should be the HSAB's and the main jets.) This might be the main circuit.

Since you have a wideband sensor, you can test this by changing the main jetting up 4-6 sizes and test driving it to see at what rpm the AF jumps to a richer reading. Then you know what rpm your carb is transitioning into the main circuit and then you can tune the correct circuit. Then just swap the jetting back once you know when your carb transitions.

Your going to be limited on how much tuning you can do with the Speed Demon carb. I used to have one too but I ran into the same problem with limited tuning features. Since you have the wideband, you can tune it as close as your carb will allow.
I was surprised too how much lower I needed to go on my jetting once I got my wideband installed. I ended up 3 jets lower on the primary side.

Note: When I first got my wideband installed, I got a pm from a member who gave me the advice of finding the rpm that the mains start. Once I knew this rpm, it made tuning the cruise much easier because I knew which circuit I was dealing with.
Some carbs the mains can start coming in around the 1800rpm range or so, and some carbs can be later on in the rpm range (like mine was stock) and the mains come in around 3000rpms.

Thanks YO7

I followed your thread on your tuning experiances and was quit impressed with the final result you were able to get and learned a lot in the prosses. I guess my question would be is it better to restrict the IAB and IFR in an attemp to get the idle curcuit to end lower in the revs or live with 3000 on the idle and reduce the main jets further to compinsate for the richness up above 3400.

I haven't been able to see exactly where the jets are coming in as you suggested but plan to as a point of reference.

You.d be better off restricting the IFRs/IABs to where you have a good adj. on the mix screws, Also see what the PVCRs are at, If you have it where you want it at idle/light cruise & the mix screws are at least 1.1/2 turns out this should be close, The problem may be in the transition, this is the area of the PVCRs, you can hook up a vacuum gauge & see how the vacuum drops in conjunction with the wideband readings, if its getting richer (in your case too rich) as the vacuum drops slighly as the PV starts opening, i'd restrict the PVCRs around .002"-.003", this should lean it out, then jack with the jets for WOT AFR. where you want it. You can tap/thread & install screw-in bleeds on any carb, you just need the pin drills & bleeds, still cheaper then a new carb.