2 questions about carbs and widebands

[5:04]

Hello fellow Pelicans. I'm still in my first week of ownership of my S, however my natural need to work on cars is really kicking in.

My first question is about what I think is a lean pop at cruise speeds while on the freeway.

I currently have a 2.7 running 9.5 compression and Weber carbs at 3.5psi of fuel pressure. While I'm at cruising speeds I'll notice the occasional pop which sounds like it's coming from the carbs and not the exhaust (I'm not 100% sure). It only happens when I'm on about 10% throttle cruising anywhere from 70-80mph. The car was tuned for elevations of 5-6000 feet and I live in Southern California. Will I be able to simple adjust the mixture to make up for such a drastic elevation change. I plan on changing the fuel filters since I understand that they need to be fresh and to get take those out of the equation. I also plan on changing plugs just to be safe since I don't know when they were last changed.

So the question is: Is there enough adjustment in the current carb set up that I can simply adjust to a good mixture? Or do I need to rejett the carbs?

Second question is about running a wideband o2 sensor. Do any of you guys run one for the track? I'm kind a paranoid person when it comes to the track so I like to have as much info as possible. It also seems like it'd be useful for tuning the carbs similar to the way i used one to tune EFI set ups.

Thanks,
Amir

[gumba]

I run dual wide band on our 3.4 race motor with 46 Webers, and now 50 PMO's. Saved me some serious grief a couple of times. I had a dual a/f gauge made by Westac. The only down side is the sensors don't last very long running 100 octane race gas.

[Joe Bob]

Dyno or sensors.....that's why people go with FI instead of carbs. Less chance going lean and burning a piston. Popping on decel is most times and exhaust leak. Rarely at idle, most unlikely at accel.

[dicklague]

AFR instrument is a great idea. Our host sells a great dual one that gives mixture, RPM and other analog input. Daytona Wego IV comes in single and dual readout models.

I have a single installed in my street car MFI 2.7 and it is great. Data logging is also a necessary feature. With the Wego IV you can review up to 2 hours of data by downloading to your laptop.


This the dual.




Here is the single:




comes as a complete kit with sensors and cables and software.

[VFR750]

I run a Innovate LC-1 controller and wideband O2, with my "new" zeniths.

Just got the Zeniths running today and I can tell I'm running too rich at cruise, and just right full throttle (12.5-13). I was able to see how I could get the idle AFR close, but low power the AFR really dropped (11:1). With only 1 turn of the idle screws, I know I'm kidding myself at idle, I need smaller idle jets.

Our Host sells the Innovate Kit.

[Trackrash]

Sounds like too lean an idle mixture adjustment or plugged idle jets. At 10% throttle you are still on the idle circuits.
I would start by adjusting the idle mixture. Changing the fuel filter is a good idea. You may also want to try adding some fuel injector cleaner to your gas as well for a tank or two.

[Steve@Rennsport]

If your car was jetted properly for 5K to 6K feet, you will be much too lean for sea level operation and that means different main jets, possibly idle jets and possibly air correctors.

My best suggestion would be to invest in an hour of chassis dyno time with a handful of jets so you can make the necessary changes.

A wideband AFR meter will allow you to monitor everything,...

[5:04]

Thanks a lot for the advice guys, I'll try to enrich the idle mix as a short term. Then I'll figure out how to rejet carbs and buy a couple of wide bands.


As a quick question to Steve or the others in here should I get one for each bank since my exhaust doesn't collect until after them muffler. I'd get that Daytona kit but it's a bit pricey and I'm an AEM distributor so 2 uego's would be a lot cheaper and easier for me.