Air Fuel Ratio and tuning

Then I certainly have some more tuning to do.

I think I'm going to step down a jet size next. I think I put larger jets in the primaries when I rebuilt the carb (and of course did not annotate it anywhere), just a guess.

So I own an Innovate Motorsports LM-2 that has the wideband O2 sensor in it. It is very nice - gives instant readouts of your actual A/F ratio.

While that is nice and all, the real problem is what A/F Ratio do I really want?

Knowing 14.7 is stoiciometric, I also know that running at that level will cause stumbling, etc.

Car Craft in their article cite an AF Ratio of around 13.0-13.5, and I quote:

"At light throttle opening speeds of 35 to 40 mph up to freeway cruise in Overdrive, the carburetor delivered consistent air-fuel ratios of between 13.0:1 and 13.5:1 which was close to ideal."

However, Ford Muscle had a chart in this article that showed many different values in their article (and I quote):



From this chart, I would want to perhaps be up more toward 14.2 for cruise, perhaps a bit more (this is for my pickup with a 360, not much performance wise).

Right now, it is running about 14.2-14.4 in low-mid RPM cruise, 13.6-14.0 in higher RPM cruise (freeway speeds) and in the 12's for power (not WOT). Have not even checked WOT.

It seems to run well, I am at about 8-10 degrees BTDC on the timing.

This is an Edelbrock carb.

I have several rods, jets and springs and I have been changing them out, seeing the effect (it really does work, and it is quite cool).

Just looking for other's experience. It's nice knowing exactly what your A/F Ratio is, but knowing what to do with that is the other 75% of the battle...


Edited by GranTorinoSport - 27-May-2010 at 6:21AM