Quote:
Originally Posted by AcampoDave
Today I got it up and running. It works exactly as advertised. My steady cruise is solidly in the 14's. It's hard to be exact at any given moment because after the decimal, the AFR is bouncing around quite a bit. I saw it bounce occasionally into the low 15's as well as the high 13's but as an average the engine was cruising at about 14.5 or so. Foot to the floor got me to high 11's and my idle was rich, in the 10's. I adjusted the mixture screws and got that into the 14's with a few bounces to the 15's upon deceleration.
What do you guys think? It seems to me like I am well within the ballpark. I suppose seeing things more into the 15's at a steady cruise wouldn't hurt but going up one rod size on the primarys may just be too much. I dunno. I'll get some more behind the wheel time with it to get a better idea over a wider range of conditions. Could I also anticipate it leaning or enriching itself as air temps change. Today it was mid 70's outside
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You can go 16-17 at light throttle/low load cruise if you have a way to add more vacuum advance at part throttle (and only part throttle). I believe you can get adjustable vac advance units for HEI distributors. Like the forum thread I linked before states, timing and afr are not independent of each other; when you adjust one you'll have to tweak the other a little.
I'm not familiar with your particular carb but if it uses rods that insert into jets like a monojet/quadrajet you can use a thicker rod and if its too restrictive/lean you can chuck it up in a lathe or drill and file/sand down the area that's too restrictive. I've done this with my Monojet.
WOT afr should be right around 12.5-12.75. Any richer wastes gas and the unburned fuel is diluting the oil on the cylinder walls. Running richer also makes the engine lazy, the added fuel cools the mix in the chamber and is harder to burn- hotter fuel vapor burns much more easily than colder liquid fuel. The forum thread I linked goes into a lot of detail about that.
Running at the "ideal" 14.7 isn't where you want to be at cruise, it adds unnecessary heat and uses more fuel than if you were leaned out to 16-17 with more timing. The unburned fuel at WOT (richer than 14.7) acts as coolant, as does the unburned oxygen at leaner than 14.7.
For idle, don't go by afr, use the "lean best idle" procedure described here, it will give you the most stable idle across varying temps/weather/altitude.
http://www.redlineweber.com/html/Tec...lean_best_.htm