I have been dealing with multiple engine issues, with the carb just being part of it. I had a bad problem with rotor phasing (resolved a few months ago), and most recently I have been dealing with pulling oil into the intake at the valley pan gasket (BB). The weather was good today, and I was inspired to take the car out and tinker. I loaded my tools and IAB and MAB kits and hit the road.
Unfortunately, increasing the MABs didn't help; in fact it appeared it made the situation worse. At this point I can get reasonable numbers at 2K cruise (45MPH), but at highway speeds it still goes pretty rich. Today I increased the MAB from .033 to .035 and at 3K (@65MPH) the AFR was swinging more wildly than in recent memory, moving almost 2 full AFR (from high 11's to mid 13's).
Earlier experimentation lead me to believe my mains are over-emulsified, so I have change my emulsion jets to .028, blocked, .028, blocked (was .028, .028, blocked, .028). With the MAB at .033, this helped control the wild swings. However, the MAB at .035 has brought this problem back. It seems I am getting too much air into the main jet mixture at small throttle openings.
I then reduced the MABs to .031, and this reduced the AFR swings at 3K. Right now, I left it here.
Previously I had convinced myself that the motor was only getting fuel from the transition at 3K cruise, but your experience made me question that. I came to this conclusion because changes in the main jets didn't seem to be having an effect on the cruise AFR, but in hindsight expecting to see the effect of a couple jet size changes with the AFR swings that are occurring is a little foolish.
Anyway, after reducing the MABs, I tried a second experiment of increasing the IABs from .069 to .072. This did help the 3K cruise AFR some but it still bounces from the high 12's to the mid 13's.
How steady is your AFR at highway cruise? Do you use vacuum advance? Have you ever checked to see what difference there is with the vacuum advance hooked up and plugged, with no other changes?
Hopefully I will get a chance to check the plugs during the week. If I solved my oiling problem, then I should be able to fully concentrate on the carb setup. I am pondering with the idea of hooking up an in car video so you guys can see what happens at highway cruise. I'm also stewing on whether my problem is in the emulsification, and whether to try reducing at least the size of the first emul jet.
Doc,
I use an AEM 4100 setup. It is very entry level but seems to work well enough for basic tuning. I have an O2 bung in each bank, and move the single sensor from side to side while testing. I figure once I get everything dialed in, just leaving it in one side to monitor the motor should be fine.
