Glad it works better.
Haven't been to where mine is about 150 miles from me now, but I'll play with it. But I've been thinking about it quite a bit, I should have known better. My apologies.
Air flows down the carb, turns in the plenum chamber, then flows down the ports in the manifold. By the time it gets under the vacuum tree behind the carb it's already separated to each cylinder. The air coming from the PCV has oxygen in it, so it dilutes the mixture in that runner, which I believe is #5, left rear. Being a single plane manifold means the air is moving slower, the area of the passages are bigger, so there's much less mixing with other cylinders, which would dilute the affects of the extra air more.
Feeding it into the carb base, it mixes with all the mixture and gets more evenly spread throughout the engine. All the cylinders get some.
When you screwed the mixture screws in, clockwise, looking for the lean stumble, that #5 leaned way before the rest did, you felt the stumble, then richened it a tad till the stumble went away again. That's the correct procedure. But, the stumble was only #5 lean, the others were still too rich. That made the CO too high overall. At that setting #5 was perfect, but all 5 of the others were still making way too much CO.
If you leaned it further slightly, the #5 lean misfired and HC kicked up.
I had sort of a similar situation today. I stopped by a friend's Mobil station, he does lots of smogs. (I'm retired but can't seem to stay away.) He had a Toyota that was doing similarv to yours. When we got the CO down where it should be, both HC and NOX kicked up. I first suspected a small vacuum leak, but propane tests found nothing. Even told him about yours. Everything seemed to check out fine ignition wise, and timing was OK. PCV was hard piped in the right place, so that wasn't it.
Someone else had already replaced the carburetor, EGR Valve, and ignition parts. The poor customer had already spent close to $1000 on it and it still wouldn't pass. ---- A challenge!
Seeing NOX go high when CO was down where it should be had me going. It was telling me I was losing a cylinder. I was about to do a cylinder balance with gasses test when I started thinking about compression, then realized one cyl was hot causing the NOX to go high.
Sure enough, a block check chemical test showed a leaking head gasket - just a small leak. Combustion gasses were getting in the water jacket, causing that end to run hot.
Just to prove it, I put in a couple of Solder Seal tins and ran it a few minutes. Block Check no longer turned yellow - it sealed the leak.
Passed with flying colors.
John is doing the head gasket tomorrow and flushing that stickey stuff from the radiator. But it passed!
There's always a reason something happens, all we mortals have to do is figure it out.
My Jeepster's PCV Valve hose is on the manifold vacuum tree too I think, but we don't have to smog them here, too old. I think I had it on the carb base when I did all the dyno testing to curve the dist and jet the carb, but don't remember for sure.
98% is Understanding it
"Don't Fix Unless Broke"
