I saw in some of the posts that energizing the carter 1bbl feedback carb leans the mixture. That is the way it works also on the 2150 feedback carb. On the 2150 they say the solenoid controls "air bleeds" which I take as another way of saying they are controlling "air leaks" to let more air into the engine, bypassing the venturi and leaning the mixture. Do you know if that is the way they are controlling the carter 1bbl? I am also assuming since they added this air bleed control, that is carb would be jetted a little richer than the normal non feedback carb, so they have control on either side, rich or lean. I am thinking if you could figure it out, you could install the proper sized jets, and block the solenoid passage entirely and convert it back to a regular carb.

 

Energizing the feedback solenoid does lean the mixture. This can be verified by watching the DVM connected to the O2 sensor, the voltage drops to zero. On my truck manually energizing the feedback solenoid at 60 MPH cause the truck to loss power, like taking your foot off the gas quickly. Next I connected a DVM to monitor the O2 sensor, then I swapped out the O2 sensor... all because everything you read tells you that feedback carbs runs to rich. But the fact is on my truck anything above 55-60 mph is on the lean side already as the carb is max out.

My understanding is there are 2 circuits, Idle and Cruise. If you take off the feedback solenoid (1 barrel carb) there are 2 openings on the top half and one larger one on the bottom half. I believe opening up the ports allows vacuum to be applied somewhere inside the carb to lean the mixture. True is I never did figure out how it goes lean,
On your carb try messing with the idle mixture screw, I bet you have a hard time getting it to go lean, I did. It is like the computer does this, not the idle screw.
My gut feeling is a feedback carb has a adjustment range of 70% to 110%, meaning most adjustment is on the lean side, for better emissions test results.
I would be surprised if you end up having to change the jets (smaller). Reading the output of the O2 sensor during a week or two of normal driving will tell.
The voltage output of the O2 will not "cross over" the .5 volt like it should, so by that standard it is on the rich side. I just don't think the MPG improvement ( if any) will justify the work involved.
It is common to see a blocker plate installed on new carbs like the one in the photo below.
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I'm not clear on where the SPOUT connector is, or what it looks like. One of the wires coming from the harness, and going to the connector for the distributor circuit board has a connector in the middle of it- is that it?

I really would like to leave my emissions system intact if at all possible- this is unusual for the truck to not run well, and I'm loathe to change a good thing.
-James Huston

 

Yes, that is it. It is C170 in the picture below.

 

Well, it was connected, but the terminals were very dirty, so I cleaned everything thoroughly and will see how I do on the drive home from work. I'll clear the codes first, and see what develops.
-James Huston

 

The SPOUT code was at least part of the issue ; the truck has been accelerating like her old self again, and climbs hills with aplomb. I still need to sort out the other codes ( and check to see if any reoccur), but I think I can safely say that was the problem.
The truck is semi-retired ( I've moved a lot of heavy machinery in the course of building my shop) , and I'm slowly amending things to improve it for truck camping. I need to do some research into the best measures to make it as reliable as possible, as fuel economy and power are, in my opinion, adequate. I may ultimately swap the 4 speed out for a five speed to better attain highway speeds, but that's a subject for another time.
Thanks, everyone, you saved my bacon.
-James Huston

 

+1 for using the word aplomb which, I really didn't know exactly. Sounds like your pickup was negotiating the grade with great élan. Test is a week from today. Bring a #2 pencil.

a•plomb ə-plŏm′, ə-plŭm′

►

• n.
  Self-confident assurance; poise.
• n.
  Self-possession springing from perfect confidence in one's self; assurance.
• n.
  Assurance of manner or of action; self-possession.

 

Thanks; I did pretty well in English class. Math, not so much...
-James Huston