I got idle dialed in and the preliminary tuning of the accelerator pump and it's doing well. The idle screws only needed 1/8 additional turn out. Any more or less and vacuum dropped off.
For some reason, when one of the transfer slots is approximately square, the other is still slightly rectangular. I guess that may just be the result of manufacturing tolerance. I found that I'm able to reach the secondary idle speed screw with a small screwdriver, thanks to the 2" spacer I'm using.
Still need to check/adjust secondary actuation and need to see if my regulator works.
The 570 was really lean for this engine in the out-of-the box tune. Reving the engine resulted in the rpm staying high for a couple seconds then coming down and it felt really sluggish. It ended up 7 jet sizes bigger to be acceptable. This 670 does seem to be a much better match out-of-the box. My O2 sensor is not working so I'll probably wait until I get the gauges installed with the new wide band sensor to get the mains dialed in. It should be good enough to drive. If the plugs fowl or mileage is considerably worse, those should be clues, too.
It's amazing how many things I found that could have been causing this problem, some seemed to be obvious and the problem still isn't obvious to me but was something to do with the carburetor. Maybe some of that contamination stopped up a part of the idle circuit in the metering block.
Lawrenceville, GA