On that ten-wheeler, the screw in the stack holds a bracket for the smoke box front.
To remove the boiler, first take off the engine truck up front. Then, the center screw that holds the cylinder casting to the boiler. After that removed the two screws holding the rear wall of the cab to the tailpiece on the frame. Then, carefully lift the boiler off the frame, taking care not to yank out the headlight bulb wires.
The drivers were quartered by fitting into a machined square on each end of the axle that has a threaded extension on it. A slotted nut-head secured the driver to the axle. To remove that head, cut a slot in the blade of a small blade screw driver. Keep it as an essential tool for working on a Varney/AN/Babbitt loco as all have the same quartering and driver attachment.
Having such a driver out of quarter means that it's either been forced, or was re-installed incorrectly As the driver centers are cast brass and the axles are steel, it could be if forced the squareness of the driver's axle hole was compromised.
A repair could be done as described, but the driver and axle set must be in the same exact quarter as all the others on the loco. Not a simple thing to achieve without a quartering jig set to match the original driver/axle setup.
Best to see if you can find a replacement driver. Not easy, but maybe not impossible.
Varney/AN/Babbitt drivers are all the same size, regardless of what loco they were on. There were two types: A main driver with a wide counter-weight and the secondary drivers all with a smaller same sized counter-weight.
Here's an All Nation Kit No. 5 Atlantic I built in 1970 at its new home in Rockford IL. Scarcer than the ten-wheeler, it also was at heart a B&O locomotive!
Ed Bommer, aka here as S. Islander.
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