Any more progress on this? Can anyone else with a 250 post the nozzle dimensions and the dimensions of the secondary nozzle size?
Yep, did some more work to make it breathe better through the nozzle as SlimJim suggested. By itself, that helped a fair amount. I also added a couple of steel pipes along the side of the firebox to help keep wood from blocking the primary air supplies.
In looking online at the new O 250 design and other gassers, I noticed that they all had firebrick very close to the secondary burn area, within inches of it in most cases. I built a C-Channel with 2" firebrick around the sides of the area where the blowtorch fires and added a 1" firebrick directly below it. My thinking here is that the firebrick getting hot and holding the heat should help ignite the gasses. This helped immensely, coupled with the more free breathing nozzle.
The last thing I tried was this morning. I removed the discs limiting the primary air flow completely. It still seemed to me that the fire in the firebox still needed more air. I played with the secondary air supply (to the nozzle area) and found that it runs best with a very small amount of air flowing there (around 1/8" of the disc open).
With all that, the results were outstanding today! I ran a mixture of cedar and elm (definitely not the best wood) and started with just a few coals around 11:00am, stove was at 179 degrees. By 12:15 it hit the set point of 195. That is the fastest I have ever had it make temp, AND - it did this with both zones in the house calling for heat the entire time! Outside temp is about 20 degrees. I checked the reaction chamber two or three times during the burn time and the blow torch was going steadily.
HUGE thanks to you, Coolidge, SlimJim and RSI for all of the suggestions and sharing your knowledge!
Here are the pics of the re-revised steel nozzle. SlimJim, I didn't have time to line the bottom of the firebox as you suggested yet, but opening up the nozzle as you recommended was key. I will get around to lining the firebox with the 1" brick in the next month or so, but for now, life with the boiler is good.