I don't have the grate over the exhaust either. I'm not sure what it does. Maybe it was an option? I think it must help coal or wood from dropping down into the back baffles. I can't see any other function. The back elbow is a non-issue. Nice to have, the original has a sort of manual "baro" in it. I never used it...
The ring around the firepot however, is another issue. It also helps keep the sheet metal in that region from burning out. I can't really tell from your photos if the ceramic liner goes high enough to cover this or not. Looks like maybe not... The second problem is that without it being in place, the air flow doesn't work quite right. Many years ago, before I had figured out how all the bits and parts went together, I didn't have my ring in place. I would get some smell of the fire while running the stove. Now that was when I was only running wood, don't know about coal. But I'd just feel safer closing up the holes without having that ring in place. Once I figured out the ring and got it in place, no more smell...
I'd go over the joints with a fine tooth comb. One spot that is problematic is the joint right on the back of the stove where the back base burner flat top plate bolts to the stove body. That seal breaks easily. I've had to re-do mine just about every year. Now, maybe that's just my particular stove, I don't know. But I know on mine that's a seal I have to stay on top of. I've actually toyed with ideas of how to improve the original design.
Just my 2 cents worth...
DJ- I'm a lurker and blossoming vintage stove addict who finally joined forum. Question: you say you have a problem with the joint where the baseburner back bolts to stove body. You also say the grate over the exhaust is missing. Are these issues related? In other words, what should be bolted together is the cast baseburner, the stove sheetmetal jacket, a rectangular piece of cast that matches rectangular shape of grate (place around exhaust opening on inside of stove), then the grate itself. So...the sheet metal of the stove jacket is firmly sandwiched/bolted between the cast iron of the backburner and the grate frame and grate ...i would think different expansion rates of jacket and cast would not matter due to it all being sandwiched together with 8 bolts.
I'm curious though... the grate has 8 holes matched with the 8 holes of the rectangular frame, jacket and cast baseburner assembly. However, on the frame that the grate sits over, there are 2 ears that fit in two slots of the grate and cotter pin in place holding grate.
: maybe this all is geared for wood/coal flexibility. In other words, if using just coal-you need no grate. Just use frame to make the inside piece of "bread" for the stove jacket sandwich. If using wood, you can bolt on the grate/frame for this inside piece of "bread". However, if you indicate that you want to switch back and forth from wood to coal, you can just cotter pin the grate to the frame instead of bolting it and disturbing the whole assembly to remove grate. The problem with this theory is why would you want to remove grate? I can see you wanting to keep wood/bark/etc out of backburner assembly...but why would you remove it for coal? I don't know....but you can either bolt this grate in place or cotter pin it without the need for bolts...or both....I'm stumped.