hello all ,i have a v.c. acclaim-non-cat.pretty old all cast iron fire box type.it seems to have been abused by the previous owner.i had to replace the combustion package.and was told to check the fire backs .well now i think i understand.there seems to be a gap between the upper und lower fire backs where they meet i noticed when i start a fire flames go behind the lower fire back and come back out beween the upper fire back to exit out the open damper.i believe the to fire backs should be tight .the middle of the lower seems to have a curve to it where it meets the upper i guess i should replace upper and lower backs?.thanks and have great thanksgiving!bill