My Tappan upflow furnace Model SGUF 140D 48 E7 has 4 burners, two of which have a unusual flame pattern. The center two burners have blue flame midway between the front and back ends at the sides and bottom of the burners as well as at the orfices at the top of the burners. This does not appear on the two outboard burners.
Does this indicate a burner cleaning issue or a burner mechanical fault?
Are replacement burner and heat exchanger parts available for this tappan model?