Single wall to double wall replacement, worth it?

[Stinkpickle]

Hi folks - I have an old Kingsman stove with a straight vertical chimney. The first 8' (or so) of chimney pipe is currently single wall which transitions into double wall several feet before passing through the ceiling. How big of a performance difference, if any, should I expect if I swap out the single wall portion for double wall? Thanks.

 

[Sodbuster]

If it burns fine now I'd say keep it. Double wall the entire way will give you better draw, but if it ain't broke don't fix it.