u/JDiddyTiddy

Hey all, I’m trying to install a liner for the Drolet 1800 I just got.
I made it down to just above the smoke shelf before I can’t go any further. The flue is plenty big for the 6” liner with an inch or so of insulation, but it narrows at the bottom. Does anyone have any advice?

The second picture is the part I’m getting hung up on. I tried grinding down the mortar cake job, but can’t get enough clearance.