Space under drop flues

[Quabbin Hill Farms]

does anyone use oil and had drop flues. I have 5" inch drop flues just windering how much space do you have under them or do you have the insulation up tight, I can't seem to get my back pan to boil has hard as I think it should. I use a 2 gal an hour 45degree nozzel in an arch 18"x 7"
Thanks

[Three Saps Sugar Shack]

the space should be minimal , and the front couple inches of the flues should be touching the ceramic blanket, did you convert from wood?... if you did , have you reduced your stack size... you should be using a stack that is about half the diameter of what it was for wood... and it needs to be outfitted with a barometric damper, also.. the 45* nozzel sounds a little tight... but if the arch is only 18" wide that may be ok..

[Quabbin Hill Farms]

Thanks good information and yes this was an old wood arch but I only rer-used the front cast door frame and stack frame so yes its still 7" in diameter how small should I go not sure if I can get 3 " pipe or a damper that small

[Three Saps Sugar Shack]

maybe 4"...