question about 18by 48 dellair evaporator

[mike first timer]

i have a 18 by 48 dellair evaporator that i added a blower onto this year i made the doors airtight.My question is should i add a brick wall or something to slow the flames down to keep them on the pan longer? The pan boils good but the back of the evaporator by the stack gets glowing cherry red.

[sapbrush]

Put A Damper On The Stove Pipe, That Way You Can Control The Stack Temp

[mike first timer]

thanks for the response.What am i looking for for a ideal stack temp?