I've been messing with coke can stoves for a little while now and have found that sealing with RTV makes a pretty significant difference. I made three identical stoves: 1. one completely unsealed, 2. one with just the outer joint sealed, and 3. one with all adjoining parts sealed (inner wall seam, outer joint, top and bottom (minus weep holes) of inner wall) and tested them against one another. I've found that the more sealing you do, the longer it takes to prime without a pan, but there is a significant decrease in boiling time.
STOVE 1
Prime (no primer pan) ~1:20
Prime (with primer pan) ~13sec
Boil time (1 liter H2O) ~14:30
STOVE 2
Prime (no primer pan) ~2:00
Prime (with primer pan) ~18sec
Boil time (1 liter H2O) ~11:00
STOVE 3
Prime (no primer pan) ~2:45
Prime (with primer pan) ~21sec
Boil time (1 liter H2O) ~7:50
