Originally Posted by Dr_KY
You don't need an exhaust stack really. They run fine with holes drilled in the lid or the cap out of the bung.
I was having a little difficulty, with wind, on my test run .... keeping the temp steady.
I narrowed it done to a couple of possible causes. Leaky lid (I put the seal back on it), and the exhaust (needed to "block" the wind from the somewhat direct path it had into the drum with just the bung cap off)