If ALL of your lower vents are closed, and your temperature is still too high - chances are that something else is wrong.
In order for the kind of combustions to take place, that allows high temps to occur, the fire needs fuel, oxygen/air, and exhaust. The WSM draws-in fresh air from below, and exhausts warm air and smoke from the top. Under normal circumstances, the WSM responds well to a reduction in any one of the three. If you close the bottom vents, it really should not be able to draw enough air to sustain a significant heat source, and should "ckoke-down".
My guesses would be one or both of the following:
1 - LEAKING AIR (SOMEWHERE?)
Did you correctly assemble your WSM? Some WSMs arrive somewhat "out-of-round" (measure the middle section across at the top & bottom in different directions, and note if there are significant differences). Most are out-of-round a bit, some more than others. I rotate the mid-section when I seat it on the lower (fire bowl), and find the "sweet spot" - where it fits together easily, and seats in all the way. If it's not properly fitting together, it could be drawing air through the gaps where the different "ovaled" sections meet.
2. SOMETHING WITH THE FIRE
Maybe you're waiting too long to assemble the smoker after you get the coals going? Or using too much fuel for a small load of meat. (although a proper, slow-burning fire, rarely causes "runaway" temperatures in a WSM that is set-up properly - expecially once you shut-down the lower vents).
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by jeremySeattle:
What do you recommend in cases where the WSM is running too hot and all vents are already closed. </div></BLOCKQUOTE>
To answer your question, we have to diagnose the problem.
- Why do you think your WSM is running too hot? How are you checking the temperature? Are you putting a thermometer in the top vent?
- Is this a consistent problem throughout the entire cook? Or is the temperature in the WSM spiking at different times during the cook?
- Is your WSM brand spanking new? Right out of the box WSMs tend to run hotter for the first couple of cooks.
- Do you have water in the waterpan?
- What type of charcoal are you using? There is some variation in brands of natural lump charcoal, though among the majors not enough to cause problems. With some brands of lump, there may be wide variations. I had a few bags of lump produced in Brazil that not only ran hot, but created enough snap, crackle and pop to put Kellogg's Rice Krispies to shame.
- Are you using splits of wood in the WSM or fist-size chunks?
Ron's supposition of excess air flow causing the WSM to run hot is a good place to start, but there are any number of additional factors that may cause a WSM to run hot.
My first question—what leads you to believe your WSM is running hot?—is probably the most important.